I remember some here having rifles of this chambering and it makes some sense to me when considering a 2.5" H&H case vs. a full-length version of the same. A 3.6" mag box should grant some throating/bullet flexibility as compared to the STW and RUM cases while giving a bump in velocity over the standard 7mmRM. My question is how much of a bump? Could a guy expect to make 3,300fps with 140's and a 26" barrel? I know I made 3,250 with a 24" 7RM, but I was standing on it pretty hard. I'd think 3,150 might be doable with 160-162gr stuff, as I did 3,250 with 165's in a 26" 300WinMag. Several here are fans of the Mashburn, but I don't know how it differs in capacity from a simple 7x300WinMag neck-down.

Just kicking around ideas, as it's that time of year...... (grin)

There's .015 difference in neck length between the Mashburn & 300 Win Mag with the 300 Mag being shorter. That difference may be made up when squeezing the neck down from the 300 Win Mag.

Jpro: The Mashburn has a longer neck than the 300WM necked down. I have never had a rifle so chambered but have necked a 300 WM down and seated bullets a few times.

I doubt there is really a great deal of difference in velocity between the two, but the longer neck of the Mashburn is helpful in arranging bullet/land relationship, especially with the shorter, lighter bullets.

Also, the Mashburn has slightly less taper than the 300WM,and is slightly blown out in forming.

I specified a H&H box for my rifle,and seat the 160 NPT even with base of neck.The COAL of the 160 AB is a bit over 3.5 and functions smoothly.

I wanted the rifle primarily for heavy 7mm bullets so I have not tried 140's in the rifle as there is little need. With Retumbo and H1000 it is easy to get around 3200-3250 with the 160,and a hair under 3100 with the 175.

The 7mm Dakota is a similar cartridge,and I easily achieved 3350-3375 with the 140 in a 24" Krieger.

I could have built to either case, but liked the Mashburn better.Had good input from Dober here and it is surprising how I easily achieved the vels that Warren Page and Bob Hagel spoke of.And it does out run the 7RM due to slightly greater capacity and COAL.Just enough more capacity than the 7RM to get the velocity without leaning too hard,especially with the heavy bullets which are very useful in this case..

When you can start a good 160 at 3200, or a 175 at close to 3100, you don't really need anything lighter.

Art Mashburn did his homework on this cartridge.

I always thought a 7mm on a .300 Win Mag case made a lot of sense. If your favorite 7 Mag is suffering from throat erosion and your rifle doesn't have a 3.6" magazine box, running in a reamer designed around a necked-down .300 Win Mag case would get you into fresh rifling. Also, .300 Win Mag brass is commonly available and it holds a little more powder. If I didn't already have a 7mm STW, I'd give this one a whirl.

Contact Tim_in_TN, he has built a couple of these and he will answer your questions. He is a great guy. Steve

Just built a 7mmX300 WBY- I thought this made more sense.

Take a look at the 284 Jarrett....

We were amazed that the .300 Winchester Magnum had never been reduced to 7 mm successfully. The wheels really began to turn wondering exactly what the volume of the case would be. We designed a different case taper, then used our traditional 35 degree shoulder along with a lead angle in the throat to accommodate 140 and 160 gr. bullets. We had a reamer made and proceeded to build the .284 Jarrett! After the case fire forming was completed, we did comparisons with the other big sevens to see where ours fit. We checked all of the cases by water volume and this is what we came up with: (volume to base of neck)

7mm Remington Magnum ..........73.5 gr. | 7mm Weatherby Magnum ..........78.0 gr.
..284 Jarrett ................................85.5 gr. | 7mm STW ................................98.3 gr.

It�s interesting to note where we are volume wise: 12 gr. greater than the Remington Magnum and 13 gr. less than the 7mm STW.

The next step was to shoot this thing! Of foremost importance to us was its accuracy. If it�s not accurate, the velocity doesn�t matter. The cartridge responded well to a variety of powders and without effort we were under our half minute accuracy with velocities appropriate for this case capacity. Our testing produced the following results:

140 gr. Nosler bullet.................................... 3450 to 3500 f.p.s.
..150 gr. Nosler bullet.................................... 3350 to 3375 f.p.s.
..160 gr. Nosler bullet.................................... 3250 to 3300 f.p.s.

These velocities are identical to a 7mm STW with a lot less powder. Even though all the 7mm cartridges are listed overbore, the question is how much overbore can you stand and still have a dependable cartridge? I do know the velocities shown are the absolute maximums for 7mm bullets, regardless of how much powder you use. The Mexican standoff: the bigger case won�t give you any more, and a smaller case won�t give you as much. This is the reason, for all the 7mm fans, we have to max out the 7mm bullet. It rounds out our performance cartridge line and gives us a big 7 that meets our accuracy criteria while producing predictable velocities. In an emergency, a Weatherby cartridge can be used in the .284 Jarrett, but I don�t recommend reloading them because the neck will be too short. Put a .284 Jarrett in your battery soon!

RD: The Jarret "is" the Mashburn .......Jarrett did not "invent" anything here........maybe the cases are slightly dimensionally different but the pratical effect is the same.Kudos to Jarrett....good idea but Art Mashburn invented it in the 50's and Page/Hagel took it from there.

