I have a strange issue going on that has a solution I can't quite put my finger on. TL:DR at bottom.

I've had a DSA SA58 11" for about 2 years now. For the first 1.5 years it shot alright with no weirdness, other than it being so overgassed that DSA wanted to take a look.

I send it in, and they end up replacing a number of parts, including the barrel.

Since that time, it's appropriately gassed, but now I'm seeing wobbling bullet strikes on paper at 25 yards. Not keyholes, but definitely stability issues and slight oval holes.

So I think, ok...maybe it's a 1-12 barrel or maybe there's a crown issue. Sure enough, there's only a crown on about half the circumference of the muzzle. I don't think I'd have problems at 1-12 for full power 147gr, and the crown thing has been somewhat debunked for causing MAJOR issues, but I got to experimenting to try and prove it to myself.

I take it to the range today, and shoot two factory 147gr M80 ball ammos - Magtech and LC. I put up 4 targets and shoot 3 rounds of each ammo into each target with different muzzle conditions: a bare muzzle, one with DSAs flash hider, one with my YHM QD brake, and one with the silencer on the QD brake.

The bare muzzle and DSA devices look fine (normal round holes). The YHM brake is bad and the brake + can is worse. It's bad enough that if I hadn't shot them myself I would have expected baffle strikes.

There are no baffle strikes in the can and no evidence of rounds contacting the inside of the brake. This is also the same exact brake and silencer combo that I used before on the previous barrel that produced no oval holes.

I'm at a bit of a loss at this point. I really wanted to shoot this suppressed. I have one additional brake (new, and slightly different config) I can install and try, but after that I'm a bit light on ideas.

Any other things I should be looking at?

TL;DR - old barrel shot fine, new barrel shoots questionably from a stability perspective, but only on muzzle devices that were fine on the old barrel and show no signs of contact with bullets.

Sounds like a bad barrel to me

That was my first inkling and why I tried the bare muzzle and DSA device (i.e. eliminate everything the barrel, and then add only what it ships and was tested with).

This test seemed to eliminate those as the problem, at least for now. It could still be a temperamental barrel that just doesn't play nice with other devices, but that seems fishy to me. I'll be able to use the other brake next weekend.

I should also add, the strikes on paper that show wobbling are pretty consistent in size/direction of the wobble. LC is basically horizontal (3:00), and Magtech is at around 4:30. I've never known bullets to wobble consistently if they're unstable, only if they're flying consistently and or hitting something consistently.

Chamber or headspace?   Wrong locking shoulder?  problems with chamber cut or finish?

I'm pretty dumb on a lot of FAL specific inner workings. DSA worked it over when I sent it in and I talked to the gunsmith personally about it when he was looking to send it back.

If they tested it with bare muzzle or their device, it's unlikely they would have seen the issue.

A bit of DS Arms barrel history I recall.

Originally DS Arms used surplus military barrels, until they came out with their 11" and 13" barrel, with short gas systems.

At that time there was a barrel maker that had a contract to make L1A1 barrels for Century Arms.

The L1A1 barrels were excellent quality and made of 4150 steel.

The contract prohibited that barrel maker from making any FAL barrels for other sales.

The first DS Arms 11" and 13" barrels were made of 4140 steel and the original plastic hand guards would melt.

DS Arms finally changed the hand guard material.

When the Century barrel contract was finished, DS Arms started selling commercial 4150 steel barrels.

Presumably, these were made by the barrel maker that made the excellent Century barrels previously.

A short time later, that barrel maker was bought by a big corporation that then stopped all commercial sales of their barrels and restricted their barrel sales to military contracts only.

DS Arms then had to source barrels from another maker.

Interesting. My original barrel would have been whatever the factory had in the 2017-2018 time frame, and this replacement barrel would have in theory been new off the line (early 2022). I'm really leaning toward the muzzle device for now, and I have a few other 5/8x24s to try first. I'll post up what happens this weekend.

To follow up, I've been out to the range twice now with a new muzzle device installed. No bullet wobble.

So, it was the other muzzle device that either caused physical strikes or distributed gas in some weird way that messed with stability. I really don't know what to make of it because I've never seen this before and I've run that device and type of mount for more than a decade on probably half a dozen hosts without any issues.

But...there's a first time for everything.

Probably the new barrel has bad threads on the muzzle end, maybe not concentric to the bore, who knows...it showed up and went away when you switched devices because one is likely closer to concentric or has a different internal diameter/etc so it changes how much the bullet is effected as it transitions from the muzzle, thru the device, then out of the end of the device.  

Or maybe it was just loose or something else.  

I would be cautious with a suppressor though based on what you already dealt with.  A nice open muzzle device or FH is probably GTG.