View Full Version : Sight in problems
May 09, 2001, 17:07
I have a STG58 assembled on a Imbel receiver the shoots about 14" low and 2" left at 100 yds with the front site screwed all the way down and the rear sight set on 200m. The kit appeared to be like new maybe even unissued as there was no wear anywhere. Finish was excellent and the stock & Handgrip were near perfect. This is the seventh STG58 that I have helped assemble and all the others took minimal adjustment to get them sighted in. All parts on the gun appear to be STG parts so I don't think it has the wrong sights on it. Everything about this STG is near perfect except it shoots way low.
I'm hoping someone else might have run into this and can share some info here.
Bent barrel? Defective receiver?
Barrel is over-timed. Look in FAQ for discussion. Make sure you look at ALL the FAQ.
Basically, whomever assembled the kit left the barrel after of TDC, when viewed from the muzzle end. When you alight he foresight pin verticallly, the muzzle swings low/left, and that's where they go.
Get a competent smith, the right tools, and have the barrel re-timed. Or, get a Casey Elliot wrench, and re-time it yourself!
May 09, 2001, 17:33
If the rifle shoots left, then the front sight is too far to the right, which means it is undertimed.
If ATDC, you rotate the rifle CCW to bring pin vertical. This moves muzzle in an arc, because you actually pivot the sight alignment plane with the tip of the foresight pin as your center. POI shifts left/low, or CCW when vieweed from muzzle. CW from buttstock.
I did this to myself on the FALO-C. Got to energetic!
Depending on foresight pin height, & your initial 'zero', YMMV.
May 09, 2001, 20:53
How much does one degree mess up the elevation?
That's easy. You simply multiply the sight height (1.75 inches) by the cosine of 1 degree, which is .99985, which gives 1.74973. Therefore 1 degree is a .0002625” decrease in height of the front sight. Divide the .0002625” change in height of the front sight by .611 to convert the 22 inch sight radius into the elevation change per yard; then multiply the product by 100. So, one degree misalignment of the barrel only gives an elevation change at 100 yards of about .044 inch (about the thickness of a quarter).
May 09, 2001, 21:00
OK, nice discussion, thanks EDMII for posting the link to the discussion, I was having a hell of a time finding the FAQ. Did you mean the FAQs at the FAL site or here at the discussion group???
Anyway, I'll check timing and get back to the group. Like I said, a friend and I put seven of these together and this is the only one that does not shoot well. I know, that doesn't mean we didn't make a mistake.
As a note, before I screwed the sight down as far as it would go, it was 16+ inches low at 50 yards. I finally moved up to 25' to finally see that it was shooting low. I'm a little hesitant to think a bit off on the timing would make that kind of error. But, we will see.
I sure appreciate the help here.
They made 4 different front sight pins. 1-4 dots marked on the sight pin base, 4 dots being the tallest. Maybe you could swap it out with a shorter one or heaven forbid grind a little off the top!
Just my $.02
[ May 09, 2001: Message edited by: FXE ]
you should be able to get a clean zero at 25m, 4cm high POI over POA. If not, you are mis-timed, and may have the wrong foresight pin.
May 10, 2001, 04:48
A bent barrel is a possibility. I left my .22 leaning against the barrel for a while and it was off by quite a bit afterwards whereas it was dead on before I did that.
A possibility. Only way to know is w/ a laser boresight device, or a closely fitting brass tube in barrel.
A smith could also chuck the barrel in a alathe for a runout check. But mis-timed is still the most likely reason.
May 10, 2001, 15:51
I don't think that it is a problem with barrel timing as it is only 2 inches left. One degree off in timing would deflect 5 inches left or right, but only 0.05 up. the best solution would be to try swapping parts (front sight, rear sight, lower receiver) with another StG and see what happens.
May 10, 2001, 16:59
Wow, thanks for all the thought you folks are putting into this, it always helps to pool the brain power. Thanks.
One of the other FALs had a very short (looked like it had been shortened)front site. I swapped front sites with it and that was also a contributing factor to getting it at least on the cardboard my target was on.
