Homebrewed M118 loads for gas guns

[NCHillbilly]

I'm Wanting to load some homegrown versions of the mil M118 rd, with the one difference being the use of Hornady 178gr A-max bullets. I have virgin LC cases,CCI 34 primers,and varget powder. I want all the velocity I can get without inadvertently disassembling my rifle. My first question: Is a gas gun(ar-10 and variants) much more fragile than a bolt gun? I'm curious about a target velocity, and if what is just right for a bolt will be too much for a gas gun. My second question: does anybody have a recommended starting load using the above components that would be suitable in a gas gun. The rifle to be used is a DPMS LR-308, 24 in st steel bull barrel, 1-10 twist. I am looking for a good 700 yd + rd.

 

[Scimitar]

I had one around 43 grs of Varget. Start at 42.5 and see what the velocity is.

 

[SOC308]

I shoot 43gr of varget in my POF under a 175SMK and it shoots the same as FGMM.

 

[GIXXER2000]

I am shooting the SIG 716, here is my load data:

Brass CBC 7.62x51, I did use the Dillon super swag 600 for the primmer pocket.
Powder Varget 43.6 gr for the A-MAX and 43.8 for the SMK
Primmer 210's
Bullets 178 A-MAX COAL 2.810, 175 SMK COAL= 2.810 max length that fits in my mag.
AVG FPS 178 A-MAX = 2497, 175 SMK 2494

When I compared my loads to some factory new FGMM 7.62x51 175 SMK which had a AVG FPS of 2496 I was right there.
I did compare to some new FGMM 7.62X51 which had an AVG FPS of 2496. I use a Magneto Speed and10 rounds to get the AVG FPS. I think I am right there with these loads. To get my AVG FPS I shot 10 rounds over my Magneto Speed.

 

[Tx_Flyboy]

My hunting load out of a DPMS LR-308 (20" bbl) is:

178 AMAX
44.4gr Varget
LC or Win Brass
Tula LRP

Works well and also use it as a match load (usually with 175 SMK or 185 Bergers out front).

This load is safe in both my 308 AR gas guns and M1A.

 

[NCHillbilly]

Thanks to all for the replies. I have a pretty good 168gr load for this rifle, but with the heavier bullet and different powder I was curious about a starting point. All of my load manuals seemed a little on the conservative side. From what I've seen here, my starting charge is coming in at about what the manual says is max.

 

[mkollman74]

My load is as follows:

LC LR brass
44.4 Varget
Fed 210M
175SMK

Has been lights out in my OBR and PredatOBR

 

[dauntedfuture]

Yes, loading a gas gun takes a little more care then a bolt gun. You can and will run into issues with extractor marks as well as primer pressure issues if your ammo is hot and or your brass is not FL sized correctly. Look for marks from the extractor on the front side of the rim of the case. In a bolt gun, sometimes a blown primer will stay in the case and you will not know your blowing primers until you try to seat another one, in a gas gun they are more likely to come out and muck up the trigger. With a 24" barrel and a good bullet you should be able to stay supersonic out to 1K. Stay away from 168g bullets, SMK 175's might work, berger or other high BC bullets will give you more velocity for the finish line. Run your crono data on the JBM ballistic calculator for verification and you need to be above 1300 fps or so to just make things work. Don't be afraid to try 155 2156 SMKs or Berger or Lapua 155s in that 1-10, they might bounce around in the wind a little better but you can push them fast and they usually shoot in a 1-10 just fine. Varget should get you good velocities.

 

[ArmyJerry]

tagged, got my 118 clones shooting 1/2 inch groups41.7-8 imr 4064 pushing a 175 smk in my bolt guns but not nearly as well in the DpMS SASS. I did get the 155s shooting well with the IMR 4895 though.

 

[fastex500]

My gas gun load was similar to above loads.

LC brass full size primed and trimmed
Federal GMM primer
hornady 178BTHP
44.2gr varget
2.820 COAL (mag fit)
Light crimp

Averaged 2720 out of a 20" lothar walther barrel. Be careful tho, it's a pretty hit load in mil brass. Start at 42 and work up.


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[tylerw02]

If you're using different powder and different projectiles, why call it M118? Just do like you would do with any other load...start low and work to the velocity and pressure you desire. My 18" gasser hit the speed with Varget at around 44.2 gr with 175 sierras. Using a different bullet expect it to be different.


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[Palehorse68]

Tagged for good info

 

[NCHillbilly]

You are exactly correct. When I started thinking about putting these loads together, The bullet was the only difference. It was my understanding that ATK was using RL-15 in the production of current issue m118 rds. I decided to substitute varget for RL-15 due to better temperature stability. Guess I should have just said long range ammo.

 

[1Sg (ret)]

tag

 

[Gunner's Mate]

here is the M118 military load data from Tech Manual