I just picked up a really nice custom 7mm barrel.....It is currently Chambered in 7mm/.300RCM but I'm going to change that to one of the following (my only choices according to my smith)

1. 7mm WSM
2. 7mm Dakota
3. 7mm RUM

I understand that I could get ammo for the WSM or RUM off the shelf, but since I load anyway, would it be advantageous to go for the Dakota....???.....Should I try and keep the weight down and use the SA WSM???....Other thoughts???

My plan it to put this into a Model 70 action....My smith recommended this because he said that the CRF Win 70 action would handle the brass much better than a 700 Push feed action....your thoughts??

Also, a McMillan stock, trigger job, and bedding job will be done....

Of the 3 you list I would pick the 7mm WSM.

Nothing wrong with the Model 70 action but I don't know if I would agree that it will handle the brass better.

I'd think that RCM case would feed consistently better than the WSM....

btw, I own a 338RCM and a 7mmWSM and love them both.

I would definitely go with a 7WSM, of those options.

But if you're building anyway, I might just go for a 7mm/.375 Ruger, just to be different

I read an article a while back when considering my 7WSM of a 1000yrd competitor who set some sort of record with a 7mm/300WSM.

Like I said, I love mine, but I don't have experience with any of the other options.

I do like the idea of the 7/.375 Ruger!

7mm SAUM

Ok, I just gotta do it but 7 Mashburn Super is the way I'd go. If not that way then the 7 WSM would be my next choice.

Dober

7sarum or 284.....they seem to have the long range thing handled.

Who'da thunk it?!

Hard to belive but true eh...

You are a better man than me Mark, a 7mm Rem Mag cuts my range day short due to recoil in a hunting rifle. A friend had a 7mm Mag Sendero in an AI stock I could shoot all day, but that is more than I want to lug around. Do you have a brake on your Mashburn? You could just get a Game Ear and then the brake wouldn't be much of an issue , I guess.

Rum...capacity is power. You can always load down but you can't load those other chamberings up to the rum level. Especially since your a reloader...you can get all the performance out of the rum that it can give. I'm very fond of my 700 in 7 rum.

Slam dunk ..7wizzum. I think I know a guy who used to have a famous one or 2.. heh ;-)

Thanks guys.....keep it coming

Ok ok.. I have had 2 or 3. 2 on a remmy 700 one on a Surgeon action.

Not sure why your smith thinks the winny action is really better over the 700. Most smith would rather work on a 700 type.

Anywho. You can run boolits up to the 180's pretty hard in the wizzum. I suppose the next question for you would be. What is you intended purpose for this stick?

1. 7mm WSM
2. 7mm Dakota Poor brass, see BobNH.
3. 7mm RUM Needs a 28"+ barrel.

Push feed action are much better with WSM's.

7 Wizzum if it were mine.

7mm RM.

7wizzum since the 7mm rem mag isn't on the list..... Nah, the 7wizzum is more effiecient than the 7mm RM anyways and always a good choice...

This is a hunting rig...

7 wsm then, like I said earleir.....

Not sure how a smith with those reamers doesn't have a 7 RM?

So assuming he does...

The 7 RM and the 7 Dakota represent the 7 done just right, not too big not too small.

I dont like the shape and throat configuration of the RUM's - just my opinion - lots more people love them.

If you want bigger - the 7/.375 Ruger is another done right, the .375 Ruger is an under appreciated parent case and in a lot of ways is "just right" but of course its really almost identical to the Dakota stuff.

The WSM stuff performs wonderfully. But if you go that route you should capitalize on the short action side of that cartridge, i.e. build a sub 6 lb gun. If you are going to build a "heavy" gun, pick a bigger case.

Really you can't go wrong, I always lean toward what the smith wants to build, and hope he puts a bit more personal effort in the build.

