compressed 308 loads?

[Scottie]

I have a decent amount of NATO brass and very little commercial brass, so I am interested in trying compressed loads in NATO brass with lighter projectiles for my AR 308. Specifically, I would like to shoot a 110 grain bullet at a relatively high velocity using IMR 8208. On Nosler's load data, I noticed the casual mention of compressed loads at perhaps 102-105%, but no real discussion about it. Are there guidelines for max powder compression and are there any issues to look out for? The idea is to use loads suitable for commercial brass in a NATO case, which is hopefully not too crazy.

[rboyes]

I shoot 110gr FMJ's using about 42.5gr 8208 in Nato brass and I have no issues with compressed loads. Velocity is around 3000 fps from an 18" barrel.

I'd worry less about the % of case filled and more about pressure signs you observe. Start at min loads and work your way up. Because of the relationship between pressure and volume, the pressure generated by a compressed load will increase very quickly. Do some load development and you may find you don't need a compressed load.

[Scottie]

You bring up a good point that perhaps real world results will differ from calculations. I was just going by Hodgdon and Nosler load data, but I trust your experience and it makes sense to give it a try. I also clipped the Hodgdon data with a Barnes 110 gr projectile and the Nosler data with Varmageddon 110 gr to show why I thought it might need compressed. The Hodgdon data is with a Winchester case and the Nosler data is of course using a Nosler case. Nosler lists the Nosler case volume as 52.0 gr of water and a Nato case at 50.3.

[co-exprs]

You can run up to about 45gr of 8208 before getting into compressed loads in most nato brass. I run 45gr under a 135gr bullet and make about 2850 from an 18" barrel. I tried 46gr under a 125gr bullet and nato, but that case was awfully full and made me nervous in the jervous. I decided to run that load in commercial brass only. It works better there, but I start seeing split cases after 2 reloads, so I know that is pretty close to the limit of what commercial brass can take. You'll have to work up to it, but I expect you will be fine up to 45gr... But no more. Another point of note... I have noticed a lot of primers falling out of LC 7.62 brass. Not sure what the deal is, but this past year I've been sorting and using LC brass for practice and local matches only.

[Scottie]

Thanks for the information and the heads up on the LC brass. My local wally world still has ZQI M80 for $10, so I keep collecting their brass.

[biglou13]

I ran a slightly compressed load. Not always necessary. Always work up to a load. And always look for reassure signs. I'm not familiar with that bullet profile. But I'm guessing that light a bullet will not compress powder. Next you'll need to chrono to see if you are getting consistent velocities. I think finding the sweet spot for bullet and barrel is more important.

[DEP44]

I'm getting 2700fps with the smk 135 out of a 16" barrel and LC brass. With std primer and 45.0gr IMR 4064. Now if I use a mag or mil primer I can go down 1 grain and get the same velocity. That's enough to make the bullet feeder drop the bullet on top of the case mouth and not on top of the powder: it keeps the bullet from tipping over when the shell plate rotates..

[DEP44]

Co-exprs, thank you for the 8208 tip! I just finished an AR 308 with JP18" barrel and my 45.0 grain 4064 load gets me barely 2600 fps in 30F temp and on top of it primers are flat beyond comfort level (start to back out). Tried some 8208 with the following results:

LC brass, CCI200, SMK135, OAL 2.760, 30F temp.

43.0 - 2650 fps

43.5 - 2676 fps

44.0 - 2760 fps

44.5 - 2800 fps

45.0 - 2833 fps

Noting that 43.0 and 43.5 have high ES (doesn't affect accuracy @ 100y much though). Getting ~0.75 moa @ 100y from 44.0 and up, No pressure signs.

Showing off my (first AR) homegrown toy.

[Stlhead]

I have been playing with benchmark for my 110grn 308 loads and have had some success. You might consider a different powder.

[ken hebert]

only because i had a ton of it on hand.. i am using 49g of 748 on a 110g VMAX, 3185fps out of a 20"