M1A Accuracy Troubles

[criticalw88]

I am getting a horizontal dispersion of about 6 moa with my reloaded ammo in my LRB M1A. Bullet and mid-case runout is less than 0.003". Cases are LC reloads from a M240 that are resized using a Redding full-length type S die. The resulting neck OD is 0.338". The bullet is a SRA 175 MK installed using a Redding competition seating die. The flash holes were chamferred about 0.02". Case necks were chamferred both inside and out using a Giraud trimmer. My starting load was 38.8gr of H4895. I am trying to match M118LR's capabilities. Actual M118LR ammo shoots 0.75 moa. I must be missing something huge to encounter this inaccuracy. Any and all advice is appreciated. Thanks

 

[FALPhil]

Since your cases were fired in a GPMG before reloading, have you checked to see if the bases are square?

 

[criticalw88]

You mean to see if head is perpendicular to the case wall? What is a good way to do that?

 

[Travelor]

I would start bringing the charge up as that seems a very light load and should be giving you only about 2350 fps. QuickLoad says you can safely go up to 45 grains of H4895 with the 175 SMK, but that 43 should yield about 2611 fps which is about right velocity wise for matching the M118LR load.

I think this will go a long way to helping with your accuracy problem as the low pressures and velocity you are getting is most likely the cause of your "problem".

As always use loading data off the Internet with caution and start increasing loads slowly and monitor the pressure signs.

Good shooting,

George

 

[FALPhil]

You mean to see if head is perpendicular to the case wall? What is a good way to do that?

Put them in your sizing die and check them with a machinist's square using the side of your die as the index.

Personally, I never use MG fired brass for anything but plinking rounds. MGs abuse brass horribly, and it's just not worth the trouble.

 

[TRECustom]

critical, when I used to shoot gas guns, I loaded LC match brass with 41.5 gr of 4064 with a 210M primer and 168 Smkhp. This ammo would shoot moa in every match M1A I put it in. The last 2 yrs I shot at Perry, they furnished LC M852 NM ammo. It was also moa ammo. An equivalent handload with 4895 was 42 grs, but neither was quite as consistent as the 4064 handloads in my M1A. Back in the day, M118 Match was loaded with a 173 gr full patch boattail that didn't shoot well in some rifles. There was also a M118 Special Ball that used that same bullet in a ball case and didn't shoot well in most rifles. Sounds like the M118 LR is much better ammo.

If you are popping the shellholder on the bottom of the die, it should straighten the case, particularly if you are using a small base die. Machine gun brass wouldn't be my choice either, but I suspect that the advice about the light load causing the horizontal dispersion is correct, although 6 moa is excessive, even in a gas gun. I am also surprised that the low power handload doesn't short cycle your rifle.

Let us know how what you find out.

Tom

 

[criticalw88]

Thanks for all the advice. I will try increased velocity loads next time at the range. I will also pick up a machinist square in short order. I cant really comment on the weapon short cycling as I single load each round - for now. I would think the possibility of a short cycle is even more likely due to a Sadlak NM grooved piston being installed. I will report back when I have new range data.