This is like pretending the 7WSM is "new"....

They have been "successfully" necking down the 300 WM case for a few decades now....Jarrett is reinventing the wheel.The Mashburn is formed by necking down,and slightly blowing out,the 300 Win Mag case.The Mashburn neck is longer.

I can (have) hit some of those vels in the Mashburn, but they are a bit over the top..

3250 with a 160 is easy with todays powders in the Mashburn.Retumbo does it and H1000 comes close enough that there is no difference.I have gone over 3300 with the 160 and Retumbo with no ill effect but it is too much velocity from the case.I run it sanely at 3150-3200....it is,after all, a wildcat.

The 140 gr loads he lists are too hot IMHO....3350-3375 is doable in both the Mashburn and Dakota cases,but 3400-3500 brings us back to the Layne Simpson days and the STW,which is pie in the sky stuff..

What he does not show is that you will do very close to 3100 with something like a 175 Partition(519 BC and not bad for a retro bullet.This raises possibilities for those that like to shoot 180 Bugers, 162 Amax, etc.) A 175 Partition at those speeds stays with a 300 Weatherby 180 to 600 yards or so....

You can toss the Jarrett, the Mashburn,and the Dakota in the same hat.....identical as three peas in a pod.


I do agree that the case balances nicely between the other 7mm's and accuracy is very good...it easily outruns the 7RM IME without going over the top;seems to require less powder than the full length blown out H&H cases like the 7mm/300 Weatherby,and the STW.But Bob Hagel figured that stuff out 25-30 years ago, too...

Overall a really good idea by Jarrett but I LMAO that he wants to take so much credit for something done in the 1950's by Art Mashburn........kinda like him glomming on to the 280 AI;or Winchester jumping onto the Gradle Express cartridges and declaring them the "Second Coming"....ain't much new under the sun...

BobinNH

Sounds like you are the man I've been wanting to ask questions of - somebody with a Chronograph & first-hand knowledge of the 7mm Dakota.

Been looking seriously at semi-big 7mm chamberings. Very interested in the 7mm Dakota, but had reservations about it as I can't find too much in the way of velocity checks for the case other than the Hornady manual (I probably don't know where to look) and worried about the strength of the brass. In terms of case capacity, Dakota claims 95.0 gr of H2O on there website which is also what the guy told me on the phone when I called. I ordered a few cases and checked them myself. Granted these were unfired and will gain SOME when fired, but I was consistently getting 88 to 89 grains of H2O filling the cases with distilled water full up to the case mouth, flat across. I saw some guys posting that the 7mm Dakota case had more volume than the 7 STW and that it would therefore match or beat the STW's speeds, but when I pressed them, they admitted that they had never actually checked it themselves AND couldn't tell me what they were getting for speeds (don't think they checked and/or don't remember/care).

My questions are(finally, right?): Have you tried bullets in the 160-180 gr & what speeds were you getting? Barrel length (24")? Powder Charges? (specifically interested in the 162 Amax, 168&180 Berger VLD's).

Also - had always heard guys complaining about Norma brass (they make the Dakota headstamp brass) being too soft in the case heads. What are your impressions of the strength of the cases (how hard can you push them before needing to break out the super-glue to keep the primers seated)? Overall impressions of the cases?

Thanks for sharing your knowledge. Much appreciated.

-Ian

Nightowl:You made me dig up my notes on the Dakota,which is also a great cartridge.

I was running 74 gr RL22 with the 150 Swift SC II for velocities averaging 3225,with very good accuracy and low spreads for 3 shot strings,like in the 6-10 fps range per my notes.

When I went to 160 gr bullets accuracy fell off; I got stringing and erratic grouping,wider spreads.....the cartridge was begging for a slower propellant with the heavier slugs and RL 25 cured the problem. I have noticed the same thing with the two Mashburns we have here,and can't say that is true with all rifles,as Dober on here has run 7828 in his for years with good results.....but as a trend in our two barrels, once bullets hit 160 gr and up, these two cases seem happiest with RL25, Retumbo, and H1000.

I can get more velocity with the 160 gr bullets, easier, from the Mashburn than the Dakota,and I suspect this is because my Mashburn is set up for H&H-length bullet seating,while the Dakota is restricted to 30/06 OAL;not much difference but it is there.

In the Dakota 76 gr RL 22 gave me 3340-3370 or so and excellent accuracy with the 140 gr AB.

78 RL22 gave me 3550 with the 120 TTSX,very accurate as well.

The loads in the Mashburn so far have been 75-75.5 gr H1000 with the 160 Nosler Partition and and AB; velocities run 3150-3175 with the NPT,and up to 3250 with the AB.

I use a fireform load Dober on here gave me which is 65-IMR4350-139 Hornady, which does 3160 (low pressure),and is, in itself a capable hunting load for lots of stuff....keep in mind this is an easy goin load and the Mashburn is easily capable of more velocity with this bullet.