Having built, ordered or just worked up loads for several 7mms this year. I have a few ideas:

The 7WSM is a very accurate round and gets a little better velocity than the comparable 7mm Rem Mag. W-W brass is pretty poor in my experience. It is a lot of work to form it from Norma 300 WSM brass. Get right at 3000 fps with 180 Bergers

7x300 Wby is a great round. About the max powder capacity for portable hunting rifles. Get about 3175 with 180 Bergers.

7mm Rem Mag. Large variance between chambers and brass. Seems to shoot best with fire-formed brass and minimal resizing. I could not match 7WSM velocities with the two Remingtons I loaded for this year. 2850-2900 fps with 180 Bergers.

7RUM. This is overkill. Got only 20 fps more velocity than 7x300 Wby with 20% powder. Horrific muzzle blast. Tough to find a load for but once found, shot great.


IF I were building a 7mm magnum of some sort and had any intention of being able to shoot factory ammo, I would do the Remington. It is not much behind the WSM and there is a lot of factory ammo and a lot of brass choices.

If I were doing a wildcat, I would do a 7x300WSM or 7x375 Ruger.

My guess is his gunsmith gave him those options of chambers because they will allow the the new chamber to completely remove the old chamber, without cutting off the chamber and starting over (which might not leave enough shank) That may also be the reason for the action recommendation, as not all are threaded the same.
Revamping a used barrel is always a balancing act between what it is and what you want.

Good point. In looking at this a bit more, part of the problem is cutting out all of the .300 RCM original chamber which needs about a .550 dia case. This precludes any .375 H&H based conversion.

I still like the 7/.375 Ruger just because, I like the parent(s).
The 7 WSM makes a wonderful light gun that you might find shells for somewhere...
The Dakota because they got it right and no one noticed.

Really they are all good, but the RUM still bothers me. And I am a bit suspect that there is enough chamber length in the barrel to cut that out, but hey I am not your smith, or any kind of smith for that matter...

Hence my recommendation of the 7/.375 Ruger

7 Dakota brass is pricey, and there's only one source. It takes very little effort to fire-form brass for the 7WSM from .300WSM brass, whether Norma, RP, or whatever. In any case, it's all better than the WW 7WSM stuff.

Well,in a factory 7mm magnum I will stick with the Remington...brass is common, as is the factory stuff,and we don't need to look at the results guys like John Burns is getting on elk sized critters with 180 Bergers at 2950 to really long range, farther tan i can shoot!. I asked John about his loads,and that is what I recall he told me.It is no real trick to get 3050-3080 from a 24" tube with about any bullet in the 160 gr range and accuracy with stuff like AB's is sterling as well.I have run the cartridge to 600 yards many time over the years(far as I can go back here) with good results.

I am surprised to hear of brass problems with the 7mmWSM. If I have to form the stuff from 300WSM brass,then IMO it falls into wildcat status.Besides, the capacity is short of what I want...my days of messing with 7mm mags of that capacity and leaning on them to get the velocity with the heavy bullets are about done.Still it's the best in a short action magnum 7mm, if that is important to you.

I like the 7mm Dakota better....the extra powder capacity really translates into more velocity across the entire spectrum of bullet weights and I think it is really the "optimum" non belted 7mm Magnum.Problem? I did not like being tied to one source of brass that I could not form from anything else,was expensive,and I had cracked cases at the neck/shoulder junction on the second firing.

The 7mm on the Ruger case is a swell idea.....brass availability and cost? I dunno...It would be a spitting image to a 7mm Dakota or Mashburn with less common and more expensive brass.

STW is great,obviously,but have never tried it in a 24" barrel, and have no idea what brass avilability is anymore.

All this leads to the Mashburn, if you want a wildcat....best design in a belted case IMHO;not too long and not too short;long neck for easy bullet seating arrangment...stupid simple to form from common 300 Winchester cases...capacity about like a Dakota,and velocities as well.

None of the drama and questions of getting to speed that I see with the smaller capacity 7mm's. It will routinely and very easily do 3050-3075 with a 175 gr bullet;3200+ with a 160,and hits these speeds from a 24" barrel with 73-75 gr of powder,so is not over the top in any category...very accurate cartridge as well.

