Long range 7mm-08 barrel length and chamber dimensions?

[mattri]

Looking at building a 7mm-08 for medium-long range (600-1k).

I know the 6.5s and the bigger 7mms dominate but I think this will be a fun project. Don't have any weight restrictions etc.

Want to use the 162-168gr bullets and be able to push them out at 2850 or hopefully a little faster without being at max velocity and above an accuracy node.

Single shot action so no mag length issues.

1) In order to keep the base at or slightly above, neck-shoulder junction what kind of freebore will be required?

2) At what point will barrel length start having a negative effect on velocity. Not "how short can I go and still reach x" but how long can it be without starting to be a drag?

 

[dennisinaz]

You're gonna need 30" to get those velocities.

 

[mattri]

Thanks Dennis, that's kind of what I was thinking: 30-32".

 

[coreydelong]

I was gonna do a 7mm build just a short time back and decided to save the funds for other projects.... like paying the mortgage!!

I got the same info on barrel length.... 31-32" finished.

Best bet on chamber info is to "cheat" and call Dave Kipp at PTG and see what guys are using, then have them make you one, or find a smith who has one. Dave basically made me a copy of John Hoover's 6.5x284 reamer specs. I'm sure Carl Bernosky probably has what you need as he did my 6.5x284 with my PTG reamer, but has a ton of other reamers in his possession.

 

[mattri]

Just ordered a barrel- 30", 1:9 with 120 freebore- here's to hoping.

 

[flatlander]

I had Kiff grind a 7-08 AR30 (his idea for the name) a little over a year ago. It differs from the usual 7mm-08 in that it's slightly improved - a little less body taper, and 30* shoulder that's .065" farther forward than a std 7-08. So far, the only bbl. I've chambered with it is a 25" Krieger on an AR10 built on J-D Machine upper/lower receivers. I bought a 1-10tw bbl off Krieger's inventory list because it was already contoured & available quickly - otherwise, I'd have spec'd a 1-9tw. Haven't had the best of luck with S168MKs; in fact, their 130MKs have out-shot every other bullet I've loaded so far. Need to check the twist rate to make sure that it's really a 1-10.

My only other 7mm bolt rifles are both 284s - I'm thinking what I need to do is chamber a 1-9tw Sendero contour Krieger with the 7-08 AR30 reamer, screw it on a SA 700, and see what it'll do. I think it'd be a fine cartridge with 162-168gr bullets, burning considerably less powder than the 284, and having less recoil. Should be a hummer with a Thunder Beast 30BA can on the muzzle.

 

[mattri]

Sounds like a fun project- I'm planning to use the 162s primarily.