Powders For 308 Semi-Autos

[Hook]

I'm new to this board, so I hope this question hasn't been asked already. I have loaded the 30.06 for semis for years and am familiar with the rule to use only medium powders such as 4895 for the M1. It is supposed to be due to the pressure peak being reached at the correct time to properly cycle the action. If slower powders, such as 4350 and 4831 are used, the delayed pressure peak can cause damage to the operating rod of the M1.

The question is whether this rule applies also to the M1A and AR10? A friend recently traded for both these rifles and wants me to help him develop loads for them. We have a lot of surplus H380 available and I have had great success with it in my bolt action 308s, although top velocities are not in the range that can be reached with faster powders. Will slower powders in the 308 cause problems in the M1A or AR10?

You input will be appreciated.

[Mark whiz]

Hook,

You need to approach loading for the M1A just like you would for the Garand - they are indeed pressure sensitive. Some of the most popular powders for the gun is IMR 4895, IMR 4064, Hodg. Varget, Hodg. BLC-2, Hodg. 4895, Win. 748, and Alliant Reloader 15. Any powder on the burn rate chart between IMR 4895 and Win 748 will work in the M1A.

Based on the NATO Specs for 7.62 ammo, you should be looking for Muzzle Velocites of 2750fps for 150gr bullet loads and 2550fps for 165gr bullet loads. Anything in these general areas will get you in the ballpark.

[Edward429451]

Thats exactly what I've been told about the M1A also, and not to go over 175 gr for bullet weight. I'm just getting ready to try some 175 gr SMK's and see how those work out.

I had mixed but excellant results using IMR-4064. 41.5 gr behind the 165's was very accurate (2.75" at 100, iron sights) but it didnt seem to meter as well as I liked. I had one round squib on me because apparently, the 4064 'bridged' the powder charge, not dropping the full charge in my RL550B, and wasn't enough to cycle the action. The bullet did exit the bore, and it was a good shot, but it made me think a little bit about maybe either hand weighing them or going to a powder which meters better, like BLC-2.

I used the IMR-4895, it metered well but the best I've been able to do with it is about 4 to 5 inches at 100 yds. The thing about this is, the group was always nicely centered on the bullseye, with no shots being more than 2 to 2.5" from the bull, so realistically this is probably good enough for all practical purposes but I wish I could figger out how to tighten it up a little more.

I bought 8 lbs of BLC-2 to load up 1200 223's I have sitting there, and should have a couple lbs left over to try in the 308, so we'll see how that goes.

[Mark whiz]

Edward,

Metering can be a problem with 4064, fortunately I throw & weigh all my rounds with an electronic dispenser/scale.

On your current 4895 rounds, you might want to play with OAL to bring your groups a little closer together - you can safely load out to an OAL of 2.830 with no feed problems on a M1A.

In fact, you may well want to try the 4895 with the 175gr SMKs. NATO spec for match ammo uses either 4895 or RL-15 for these larger bullets loaded to an OAL of 2.830.

[Edward429451]

The 4895 load was:

165 gr SGK (spbt 2145)/41.0 gr IMR 4895/Fed210 LR Primers/ FC brass (2.010)/ 2.810 OAL

Most 5 shot groups averaged 4.5" with no two shots touching. All five were pretty evenly spaced out at like 12, 2, 5, 8, and 10 o'clock respectively, but centered nicely on the bullseye but no bullseyes. got a target of a 4.25" group but digital camera is on the fritz. I cant discount that it may be me too. I shot most of em prone and always with iron sights. I want to get good with the irons before splurging on a scope, but a scope would probably help me shoot better too to better evaluate my ammo. Its a vicious circle! Maybe I should scope it just to test the ammo and then take it back off and try to duplicate with irons. I hand weighed a bunch of 4064 loads but the mountains are full of snow so I haven't tried to get up there to shoot any yet.

I could try seating them to 2.830 and see what happens. I'll try some 4895 behind the 175's too. Might as well load if I cant go shoot. I gotta knock out thos 223's first though, already set up for em.

Shoot straight.

[Mark whiz]

Edward,

That load is pretty much within the standard range. If memory serves me correctly, I believe Scott Duff recommends 41.5gr of 4895 with 168gr SMKs set to an OAL of 2.80 - while Zedicker says 42.5gr of 4895 set to an OAL of 2.830.

I may have those two gentlemen backwards - but since neither one of them are by no means a slouch, either load ought to be real close to perfect.

[Edward429451]

A couple hours netted me about 600 223's last night. Man, I love the 550B!.

Ahh, the money and time saved in load development, due to the internet! I haven't really been loading 308's very long. I probably cut out a couple years worth of R&D by talking to others via the boards. You guys are great!

Somebody was telling me something about reaming out the charge bar a little bit on the Dillons measure, so it'll measure 4064 more accurately without bridging...something like that.

Anybody here ever do that?