I am going to start shooting service match competitions and want to blow some dust off my old M1A I have not touched in years.

Rifle is a 80,XXX serial number with
NM Flash Hider
Sadlak Spring Guide
Shimmed Gas Cylinder

Other than that its all USGI parts with a chrome lined HR barrel that has printed 1.5 MOA goups at 100 yards with Q3130 when it was in a very tight USGI fiberglass stock.

I planned on getting another fiberglass stock and a 1903 leather sling just not sure if a trigger job and welded gas cylinder is worth the investment.

This is just a stop gap until my budget allows building a DCM AR15 as I am well aware of the upkeep and dollar amount needed to shoot a NM M14 compared to a DCM AR.

A 1.5moa group in a tight stock isn't too bad. No you probably wont see a change unitizing the gas over a shimmed one. Yes a nicer tigger pull really helps. I'm figuring you don't have match sights.  I'd invest in them. I'd be looking to steel bed the rifle properly in whatever stock you figure on.  Std Gi barrel could be improved upon. At least a med contour Krieger would be nice. There is a lot that can be done. All depends on money and interest mainly.

If that will hold 1.5 MOA then don't do anything to it. If you can shoot just half as good as the rifle you will be shooting Master Class scores.

Your rifle is already to go. Work on your standing position and work up a good load for the 600 yard line.

Get the trigger job.  It's worth more than whatever parts you put into it.  Gunsmithing is what will make a difference, not drop-in parts.  Make sure that your sight tension is correctly set and that you get positive movement of the aperture when you reverse directions.

 

Yeah, but if you read it close the rifle did that in a stock it once was in. Apparently it isn't in that stock anymore and there wasn't any further info to how it shoots now in the stock it is in. Total lack of info to guess it all.

I did sell the fiberglass stock that I had. It is currently sitting in a GI Birch which does not lock up nearly as tight.
A rebarrel is out of the question due to money but I forgot to add it has standard sights.

I did shoot a M14 NM rifle in a service match through the military and used M118 circa 1980s production through it.
But I dont know if that ammo is a good start for a GI chome lined barrel.

I though 168 Sierra Match Kings were a good starting point.
The person I bought it from gave me all the dope on the elevation for 147 grain ball so its just gonna be fine tuning from there.

I would take that rifle to a match or two, and see how it performs, then make some modifications. You'll have a lot to learn when you start NRA High Power, such as learning to use your sling, positions, etc. 168 SMK's perform fine at 600 yards.

I only use an LRB M14 and an M1 Garand for XTC and MRP matches, I don't see that I have much more up keep on these rifles than an AR, just my experience, others will differ I'm sure. No doubt the AR's are easier to shoot accurately than the big guns.

For Long Range (1000 yards) I use a match conditioned 1903A3.

I didn't do a lot of testing before I unitized my gas cylinder so I can't really say what it did.  You can tweak the dwell time by taking material off the end of the piston.  You are limited to a 4.5lb trigger in service rifle, you may be close to that now.  The trigger group is fairly easy to adjust with very minor honing.  SA used to do trigger jobs for $25.  The Sadlak guide is a good upgrade, the reamed FS is OK but not really needed.  I did ream mine only because I had the correct reamer.  

I can average 1moa with a Wilson med contour NM six groove barrel.  The same loads in my GI iron sight rifle, (H&R) barrel shoots 1.5-2moa.  That opens to 2.5-3 with DAG surplus.