73 H1000 gives 3075 or so with the 175 NPT. I have wiggle room with all these loads and they are by no means over the top.My pals rifle seems to need one more grain of powder to hit the same speeds.He also does 3250 with the AB and 79 gr Retumbo,everything seems OK.

OTOH my rifle pushed to 3300 with the same load ;no pressure signs but I am uncomfortable with that load.

I got awayf rom the Dakota for a few reasons; good as it is, you might as well have a wildcat because both with it,and the Mashburn,you are sunk either way on a trip if ammo gets lost.

Second, brass is $2 bucks a pop for the Dakota,and I cannot easily form it from anything else.Some suggest the RUM case to form, but the extractor of the Dakota 76 is set up for the Dakota casehead;using RUM cases could result in malfunction.

OTOH the Mashburn is easily formed from (relatively) inexpensive 300 Win Mag cases, which is everywhere.Forming cases is no sweat and can even be done without a bullet FF load.

Plus, if I ever get sick of the wildcat thing, my rifle could easily be rebarreled to a long throat 7 RM....not as fast of course but still good.

I have not worked yet with any Berger bullets, but recently got some 162 Amax,which I suspect will do 3200 or so pretty easily in the Mashburn.

I have experienced the "soft brass" issue with the Dakota,and cases split near the neck/shoulder/ case body junction on occaission on the second to third firing....not a lot, but enough that it bugged me.

All the velocity figures you see,whether in the Dakota, or the two Mashburns, were taken from 24" barrels...all have been Krieger #2's, 9 twist,on all three rifles.

Like any rifle nut case who works with a wildcat, I like to think the Mashburn is the optimum 7 mag,however delusional that may be ....it works swell in an 8 pound rifle and 24" barrel and you don't have to lean hard on it to get a step up in velocity over the 7RM.In larger cases like the 7RUM and STW you get more vel, but burn more powder,and mostly these are 26" barreled rifles.In any event the Mashburn gets as much velocity as I can use for my purposes,and does not kick me into next week from a relatively light rifle.

Hope this helps.

Nightowl,

I'm currently working with a 7mm Dakota with a 24" Lilja barrel on an M-70 Classic Stainless.

Load development is far from complete as I've yet to achieve a happy combination of velocity & accuracy.

I'll be happy to share my results so far, feel free to PM.

It sounds like a good 160-162 at 3200 could be the answer to many questions.....

The 7mm Dakota or the 30 Newton necked down to 7 makes more sense than anything else out there.

Ditto with Bob. My Mashburn is a rechambered 7 Rem from Brown Precision. It turns 3269 over my chrony with 76 gr. of RL-25, a 162 gr. Interlock or 160 gr. AB, and an AOL of 3.565. I use Federal Gold Medal .300 Win cases and fire form with 20+/- gr. of pistol/shotgun powder and cream of wheat. Cases capacity, to the top of the neck, is 90 gr. of water. The barrel is a 24" Shilen in 8.5 twist. I love it to the point that I am building a lighter one, about 7.5 lb. just for fun!

Art Mashburn/Warren Page got it right the first time!!!!! The Dakato is an answer to a problem no one ever asked.

JPro, the 3300 fps figure is an easy one to attain with the 7mm/300 Win Mag. I never seen a Mashburn case either, but if body taper is different then there is custom dies to be considered. The 7mm/300WM can be done with a 300WM body die $25.00 and a set of 7 Rem Mag FL dies $35.00. I just tried this fall a load with 72 grains of N560 and the 140 Nosler Accubond and was looking at groups in the .4" out of the Krieger barrel. 3300+ fps.

I think so....makes it tough to justify much else.....

Which of these cases you get the velocity from really does not matter; I think arguing over which of them is inherently superior to the other is pretty much a waste of time because they all do essentially the same things,ie , provide just enough more capacity and hence, velocity than the 7RM,while not jumping clear into the capacity of an STW or RUM...which are fine too, if that is what you want.


SU's suggestion of the Dakota or the Newton case(another oldie present today in the 375 Ruger),and Tim's suggestion of the 300 Win Mag would be equally good,because capacities are so similar in all cases.....I do find it funny that even though the Mashburn set the standard for this capacity level in a 7 mag 60 years ago, only Dakota had the foresight to give us a factory offering equivilent....and anyone moaning loud and long about "slow" 7 Rem Mags can fix it easily with a pass of the reamer and a Mashburn, Dakota, or 375 Ruger necked down.....that'll fix it!

Keep in mind that the 300 Win Mag case did not exist when the Mashburn was cobbled together,and that is likely part of the reason it has a straighter taper to the case.Art Mashburn messed with a FL H&H case necked to 7mm(likely similar to the 7mm/300 Weatherby and STW).....but found it not as good as the Mashburn we talk about here,which is why this one is known as the Mashburn "Super".

I think Ruger missed a good bet in not giving us the 375 Ruger case necked to 7mm.If they had,I would not have a Mashburn....not much need.

In the end,there are lots of ways to have a case of this capacity and it's a shame the factories have not really given us one....if they had we would not have to be discussing wildcats at all...

Docbill: I have not run RL25 in my rifle yet,having sort of settled on those H1000 loads for the time being. My pal has run it in his with results similar to what you get from your rifle.

