Several months ago I had an AAC muzzle break installed on my DSA SA58. I finally took the rifle out and at 25 yards, I found my shots were going WAY left. I had to shoot to the right of the target to get something to print. Even shooting off with a bench rest and irons. The gunsmith that had done the work is no longer in business. Could the barrel have been re-installed off center?

Look for copper marks on your end cap.  Sight down the bore from the chamber and see if you can see one side of the end cap  or a baffle, more than the other side.  

Could be non-concentric threads, or a bad thread relief cut.  Look at the rear of the mount and see if there is any gap at the barrel shoulder.

Yeah, this happened to me.  Not the same brand.

Huh, L I B
The muzzle break is off and I see faint copper marks on the on one prong of the muzzle break. IN THEORY this should be an easy fix (It usually happens to be the contrary with me).

Can you be more specific about the work your gunsmith did?  Was the barrel re-threaded?  Was it actually removed?  The FAL barrel is threaded into the receiver to (I believe) approximately 120 ft-lbs of torque.  It's going to be difficult to install it off-center.

Just changing muzzle devices can drastically affect bullet impact.  Usually this is due to a combination of the how gas moves differently around the bullet as it leaves the bore with different devices and the torque applied while installing the muzzle device affecting the barrel harmonics.

I've seen a 6" lateral shift on one of my SBR guns just by changing from an A2 flash hider to a Surefire brake.

The SA58 muzzle break was removed (I don't know the exact process he needed to do to complete it). An AAC Blackout 51T 9/16-24 thread Muzzle break was installed and re-parkerized (again, his exact process is unkown). Don't know if the barrel was retreaded for the new muzzle break or if the existing threads were used. I'm now concerned that the muzzle break CAN'T be adjusted and a new barrel would have to be installed.

If the threads are bad, you could have a pro cut and re-thread. Unless you "need" a full length barrel

It's a 16" barrel. Which means I don't have much to work with. I'll still need a pro to take a look at it for possible solutions. I wish the gunsmith that worked on it was still around. Beings that its their mistake.

Sorry to hear that I know it sucks!

I've been threading FAL barrels for 15 years now, and usually when this happens it's because the barrel was threaded without using a lathe and the hand tools used (even if it has a bore guide) thread the barrel out of line i.e. not concentric, if your brake has a tight inside tolerance it wouldn't take much for the bullet to be able to strike the inside of the brake. I always take the barrel off the receiver when I thread a barrel. Unless the receiver will fit through the spindale hole then I just put the whole thing in the lathe. Point is to be totally concentric which is very important when using a suppressor, or a brake with a tight tolerance on the ID, a lathe should be used to cut the threads to make sure they are concentric.  

You can take the brake off and shoot a few shots and see where it is hitting without it, but if there are copper marks on the inside of the brake they are from bullet strikes.

It could be your gunsmith didn't thread it off center and it was slightly off prior to you giving it to him because if you had a flashider on it before most likely the ID of it was much larger and it allowed plenty of clearance so you would have no bullet strikes.

Good news is, worst case would be just put a muzzle device with a larger ID on it.

Forgot to put that being it was a DSA "muzzle brake" most likely it was a ban gun and had the brake was soldered on, he could have overheated the barrel trying to get the brake off and it warped a little.

Nuts, I do remember him saying that he had to do that. Guess I'll have to see where the rifle shoots without the break and go from there. I really liked my plan of putting a can on my DSA.

Some FAL barrels were also made with their bores not perfectly centered too.  A cut back barrel and someone cutting threads referenced off the outside diameter instead of the bore would show problems too.  

I've seen more than one post of FAL files about Imbel barrels IIRC having this issue show up when cut back.  No personal experience like JMB's encyclopedic first hand FAL work.

Does ADCO work on them? If so then ADCO is the fix for your FAL.

Steelon steel, those would be Argentine barrels that the bore is off center.

I am pretty sure Sarco is the one who was selling them.

Problem is no way to tell until you cut the barrel.

I have cut, crowned and rethreaded a few of those for customers and actually when test fired the slightly off center bore didn't effect POA/POI  but YMMV.

So looking at options. Like ordering a new barrel from DSA? Or finding an another FAL barrel from another Vendor to be cut down and threaded with my break installed? Looking at different gunsmiths like ADCO or Arizona Response Systems?

...Someday, All my weapon projects will be done and all them will work flawlessly...

Thanks for the info JMB.  

Good thing I'm not big on cut back barrels, i like them OEM even though they're still clones.

Well, The Fal went to Gunplumber and the previous gunsmith cross threader the muzzle break on crooked (...hurray...)  So now its in good hands and will be made right. Plenty of time before my can paperwork gets here.