I bought a new 16” DSA 58 in 2004. I have not shot it more than a few hundred rounds due to a vertical stringing problem. I should have contacted DSA immediately but one thing led to another and the rifle got shuffled to the back of the safe. It has been out to the range only a few times since. Because  of the stringing it just isn’t much fun to shoot. The purpose of my post is I read on here years back a trouble shooting process for diagnosing this. Fire a mag with single rounds one at a time to check for better group, how to check bolt/carrier fitment, how to check the gas pistons not too long, etc. I have searched in the archives, can’t find it in the 20 pages of old fal topics. Can anyone point me to this, or have a good step by step for diagnosing FAL accuracy, specifically vertical stringing problems with the FAL?

And to all those well meaning soals, yes I am aware the FAL is not very accurate, I am an experienced shooter, it’s not a practice issue, two separate proven optics used, both mil surp and commercial ammo tried, all that. The rifle has a mechanical vertical string problem, to the tune of 8” up and down at 50 yards off bags with a good scope on a DSA mount, warne rings, and no the scopes not loose.

Thank you to any who try to help.

Vertical stringing is a known issue with the FAL, but 8 inches at 50 is absurd. It should hold 4 moa or so at 100 with decent surplus.  Chamber and fire one round at a time individually from the magazine.  Take the mag out when firing.

I recently got a lot more spare time. This problem is on my short list now. Will be addressing it soon, that’s why I’m looking to do it all in one range trip. One thing I read but don’t remember was the gas piston length, seems when they reused some of the surplus Bbls they were trimmed and the gas pistons ended up too long. Stuff like that I remember seeing but just don’t remember all the details of what/ how to check.

I would be very happy with a 4” group at 100.

And I realize my OP was not perfectly specific, the gun is a DSA STG58. The ones they used some surplus parts to make.

It is a known issue with the FALs to have vertical stringing.

I have a G1 clone that shoots tight. I just do not use the removal flash hinder that came with it. To my understanding, that would throw the groups to a large group in the size of Texas.

In for info. My FAL is somewhat disappointing with surplus, but shoots ok with reloads (and decent with "match" reloads).

I've had some luck with messing with gas system clicks, but I admittedly don't feel like I have a solid grasp on how to tune or check like what's described in the OP.

I don't have much experience with these rifles, but a couple ideas I have based on my perverted way of doing things.

How does it group with the gas plug in the "off" position?

If the gas piston length is a likely suspect, how about getting hold of another piston to try for comparison.  If it shoots the same, try shortening the extra piston slightly and see if there's an improvement.  Either way, your original piston remains untouched.

Thanks. I have shot different ammo types and weights, different scopes. I have not tried the gas plug off, one round at a time in the mag, or anything like that yet. Just trying to get my info together then I’ll take a half day when I’m not rushed and go try to narrow down the cause

With the tilting bolt design, the varying upward pressure on the bolt from rounds in the magazine is known to cause verticle stringing.

Some ideas from when I used to build these:

1. Make sure your gas tube is fully screwed in and that the retaining pin is secure. This interface is a pain in the ass.

2. Track each shot's PoA vs. PoI. Sometimes you get a problem where rounds from one side of the magazine hit a different PoI than rounds from the other.

3. Measure your headspace. This could be set anywhere from 1.630" to 1.638" and still function fine, but it could be big and sloppy. I had better luck with tighter headspace in the FAL (1.632").

4. Remove the muzzle device and shoot if you haven't. That Stg. 58 device is the shittiest one for accuracy in my experience.

Vertical stringing is a known issue and has been for quite some time. Check out the British research on the subject. The FALfiles used to have quite a bit of info on the subject as well but I don’t know if it survived the crash. Yours sound a bit extreme, 8” at 50. Most FALs will shoot 4-6 MOA.

I thought it had a positive impact on group sizes due to the way it affected the harmonics. I really don't remember anymore, and only have combo devices and therefore can't test the theory. The Portuguese m962 clone I put together with a bare muzzle was a great shooter, so you may be right.

As others have said..Vertical stringing is pretty common..I see it in nearly all of my targets..
These were all shot from bolt release and then 5 rounds within 45 seconds and all on a rest (resting it on the front of the receiver)...Except the last one..lol

HSM 168gr Sierra HPBT circa 2012 or so early in my fal experience..


HPR 168gr HPBT out of the same rifle and same range trip..I dont think this company is around anymore..


Same rifle but years later and a locking shoulder change (And nearly blowing up the rifle handloading)
Federal Fusion 165gr


Hornday Blk 168 Amax (same target as the fed Fusions.


Group on the upper left is the wifes..Mine is the 4 shot with the vertical stringing..(Checking zero based on where we rested the rifle.)

The Steyr device could actually be the best on average for all I know. My examples shot better without it.

Now that I think about it, Steyr kits never shot as well as others for me despite the internet renown.

I agree. I had six and they didn’t shoot as well as my one IMBEL.

Thanks all for the input

Take the upper off, remove the dust cover, put the bolt/carrier back in and move it to the locked position.

Now see if the bolt/carrier combination in this position can move up or down.  If so, how much?

Report back.  Solutions vary.

Im just curious what the solutions are.

It depends on where the slop manifests.

If the bolt is loose in the carrier, material can be welded into the carrier to force the bolt to a repeatable lower position.  That's the easy one.

If the slop is in the rail cuts things are tougher.  You basically weld material onto the tops of the ears of the carrier.

Sometimes, if you have multiple set of bolts/carriers you can find a combination that minimizes the slop.

You could also weld some material to the flat on top of the ejector block.

Basically, you have to remove the slop when the bolt/carrier is in battery.

FALs can sometimes be made more precise by adjusting the mating surfaces between the bolt and carrier to better center rounds locked in the bolt with the chamber. Basically, FALs will sometimes end up having a bolt that is holding rounds off center/tilted up to the chamber and can also vary some from round to round. You want a solid and consistent bolt and carrier lock up and a bolt that ends up level and centered with the chamber when the top round of the magazine is applying pressure. I'm not sure I would blame the tilting bolt for vertical stringing though. An off center bolt can cause rounds to be held with tilted pressure inside the chamber and bullets to enter the barrel unevenly which causes an unbalanced bullet. Once an unbalanced bullet travels down the entire length of barrel, precision will suffer, but it will suffer in any direction, not vertically alone.
If only vertical stringing is happening, I would blame barrel whip or vertical barrel movement rather than the bolt lock up. I've never owned a 16'' FAL but I would assume barrel whip would be minimal due to the barrel being shorter than usual?

Thanks for the replies. I was injured since my first post requiring surgery. Long recovery,  can’t drive, etc… troubleshooting and addressing this has been significantly delayed.