Those critical are dismissing out of hand....have not tried it;they are "interpolating" and "guessing"....those who have built one are pleased.Out of quite a few now, only one had an issue,and he had issues early on chambering brass....he was new to wildcatting. I have had zero issues.

We are learning,and some are forming cases with just the FL dies..no Form/Trim....one chap just forms cases in the die, no fire forming, and drops in 77 gr Retumbo and 150TSX for 3240 from a 24" barrel.Uses the same load the second time around.

All reports are the same as to velocity, everyone coming to the same results even with different powders.7828,H870, Retumbo,RL25,H1000....Reminton,Winchester, Krieger, Brux barrels...it seems not to matter....results are uniformly the same.

Sorry to say, but Art Mashburn got it right 60 years ago and guys like Hagel and Page confirmed it.There simply isn't anything any better out there.....after dicking with about every 7mm cartridge under the sun,it's the only one I want to run anymore.I can't look at a Remington without wanting to punch it out....

If it is speed that one wants, then the 7mm RUM is willing ready and able

It's a 23" tube guys... For economy sake roll a WSM or a SAUM and go forth.. For your hearing sake do the same...

W

More powder doesn't mean more better... wizzum will serve purpose more better.

If you want lighter bullets, sure;not for the heavy stuff.The larger cases do it better.Had enough of trying to get the velocity from small cases without going to the ragged edges.

7mm ultra is king more powder more velocity simple as that

Till of course we get to the 7mm Dober...aka the 7/378 Wby where does it all end...

I'm with Bob, for me the Mashburn is as good as it gets.

Dober

7X57 or 7/08....throw away the magnum.

I could easily get on board with that but I think he already has the magnum bolt face.

scenar shooter ask your latest client what he'd choose. Better yet what caliber did he take the mulie with ;-)

You mean this guy? George likes his 7WSM.

exactamundo....

The brass "problem" is really not a big issue. Just buy RP .300WSM brass or the Norma stuff, anneal the necks, run it through the off-the-shelf 7WSM sizing die (no need to order expensive dies), and load it up. Presto. I run all my new brass through the sizer before loading it, anyway, so using .300WSM brass is really no extra work for me.

I get 3105fps from 160gr bullets with the 7WSM, and that's plenty of velocity for me. My crappy WW brass is on its 5th firing, and still going strong. I don't think I would see any tangible benefit from having 3200fps with the same bullet



It's not that hard to find decent .375 Ruger brass these days, and I would guess that it's probably cheaper than buying brass directly from Dakota.

There are lots of good options these days. If the OP wants to stick with a SA, then 7WSM is stellar. If he wants to go LA, then instead of following the flock and going Mash, the 7/.375Ruger would be lots of fun

Yup..that be the one ;-)

Was he running the NXS 2.5-10X on that?

You make it sound, Oh, so simple! The 7WSM shoulder is considerably further forward than the 270 or 300. Making it out of 300 brass requires forming a false shoulder and then fireforming. Once this is done, you can just load them up with your standard dies.

Also, why do you run your brass through a sizer die when it is new? New brass does not need to be resized unless you are loading a wildcat. This is a good way to bump a shoulder back and create head separations. Having made my share of 7WSM brass, I have found the best way form the false shoulder, load the case with 18 grains of Unique, top with Cream of Wheat (COW), press a bar of ivory soap into the neck to seal it. This makes reasonably sharp necks and has an danger range of about 8'. If you live where you can make noise, you can fire-form at home.

If you are simply loading this up with your preferred bullet and shooting it, you are wasting expensive bullets and, to some degree, barrel life. I have found that doing this does not result in great accuracy and not the same velocities either. Once it all fired, you work up a new load and start over??


Of the choices he gave, to clean up his chamber, the 7WSM is the best choice. If a 7RSAUM will clean it up, this would be good too. The worst choice is the 7RUM. In a barrel that short, you would not get velocities any where near what is expected for that over-bore cartridge.