If you have throat erosion, a simply ream job will not fix it. Most barrels don't have enough shank to sufficiently set a barrel back. Besides you might get a couple of hundred more rounds...maybe, but it it is a waste of time and money. Rebarreling is the better solution by far. Barrels are not that expensive, but pulling, reaming and head spacing are, unless you can do it yourself. Flinch

Jeeezzz, Bob, relax. I was just trowing out a suggestion.

RD: I'm relaxed .....that's how I relax.....none of it was directed at you personally

Just kabitzin'

It's a good suggestion......

And tough on reamers......

BobinNH:

Thank you very much for taking the time to reply and share your data. Sounds like a dandy of a cartridge. Any experience with a 7 STW or 7mmx.300 Wby to compare to the Dakota?

-Ian

The info about the dies is good to know. Thanks for your take on the matter.

I keep jumping back and forth between a big 7mm and the plain 300WinMag or 300WbyMag, as this one is going to be just a hunting rifle.

JBM yields some interesting info:

Allowing for a 7" vital zone and zeroing for Max Point Blank (about 300yds +/-), the big 7mm's look pretty good both near and far.

400yd performance of 300Wby with 155 Scenar at 3,450FPS.
Drop = 6.9"
Wind = 8.9" at 10mph
Vel = 2,630FPS

400yd peformance of a 7mm with 162 Amax at a "lowly" 3,200FPS.
Drop = 8.7"
Wind = 7.5" at 10mph
Vel = 2,590FPS

At this range, the 7mm will drop about 1.8" more but drift about 1.4" less. Impact speeds are nearly the same with the Scenar being 7 grains lighter and starting out a full 250FPS faster. It looks like the .30 cal doen't hold onto its velocity edge for too long, which is interesting considering that few folks shoot game animals out past 400yds. If they do, the comparison gets way uglier. I knew that speed is fleeting but BC is forever, still I didn't realize it would matter as much in instances inside "normal" ranges. That 162 is something....

Jpro: That has always been the attraction of 7mm's....that 162 is the ballistic equivilent of a 30 cal weighing (what?)...200+ grains?,which is really the right comparison.And how much powder do you have to burn in a mag 30 to get that heavy 30 cal bullet to 3200 fps?

Answer.....a lot;along with the recoil.

If you want to go "light" with the 7mm I know the Dakota (Mashburn, 300 WM case,etc)will likely start 120TTSX at over 3500;just a junior version of that 300 Weatherby load you cite.

Actually a garden variety 7RM will start a 140 BT or AB at 3250,and with the 300 yard sighting you list above,will only be down 8-9 " at 400,and about 26" at 500.If you are going to shoot light bullets, I would not bother with a necked down 300 Mag,or Mashburn, etc.It is just not worth the effort and expense of a wildcat.

The Nosler manual shows loads for the 7mmRM of 3300 with a 140, so a 300WM necked down is not worth it;neither is the Mashburn. The real advantage of the larger cases is with the higher veocity of the heavier 7mm bullets.

The figures look correct based on 300 yard zero....even a crummy 160 gr Nosler Partition started at 3200 will only be down about 9" at 400 from a 300 yard zero.

For chuckles, run a 175 Partition (BC 519) at 3100 or so, against a 300 Weatherby with 180's at 3200.It hangs pretty close....and it takes a lot less powder in the 7mm(about 73 gr in my rifle),to get the 175 to speed.

Despite the din over real LR shooting, I have never had to go beyond 400 for my BIGGEST bucks;most were half that distance or under.

Flipping through a few manuals and looking at the 7RM, 7mm Dakota, 7STW, etc., I did find where Hornady's last manual (2006-2007?) showed 3400FPS with 140's and 3200FPS with 160/162's when loading for a 26" factory 7mm Wby Mag. That sounds like a lot of performance from that case, although I hear 3450FPS fairly often from guys shooting factory 270 Wby Mags with 130's. I'd imagine the Mashburn or 7mm/300Win could make those numbers without straining quite as hard, considering the slight bump in case capacity over the 7mm Wby Mag.

Jpro: As usual, you're very observant...

The 7 Weatherby case is about the same size and capacity as the 7RM (although you hear different things from different people on that,all you gotta do is look at the two cases)

The 7Weatherby gets its velocity advantage from three factors:Longer throats(freebore,really), generally longer barrels(most data is 26" as are most rifles),and factory and manual loads at higher pressures.

In contrast to the 7RM,which, while loaded to 06 length as well, is not loaded as "hot in factory ammo;and manual data reflects the same(Federal told me they load to 58-59,000 psi.

Lines can get hazy when conmparing the 7RM, 7Weatherby,and Mashburn.

I have several times had 7RM's made up with leade/chambers cut to accomodate 160's and 175's with bullet base seated to base of neck,ie longer than factory standard.....my loads and velocities then nudged up to 7mm Weatherby vicinity,not quite so high because I was unwilling to load that hot....but close.

The Mashburn is not hugely different than the other two,gaining its' velocities from slightly more capacity(slightly longer case and blownout a bit) than the Weatherby amd Remington,and longer OAL than either...

