It's a base Springfield M1A in a Sage chassis.  Spent $2k on it. as it had been unfired (supposedly).  I figured, 'Hey, slightly used gun + chassis is over $2k...decent enough deal' and it also came with a couple accessories that should have pushed the price up a few hundred more.  After taking it out to the range and shooting it, I can't be satisfied with its accuracy.  Actually shooting it was a pleasure, just not satisfied with the overall performance.  This is even after knocking down expectations compared to modern semi-auto rifles. I already have a list of upgrades that is approaching the cost of a Springfield M1A.  I should have gone the, "buy once, cry once" route.  Still debating getting rid of it and spending the money on a Fulton Armory.  What say you experts and enthusiasts?

I don't know what your criteria is for "not satisfied with its accuracy" but speaking to the generalities, the M14 system shoots to battle rifle accuracy, ~ 4 moa @ 100 yards.  Most battle rifles are designed to be rugged, reliable, and accurate in that order. Repeatable accuracy depends on controlling variables, and the M14 system has a lot more variables than .308 ARs, and are usually less accurate. A nice tight DPMS or Armalite .308 will run sub-MOA with the right loads, but a M14 needs work to get it there, and more work to keep it there.

I looked at that Sage chassis online, and I'm not convinced they are building to competition specs.  To get the M14 to shoot consistently under battle rifle accuracy, you need a rigid full stock that is at least skim bedded, and more realistically, the receiver needs to be double-lugged and secured to the stock, + bedding.  Then there's a host of other refinements & tweeks to put the holes close together, but that's beyond the scope of this reply.

and here we go...

OP, I cannot speak to the Sage stock.  If you buy an M1A that is in a wooden stock like some Fulton Armory models might be, it's not going to reach it's full accuracy potential.  You'll need to have it bedded, or put into a tight fiberglass USGI stock.  But it won't require double-lugging and bedding to shoot less than 3-4MOA.

I have several M1As that shoot 1" at 100 yards, consistently, with Portuguese surplus ammo (which is very accurate ammo for milsurp), in tight fiberglass USGI stocks.  I've also done the other tweaks, such as unitizing the gas system, using National Match front and rear iron sights, and replacing the oprod guide with a National Match one.  They are not going to be sniper rifles or compete against a free-floated AR.

Buy a box of Federal 168 or 175 grain Gold Medal Match ammo and get back with us.

I have never been happy with FMJ ammo in any caliber. It's designed for penetration, not accuracy.

Clean the barrel thoroughly then shoot for groups.

That's what I was shooting, 168 to be specific.  Was shooting about 4.5 MOA.  This is scoped btw.

OP sounds like something is loose and rattling. Check your flash suppressor and the front band.

Or, you may have a barrel with some corrosion near the muzzle.  I had a SOCOM with corrosion from the factory on the lands and grooves an inch inside the muzzle. It was replaced under warranty

Or your crown may be dinged.

I agree something is probably loose. Usually it's the scope base and/or scope rings, but there are many screws on a Sage chassis stock.

The Sage EBR stock eliminates any need for bedding. Double-lugged receivers used to be fairly common in CMP matches 30 years ago, to obtain greater longevity from a bedding job. That's really all they accomplish. If you're not a really high volume competitive shooter, you can bed a standard receiver in a traditional stock, and it'll last a long time. Removal from (and re-insertion into) the stock is what wears down the bedding.

I have one that'll do 0.75 MOA with no bedding (in a GI walnut stock), which is exceptional. That's usually about as good as they get.
They served as sniper rifles for many years, but an AR10 type is way better.

For yours to only do 4.5 MOA with 168gr there is something wrong somewhere.

Sell it and buy an AR-10 or SR-25 or something

The Sage uses a "barrel whip" adjustment screw since the gas system isn't held secure like the original GI stock holds it. The screw may have come loose, allowing the barrel to move on firing.

https://www.youtube.com/watch?time_continue=1808&v=wtIW9xHhKIY

I'll check the chassis over to make sure all is well.  Unfortunately, I won't get to verify for a little while.