I really like the SAUM. Too bad they are DOA.

i went the 7/300wsm route. ordered a 7/300wsm sizing die from rcbs (already had a match seating die) and use 300wsm cases. i do turn the necks but thats only due to having a tight neck chamber (.315)
my accuracy load uses the berger 180's, RL25 and fed match primers at about 3050fps great round and wouldnt hesitate to recommend.

Hey Pat, what bullet do you and your friends/clients like in the 7mm-08 and WSM? Flinch

That's because it is. I have found that many pieces of WW 7WSM brass have dinged or out of round case mouths, hence the reason why I run them through the sizer before loading them. How is neck-sizing 7WSM brass different from creating a false shoulder in .300WSM brass? It's the same process. My "fire-forming loads" are every bit as accurate as my main loads, and I'm getting 3050fps from a 140gr bullet, aka .280Rem performance. Even my fire-forming loads kill stuff dead, and ring the gong with impressive accuracy. I was out shooting at a dinner plate-sized rock a month or two back at 1120 yards with my fire-forming loads. Didn't seem to have a problem smacking it. My full-house loads get that 140gr bullet to 3295fps, and those are what I typically use for hunting.

Works just fine for me, and all my loads turn in MOA or better accuracy. Brass forms just fine like this, and I'm on 4x firing one particular batch of FF brass, and it's still going strong (could use another annealing, perhaps).

I'm a bit slow here today so forgive me but that 3295 is with your WSM right Jordan?

Thx
Dober

Hey Jordan, question for ya' - are you saying the 300WSM's existing neck size (approx. 0.338") is large enough to use as a false shoulder for the 7mm WSM? So just sizing the neck, since the 7mm WSM has a shorter neck, leaves a false shoulder? Are you seating the bullet into the lands for fire forming?

7 WSM!

Yessir

Yes, and yes.

Jordan-if you don't mind, how much and what are you burning with this?

Thx
Dober

I use a die that has no body in it- I just bump the neck maybe a 1/16" of an inch. I use no lube and it takes just a second. Forming the false shoulder requires setting the die up just perfect to make the brass snug on chambering.

If you are running your brass through your full length dies first then you are having to lube and clean them. That is a lot of time and work for accomplishing nothing. Try just bumping them with a tapered expander ball. Hornady makes the best one for that. Generally the only dents are on the very edge of the mouth- the neck itself is fine.

I just don't see the point going into the field with those half- power loads. If your fire-forming loads are as accurate as your real loads then you have some work cut out for you to find the better load. The fired brass should be perfectly straight- not something that can be said for the new brass.

Well, look....the good thing today is you have lots of choices and what you want is based more on the action/rifle you are drawn to, or have as a donor.

Clearly, what you have today is an embarassment of riches, and a 7mm to fill every tiny niche.

I'm a M70 guy,like long actions and hate bullets peeking bashfully from the confines of cases...I like 'em seated long and hate pushing cartridges.If I want 3200 from a 160, I want it "easy", so I like a case with capacity.Years of handloading have taught me, if you want velocity, get a larger case.Balance plays a role.

Others like the shorties and the WSM,Saum,7/08 fits the bill.Or if a guy is lucky enough to have an Oberndorf, properly dimensioned, hanging around,the 7x57 is really the only choice

Others have actions hangin around,want to stay within the confines of what they have available...seems there is a 7mm to suit needs.Today you can have what you want.

Hey Dober,

It's 63.5gr of RL17 and CCI250.

Both the FF load and my regular loads produce sub-0.5MOA, and even my worst loads will do MOA. I won't use anything that doesn't produce at least this level of accuracy in my serious rifles.

I mostly use the FF loads for practice. But then again, I like practising on steel, paper, and other things when I'm not killing stuff.

This is the thing I find interesting about this loading stuff (just a comment here nothing else) but the Alliant site lists a 145 along with the same load going @ 3166.

