I'm hoping someone could point me in the right direction on this issue. I've been loading a 311299 in my M1A for a while now. With the load I use, I've always noticed groups with a degree of vertical alignment. A while back I was shooting from 700 yards and had five shots land with a vertical spread of 25 inches, and a horizontal spread of about 4 inches.
Anyway, I have two copper jacketed bullet loads which I use for this rifle, and both perform well without any noticeable stringing.
Today's series of events:
Two ten round cast bullet groups (H4895) - Vertical stringing in each.
One five round 175 Gr. HPBT group (BLC-2) - Nothing abnormal, good accuracy
One five round 149 Gr. FMJ group (BLC-2) - Nothing abnormal, good accuracy
One five round cast bullet group (H4895) - Vertical stringing
-Alloy is Lyman#2
-I'm shooting with a bipod from a normal bench.
-The load is moving at around 2000 FPS
-1 in 11" twist rate
-I'm using surplus military brass (sorted by manufacturer) and CCI 34 primers
-Powder is H4895
-Annealed .014 Amerimax aluminum gas checks made from a FC III (not possible to remove by hand).
-All bullets were weighed and sorted to within 1/2 grain of the mean (doesn't really seem necessary).
-No buffer, tried adding some and reducing the load then working my way back up. No improvement.
-Tried another type of primer (Fed LR). No improvement.
-I use a rear bag with the bipod but haven't tried shooting from a lead sled or anything like that.
How much truth is there to the idea that slow moving cast bullets are more susceptible to recoil? I'm also trying to understand if it's a powder burn rate or temperature issue. Any ideas or suggestions on what else to try would be great.
Thanks,