I have a couple of "Loaded" M1As that I bought back about 10-12 years ago. They have mostly been sitting in my safe but I want to start shooting them.
One has a standard GI weight barrel on it. The other a heavier more like match grade barrel on it.
My assumption is the standard barrel has a twist rate that was designed for the 147 gr NATO round. Is that a 1/11 twist?
I assume the heavier barrel has a 1/10 twist and was designed for the heavier 168 gr bullet.
I have no way of measuring the twist.
My first question is do my assumptions sound correct? What does SA produce?
My second question question is can I shoot 150 gr bullets in the heavier barrel if it was designed for the 168? How about 168 in the lighter barrel?
What are the parameters for twist rates and bullet weights in the M1A?
The GI twist is 1:12". The medium weight barrel that comes on the loaded is a 1:11". Shouldn't have trouble shooting anything really in either.
Originally Posted By Flash66:
I have no way of measuring the twist.
My second question question is can I shoot 150 gr bullets in the heavier barrel if it was designed for the 168? How about 168 in the lighter barrel?
What are the parameters for twist rates and bullet weights in the M1A?
How can you have "No Way Of Measuring Twist"? All you need is a cleaning rod, a cleaning patch, a ruler, and a piece of tape (Scotch/Duct/Adhesive/etc). Start a tight fitting (won't spin in the barrel) patch on the cleaning rod (breech end).
Pull the rod to the front until the patch engages the rifling. Put the tape on the rod flush with the muzzle.Make a mark on the tape at 12:00. Pull the rod to the front until the index mark has made one turn and is again at 12:00.
Measure the distance from the muzzle to the tape. THAT IS YOUR TWIST.
As was mentioned above, the USGI standard barrel was 12" twist. And, that was designed for the M80 150gr bullet as well as the M14NM 173gr bullet. 10" to 12" twist will handle anything from 180gr and down.
Originally Posted By 30Caliber:
The GI twist is 1:12". The medium weight barrel that comes on the loaded is a 1:11". Shouldn't have trouble shooting anything really in either.
Thanks.
That was the info I was looking for.
It sounds like I can shoot 150 gr in either one of my M1As.
