M1A stringing

[biscuit75camaro]

shooting my M1A in a sage EBR chassis at 100 yds it starts to string shots downward after about 5 shots like maybe 1/2in every shot till it stops at abt 7in below my zero. i know the bbl is getting hot but is there any way i can fix this? and no the bbl screw on the front of the sage isnt touching

 

[kraigWY]

Re: M1A stringing

Have you tried cleaning your gas piston/cylender?

Have you made sure you (lower part) forearm isnt contacting the barrel group?

What type of rod guide do you have (round or flat)? Is the op spring binding?

Is your flash hider/front sight assembly loose?

 

[nbkky71]

Re: M1A stringing

Are you shooting iron sights? If so, check the following:

- loose nut on the windage knob
- worn elevation pinion
- worn rear sight spring cover

 

[biscuit75camaro]

Re: M1A stringing

Im pretty sure my gas cylnder isnt super dirty and the sage floats the bbl past the op rod guide. My oprod is the flat springfield one. The flashhider is tight and and so is the setscrew

 

[biscuit75camaro]

Re: M1A stringing

Its got a scope on it mounted on the sage front handguard and the stripper clip rail

 

[Mike Petersen]

Re: M1A stringing

How tight was your gas lock when you installed it? Do you have a crush washer or shims? Too tight of a gas lock will cause what you are having.

 

[Frank Green]

Re: M1A stringing

Your gas plug being to tight shouldn't do it. Taking it on and off and tighten it to a different point will cause zero to change but not stringing. That's why you put a dab of paint on the plug and cylinder lock (figure 8 nut) so when you take the plug on and off you tighten it to the same spot.

The gas cylinder nut (figure 8 nut) should start to contact the gas cylinder at about 4:30 and you should be able to pinch it to the 6 o'clock position and then put the gas plug in. To tight a fit on the figure 8 nut will bow the barrel up and effect zero but shouldn't really cause stringing.

Your gas piston and cylinder for best accuracy should be cleaned every say 200-300 rounds. You can buy the proper tools to scrap out the inside of the piston etc....if to much carbon build up it can cause to the gas pulse to be different and effect accuracy and function of the rifle.

The two main things that will cause stringing is a problem with the gas pulse which usually is a piston problem or the bedding of the stock.

Easy way to fine out is to turn off the gas system at the gas cylinder like you would for launching grenades. You end up with a bolt action rifle.

Load a mag and pull the op rod back and let the bolt go home under it's own weight etc...shoot some groups. You just have to manually operate the rifle that's all. If the gun groups good and consistent then it's a problem with the gas system and like I said usually it's the gas piston. The piston could gauge fine but they found out years ago for what ever reason one gas piston from another can cause the gun to cause accuracy differences because of the gas pulse. If the gas pulse is off the bolt could start to open before the bullet has left the gun/barrel. Hence accuracy problems.

During shooting the gun operating the gun manually and it still strings than you have to start with the stock and the bedding. Fix that first and shoot it again. If it groups then it was your bedding of the stock.

You could have the gas system and bedding giving you grief at the same time but do the above test and it should get you on the right path.

This is all assuming you have no issues with the sight and scope and good ammo etc...

Later, Frank
Bartlein Barrels

 

[biscuit75camaro]

Re: M1A stringing

Thanks for all the info guys im gna try all of those things now that i know what to look for maybe i cn get it to shoot alot better. And the EBR stock came with a crush washer so thats what i used

 

[Frank Green]

Re: M1A stringing

Again I'm not familiar with your stock but a couple of other things to look at.

Was the gas cylinder and plate unitized? Usually the gas cylinder plate is tig welded to the gas cylinder to make them as one unit.

Also do you put a little grease under the gas cylinders plate lip to where it touches/rubs on the fore end of the stock? (This assumes it does touch the stock and set up that way?)

If this plate is not permanently attached to the gas cylinder etc...this can cause problems as well.

Later, Frank
Bartlein Barrels

 

[solidarmy]

Re: M1A stringing

I am having a similar issue with my scout in Troy MCS. When shooting 5 round shoot groups I get 3 of the rounds in a 2MOA group with 2 vertical fliers. I do not believe it to be me, however I have been wrong before. My scope is a Bushnell Elite 3200 10x40, and I was shooting 155 AMAX reloads. After reading this thread I notice my new SEI USCG muzzle break was slightly loose, would this cause my poor groups?

 

[Krazny13]

Re: M1A stringing

Check for movement between the receiver group and stock. If everything else is tight, there may be just a hair bit of play in the fit up that's causing this drift until the receiver shoots itself into position.

Also, free floating an M14 isnt always the best thing to do. Most match prepped M14's were built to have draw pressure, (via the Unitized gas cylinder) largely due to the harmonics of the barrel and gas system.

