Hi, this is an update on my 7mm Mashburn Mag load testing. Around May
last year, I had my custom 700 re barreled. I went with a Douglas 25"
in the mag contour to fit my stock. And using my PTG reamer my gunsmith
re did the rifle for me. It was throated to 175 Nosler at 3.600 and 0.020
jump to lands. So up till Oct. last year I finally found several good
loads and near max or max in the loads. On 1/21/15 I finally went out
to the range to test my loads.

Bullets used in the test:

150 Nosler Solid Base (old, not made any more)
160 gr Nosler AB
160 Nosler Part.
160 Rem Bonded CL
175 Sierra BT
175 Nosler Part
175 Nosler Part Semi Pointed

25 inch Douglas barrel long throat
All brass neck reamed WW 300 Win mag once fired
All primers Fed 215

Total of 32 rounds fired, 4 round strings

175 Nosler 74 H1000 3.575 OAL 3043+, 3008-,3029 m

160 AB 75 H1000 3.580 OAL 3153+, 3116-, 3139 m

160 AB 77 H1000 3.580 OAL 3217+, 3192-, 3198 m

160 Part 78 H1000 3.550 OAL 3237+, 3230-, 3253 m

160 Rem BCL 75 RL-25 3.525 OAL 3148+, 3124-, 3132 m

175 Sierra 71 RL-25 3.565 OAL 2946+, 2929-, 2938 m

150 Nosler SB 72 IMR7828SSC 3.558 OAL 3177+, 3155-, 3167 m

175 Nosler Semi Pt. 72 Retumbo 3.510 OAL 2920+, 2904-, 2910 m


Notes: When I went to load these rounds last Nov. I had to use a
new lot of H1000 powder. The new lot is a little hotter and the
77 and 78 gr loads were a little hotter than what I got in my
load work up last year. So I will work again with the 160 Part
from 75 gr of H1000 up.

The most accurate loads fired last year were:

162 Hornady SPBT 75 H1000 3.510 OAL # 215 3/8" 3 shot pulled #4

175 Sierra BT 71 RL-25 3.525 OAL # 215 5/16" 3 shot pulled #4

160 Part 78 H1000 3.565 OAL # 215 2 shots landed in 3/8" pulled 2
it may work. In velocity test it has 3 fps spread

The 175 Sierra load had a 8 fps spread

I am leaning to the 175 Nosler as a favorite.
I really like my Mashburn rifles and the 700 is a great rifle.

Have you done any work or testing with lighter bullets? 120's-140's?

Hi, I have only loaded 139 to 140 gr for fire forming use and 150 to 175 for hunting loads. I have used some 145 Speer and 150 Hornady and Nosler for fire form use when I did not have lighter bullets. Thanks Randy

Thanks anyway. My 7Mashy is a deer only rifle, even though it certainly can do more than that. Don't need the heavies for Mule Deer.

Thanks for the updates and load data, anyway. I can perhaps use your 150 data as a starting point with 140's.

I have used 70 gr of IMR 7828 with a 150 to 154 gr for fire forming. Randy

I fireform mine using the COW method and don't waste bullets or much powder.

Not to hijack, but what are you using for your COW? Mine formed alright, but I still had a bulge in the base of the neck compared to Dobers fire forming load of IMR4350 and Hornady 140s.

Great info. Should have mine in a few weeks. Nearly 3200 with the 160 PT's looks pretty deadly. As does the 175 PT just over 3000.. Great intel. Thank you.

My COW technique is pistol/shotgun powder; I have used Unique, Blue Dot,and others. A bit of toilet paper as wadding and then Cream of Wheat because it fills better than corn meal followed by a plug of canning wax. I have formed several hundred rounds with no losses or failures. YMMV

Interesting, I just stacked cornmeal on top of 14 grains of Titewad, but never used a "wad" to layer between the powder and cornmeal. I'll have to give that a try.

I scored and 8lb jug O H1000 so I'm going to experiment with 150 E-tips and get a little less compression compared to the very long 168 LRXs

I'm using 13 gr Alliant Bullseye,large PISTOL primer,RCBS corn husk tumbing medium(no polishing compound in it),and a wad of tissue paper.

The cases come out fine and I then run full house Mashburn loads from there. Works the berries.

Of course i also run the Dober FF load of IMR4350,139 Hornady. Can hunt with that load easily.

The Chanlynn barrel is 26 inches and has a 1-10 twist.

The load is a 168g Berger classic hunting bullet with a Norma case and a Tula mag primer.Powder is H1000.

