Which BIG 7mm?

[Topshot]

I am looking down the track at building a BIG 7mm Magnum rifle and would like your opinion of which one of the big ones is the best all round cartridge.
7mm RUM, 7mm STW, 7mm AM etc, etc.

Some of the considerations I am thinking of are Accuracy, velocity, reloadability, cost and availability of quality brass.

All opinions welcome.

 

[Ernie]

The only big 7mm I have (two barrels actually) is the 7mm Dakota.
Basically a twin to the 7mm STW.
Very pleased with it, but you can surely go with more horsepower if you want-Personal choice.

 

[MontanaRifleman]

Topshot, I have been thinking about this same question.

I lean to the 7mm RUM or a 7mm-338 Lapua wildcat.

The 7 RUM is the most potent legit (non-wildcat) load available. You can get the Sendero out of the box and they are supposed to be quite accurate that way. With a little fine tuning like a trigger, some skim bedding, custom dies, it could possibly match some customs in accuracy. After the barrel is burnt out, a custom could be fitted to it along with blueprinting the action, etc. The only available brass that I know of would be from remmington or getting some Nosler in 300 RUM and necking down. The Nosler would probably be better brass and costs about $56 per 50 I believe.

With the 7mm-338 Lapua, the advantage here would be the availability of Lapua brass. I think it would have slightly less case capaciity than the RUM so probably a little less velocity, but more than the Dakota or STW. You could also work with your smith and modify/improve it slightly to boost the performance a little. I think this would be working in the direction of the 7 AM? The other advantage would be that this would be a custom or partial custom, depending on the components you use. I would think you would want to keep the reamer for custom dies and follow on barrrels. The disadvantage would be increased cost and waiting time.

My $.02

 

[jimbojeweller]

I am thinking about using the 375 ruger case necked down to 7mm for my next build. Still doing the research at the moment but so far looking like it may be a winner

 

[MontanaRifleman]

I am thinking about using the 375 ruger case necked down to 7mm for my next build. Still doing the research at the moment but so far looking like it may be a winner

I was thinkung about that too a while back, but I think the Dakota is a better option in that category, JMO

 

[jimbojeweller]

Maybe for you guys in the States but brass could be an issue here in Oz for that round. I am in the process of trying to find out possible velocities and optimium barrel length (with the 7mm/375 ruger) as i would like to keep it down to a minimum. 24" if possible You got any interesting info? If so please post

 

[MontanaRifleman]

The 7WSM might be the best ticket in a 24" barrel. Most posts I read on that cartridge gives it an advantage over the RM, but some say not much different. Not sure how a 24" barrel would affect a 7-375 Ruger?

I shot a 7RM for years, it was a good rifle, but I dont like the belt on the case.

 

[ss7mm]

I am looking down the track at building a BIG 7mm Magnum rifle and would like your opinion of which one of the big ones is the best all round cartridge.
7mm RUM, 7mm STW, 7mm AM etc, etc.

Some of the considerations I am thinking of are Accuracy, velocity, reloadability, cost and availability of quality brass.

All opinions welcome.

I've had a 7mm AM for a while now and have taken several animals with it and consider it the best "big" 7 there is. It shots anything I feed it, from 200 grains down to 160 grains great and the long range, down range, performance makes it a ball to shoot.

Accuracy is outstanding, velocity can't be beat, reloads very easily and the Lapua brass can't be beat. What more could you ask for.

 

[MontanaRifleman]

I've had a 7mm AM for a while now and have taken several animals with it and consider it the best "big" 7 there is. It shots anything I feed it, from 200 grains down to 160 grains great and the long range, down range, performance makes it a ball to shoot.

Accuracy is outstanding, velocity can't be beat, reloads very easily and the Lapua brass can't be beat. What more could you ask for.

That sounds like a dandy round, do you mind sharing the kind of performance you're getting with it and how much powder you're using and what kind of barrel life one should expect?

 

[ss7mm]

I have a 32" Rock barrel and have pushed the 200 grain Wildcats at up to 3400 fps although the best accuracy is around the 3200 fps mark.

Several deer and one elk have all been one shot bang flops. I'm using WC872 powder and the loads range, depending on bullet weight from around 96 grains up to about 102-104 grains. I know others that have a different lot of WC872 use slightly different loads. It seems like no matter what I feed it the accuracy and performance is great from the 200 grain WCs down to 160 gr. Accubonds.

Accuracy and performance make vital zone sized rocks easy targets out to and beyond 1000 yards. I'd guess, and Kirby probably would agree, that hunting accuracy should hopefully last to about the 1000+ round count. I know of a 270 AM with almost that and the last I heard it was still going strong.

994 Oh Bleep Moment video by ss7mm - Photobucket

Two shots at 994 yards on rock in video above.

 

[Topshot]

The 7mm AM, is that the .338 Lapua necked down ti 7mm?

If so dose it keep the original shoulder angle?

 

[ss7mm]

It is based on the 339 Lapua case but the body taper, shoulder angle and location are all modified.

 

[Fiftydriver]

I would also like to add to what SS7mm has already mentioned. If your concerned about fireforming brass for the 7mm Allen Magnum, don't me. You can get formed brass from me that is ready to load and shoot with accurate high pressure loadings which will save on time and especially with your barrel life. Making it no different to load for then any factory chambering.

I do charge a forming charge and cases are formed to custom order, not in stock ready to roll but generally does not take to long to get them headed your way. YOu can supply brass or I can supply everything.

The 7mm AM may not be the best choice for what your looking to do, but it may be. All depends on what your goal for the rifle is? If you will be hunting out to 600 yards but no more, the 7mm AM is really not needed, it will certainly work and work great but there are smaller 7mms that will also work and offer a bit better barrel life.

If you want +1/2 mile reach and especially if you want 1K reach, it would be hard to beat.

At the moment, the 200 gr ULD RBBTs are not available for sale but when new owners crank up Wildcat Bullets again, they will be available so they are not gone forever.

The 180 gr Berger can be loaded to very good performance. They tend to not like to be loaded much over 3250 fps which is a very comfortable load in the 7mm AM. In fact, 3400 fps with this bullet weight in a 27-28" barrel would be easy to reach, bullets just will not take it so we have to limit velocity to some degree.

in the 7mm RUM, you will see 3100 fps or so with the 180 gr with similiar pressures that the 7mm AM will get you +3200 fps with the same bullet.

Really comes down to what goals you have for this rifle and until that is well defined, its hard to recommend any chambering. Anything from the 7mm-08 up to the 7mm AM will work in many different applications so we just need to know what your goals are.

 

[Ridge Runner]

I can't say enough good about the 7mm AM, after my third season with it all I can say is, incredible!! and I've never shot the 200's (well maybe a couple) I shoot the 160 accubond at 3575 fps in front of 110 gr of WC872, it clocks 3575 fps.
If anyone is curious the case capacity of H2o for the 7mm AM is right at 122 gr. a pic of the last deer I took with mine

RR