20" 7mm barrel - which cartridge (LA)?

[ormandj]

I've got a 20" 7mm barrel, 1:8.5 twist, MODBB steel CF #13 (Rem Varmint/Sendero) I need to chamber. I have a long-action standard and magnum bolt face available for this. It will be in a sub-10lb, including suppressor, lightweight build. The intent will be a mix of hunting and range use (obviously not competition, but it will see a decent amount of use on steel out as far as I can make hits with it accurately.) I'm not looking for a recoil monster/no barrel life like a 28 Nosler, especially with a lightweight rifle.

I'm currently leaning towards 7 SAUM, but I'd love other opinions, as well. 284 Winchester seems neat, but I don't think the velocity will be there for the longer stuff with the shorter barrel (I found very little feedback on short barrel 284 velocity with 180gr in forum searches, so feel free to correct me.)

Bullet choice is still undecided by probably the 175/180/184gr Bergers, most indicate the 175/180s are the easiest to get shooting well, and I'm sure both will perform well on game, so they are likely.

 

[Supersubes]

Theres nothing weird about any of those cartridges in a 20” barrel. Theyre all gonna suffer a 120 fps loss of speed as compared to a 24 inch barrel, approximately.

The 284 is very dominant in f class, and lapua make brass for it now, so very capable at long range. The 280 ackley is right there with it, but no Lapua brass. Nothing wrong with the saum either.

 

[ormandj]

Sounds like the speed loss is worse in 7mm than the 6.5mm and 6mm stuff I’m used to which is generally closer to 25fps per inch. Thanks for the tip, I’ll pull some 24” load data and see where that lands me.

 

[Supersubes]

You could use 25 fps for the calculation. If you want. Its an approximation only.

 

[Schw15]

7 saum is one of the best efficient cases. But I think the extra wsm case might be helpful for you in the 20 inch barrel and 180 grain barrel. 7 mag throated long isn't to bad either. Honestly whatever brass you can find I would run with it.

 

[Steel head]

Yea
Any of the popular 7mm’s will do, 284, 7SAUM, 280AI and 7RM

 

[BadAccountant]

280AI gets my vote.

 

[Rocketmandb]

The Sherman 7mm would be another option (assuming you reload).

 

[Dead Eye Dick]

Something I would want to build just because it was an interesting cartridge from my youth (which was a long, long time ago)
Not in the 7mmRemington Magnum Class but just below it. The 7x61 Sharp and Hart. Brass might be difficult but it seemed to be a great cartridge, that had magnum power without quite as much magnum issues.

 

[JCARL]

Another upside to SAUM over long action options is the free 1/2" of barrel length, all else being equal.

 

[ormandj]

Well, already went with a 280AI. Just need to put together a dummy round and get a reamer made. I have a long action Lone Peak Fuzion incoming for the build.

 

[Mike Casselton]

See, that's the spirit.
Building a rifle because you have a barrel is like buying a rifle because you ended up with a set of dies.

Lots of us are guilty of the above.

 

[ormandj]

See, that's the spirit.
Building a rifle because you have a barrel is like buying a rifle because you ended up with a set of dies.

Lots of us are guilty of the above.

It’s far worse than that for me. I’ve built rifles because I have N568 powder I don’t know what to use in, a few ZCOs laying around with no rifles, and once because someone gave me brass they had no use for. It’s a bad affliction.

 

[beetroot]

Do some searches on the NZ hunting and shooting forum, quite a few guys there running short barrel 284s and 7mmSAUMs.

I think I'd go 284 if recoil and barrel life is important.