Larry Gibson
posted this
30 October 2015
Years ago I had access (military SF arms) to several M1903A4s in new condition and several M1903s and M1903A3s. The A4s all had 2 groove barrels as did about half of the A3s. The '03s all had 4 groove barrels. Our goal was to find out how well they did at 100 (reduced NMC), 200, 300and 600 yards with cast bullets (311284, 311299 and 311331). Interest was also in 100 yard increments to as far as 1000 yards for use. This was during the post Viet Nam period when we received no ammunition for training.
We tested the rifles with cast bullet loads developed by me using the common methods (alloys, powders, etc.) of the day ('70s). We found with “accuracy” loads in the 1850 - 1950 fps range (yes I had an Oehler chronograph back then) with both bullets that accuracy was pretty much equal at 100 and 200 yards between the 2 and 4 grove barrels. At 300 yards the accuracy with both bullets began to definitely favor the 4 groove barrels. Beyond 300 yards the 4 groove barrels consistently were more accurate with all 3 cast bullets. Those loads held very good accuracy to 500 yards but were going sub-sonic after that and none did well at 600 yards, at least not as well as they should have given normal group expansion. If the velocity was boosted to 2050 fps accuracy was better at 600 yards but not as good at the closer ranges. Obviously the transition from sonic to sub-sonic was the cause.
Yes I have and have read (numerous times)the Remington test “proving” the 2 groove barrels are/were more accurate but our tests did not demonstrate that with cast bullets or with M72 Match ammunition we acquired (courtesy the Oregon National Guard). The 4 groove barrels proved the more accurate at 300 yards or farther.
The main reason for the 2 groove barrels was they could be produced faster and cheaper than 4 groove barrels. Given that fact if the 2 groove barrels were more accurate than 4 groove barrels wouldn't all the match shooters be using them? Wouldn't the military still be using them? If you look at the muzzle end of a 2 groove barrel you can see the elliptical shape the bullet comes out in. I believe that shape does not lend itself to as good a balanced bullet as from a 3, 4, 5 or 6 groove barrel. it is the greater imbalance of the bullet that causes the less accuracy at longer ranges.
LMG
Concealment is not cover.........