308 win and 308 win service rifle question

[nevadamatt]

I have the 7th edition hornady book and there is two diffrent choices for 308 win. or 308 win service rifle. I am loading for a dpms ar 10 24 inch with 1 10 twist rate. My question is which should i use for this rifle? Is there a big diffrence in the data that i should be aware of? Also is the 178 gr a-max going to be the right choice for this twist rate?

[Jim White]

I have the 7th edition hornady book and there is two diffrent choices for 308 win. or 308 win service rifle. I am loading for a dpms ar 10 24 inch with 1 10 twist rate. My question is which should i use for this rifle? Is there a big diffrence in the data that i should be aware of? Also is the 178 gr a-max going to be the right choice for this twist rate?

Hopefully I can assist but, being up front, my service rifle experience is with the M1 Garand & M1A/M14. THe AR platform may be a tad different. Does the manual imply what type of service rifle? And last of all, what are you going to use the rifle for? If for target shooting, I'd use the service rifle section. If for hunting, I'd do some research and try to find out how durable the AR platform is to higher port pressure with slower burning powders.

Powders: One reason there is a different section for the 308 service rifle is the M1 is very susceptiable to excessive gas port pressure and over a period it tends to wreck havoc on the long op-rod. The M14 is the same but to a much lesser extent due to a different gas system design. Where an AR fits is unknown to me, my guess being it doesn't matter because of the gas system design. IIRC, the powder recommended for a M1 falls between 4198 & N540 due to the op-rod issues. Generally speaking, the powders such as 4895, 4064, RE-15, Varget, N140, N540, WW748 (and a bunch of others thats too long to list) are prefeered. See this link for additional info:
http://www.lapua.com/fileadmin/user_upl ... de2009.pdf

Bullets: Another reason, hunting bullets may make good target bullets but target bullets rarely, if ever, make a good hunting bullet. I've never tried the 178 AMAX, I've always stuck with the 175 SMK for my rifles and some fellow competitors would use 185 Bergers in the M14 (before the 175 was introduced). Although I've never tried it (but I've read/heard) a 180gr bullet in a M1 with the required velocity needed for 1000 yards may be a tad hard on a steady diet. Target bullets are designed for accuracy, not special effects (35 Bergers in 2204). My two M1A's have 10 twist single-point-cut barrels. Oddly enough, my M1's sport genuine USGI 7.62 barrels (chrome lined too) and they shoot very well. Incidentally, I've read that both Kreiger & Obermeyer rifling is cut on surplus military equipment.

Primers: Service rifles including AR's by design have free floating firing pins. When the bolt is dropped/cycled the firing pin continues to travel fwd (ever so slightly) and strikes the primers. Federal primers have a reputation of being soft as does Winchesters (non-nickel). Some have shot them for years and has never had a problem. Others have complained of slam-fires or out-of-battery fires. In any event, when reloading (with any firearm but especially service rifles) make darn sure the primer is fully seated (no high primers).

HTH,

[acloco]

Jim has walked the path and spoken....his info is spot on.

[nevadamatt]

Thanks for all the info Jim it is much more then i was thinking i would get! It talks about the m 1 and m 14 in the book but it also mentoned the ar platform but, only once. The gun will be used for target only (way to heavy to pack around with me) so i will use the data for the service rifle. I would like to shoot some F class one day with it ,but i have alot of work to do before that. thanks again for all the help.