Something that I've thought about and chewed on for a week or so is the possiblility of a problem where the upper receiver and the lower receiver register and latch. Although I have looked at this indepth and compared the overall fit and latch up with the other FALs and this one looks exactly the same as the others, if there were just a few thousandths error at this point in the sighting radius it would be enough to make a large error down range. I'm wondering if the latching lug on the upper receiver could be a few thousandths to thick???
Also, if the face of the receiver is not perpendicular with the centerline of the receiver threads this would cause a sighting error.
I read the FAQ where someone, put their math skills to work on the timing error and how it relates to sighting. If I had a large error in windage, I could buy the fact that my FAL may be timed wrong. But my error is, for all practical purposes, elevation. A shortened front sight, screwed all the way down, and still cannot get it closer than 12-14" below the POA at 100yds. It seems to me there might be something else coming into play here besides barrel timing. But, I'm still going to check the timing.
Sorry for such a long post.
Don't take this the wrong way, but are you sure that the Pin is all the way down? The reason I ask is, I've refinished a couple Parts Kits, and have ran into a few things that have caused the pin to stop before hitting bottom.
1) Glass Bead Media or other $hit in the bottom of the hole. I looked at it and couldn't tell but stuck a small screwdriver in the hole gave it a twist and dug out crud!
2) Spring too long/thick and was compressed against itself before pin would screw all the way down.
Just trying to help!
May 10, 2001, 23:41
Your rifle wouldn't happen to be a CENTURY rifle would it? If it is, then it is highly likely they put the wrong rear sight on your rifle.
Some Century rifles are the worst sort of hodge-podge FrankenFAL abominations. If you have a tall gas-block inch-pattern barrel, and it is mated to a metric rear sight, then you need an Argentine/Izzy rear sight...or you can just shoot at close-range targets with the sight on the most distant setting.
High Israeli/Argentine Rear Sight Assembly,
Part #106-A - $30.00
(or just the aperture for $10.00 at http://www.dsarms.com/SA58Rifles/FALschematic.htm )
If you have a Century, you better go ahead and replace the gas piston now. It will be the next part to fail.
May 11, 2001, 21:15
You know there was a lot of crude in the sight hole, but that was flushed out when I cleaned the rifle before assembly. Spring to long? Not any longer the the springs in two of the other FALs.
Not a Century arms gun. This gun appeared to be unissued, it was that good a kit. There was no wear on anything. The finish on the barrel was as good as the finish anywhere else on the gun. I'm 99% sure this is a kit from one gun.
Farmer from Hell
May 12, 2001, 12:08
I think its shooting too low to be just the barrel timeing. Its got to be something more simple. I almost want to say the barrel is bent [gasp]. This could explain why it isnt shooting high at 25 yds. If all the parts came from the same demilled rifle then its unlikely you have the wrong rear sight.
May 12, 2001, 13:57
I see a problem with the "bent-barrel theory."
If the barrel really is bent, the incident causing the bend must have been some random traumatic event. What are the odds that the bend would occur is such a way as to cause the shots to go low on an almost pure vertical path? Not very likely.
overdriv says there was a lot of crud in the "sight hole." Uhhh...like maybe from a sandblaster? Sounds like somebody refinished a miscellaneous-parts kit to me.
Try the Izzy/Argie rear sight.
Remember, .006" movement of either sight will move your point of impact one inch at 100 yards.
Originally posted by Uncle Buck:
<STRONG>I don't think that it is a problem with barrel timing as it is only 2 inches left. One degree off in timing would deflect 5 inches left or right, but only 0.05 up. the best solution would be to try swapping parts (front sight, rear sight, lower receiver) with another StG and see what happens.</STRONG>
I was mis-timed about 2-3 degrees. It was hard to see w/ the naked eye, and only the 'long tubing trick' showed me the difference. I was about 6" low and 4" left.
Re-timed to TDC, problem solved.
May 13, 2001, 23:16
The kit in question here came to me as a sort of peace offering after I bitched to our supplier about one of the first kits having missing parts. He said it was one of his best. Aside from shipping marks the kit looked new, unissued. But like all the kits from this source it was filthy dirty, like they had set around for months, years and had dirt blow in on them. Any oiled part (practically everything) was crudy with grit and dirt.