Also keep in mind that established velocities for the Mashburn, and lots of data that hangs around from Page and Hagel, were from 22" barrels in Page's case, and 24" from Hagel,who also worked with a 28" Ruger +1...

A lot of this is the reason why you see guys on here say the 7RM is not that "fast"...they are not wrong, but are often working with shorter SAMMI throats, short cartridge OAL,and are not loading to Weatherby pressures.It's throats and barrels....

The Mashburn sort of strikes a good balance (from what little I have seen so far)....enough small but important things conspire to provide just enough more capacity to provide the velocities Dober has stated here; and that I am seeing from two rifles back here,in 24" tubes...ie very easily hitting 3075 or so with the 175 gr bullet;and 3150 to 3250 with the 160's.I know Docbill on here is also getting 3250 with 160 and RL25;my pal, Matt gets it in his rifle with Retumbo.

And don't forget that we have powders that Page and Hagel did not....mostly they used WW II H4831; we have things like Retumbo, RL25, H1000.

Jpro, if you will drop me a PM with your email address,I will forward Bob Hagels article from Rifle Magazine on the 7 Mashburn, which is a great read and explains the cartridge and comparisons to the other 7 mags, better than I can. I think you will like it.

That would be much appreciated! Sending a PM......

JPro-if you decide to build a Mashburn feel free to get ahold of me for some load data. My 3rd barrel with the round is about toast and I have a load or two you could try.

If you build it, it'll quickly be one of your favs, especially when you begin to stretch out the ranges a bit.

Dober

In Hagels article, which also appears in the Big wildcat book from Wolfe publishing, he states that when the 7 Rem is throated for 160's seated to the base of the neck the Mashburn and 7 Rem are about 100 fps. different when loaded to the same pressures. The 7 Rem. is a lot better than most think if throated/loaded properly. I use 7 Roy data as my gold standard because the Mashburn is about 4 gr. water capacity different but the Weatherby has freebore. A swap out in my estimation.

Warren Pages obsession was with sectional density and BC and for a kicker he despised recoil because of its deleterious effects on shooter performance. He always sounded SOOO right to me. A technical genius with a PRICKLEY personality.

Dober taught me ....

Appreciate the offer and will certainly keep that in mind. I've got no real "Long-Ranger" in the stable at the moment.

Gotta modify that JPro, everyone needs a big dawg driver in their bag...grin

Dober

Why not the 7MM UM? I have one in a Sako & its a great long range round. Shoots at greater distances than I am capable of.

It's just a bit too much of a good thing, considering the powder appetite and the OAL/magazine constraints.

anybody messed with the 6.5 weatherby?

the guys at mcwhorter custom rifles have been cranking those out. Claiming 3300+ with 140s.

Same for the 6.5/300 win mag.

I bought a McWhorter in 6.5 WBY three weeks ago but I haven't had a chance to chrono it yet. I plan on taking it out this weekend or next to see what she pushes a 140gr. VLD at.

is it possible to take a regular 7mm rem mag and ream it out to 7mm mashburn?

79: What rifle?

Pac-Nor makes barrels for a 270-300WM...I'm having trouble getting that thought out of my head....

I would be reaming out a remington savage or tikka. I like the 7mm rem mag but the last one that I loaded for wouldn't give me more than 2950 with a 160 even with slow powders. I would like 168s to 3000-3100 easily and do it out of a 24 inch barrel.

The Remington will work nicely...no magazine alterations and long enough tohandle the heavier 7mm bullets.Good choice!

No the manuals do not load them at higher pressure, just the opposite. Cause some clown will use that info in a gun that was built with no FREE BORE.

I get 140s out of my 7mm WBY at 3400 with a 24" barrel my 300 Wby gets 180s out at 3300 and 200 at 3100 with a 26" barrel

Oh.....not sure I follow.........most manual data gives the caveat and warning about Weatherby Freebore....

.....and meant that it is loaded to higher pressure in factory ammo than 7RM is;and charges are substantially higher even though case capcity is similar....I don't see how those velocities would be possible from a case of essentially the same size as a 7RM, without the higher presures...but who knows.

Well Bob you got two out of three right it's freebore and factory loads are hotter

Well joe that sure could be;that freebore will allow you to burn more power....but I still suspect SAAMI pressure spec is higher for the Weatherby stuff than most factory 7RM..

..anybody know?

I have factory Weatherby rifles in calibers from 257 through 340 and every one out does the manuals. In fact they run with the specs of Roy's old Weatherby load data.

I never even could get close to 3300 with a 300 wtby fibermark without having BAD pressure signs... just wasn't safe in my eyes.... you could get high 3100s and that was about it maybe right on to 3200....

Roy hotrodded them for sure.

I've never seen a 300 Bee go over 3200 with 180's either...

Dober

know five of them doing it right now on a diet of 7828, been using it for years running those speed tell the necks wear out

7828 would be my go to to try as well, never done it yet though...grin

How much you pouring to it?