Gotta be a fun rig to work with!

Dober

I've always heard they were efficient. Time to throw the 7mm rem mag in the trash can and get me one of those wizzums........

Yeah, I seem to get higher velocity out of this barrel than what some of the load data suggests. I get nearly 140fps more velocity out of the 162gr A-Max with IMR7828 than what IMR reports (I'm using 0.5gr more than their max load, and they use the 162gr BTSP, rather than the A-Max). As you've pointed out, I'm also getting about 130fps more with the RL17 140gr load.

My drop data out to 1120 yards suggests that these chrony-measured velocities are accurate, too.

I don't doubt their accuracy, I'm a believer in fast and slow barrels. I've seen it often enough to make me firm in my beliefs on it.

Merry Christmas my friend.

Dober

Side note Jordan, I might be in Calgary March 21st for a Chris Tomlin concert maybe we can grab some lunch?

Dober

Dober,

Merry Christmas to you, too! I hope you're enjoying this time with family and friends

If you end up heading this way in March (or any other time), please let me know, and I will definitely make myself available to grab some lunch! It'd be nice to finally meet the Dober dawg *grin*

PM inbound with phone number.

They aren't more "efficient". ........people load them hotter,to higher pressure, and get more velocity......(ask Johnny B;they have run the tests with the 300WSM and 300H&H)

Even Federal will tell you that,if you ask them.

Since most all of us have no way of accurately reading pressures,we don't "know" what level we are really loading to.....we can only "guess". If we take two cartridges of similar capacity (82 gr vs 82.2),keep all things equal,and one goes faster than the other, it is only because we are loading it to higher pressure....there are no other reasons.There is no "magic" in a short fat case.(Although in barrels of the same length,a bullet from a short/fat does have a bit more barrel to travel through.)

I have (many times)loaded a 7 Rem Mag to the same velocities shown here for the 7mm WSM.....why? Because I loaded it hotter.....one load with a 160 gr bullet showed 3080 from one rifle, and a bit over 3200 fps from another of the same length(!).

Clearly, the load was fine in one rifle, and too hot in another,although I had no outward "signs" of pressures.

There is no "magic" in a case of equal capacity vs another of the same capacity but a different shape....if one is going faster than the other you are loading hotter,or something else is not "equal".

Merry Christmas

Yup, good post

Mr. B will take issue with the notion of fast & slow barrels, too. Velocity = pressure. Higher velocity (than published data) = higher pressure.

That's regardless of a lack of the classic pressure signs.

Or so I'm told.

140gr factory NBT's run 3300 out of a 7wsm. The holes generated by close range impact are impressive.. I've got a few pics around here somewhere..

I bet! The 150 NBT is supposed to be a tougher bullet, although the one time I used one on a deer from my 7-08, it was pretty explosive.

You miss your 7 WSM Calvin?

7 Mashburn Super AI best of the best

No. I have a 7saum that shot just as well, and just about as fast as the 7wsm. And I like the trigger and stock better on the saum.

Ah, a SAUM guy.....

I don't think so. Different barrels have different chamber dimensions, bore dimensions and variances, etc. Some barrels are faster than others because they build more pressure with the same load.



You're told correctly, but a powder charge that generates X velocity in a loose, long-throated, sloppy-bored rifle, will generate Y velocity in a tight-chambered, short-throated, tight-bored rifle.

I had a long conversation with him about this. My intuition is as you say

However- if I understand him correctly- the influence of those variables is trivially small in modern factory rifles, "pressure signs" notwithstanding*, and in fact pressure and velocity do correlate very closely, across rifles.

*most pressure signs are signs of sloppy tolerances stacking up funny in various ways

That's the condensed version, and filtered through ME big time, so let me be clear, this is me saying what I think he said, grin.

(because my intuition says, as I believe yours does Jordan, that one can derive a minimum pressure needed to make a velocity. However, one cannot derive a maximum pressure to make a velocity. Therefore, the two do NOT correlate both ways. And yet, pressure testing equipment tells a different tale, apparently!)