 

[M21guy]

Re: M1A stringing

One thing that was touched on but not in great detail is the gas piston itself. If your piston has any sort of pitting it can cause the issue you described. I've seen it first hand. It's a very minor looking thing, but it can make a huge difference. With pistons the rifle can be funny if you decide to change it. One rifle may like a piston, the next might like another. Two pistons from the same manufacture may have two different results in the same rifle. It can dive a man to drink. The best way is having a handful and try each out, however most don't do that due to cost. I'm found of Sadlak TiN coated pistons, they have always made a positive difference, but it is subject to the rifle.

That and this is off subject for your particular problem, but I noticed your build. Do yourself a favor an replace that flat spring guide with a NM rounded one. It smooths out the action nicely. It's a drop in part, that is just a must. You'll be thankful you did. Sadlak or Badger makes good ones. Sadlak is a tick cheaper I believe.

 

[Frank Green]

Re: M1A stringing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dfclin073</div><div class="ubbcode-body">I am having a similar issue with my scout in Troy MCS. When shooting 5 round shoot groups I get 3 of the rounds in a 2MOA group with 2 vertical fliers. I do not believe it to be me, however I have been wrong before. My scope is a Bushnell Elite 3200 10x40, and I was shooting 155 AMAX reloads. After reading this thread I notice my new SEI USCG muzzle break was slightly loose, would this cause my poor groups? </div></div>

I didn't even get into that. There are a couple of things you could check with the flash hider. Most match built guns the flash hider is reamed out. This is to ensure proper clearance when the bullet exits the barrel it not hitting the flash hider on the way out. Also the castle nut that holds the flash hider on if it should come loose the flash hider is loose and will cause harmonic/vibration issues as well as possibly letting the bullet hit it and both of these things will cause accuracy problems.

The castle nut when you tighten it up can be over tighten and this could cause the barrels dimensions to change internally and again cause accuracy problems.

Grab some red loctite or at least some blue loctite. When assembling the flash hider and castle nut put some loctite on the muzzle threads. Tighten your castle nut so the assy is tight and not loose but don't crank the day lights out of the nut. Let the loctite set up. You can speed up how fast it sets up by applying some heat from a propane torch. Don't use an acetylene torch! This will keep the nut from vibrating loose while shooting.

I don't think a loose flash hider will cause stringing but I think it would more effect just loose/big group sizes.

Later, Frank
Bartlein Barrels

 

[Greg Langelius *]

Re: M1A stringing

This used to be a chronic issue with Garands. The upper handguard would swell and extend when it got hot, warping the barrel downward.

Unless you knew what to look for, it could be very frustrating. Trimming about 1/16" off the upper handguard's length so it would float fore and aft cured this issue as a generic fix.

No idea if this is your problem, but your post twigged the memory.

Also, M1/M1A/M14 bedding, as I was taught, involved setting it up with a small downward flex preload in the barrel, to eliminate vertical strings. The manner of function the gas system employs tends to accentuate this, and the preload tends to cancel it.

You can test for this by shimming between the front band and the underside of the stock relief that fits into it. This temporarily estabishes a preload and may also pinch the barrel and stock together, ala a barrel pressure pad.

The N/M flash hider has a reamed forward opening to prevent bullet strikes, which might be aggravated by a loose hider. I would not count on this as a permanent fix, but it can serve to motivate one to seek a more proper bedding job.

Some of this may be Rube Goldberg; but when we did it, it worked.

Greg

 

[M14]

Re: M1A stringing

the scope is on the handguard. the screws could be loose or your scope or rings could be loose. take it off and shoot with irons to find out for sure whats going on. piston would be suspect for me too, or the op rod block is messed up or canted in a bind with a loose screw somewhere.

 

[bzinbv]

Re: M1A stringing

I'm having this same issue with a new Sage build, serious vertical stringing, sometimes 2" high then 2" low at 100 yards. LRB M25. Took the scope (USO) off and had the same issue with irons, so it is not the optics. Tried the barrel tension set screw backed out and with downward pressure, no difference. Does it with a can on it or a USGI flash hider. My next trip to the range will be with the rifle in a wooden stock to see if the problem is related to the Sage or the barreled action.

 

[GoBig]

Re: M1A stringing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Frank Green</div><div class="ubbcode-body">
I didn't even get into that. There are a couple of things you could check with the flash hider. Most match built guns the flash hider is reamed out. This is to ensure proper clearance when the bullet exits the barrel it not hitting the flash hider on the way out. Also the castle nut that holds the flash hider on if it should come loose the flash hider is loose and will cause harmonic/vibration issues as well as possibly letting the bullet hit it and both of these things will cause accuracy problems.

The castle nut when you tighten it up can be over tighten and this could cause the barrels dimensions to change internally and again cause accuracy problems.

Grab some red loctite or at least some blue loctite. When assembling the flash hider and castle nut put some loctite on the muzzle threads. Tighten your castle nut so the assy is tight and not loose but don't crank the day lights out of the nut. Let the loctite set up. You can speed up how fast it sets up by applying some heat from a propane torch. Don't use an acetylene torch! This will keep the nut from vibrating loose while shooting.

