7MM-08 A.I. Performance ?

[th82457]

A couple of questions for those who may have built a 7mm-08 improved for hunting purposes. What velocity increases over a standard 7mm-08 can be expected with 130 to 150 hunting bullets ? Also, I assume this conversion would feed better from a straight line clip or magazine due to the 40 degree shoulder and reduced body taper ?

Thanks,
Terry

 

[XTR]

A couple of questions for those who may have built a 7mm-08 improved for hunting purposes. What velocity increases over a standard 7mm-08 can be expected with 130 to 150 hunting bullets ? Also, I assume this conversion would feed better from a straight line clip or magazine due to the 40 degree shoulder and reduced body taper ?

Thanks,
Terry

It is the internet, so you may see some crazy answers, but in general the increase in case capacity when you AI a 308 based case is only in the range 3% or 4%, so you should get a corresponding velocity increase. (so a bullet you can push at 3000FPS with a straight 7-08 you can get about 3090 to 3120 with an AI) One thing to remember is that it is likely that someone who does the AI thing is searching for as much MV as they can get, so their load work may well be for max velocity.

Personally, I shoot a straight 7-08 hunting rifle with a 24" Rock Creek button rifled barrel. It will push 140s in the vicinity of 2900 to 3000 FPS pretty easily. In hunting applications at ranges that one would shoot a 7-08 at animals (500 or so max) I don't see much benefit to the AI.

There are cases that I'd really like to do an AI on, like a 30-40 Krag for a single shot (maybe even make it a 7mm based on the case) but the 308 family just doesn't get much gain for the work. Once again, it's the internet, so you will get differing opinions, and in the end it's your rifle, so do what you will.

 

[flatlander]

I tend to agree with XTR's assessment of going the Ackley route with any of the 308-based cartridges. But, if you're looking for something a little different than all your friends are running, and not needing to trim as often (if ever) is worth it, then go for it. Just don't expect 280 Rem or 7 Rem mag velocities out of it.

My personal experience with improved chambers in the 308 family of cartridges is limited to 260 Improved 30*, and a very similar 7-08 case. Since I've never ran rifles chambered for plain 260 or 7-08, I can't give any comparisons where velocity is concerned, but I'm not getting numbers out of the ordinary with the 260 Imp.

 

[mattlewis]

I agree with everything above.

Mine feeds perfectly out of a regular rem 700 staggered magazine.

 

[kmon]

308 family of cartridges the biggest advantage of going to an AI chamber is less trimming of brass since it stretches less.

There is not that much velocity gain.