???????

Yeah... lol... crappy post.

Basically as I understand it the notion of fast and slow barrels is, practically speaking, false.

Take two modern factory 22" 30-06's running 180's at 2875 fps. One has a sticky bolt lift and short brass life; the other does not.

The common wisdom is to say the rifle running that speed "cleanly" has a fast barrel; that it is making that speed at safe pressures, while the other rifle is running at a higher pressure to make that speed.

In fact, they are at very similar pressures, because pressure can be accurately derived from velocity. However, in our hypothetical example, the rifle showing us pressure signs has lugs machined crooked (sticky bolt lift) and a sloppy chamber (shorter brass life).

This, I am told, is what modern pressure testing equipment shows. Velocity = pressure = velocity. The notion of fast barrels that make high velocities, beyond what the "books" get for instance, without higher pressure than the labs measured, is false. Barrels getting higher velocities, are doing so at higher pressures.

Hey Jeff,

I think you've got two separate ideas crossed- the existence of fast and slow barrels, and the idea that pressure=velocity.

I agree that total pressure equals velocity. We have to remember that pressure is what moves a bullet down the barrel. Period. Expanding gases from deflagrating powder create pressure which pushes the bullet down the bore. That pressure builds as powder burns, peaks, and then gradually declines. The velocity that the bullet carries out the muzzle is generated by the total pressure that has pushed that bullet, from start to finish. When we talk about traditional pressure signs, we're talking about signs of peak pressure only.

So while total pressure does equal velocity, we have to use consistent variables when comparing peak pressure. This is because peak pressure is largely dependent on the burn and pressure profile of the individual powder at hand, in the cartridge it's being burned in, and may not adequately reflect total pressure unless the pressure profiles that we are comparing are the same.

Pressure is affected by chamber dimensions, throat dimensions (and consequently OAL), bore dimensions, etc. This is why one rifle may make 3100fps with a certain load, and another using identical components, will make 3300fps. I have also heard JB say that if your rifle doesn't make the velocity that the books say it should, it may be a safe idea to add powder until you reach that velocity, assuming no traditional pressure signs are present. This is simply because the dimensional variables in one rifle are different from another rifle, which affects the pressure and velocity that a given load generates in both rifles.

So yes, my rifle and load are generating more pressure than what is reported by IMR in their load data. But if I'm using a book load, and I'm not seeing traditional pressure signs, I'm not too worried.

Well, no, that's not what I'm told is correct.

The variables you mention- chamber dimensions, etc- have an effect, but it's a very minimal effect on velocity. In your example, the rifle making 3300 fps is running at considerably higher pressure than the one running 3100 fps.

Hey- my intuition is in line with what you are saying, and, what you are saying is certainly the conventional wisdom. However, pressure testing equipment says otherwise.

I'm sort of in the same boat looking for a 7mm hunter, but I don't think any of those you listed are on my short list. The 7mm Dakota would be except for the brass issue that has already been covered. The 7mm RUM has had some problems with pressure in a case that size according to some reputable sources that have had to deal with returns of those guns. The 7mm WSM is so close to the 7mm Rem Mag that I don't see an advantage where ammo selection is concerned. You can get 7mm Rem Mag ammo about anywhere. The MV is pretty much a wash where the 2 are concerned.

Win M70 vs Rem 700 is just a preference thing. Either action will do just fine, but it sounds like he's concerned about the rebated rim. All of my rebated rim rifles are push feeds (Rem 700 or Sako on a 300 RUMs & a 338 RUM )and I haven't had any issues there at all.

Dober,

I like your choice of music...

Marty

Does that account for such things that (allegedly) reduce pressures and thus allow you to put more coal on the fire, more velocity at the same pressures? Bullet coatings or bore coatings?

