M1A barrel harmonics

[10X]

I am looking for some sophisticated M1A super match tuning experience.

Has anyone experimented with flash hider tension and gas plug tension to see how those affect groups? If so, what were the results you had?

1)Does the tightness of the flash hider in the barrel splines have any affect on accuracy? Snug versus so tight you can hardly tap the flash hider on the barrel?

2)Did using more or less torque on the castle nut gave a looser or tighter group? Has anyone added thin shims to line up the castle nut slots with a desired torque for the set screw? Did that affect groups?

3)Does more or less torque on the gas plug do anything for groups?

 

[cuervo]

I have read where shooters have experienced a change in groups based on the tightness of their gas plug, but they didn't draw a correlation between how tight it was to the grouping. Most put a notch in the gas plug and lock to make sure they tighten them to the same spot everytime.

I've never read anything on the flash hider beyond reaming it to NM diameter and making sure it is on straight.

Maybe post your question here, too:
http://www.jouster.com/cgi-bin/garand/garand.pl

A good person to ask on that site is Gus Fisher.

Please post any results here.

 

[Peter M. Eick]

1) Flash hider tension does not seem to matter to mine and mine is quite tight.

2) Castle nut does not seem to matter as long as it is sufficiently tight.

3) Gas plug matters a lot. If this gets loose your groups go to pot. I use the wrench and a gas plug wrench to put it on. I actually have a torque I set it to but cannot remember it off my head.

My SuperMatch will do the following at 100 yards and 50 shots per group.

 

[30Cal]

The flash suppressor should be tight--really tight--as in driven onto the barrel with a mallet.

Gus Fisher said they noticed that rifles generally didn't shoot as well when the castle nut was torqued down extra tight. Some of the service teams would back off the dog screw 1/4 turn and glue it in place to keep it from exerting a moment at the muzzle (the guy out here that works on my rifle threw away the dog screw and just loktited the castle nut in place). You should back the castle nut off as necessary (do not continue to tighten past snug) to get the dog screw to drop in.

I paint a witness line across the gas cyl plug and tighten back to the same place. The USMC team went up to 22ft-lbs for a while (although the spec is 15).

The teams tested at 300yds with a rack--and even then the differences were subtle.

 

[30Cal]

One more thing--they say that the rifle will start to shoot funny when the gas system gets dirty or the gas plug get's loose. I clean the gas system pretty regularly, and I've never been able to say with confidence that the rifle was having a bad day. My best 3 shot groups ever were fired with a loose gas plug. Go figure.

 

[10X]

Thanks for the info and experience. This will let me focus time and ammunition on the things that should make a difference.