I know nothing about the Sage stocks.  But if that's the case, then it's possible that the gas system could be sliding back and forth.  You might want to remove the gas system and lightly peen the rails on the barrel where the gas system slides on, so that it's held on firmly.

This.

I was an Armorer back in the 60's for a while and had some 350 M14s to take care of.  I took many to the range to test after servicing them and most were 3-5 MOA shooters; just like they were designed to be. I love the design and so I bought a NIB M1A 7 years ago, however, mine is in the traditional wood stock that I've shimmed and added a NM rear aperture to the rear sight base to give me NM sights (at least in vertical adjustment).

As the last number of years Springfield have included NM front sights on all their M1As as it's cheaper to inventory a single item than two different ones.  Using my 168grn handloads, it will produce 1.5 MOA groups at 100yds which is plenty accurate enough for me for an irons only rifle.  In fact, I use it to shoot at a 12" steel plate at 400yds so it's accurate even at mid distances.

As has been said, the basic design of the M1 Garand / M14 operating system is designed for ruggedness and reliability before accuracy as it's first and foremost a Main Battle Rifle. To get 1 MOA or less requires a tuned precision shooter, not a Battle Rifle.  I've found that the most cost effective thing to do is to get a NIB M1A and put a National Match rear aperture in it giving your NM sights and then shim the stock.  Both are do-it-yourself projects that can yield good results when combined with precision ammunition.

Ammo, groups, optics?

OP you might also find more info at The M14 Firing Line forum.

The chassis system eliminates any need / requirement for bedding because its a chassis......
Perhaps you should educate yourself a little more on how the Army actually puts them together because they get very good accuracy using stock M14 receivers and USGI barrels.

M14 EBR

I have a Loaded that's sub 2" MOA-ish. All I've really added internally was an NM spring guide. I never really expected it to be much better than this. It's scoped and setup to simulate a poor mans USMC DMR. I love that gun

I'm ordering a few new drills and other tools this weekend.  Going to do a break down and scrub of the proper parts and reassemble.  I may get to shoot it a couple weeks after my kid is born, but we'll see.  I'm noticing how small the market for M1As is currently therefore selling it is looking less likely, but it's still an option.

Pull off the flash suppressor (there's a tiny allen-head set screw beneath the front sight base that holds the castle nut) and take some digital pics of the crown and bore for us.

Not to come off as an ass but are you sure the shooter is not the factor?  Have you had another shooter or put the rifle in a sled to remove as much human influence as possible.  Hell I have bad shooting days and it seems I cannot hit the broad side of a barn.  Also try different ammo just because you try one type and the rifle does not produce the result you expect does not mean it is not ammo related.  My SCAR will shoot 1MOA groups all day long with 168FGMM but if I move up to 175 the groups open up to 2MOA easy.  Also my M1a loaded does not shoot BH 168 match ammo all that great but devours FGMM 168 or 175.

Meanwhile i put together a M1a scout squad "DMR" kinda setup, rail, 4-16x, bipod, check riser yada yada, Over a year ago and i havent even gotten to shoot it yet :(

Damn OP !!!!! Sorry to hear about your rifle but something is off with your rifle somewhere and is not representative of most M1A rifles. My scout is shooting anywhere from 1MOA to 1.5, 1.75. I'm not an MOA all day shooter so part of that is on me. Someone might have buggered up that build somewhere installing it in the chassis. You might want to tear it down and reassemble it ?

I plan on pulling things apart and putting them back together this weekend or next week at the latest.  I have pretty much all the tools now.  I do want a different muzzle device, but I'll save that for a nother date.

Prime suspects (since the rifle is in essence, bedded):
1.  Scope or mount
2. Scope or mount
3. Scope or mount
.
.
9. Scope or mount.
10.  Something else.

Mounts are notorious for disappointing.  The M14 just isn't well setup for it.

How's it shoot with iron sights?