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Posted: 6/16/2007 5:23:00 PM EDT
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I am trying to figure out what can be done to fix a wondering zero problem on an SA Standard M1A. I am not looking to make it shoot groups like a National Match, but a group would be a big improvement over the patterns it shoots now. Any information would be greatly appreciated! Thank you. |
Check the loose nut behind the stock first . Are you flinching ?? Time for a ball and dummy drill .... Is the front sight tight ?? Rear sight loose ??? Rifle sets in stock tight ?? Head space GTG ??? The list goes on , more info needed , post a target of your groups ( atleast 10 rounds ) Trigger control , breathing , are important . Can you do this ??? Are you shooting off the bench ??? |
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Is your rear sight loose? Wiggle it around. If it moves too much that's bad. If it moves too much but doesnt spring back, thats really bad. There's a procedure in Duff's book for peening the sight base to tighten it up, and increasing the spring tension. Also, how many clicks up is your 100 yard zero. If it gets up past 12 or 15 the rear sight wont be as stable as if the zero were down at 8 or 10. |
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Read this thread on groups: The Trouble with Three Shot Groups How are you shooting for groups? Are you doing three shot groups and seeing the zero "move"? (See thread) The rifle should group if you put enough rounds in a group, it just may be bigger than you want, and thus an accuracy problem. |
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Without knowing your shooting ability it is impossible to know what exactly is going on. Are you using; NPOA? Muscle relaxation? Breating techniques? Trigger control? Follow through? Proper shooting positions? Gas plug nut tight and marked for movement? just a few variables... |
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Thank you for all the replies - and yes, still wondering about the wandering. This is a pre-ban so it has a flash suppressor with baynet lug. Several shooters have tried shooting this M1A, so it is not operator error. Although the nut behind the stock is most definitely loose! This rifle has been fired with both iron sights and scope, both resulting in patterns rather than groups. Most of the sessions have been 20 round strings. I do not have pictures of targets and probably would not be able to post any for some months to come. If this information helps to narrow things down let me know. |
OK, that's some of what I was getting at. If I understand you, a "pattern" is just an unacceptably large group. If the calculated center of impact for the "pattern" is relatively consistent with respect to the aiming point (see the linked thread for how to calculate this) then you don't have a wandering zero, you have an accuracy problem. Just how large are the groups? And at what range? |
Hmmm, is your scope mount a Springfield brand? They have a habit of shooting loose. it could be a reason for a machine gun beaten zone type pattern. |
Good suggestions for things to look at above. One thing I would add is to remove FS assy and inspect muzzle crown/rifling at very end of bore. Possible that it has been damaged by someone using a metal cleaning rod without rod guide. As KG said, you need to look at a few areas and narrow things down a bit. |
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There are lots of little things you do to a "standard" M1A to make it shoot better. Nothing is the be-all end-all to fixing it. It's all the small stuff + Have the action Bedded + Get the NM Operator Rod Spring Guide + Have a NM flash supressor put on + NM Gas Piston Frank |
Sir, just a few comments in addition to the answers already posted. My first suggestion is to check the sights. The allen screw that holds the front sight to the flash suppressor base sometimes can back out or become loose. Check to ensure it is tight. The spring cover of the rear sight can be loose on the rear sight rack. Make sure the spring bears evenly on top of the sight rack. Check to make sure the rack is tight in the rear sight base. They can and do move laterally if spring tension is to light. The heart of an M1A is the gas system. I assume the gas cylinder of your rifle has not been unitized. You should make sure all the pieces fit properly on the rifle barrel and that the gas plug is tight. Ideally the gas cylinder should be unitized by welding, in conjunction with glass bedding of the receiver. The forward stock ferrule should bear evenly against the lower lip of the gas cylinder plate with some tension between the two surfaces. On rack grade rifles this seldom occurs and can usually only be achieved by bedding the receiver. Try removing the gas cylinder plug and loosen the lock. The lock is the piece that threads onto the barrel that looks like the figure eight. The gas cylinder plate should fit snugly on the splines and firmly against the shoulder machined into the barrel. When you tighten the cylinder lock it should be as tight as you can get it by hand at the seven o'clock position. Tightening the lock further should be accomplished using the gas cylinder wrench intended for the purpose, the one I use I bought from Creedmoor Sports. If the lock does not tighten in this manner, you can make shims in the shape of rings to fit over the barrel up against the barrel shoulder and behind the gas cylinder plate. On the chance that your gas cylinder has been unitized in the customary SA manner, check to make sure the two flat head screws in the rear of the gas cylinder plate are tight. Even if they are tight, take them out one at a time and put some loctite on them and retighten them. Once you've tightened both screws stake them in place. HTH, 7zero1. |
| Just like said above, I'd bet it's your gas system. I'd say there is a good chances the gas cylinder is loose on the barrel. If it's tight, clean the carbon out of the piston and gas cylinder cap. Carbon build up in those two items can blow the accuracy of the rifle until it's cleaned out. |
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