Dober

(side note, I know I could get there though if I really wanted)

85.5 in Rem cases for 180s

215's?

cci 250s

you most of been running to fast of powder and was it a 24" barrel?

run a 26" barrel and quit cutting them to 23"

Barnes #3.... out of a 24 inch bbl.. using 180 XLC there are several loads that exceed 3200 ...from the 24 inch test bbl using 86 grans of 7828 gives 3261 with the XLC 180 grain....I do not use the 180s ..I only shoot the 200 BBC and 220 NP...using H870...in my MV 300...kills critters dead...so why change??

Bob,
I'd love to see the article too. Sending PM

Had a guy here too, ran some good speeds for years with a 25-06. Running 257 wtby speeds. His was all fine too, until the gun locked up because the lugs beat the recessess so bad you finally couldn't unlock em..

Now I'm not saying 3300 is unsafe BUT I"d have to see some kind of pressure test to verify... even with the Oehler system to compare factory to reloads would make me happier....

True enough I love the 23" length but for this load I was talking 26's...

Dober

if I went with a remington 700 I would have to have the barrel pulled and reamed? What are you running for dies?

I'm running RCBS for my Mashburn

Dober

how does the accuracy of the mashburn compare to a 7mm magnum and a 300 win mag? Would like to get good velocity and between .3 and .5 inch accuracy...

does reaming the barrel require that the gunsmith take it off?

how many dies do I need...a form die and a 2 die set..??

are there gains to be had by neck sizing?

Could a 7mm weatherby on a remington 700 classic be reamed out to mashburn specs?

Is a detachable magazine for a remington 700 going to be big enough to take these shells?

has anyone here seen this guy calls it the 7mm practical.
The 7mm Practical

The design premise for my version of the 7mm-.300 Win Mag was to obtain maximum power from the 7mm bore without excessive wear, suitable for the volume of shooting (practice and hunting) I prefer from a long range rig (approximately 12 shots per week on average). The cartridge is intended to be used for hunting light to medium weight game from point blank, out to true long range distances. The case capacity is what I consider to be optimum for a balance of efficiency versus effective power at extended ranges.

The 7mm Practical has other user friendly advantages. These include a long neck, longer than is found on the Win and Rem magnums, both old and new designs from the 2.5" magnums through to the WSM/RUM�s, many have a neck length of up to 6.8mm at best. The longer neck helps bullet to bore alignment immensely. Rather than trim the brass, for the first several firings, the brass is allowed to grow until it reaches the desired length (see notes below).

There is no need for special dies or special operations when reloading for the Practical. Simply use a standard 7mm neck die and 7mm Rem Mag seating die and get straight into maximum performance. Bullet jump is dictated by the separate throat reamer and each rifle should have its throat cut to suit its magazine box thereby minimizing bullet jump.

The Practical has a 30 degree shoulder, duplicating the WSM/RUM shoulder angle as opposed to the parent .300 Win Mag which has a shoulder angle of 25 degrees. The idea behind the change in shoulder was to assist positive head spacing at the shoulder with hand loads and to some extent, it was hoped that it would encourage case neck growth based on my experience with the RUM and WSM�s which seem to display rapid neck growth. To be honest, I do not know if the change in shoulder angle actually made any difference. It�s certainly not a point worth pushing.

The Practical is also intended to make use of an easily sourced parent case. The belted case is also easy for gunsmiths to work with, without need of custom head spacing gauges. The Smith can use standard 7mm Rem mag go and no go gauges to check fit. In this way, the fire forming load utilizes the belt and gives It (for once) a useful purpose while consecutive loads are head spaced at the shoulder for optimum accuracy.

Above all, the Practical was designed to do what its name suggests, to provide a simple, practical cartridge for precision long range hunting. Don�t get me wrong, the Practical is in no way as efficient as something like the excellent .308 Winchester. If I had my way, it would be mandatory for every licensed western hunter to own a .308, the arms officer would give you one after he or she ticked the last box. For 50 cents, you could upsize to the .30-06. No, the Practical is relevant to the pursuit of optimum magnum performance.

Pacific Tool and gauge made the reamer for the Practical as well as the separate throat reamer. The reamer was perfect, as can be expected from PTG and the turn around time was incredibly fast, certainly beyond expectation. True-Flite NZ Ltd (Gisborne, New Zealand) blueprinted the M700 action I used as the platform for the build and fitted a button rifled barrel of their manufacture along with a PTG recoil lug and Barnard extractor. The stainless steel barrel has a twist rate of 1:9�. I also used this opportunity to trial True-Flite�s new 6 groove 7mm barrel which will eventually be offered along with the current 4 groove canted land design. Three weeks later, I was lucky enough to have a client want to try the Practical using True-Flite�s 4 groove canted land barrel. Results were as can be expected from True-Flite, simply outstanding for both rifles. Show off bastards.






The 7mm Practical
Max case length 2.657 (67.5mm)
Trim cases to 2.645 (67.2mm)
Neck length for the practical when trimmed is .289 (7.3mm). Several shots are required before cases will grow to the ideal 2.645 length.