I don't think a loose flash hider will cause stringing but I think it would more effect just loose/big group sizes.

Later, Frank
Bartlein Barrels </div></div>

Frank...you give great advice!

 

[Valken]

Re: M1A stringing

Check that the barrel has clearance around stock or what ever the hand guard your using. Check check gas system.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Grab some red loctite or at least some blue loctite. When assembling the flash hider and castle nut put some loctite on the muzzle threads. Tighten your castle nut so the assy is tight and not loose but don't crank the day lights out of the nut. Let the loctite set up. You can speed up how fast it sets up by applying some heat from a propane torch. Don't use an acetylene torch! This will keep the nut from vibrating loose while shooting.</div></div>

Do not us Loctite on the castle nut in fact use some anti seizing compound. The set screw is what keeps the the castle nut from rotating. The carbon that builds up from firing the rifle will make it hard to remove the castle nut as it is with out the help of loctite. And what ever you do DON'T USE RED LOCTITE. It takes a torch to loosen up Red loctite and you don't want to heat up the muzzle over and over again removing red loctite. I once used red loctite on a set of rings cross bolts (not knowing any better) and I ruined the rings by heating them to break the red loctite loose. Sorry but IMHO this is a very bad idea.

The swapping of pistons is another excellent idea. Good luck good shooting

 

[biscuit75camaro]

Re: M1A stringing

ok i know its been a lil while but i jst took it to the range and put a leupold 3-9 mark ar mil dot on it. i loosened the figure 8 nut off one turn, checked my gas system and flash hider. 1" to 1.5" 5 shot groups is what i was getting when the rifle was cool. i used 168 gr smk and 42.5 grains of re-loader 15. thanks for all the advice guys

 

[GoBig]

Re: M1A stringing

I'm going to buy a new gas plug...the Sadlak TiN...I'll report back.

 

[bzinbv]

Re: M1A stringing

Update on my Sage stringing issue, went to the range with the action in a wood stock, stringing was worse. Took the gas piston out to single fire and the groups got much better, indicating it might be a timing issue. Re-installed it in the Sage with a new Sadlak piston and new op rod spring, still had some vertical stringing. Played around with the barrel tension screw, tried shooting with and without the can, varied the gas plug vent hole diameter and finally tried it in the Sage as a single shot. Best I could do was about a 2 moa group at 100 yards.

My current game plan is to try some M852 or M118 LR just to make sure it is not ammo related, currently I'm shooting Berger 155.5 Full Bores which I have found to be a very tolerant bullet. I also want to make sure the trigger group is locking down the rear of the action with enough force, I'll just shim under the heel for now. The barrel crown looks good, I may just have a barrel that is not that great. I've got a new Krieger coming that I'll spin on and chamber if the previous items don't help.

 

[bzinbv]

Re: M1A stringing

Another range report, took the Sage back to the range and tried it with a 0.020" shim between the stock and the heel of the receiver, this insured there is plenty of lock-up from the trigger group. No better. Tried some M852 and it still shot about a 2 moa group, I was focused on being straight behind the rifle and broke each shot clean. Tried shifting my rear bag from the back of the stock to the bottom of the pistol grip, no change. I've built rear lugged M1a's and bedded them in McM stocks, they certainly would shoot under 1/2" groups with iron sights, so I know my way around the rifle. I also switched out the bottom op-rod guide retaining screw from a button head to a cap screw so I could be sure it was tight.

Next trip I'll try to increase the downward pressure on the barrel using the tension screw, could be I was not aggressive enough the previous trip. Should have tried that today but I spaced it out. After that comes the Krieger.

 

[aussiem1a]

Re: M1A stringing

I ended up selling my sage stock it's nice to look at but not that practical I went back to a GI stock much better

 

[bzinbv]

Re: M1A stringing

I re-barreled with a new Krieger medium weight this past weekend, headed to the range today. The rifle now prints 5 shot groups in a 1" dot @ 100 yards, good enough for its intended use. The vertical stringing is gone. I left the op-rod roll pin out, I think this might reduce barrel/action/stock alignment changes as the barrel heats up. I should have thought to try to remove it before swapping out the barrel.

 

[biscuit75camaro]

Re: M1A stringing

im glad u got you rifle to shooting good man. im going to take mine out to 800yds in the next couple days. how long is your barrel? im seriously thinking of going with a med. weight 18in bbl to help with moving through the woods or in a deer stand. but i dont want to give up any accuracy. any advice?

 

[bzinbv]

Re: M1A stringing

Biscuit: I'm using a medium weight 22" 1/11 twist. You are going to loose some velocity running an 18", I'd leave the barrel long and remove the flash hider if you want a shorter overall length. I've never chrongraphed anything less than 22", but I bet you can do a search to find the delta.