Measured 10 feel from the end of the barrel with my old Oehler model 33 with a 10 foot spacing.4 shot groups except where noted..No errors on the chrono at all this session..

72g 3 shot
L.. 2970
H.. 3051
ES.. 81
A.. 3013
SD.. 40

73.5g
L.. 3035
H.. 3041
ES.. 16
A.. 3032
SD.. 6

74.5g
L.. 3083
H.. 3125
ES.. 42
A.. 3099
SD.. 18

75.5g
L.. 3118
H.. 3137
ES.. 19
A.. 3126
SD.. 8

76.5g
L.. 3162
H.. 3186
ES.. 24
A.. 3171
SD.. 11

77.5g 3 shots
L.. 3215
H.. 3231
ES.. 16
A.. 3221
SD.. 8

Im thinking a person could actually run the 77.5g load but just looking....im afraid they would open the primer pockets over time. Ashame as the 77.5g load shot the second best accuracy at 400 yards.

I ended up running the 75.5g load of H1000 with a seating depth adjustment.Say about .03 off that lands.
The load I hunted with gave a 2.5 inch and a solid 1 inch group at 400 yards before the season.
Might be just a touch slow.But when it shoots like that.
Ill take it everyday and on sunday..

Thanks for the info guys and the comments. Beretzs I am looking forward to hearing about your rifle when it is done. Randy

One of my Mashburn guns likes 76 gr RL-25, 162 gr Hornady interlock, Federal 300 Win case. Avg is 3275. I have reloaded the cases until I have needed to anneal and then keep reloading the cases. I have had no primer pockets open up. This is going on 10 yrs. now for this rifle.

Docbill, I will give that load a try. Randy

DB

I found Rel 25 pretty dirty compared to H1000.

dave

H1000 seems to make many of the various 7mags sing. However I prefer H4831 with 150's and below.

OP, try out some 180 scenars as an accuracy bullet, they are pretty impressive. Like dave, the 168 berger classic also shot superb for me (7 weatherby). Wonder if D7's 10 twist would shoot the 180's?

Rosco I may give them a try, 7mm bullets sometimes here in the Dallas area are not a big selection of types. For some reason in this rifle H1000 out runs RL-25 and Retumbo. Randy

I found a few lb's of H1000 and an 8 lb jug of RL33. I am thinking RL33 might be good in the Mashburn?

Anybody have any experience with it?

Hi, I like H1000 in my 700, it acts as a slower powder than RL-25 and Retumbo taking a few more grains. RL-33 looks like something new to try, do they have 7mm Wby data out for it? Randy

Randy I think 33 might be on the slow side but maybe with 175-180 gr bullets? Ya never know.

Thanks Bob, I thought that It might be a bit slow. I really like H1000 and will try the old semi pointed 175 Nosler with 74 gr H1000. Randy

I have some RL-33 to try with 175 Sierras. My second Mashburn likes 74 gr. H1000 for 3060 fps. with 175 Sierras/Noslers.

The Mashburn is a very nice round, & I'm not attempting to belittle it in the least, but I've gotten those same velocities out of a couple of long throated (to seat 160 Partitions to the base of the neck) 7mm Rem Mags w/o all the hassle of the fire formed case.

MM

I agree with you just one thing nice about the mashburn is you don't have to lean on it to get it there. I built mine to have something different. I knew it wasn't going to accomplish something that hasn't already been done.

That's it in a nutshell. Yes I have had a few long throated 7 rem mags, set up in a 3.6" box and throated to take the 160 Partition seated with base of bullet even with base of neck. velocities approach but don't equal, the Mashburn.I did it because Hagel and Wooters said it was a good way to go.

And I always had the feeling that I had absolutely maxed out the 7Rem Mag.OTOH the additional capacity of the Mashburn gets 3150-3200 with a 160 rather easily. Max out a Mashburn, you are at 3250. I have yet to see primer pockets opened operating the Mashburn at those velocities.

The other problem with the long throated 7 RM, is that if you throat to the heavier bullets to optimize it in a long magazine, shorter, lighter bullets will have "jump" to the lands. The neck is too short. And you still will not have the capacity of the MashburnThe longer neck of the Mashburn helps alleviate some of this.

Does this matter? To some it does,if they like everything "just so". Holding cartridge OAL to 30/06 levels the 7 RM may be ether because that's how it was developed and designed. But in a 3.6" box, the Mashburn is the better tool.

Thing is, comparing the cartridges is a hollow exercise. The Mashburn came first;it was designed to be (what Doc Bill said this afternoon on the phone) a "cheater" 300 magnum....give a 175 gr bullet over 3000 fps. Without the bounce of a 30 caliber magnum.There really was nothing else that did this.