Not an expert but I always thought that was the original draw of moly. It made the bullet very slippery which lowered pressures and thus allowed the reloader add more fuel to the fire and get higher velocities at the same/original uncoated pressures.

Thx Marty you're welcome to join us in Calgary.

Dober

Sorry for the hijack, but I am going to have to agree with Jordan here. My understanding of "fast and slow" barrels is...

Let's say .30-06 gun "A", 22" bbl of military manufacture, 6 - groove, "short" throat, and minimal cross sectional bore area.

V.S. gun "B" of modern manufacture, 22" bbl, 4 - groove, of generous throat (think Wby) and "large" cross sectional bore area.

So when I stuff factory ammo in either gun (granted its loaded on the mild side) I get nearly the same velocities in either barrel. Are the pressures close, probably.

Now I handload...starting at 47 gr of 4350 - both guns OK and duplicating factory velocity, about 2750 fps. Now try 47.5 gr, gun A shows all sorts of pressure signs and case head expansion, and still only gets to 2775 fps, time to stop. Gun B no pressure signs and still gets 2775 fps. In fact gun B gets all the way to 2900 fps and almost 50 gr of powder!

What I think is happening, is gun A slams its bullet into a relatively small bore, in a short throat very fast, creating a pressure peak very early, and regardless of trying a powder with a flatter pressure curve, you still get early pressure problems, limiting velocity. Now gun B "eases" that same bullet into the barrel, giving time for a powder with a flatter curve to add its energy over a longer section of barrel, forcing the peak pressure to be later than gun A. The result is the ability of gun B to generate a higher velocity by sustaining a higher pressure over a longer section barrel. Make sense?

Higher pressure only equals higher velocity, all else being equal. Barrel, chamber and throat dimensions vary greatly from gun to gun and have a huge effect on how much and when peak pressure is realized. Again think Weatherby. For all practical purposes a 7 Wby and a 7 RM "should" perform nearly identical, as they have nearly the same case capacity. However, every reloading manual will show between 100-200 fps advantage to the Wby for the same load at the same pressures. Why - its in the throat. Does that make some barrels "fast" and some "slow", I think so, but that's only one reason, perhaps the easiest to visualize, but there are many other factors that affect when and where a particular barrel generates peak pressure.

At one point or another,we have likely run into a situation where pressure seemed too high and yet velocity was not up to par for the cartridge. Here we have "pressure",but not velocity equal to what is normal for the cartridge.I have seen this,and we even did the corrective work to the barrel, to bring velocties up to a more normal level...it was a PITA.

In about every instant,I have found that the answer to sub par velocities in a given case is......a larger case.

If you can't live without 3200 fps with a 130 gr bullet in your 270,then maybe you should buy a 270 WSM,and get the velocities easily......this has worked every single time I tried it.....and I spent a lot of time,components,barrels,and money trying to circumvent this basic rule. It can't be done predictably.

Hmmm, we're saying the same thing here, I think.

Let's try this another way- you said "In your example, the rifle making 3300 fps is running at considerably higher pressure than the one running 3100 fps." There is no question that the rifle that gets 3300fps is running higher pressure, but the question that I was answering, is "why?"

If both rifles are running the exact same load, then what accounts for the difference in pressure and velocity, if not for the dimensions of the chamber, throat, bore, etc?

Shooting Times West

Ifn the barrel's prior address was MT then I suspect it was a very good snag.
Some of the consideration comes down to the rifle action your using and how much hobby ya want. The Dakota would be great but pricey brass. The Ruger may be about the same price in the end-don't know for a fact.
I suspect a Lazzeroni firebird cartridge would fit and be a bunch of fun. Don't think it would be cheap but long range shooting rarely is.

To all the belted mag suggesting folks- ya missed the point.