Test rifle


Rifle: M700 action (trued).
Bolt fitted with Barnard Precision extractor (very nice extractor, finished the project off perfectly).
True-Flite Ultra Match 28� No.4 fluted (same contour as Lilja).
PTG recoil lug.
HS Precision (AKA Sendero) stock. Rifle is bedded full length of action and knox (i.e the barrel parallel).
Leupold 4-12 power scope, retro fitted with target turrets. This will eventually be replaced with a higher power scope and canted base however; the Leupold has kept the rig more compact and portable than expected.
Standard M700 trigger set 2lb.

Note: The 28� barrel was chosen for two reasons, the first was to minimize recoil by extending weight forwards, the second was to ensure maximum velocities- especially if my calculations and predictions turned out to be wrong, I didn�t want to say goodbye to those RUM velocities! I must point out, I hunt with a 20� barrelled .308 as well as the long barrelled magnums. I find that both configurations have their strengths and weaknesses. Generally, I do prefer a long barrelled rifle, even for bush hunting. To some extent, my preference to the longer barrels probably comes from growing up with the .303 SMLE (25.4� barrel) and Swede (sporterised to 24� barrel).

Components

Winchester .300 Win Mag brass
Federal 215 Magnum primer (*also 210 standard primer)
ADI 2217 (H1000) and ADI 2225 (Retumbo) powders.
Hornady 7mm Magnum generic neck sizing die used for reloading . This die has a 30 degree shoulder suitable for the 30 degree angle of the Practical. I tried to use my Forster 7mm Rem Mag bench rest neck die but it had a 25 degree shoulder and bumped the case shoulder before all of the neck was fully resized. This caused difficulty chambering rounds.

No special care was taken with the reloading steps. Any intermediate experienced hand loader using normal reloading practices can duplicate these results.

Max COAL�s
Berger VLD: 92.1mm (3.625�)
Amax: 91.7mm (3.610�)
Hornady SST: 90.1mm (3.547�)
Hornady Interlock: 89mm (3.503�)
Sierra ProHunter: 87.6mm (3.448�)
All test loads were seated 1mm (40 thou) shorter than the max COAL. Bullet seating experimentation will be carried out at a later date.


Test loads
Bullet Powder Charge Av. Velocity ES Fps Group Comment
180 VLD Hunting ADI2217
(H1000) 74 3075 40 1.990
74.5 3100 21 1.075
75 3152 23 .520 left cartridge in chamber waiting for wind gusts, heat caused increase in velocity and vertical disp. It is possible that the Group �should/could� have been .3�
75.5 3155 14 .300 Very good
76 3160fps 60 1.6 Near max. Note the plateau in velocity of 3150. Cannot seem to go past this with 2217/H1000. Case life still OK.
180VLD Hunting ADI2225
(Retumbo) 75 3144 49 .720
75.5 3168 79 1.625
76 3170 7 .740 Near max, safe




Bullet Powder Charge Av. Velocity ES Fps Group Comment
168VLD
Hunting 2217
(H1000) 75.5 Yet to test
76* 3220 7 .155 Excellent, good light game long range load
*Fed standard 210 Primer used in order to lower ES.
76.5 Yet to test
77 Yet to test
168VLD
Hunting ADI2225
(Retumbo) 75.5 Yet to test
76 3210 60 .275 No good at 1000 yards due to velocity deviation. Change of primer or .2gr incremetal load development needed
76.5 3226 17 .420
77 3346 45 .770 Near max, safe



Bullet Powder Charge Av. Velocity ES Fps Group Comment
162 SST ADI2217 75 3200 60 1.000
(H1000) 75.5 Untested. Suspect sweet spot
162 SST ADI2225
(Retumbo) 75 Untested
75.5 Untested. Suspect a sweet spot.
76 3273 5 1.000 Shame this won�t shoot better. Need to experiment with seating depth.
76.5 3333 50 1.6
77 3330 34 1.4 Safe load, no max pressure signs. Note plateau in velocity at 3330fps.



Bullet Powder Charge Av. Velocity Dev. Fps Group Comment
162 Amax ADI2217
(H1000) 76 3200 12 .275 Fed 210 Primer. Taken
goats out to 1130 yards with this load, very effective
76.5 3230 15 .78
77 3275 14 .320 Good load
162 Amax U.S 869 85 3200 2 .7
85.5 3230 19 1.2
86 3250 5 1.2 Poor groups may well be associated with excessive fouling. A lot of rounds were fired prior to these groups (testing effects of bipod versus sand bag versus day bag). Retest at a future date will confirm.



Fire form load: 140gr ProHunter, 73 grains ADI2217. Velocity 3127fps, deviation 10fps. .5mm jump (20 thou), Groups size .460 for 5 shots.
Tables above will be updated if and when I have an opportunity to test. Some changes will also occur as the barrel and throat wears in. Round count at the end of the above testing was just under 100 shots. Velocities and loads will change by .5 grain and 50fps as the bore wears in.


Some conclusions

The case has plenty of powder capacity, no charges were compressed. I designed the Practical to have a separate throat reamer so that clients could match the COAL to their available magazine lengths. One could easily build this on, for example, a Winchester M70 action with a magazine length of 92mm, can use a shorter COAL and still have plenty of case capacity for the same or similar velocities.