At the time,the 7mm Weatherby was proprietary, had a 12 twist, and shot 139 gr bullets.It would not stabilize 160 gr bullets...at least then. The Remington came later,and was designed to fit a 30/06 length action and approximate Mashburn velocities, not the other way around.

Case forming is something I used to worry about; for years it kept me from building a Mashburn. I got over it. I can start after breakfast,and by mid afternoon will have turned 50-100 300 Win Mag cases into spanky new Mashburn cases, sealed in plastic bags,and ready to load to hunt about any soft skinned game, anywhere.That includes a break for lunch and driving time to the range. For me and friends who like the cartridge due to its easy going nature and delivered high velocities,this is no big deal.

And after I fire them the first time, it's like loading any other cartridge.

It may turn out I don't even have to do that if i don't want to.....but that's another story.

Bob, to each his own & I see you're drinking the kool aid & are enamored.

But 3170 with the long throated 7 mag is a relatively easy number to achieve w/o leaning too heavily using RL-22; if another 100 FPS is of enough value to you to do all the brass work that the wildcat requires, then by all means, proceed.

At 3170, the extra 80 FPS velocity of the Mashburn doesn't mean much & in fact, in reality, I'm done with the all mags (except the 338) as I am firmly of the belief that a 270/280/30-06 is plenty good for all NA non-dangerous game out to 500 yards; if you really, really intend to regularly shoot longer, then the extra velocity of the mags has merit.

I like the KISS principle, but that's not everyone's cup of tea: as such, YMMV.

MM

MM: I'm not into kool aid and I don't get enamored easily I shoot and load to learn and look at what the numbers tell me.

I have not seen 3170 from a long throat 7 RM without very short brass life.The cartridge was never designed to hit those velocities routinely with a 160 from a 24" barrel....even its designers didn't (Les Bowman) didn't run it that hard.3170 is all it can give with a 150.


I can easily get close to 3300 with a 150 from the Mashburn,over 3200+ with a 160 and close to 3100 with a 175. No 7 RM can do that and last more than 2-3 firings..and with single based powders;not double based which will fool a lot of people with over the top velocities.

Besides, long throating a 7 RM is nothing more that 'wild catting".

The Mashburn is simply a larger cartridge and moves heavy bullets faster....which is what the case is all about. If it were not "good" you would not see so many new designs looking to do nothing more than duplicate its' ballistics with the heavy 7mm bullets.

I love these conversations about it with people who never even have loaded and shot one.

Why shoot a 7 RM when you can shoot a 280AI; why shoot a 280AI when you can shoot a 280? Why shoot a 280 when you can shoot a 7/08? Point is velocity gains usually come incrementally,and the bigger cases always win...and it's up to every one to decide where that balance is for them. But I can't take seriously cartridge comparisons based on inflated figures for smaller cases loaded to redline and then compared to bigger cartridges.....common on here and that's the real kool aid.

Maybe I should have just described the kool-aid drinking & being enamored as looneyism........... Probably a less offensive description.

What I have trouble understanding is that some people simply don't understand that other people just don't need nor want what some other people do.

I've gone to standard calibers because I've tended to move to lighter weight rifles, around 6 3/4- 7 1/2 lb, scoped.

As such, I simply don't want them chambered in the Big 7's or 30 caliber magnum rounds for a variety of reasons including that they don't fit well.

Accepting the limitations of standard calibers in terms of absolute range practicality is a part of the equation.

So you see, I haven't tried the truly wonderful Mashburn or STW not because I think they don't perform as advertised, but simply because they don't fit my needs or profile.

If I felt the need for a Mashburn, I'd do one tomorrow as it's likely the best ever of the Big 7's.

MM

MM I understand....I understand...!!!!


In my posts on the cartridge I am passing along information and NOT advocating for ANYONE to build one,and never have.

Those who want to can and those who don't see the value are free to use whatever else they want.

I only report on what it does...people misinterpret this to mean I think everyone should build one. Not true at all.

I get PM's and Emails about the cartridge all the time...my first question to them generally is...."Are you sure you want to do this....and why?'

If they don't know "why" they should stay away, from any wildcat, not just this one because the reasons for getting one has nothing to do with it being the "best" or anything like that.

And I certainly don't care at all how it compares to other 7mm magnums,although comparisons are inevitable. I had an objective...move 175's at close to 3100,and 160's in the 3200 fps range. It does that. That is all I care about and don't care at all that some others may do the same thing.

So look at what I post as being a "report",not advocacy.

Always knew you were a really smart guy............

MM