I have a 7mm Dakota and I like it. I have bought most of my brass 2nd hand. Some new, some once fired. I have brass that has been shot 4 time and still in great shape. It seems to come up for sale from time to time here in the classifieds. I have bought 160 pieces here since 2009, enough to last a long time. I have not been able to get 3200 out of 160 bullets yet, mine has a Borden action, Lilja #4 barrel 26" lg. My bolt lift gets heavy at before I reach 3200. My hunting load is 160 NAB at 3120.
If I had it to do over again I would go with the 7 WSM probably and be happy at 2950 to 3050 with 160's. It depends on what velocity you are after and are willing to live with. I like my Dakota, just do not think I would do it again.

I have over twenty 7mm's and have built about every wildcat. The 7mm RUM eats barrels fast. I had two and throat errosion was swift. The 7mm stw and the 7mm Dakota have the best performance before getting into severe barrel burners. I like the 7mm Dakota best because the short case allows for seating the bullets out to the lands while still beeing able to feed through the magazine. Not much velocity difference between it and the 7 RUM. The 7 wsm is just to slow with the high bc bullets for me. The purpose is to get to long range with enough power to get the job done and the two best at that are the 7mm stw and 7 dakota before getting into a barrel eater.

I agree with this and would add the Mashburn in a wildcat because it is just like a Dakota,and made from easier to get and cheaper 300 WM brass.Bullet seating and cartridge length is similar to the Dakota as well.(You could fit the Mashburn in a 30/06 length action,but every standard M70 or M700 in the world is H&H length anyway,so no difference). I set the Mashburn up for 3.5-3.6 OAL.

I had the Dakota and it's nice;if it became a mainstream factory cartridge I'd be all over it again.In the meantime, the Mashburn will "do".

the Mashburn won't clean up the OP's 7/.300RCM chamber though.

How does the 7/.375Ruger compare for useable powder capacity ?

I think they'd be pretty close....the 375 Ruger might be a lot like the Dakota.

I know there is virtually no difference between a Dakota and a Mashburn.

Did we decide on the 7mm weatherby yet?

Always good...

But I would not want to build one with a 24" barrel,and depend on it to get any more velocity with a 175-180 gr bullet than a 7 Rem Mag built similarly,given that the two cartridges have about identical capacities.

No doubt some examples of rifles chambered for either cartridge will get a 175-180 gr bullet to over 3000 fps, but pressures would have to be pretty high,and vary rifle to rifle enough that I would not take a chance on a build....

I have noticed that the 7mm's of Dakota, Mashburn, and STW capacities do it all so much easier and routinely....this is confirmed over several rifles now, with velocities comfortably exceeding 3050-3100 fps with 175's and 180's,and from a variety of barrels....discussions of "fast barrels/slow barrels" being absent from the results.160's hit 3200 with little fanfare.

This is the reason, when I decided I wanted a rifle to do those things,I excluded the cases with capacities like the 7 Rem Mag,Weatherby,and WSM....all are too small for the job across the board IMHO.No substitute for capacity.

I think I'd go that way if I was going large.

700 WSM, it is doing well in the 1000 yard target competitions so there is a good chance your rifle would have good accuracy.

I have a 300 WSM in a M700 SPS and it feeds OK, sometimes getting the 3rd round down in the magazine is tight but can be done. Like some other M700s it is an accurate rifle.

The M70 short action is longer than the M700 short action so you could have a longer throat and load the bullets out farther for more powder capacity. Or an idea I have been contemplating in a future build, have a freebore throat built tight enough to help the bullet straighten itself before hitting the rifling.

Except you missed the point in the original question where the person explains that he has a barrel that is currently chambered as a 7mm RCM.

And the barrel length is only 23"...WSM or SAUM


W

Barrel lgth makes no difference in this case. The existing chamber WILL NOT clean up for conversion rechambering for a H&H based case. Magnum Man

Was referring to all the long action larger cases.. Seems a bit much with the slightest cleanup your into the 22" range...

W

I agree, not sure a 23 inch RUM would make much sense but a Dakota or Ruger might not be so bad. Then again it might be worth sticking with the RCM. All the rage over the 280AI, would be the same same.

Mashburn.....stop guessing....