MILSURP brass powder reduction

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Bixster_inc

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Looking to put together some rounds for my CMMG MK3 using the following.

Hornady Match 168gr BTHP
Varget powder
Remington 9 1/2 primers
LC brass (head stamped ‘12-‘14)

Looking at Hodgdon’s website using varget/168gr BTHP they recommend a starting load charge of 42.0gr and a max of 46.0. A lot of information out there for reduction in LC brass ranging from 1.5gr to 10%.

My question is am I reducing from min or max loads? With my limited knowledge -1.5 from 42.0 feels better than 10%.

Thanks in advance.
 
.308 should have 56g H2O capacity. A Load Data article measured the volume to be 54.6g H2O. 7.62x51 is rated at 52g and the same source measured it at 52.8g. A QL calc shows that 42g Varget @ 2.80" COL in a 54.6g volume case would give you a peak pressure of 50,964 psi while a 52.8g volume case will get you a peak of 55,322 psi.

Although 42g in the LC case is right at the peak of .308 specs, it is below 7.62x51 NATO specs and probably safe in your gun. If your brass is of the lower volume, you might have a little crunching of the grains even at 42g because you are about 4% compressed. You should be OK even at 40g and I doubt you'd know the difference of 100 fps lower MV.

I shot that same combo in my 788 and was perfectly happy punching holes in paper with tiny groups at 38g and averaging 2460 fps..
 
.308 should have 56g H2O capacity. A Load Data article measured the volume to be 54.6g H2O. 7.62x51 is rated at 52g and the same source measured it at 52.8g. A QL calc shows that 42g Varget @ 2.80" COL in a 54.6g volume case would give you a peak pressure of 50,964 psi while a 52.8g volume case will get you a peak of 55,322 psi.

Although 42g in the LC case is right at the peak of .308 specs, it is below 7.62x51 NATO specs and probably safe in your gun. If your brass is of the lower volume, you might have a little crunching of the grains even at 42g because you are about 4% compressed. You should be OK even at 40g and I doubt you'd know the difference of 100 fps lower MV.

I shot that same combo in my 788 and was perfectly happy punching holes in paper with tiny groups at 38g and averaging 2460 fps..

I went with 40 gr, my shootin’ spot has a 420 yard span I can set up my 8” steel target at. Once dialed in (and hopefully having a good nerves day) if what I made isn’t as good as my off the shelf Win 180 gr/mail order LC 168 gr I’ll re-evaluate and apply to the next batch of 100. If anything I’ll be my issues are the slight discrepencies my trimmer is giving me, that thing is impossible to get on the money.

Can I just say it feels AWESOME to finally start turning those buckets of brass that have been accumulating in the garage collecting dust into usable* rounds? Kinda had to sit back and admire how those fancy MTM cases looked stacked in my ammo locker next to all the rest of the $$ I’m not putting into my retirement fund.


* = yet to be determined if rounds are “usable”
 
308 is very forgiving I’m sure they will be on par with the factory ammo.
I use LC brass and commercial data. Most the good loads I’ve found were around 1 grain short of max loads. Start where your comfortable as long as it’s at or above published minimum. Load 5 rounds and go up a grain and load 5 all the way to max. See what’s most accurate and play around with .5 grain increments around that. Go down to .1 grain if your not satisfied.
 
My question is am I reducing from min or max loads? With my limited knowledge -1.5 from 42.0 feels better than 10%.
When a published source supplies a starting load and max load they are just that. Use the starting load as published and work up stopping at the max.

Sources like Alliant list only one charge in their data, that is the max charge. This is where you decided that charge by 10% to find the starting charge weight.

Why did you charge two full grains below the starting charge weight?

Good luck, be safe.
 
When a published source supplies a starting load and max load they are just that. Use the starting load as published and work up stopping at the max.

Sources like Alliant list only one charge in their data, that is the max charge. This is where you decided that charge by 10% to find the starting charge weight.

Why did you charge two full grains below the starting charge weight?

Good luck, be safe.

40 was the middle road between the 3 recommendations I received prior to seating the bullets. I think at this stage as long as the hits are consistent and the rifle cycles I’m good. If after these are gone and something is still to be desired I’ll adjust up.
 
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