The kit is not a mumbo-jumbo of parts. I'm certainly not ruling out the barrel being mis-timed, we aren't experts, we could have botched the timing. But, we aren't rookies either. I only throw out my ideas so you folks can chew them around and maybe share you're thoughts and expertise. As soon as my machinist friend gets back from vacation and we get time, timing will be checked for sure. Hell, I hope it is timing, that would be easy to fix.
Again, I sure thank you all for all the thoughts and suggestions. I'll for sure report back when I resolve the problem.
Did you add a muzzle brake or shorten the barrel or both? My Century Stg sights were perfect until I had the barrel shortened and a muzzle brake added. It started shooting way low, I changed the rear sight to an Izzie
part to fix.
October 07, 2001, 12:12
As a follow up to this post, I'd like to thank everyone for their input, and offer this information.
I checked the timing and it proved to be as close as humanly posible. The front site was checked and double checked, no problems.
After much deliberation, I decided to try to bend the barrel to see if I could remedy the problem. Something had to be done as the rifle was useless as it was.
I put the barrel in my press supported at the flash hider and the base of the barrel/receiver junction. I installed a dial indicator under the barrel just behind the gas block, where I had decided to put the pressure for the bend. I was looking for an initial deflection of .010". I put .100" deflection in the barrel and released the pressure. The indicator returned to zero. I continued in .025" deflection increments till it finally retained a .018" deflection with a .250" push. More than I wanted to start with but that is what I got.
At the range, with the shortened front site all the way down, the first two rounds printed 10" high. I made an adjustment and the next two round printed 8" high. I made a larger adjustment and it printed 4" high. At this point I decided to install the original length front site. The next two rounds printed 2"high, pretty good guess. Another adjustment & two more rounds put it in the bullseye. Four more rounds resulted in two more holes in the bullseye, the other two just opened up the other holes.
So, it appears this may have fixed the problem. Maybe not addressed the root of the problem which I have yet to figure out, but from my initial outing with it, it looks good. Will put it out to 100 & 200 yards as soon as time allows, can't wait.
Radical surgery for sure, but maybe one needs to look at it as straightening the barrel instead of bending it. :) The one thing that bothers me about the procedure is that the defection most definitely occured in the area of the gas block. You can't see the bend but I'm sure the barrel would take the defection at the smallest, weakest part of the barrel. If it shoots good out to 200m, I'll be happy and feel very lucky.
October 08, 2001, 04:47
Spring too long/thick and was compressed against itself before pin would screw all the way down.
Whooa! Hold the phone, Jack!
Are you saying that there's supposed to be a spring under my front sight? I've been messing with my front sight since the day I bought the gun. It loosens and turns when I'm shooting. Finally, just the other day, I got sick of carrying a screwdriver with me to go shootin, so I sighted it in where I wanted it and permatexed the unholy bejeebies out of it.
NOW I find out there's a spring that apparently holds the tension.
It's true what they say - the stupidest question is one that isn't asked.
October 08, 2001, 06:57
Depends on the gun you have - if it's an STG-58 type then definitely yes. I don't think the L1A1 type front sights have a spring (or I'm missing one, too) :D
October 08, 2001, 15:08
You've got a few choices, yankytrash. Somebody must have the little spring in stock... Gunthings or L/FN for example... for a buck or two. Or, you could get DSA's $30 spring pack and enjoy new recoil, gas piston, sear/trigger return, and firing pin springs... along with the otherwise useless springs you'd never need or wear out in 100 years, like your missing front sight spring.
Or just "stick" (haha sorry) with the Permatex. In the future you may have to "remove" the front sight with a drill, especially after a few hundred rounds' worth of gas fouling forever glues it to the gas block... but as long as you keep using the same ammo, you've solved your own problem for all "intensive purposes."
October 08, 2001, 17:14
Very funny, Radio ;) (you had to be there).
Luckily, my local hardware store pulled through for me again. Found the perfect spring, it was just a little long. Cut it and it fit right in place.
Now I wonder if the set-screw will stay?...
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