I believe that the Federal 210 primer is perhaps better than the 215 Magnum primer for lowering extreme velocity spread in order to reduce stringing out at 600 yards and beyond. The 28� barrel ensures the powder is burnt without loss of muzzle velocity.

So far, the numbers (extreme accuracy) look thus for the 7mm-300Win Mag with 28� barrel:
162gr 3250fps (Confirmed in second rifle)
168gr 3220fps
180gr 3120fps

The upper limit for this rifle (sub .6MOA accuracy/ case life) appears to be:
162gr 3270fps
168gr 3226fps
180gr 3170fps

Averages are:
162gr 3250fps
168gr 3220fps
180gr 3150fps

The average velocities listed above are approximately 125fps faster than a 7mm Remington Magnum of the same barrel length. I have been able to duplicate the velocities of the 7mm RUM with 162 grain bullets but am slightly behind with the 180gr VLD. Ultimately, the Practical is producing 7mm RUM performance with 16 grains less powder. Yes, I have had to use a long 28" barrel but this itself has paid dividends in terms of decreased recoil while allowing me to use mild loads with excellent case life.

My last three RUM barrels achieved 3180fps with the 180VLD from 26� barrels which is a theoretical 3250fps when corrected for a 28� barrel (35fps per extra 1� barrel). This is approximately 100fps faster than the Practical's average speed. The 7mm RUM's extra 100fps is not (to me) worth the problems of barrel wear and load inflexibility and finicky accuracy with regard to the excessive bullet jump. The 7mm RUM also produces extra recoil from the powder charge alone, producing significant recoil when loaded with a small felt wad rather than a projectile. Case life was always poor in the RUM, regardless of its 65,000psi design parameters and regardless of throat length. When the primer pockets weren�t expanding, the case necks were splitting, regardless of annealing. In the Practical, I may yet achieve higher velocities with the 180gr VLD and match the RUM. There is still great room for experimentation with powders and seating depths.

One last odd aspect is that ADI2217 (H1000) and ADI2225 (Retumbo) appear to be almost identical in burn rate in this cartridge. ADI 2217 produced several accurate loads as well as low ES, a generally excellent powder.

I Have already completed a second rifle in 7mm Practical (M700 SS Laminate) for a client and the above load data produced the same set of results in that rifle. Both barrels are of a completely different rifling design yet pressure, velocity and accuracy relationships appear to be identical. A third Practical is to be started this week (20th Sept 2010).

Imartin:Excellent post and very cool cartridge. I enjoyed reading that....you've reinvented the 7mmMashburn Super with a shorter neck

I'll take the 162 at 3150fps from a 24" spout please.

Hold the fluff...............

The Mashburn did that 60 yrs. ago albeit with different powders. Art Mashburn built Warren Pages first Betsy in 1950 +/-.

Geehee, the wheel is invented again.

Pretty tough to get excited about a l/a duping s/a performance.

Especially when wearing a belt................

Or having to employ 4 extra inches of barrel when other cartridges will get you there with 24".

Tough crowd...but encouraging to know that a few folks still shoot....................(grin)

Mark Penrod will be converting a Model 70 Classic Stainless (currently a .300 Bee) to the Mashburn.

Rifle hits USPS this weekend.

hey bob here is that guys website if you want to see his other stuff.
http://www.ballisticstudies.com/Resources/Articles/The+7mm+Practical.++A+Practical+Magnum..html

Can't disagree with that......... Once it leaves the spout,doesn't matter whet engine got it there......

I'd cite that handy/dandy prior to launch,is very easy to discern however..............(grin)

Stick: Yes I have made a habit of that over the years...an old favorite 7 Rem mag,now long gone and "worn out" was trimmed to 7.25, scoped, made by Butch Searcy....notwithstanding the handicap of the heavier M70 action....I used it everywhere through the 80's and back then it was unique,as there were fewer ways to get them "lighter".....with H&H box and .285 groove 24" Krieger,it did 3125 with 160's;3275 with 140's and carried like dream.

There have been two or three others similar.....

It is easier to "get there" today,but with all that the Mashburn is 7.9# with 6X Leup on board...not contemporary "light" but at 61 years of age I ain't complaining yet....maybe soon

Too easy to have the cake and eat it too...to be making concessions.

Ringin' bells is what it's all about...............

You should be!!!!!!!!!!!

Ha! Not me!

I don't know how you're still able to get around, being a year older than me and all

Holy crap. Mutual Admiration Society.

Get a room you two old fogeys.

Ps 7mm Rem Mag Rocks!!!!!

I knew the truth would come out sooner or later. Now I see what all the hype about the sheep and greet is.

280Ackleyrized,

Don't be changing my quotes. Not something I think is funny.

You want to be cool you say what you want but keep my quotes as said.

In fairness,few can say dumber schit than you,under the pretense of trying to avoid same..................

I can think of one .........

Top a $6K B&C stocked rifle,for the win.

Even folks stupid as you,can see the light.

Though in fairness,you's way in over your head,but it do add to the humor................

Will it be ugly camo and have a skull & crossbones on it ?

Never seen anything but topflight wares,rating the Jolly Roger.

Neither have you.

Laffin'!..................