SIG Talk banner
  • Notice image

    SigTalk is a forum community dedicated to SIG Sauer enthusiasts. Come join the discussion about Sig Sauer pistols and rifles, optics, hunting, gunsmithing, styles, reviews, accessories, classifieds, and more!

A couple of 516 Issues

9K views 61 replies 19 participants last post by  Pit 
#1 ·
First let me say this is my first AR15 style rifle and that I cleaned all the factory gunk out and relubed it the same day that I bought it. I have about 500 rounds through my new 516G2 rifle (03.28.13 build date) and I'm having a couple of annoying issues. Let me say for the most part the gun performs very well. It is accurate, goes bang every time you pull the trigger (at least when a round is chambered), and has a strong ejection.

Issue #1:
I can almost never get the rifle to lock back on the last round. I'm using Federal white/brown box 5.56 55gr, PMC xtac 55gr, and CCI Speer Lawman 55gr. I'm using brand new Pmags (gen2 and gen3) and have tried about 6 of them (including the one that came with it). I don't have any USGI mags currently, but I would have figured the new Pmags would have worked well. After my range session yesterday I can only remember it locking back maybe twice. I have also tried using a new Sprinco enhanced spring and ST-T2 heavy buffer with the same results. I also have tried the normal and adverse gas settings with the same results. I am just having a tough time getting it to lock back after last round.

Issue #2:
I have an issue getting the rounds to cycle sometimes. It's not all the time, and it seems to happen most with the CCI Speer Lawman 55gr. Changing the gas setting to the adverse setting seems to fix this issue 100%, but then Sig recommends not to run this all the time. I'm not using **** ammo (at least I don't think I am). I would think the ammo I'm using would work fine on the normal setting. And some people say this issue might be a break-in issue and eventually the gun will loosen up. Well I'm probably at about 500 rounds now and still having issues. Ammo is not cheap anymore or readily available either.

I called Sig CS about 30 minutes ago and told them about the issues I was having. The first thing she asked me was what kinda ammo I was shooting and I told her Federal white/brown box, PMC xtac, and CCI Speer Lawman, and then she said what about ammo weight...and then I told her oh, they are all 55gr. Then she said that was probably the problem because this gun is really made for 62-65gr ammo. I was kinda puzzled by this because I have always thought that the 5.56 55gr brass ammo was pretty standard stuff and should be easily handled. I told her this info about not using the 55gr ammo was not in the manual and she said she was aware of this and that she wishes it was in the manual. She said that the 1:7 twist barrels are always going to do better with 62gr+ rounds. Has anyone heard this/agree with this or is this complete craziness? I told her that I would try some heavier rounds to see if that made a difference before I decide to send the rifle off. I mean she seemed nice and said that I could always send the rifle in if I thought something was wrong with it, but I figured I would post on here and see what others thought.

(I'm also starting to see reports on the internet of people having similar issues as me with their 516's and some are having a lot worse issues.)

This is my first Sig and I'm hoping I can get these issues resolved. Thanks!
 
See less See more
#2 · (Edited)
Just my two cents, not sure if it'd help at all

Have you tried using generous amounts of grease for the internals, buffer tube included?

I suspect that SIG rifles are really "tight" from the factory.
 
#3 · (Edited)
Just my two cents, not sure if it'd help at all

Have you tried using generois amounts of grease for the internals, buffer tube included?

I suspect that SIG rifles are really "tight" from the factory.
I wouldn't say overly generous, but I'm using Fireclean which is a thinner lube to begin with (not really a grease). I have put multiple coatings on it since it bonds with the metal.....spring, buffer, bcg, charging handle, etc. It's not overly wet, but it's not dry either.

I will say this though...my last trip to the range I put a few extra drops all around the bolt area and it was definitely wet then....still didn't seem to help.
 
#6 ·
Have you removed the Gas Valve and cleaned the inside at the very bottom where the cross-connect gas-port hole is? That hole is only about 0.015" diameter and if is restricted with carbon or wet cleaning agent, the pushrod will not cycle strong enough to force the bolt carrier back to clear the empty magazine.
 
#8 ·
I'm not exactly sure what you are talking about here....are you talking about the gas adjuster which disassembles from the push rod that has a few diff size gas holes (for the diff gas settings)? If yes, then yes I have cleaned all this and sprayed with degreaser and made sure those holes are clear.

If no, then please tell me how I can do this.
 
#7 ·
Humor me and try some grease.

I like the way it leaves a thick "layer" for the moving parts to glide on.

At the gas port - no grease there. Just a drop of oil.

I know I'll get some flak for this - but my chambers are always oily. The grease separates, and oil creeps to these areas.
 
#10 ·
I guess I'll try running some heavier bullets through it the next time at the range to see how they do. It's possible I didn't clean the pushrod/gas valve assembly well enough. I took it apart, sprayed with degreaser again, and made sure the 3 gas settings holes were clear as well as the little hole below those.
 
#12 ·
That's what I figured....accuracy of heavier bullets make sense, but I don't see how the 1:7 twist would affect cycling. The gun is definitely pretty accurate for me. I'm only an "ok" marksman, but was easily getting 1-2" groups at 50 yards with various 55gr loads.
 
#13 ·
Yes, but is not it is not a gas adjuster, it is the Gas Valve as identified in the manual. There is one small hole at the very bottom. Have you removed the buffer assembly and removed the heavy preservative grease from the spring and buffer so as the buffer is not sluggish? Clean out the inside of the buffer tube with a 10 gage shotgun brush with a few patches wrapped around it. Wipe off the surface rust from the spring coils and allow to dry. Apply a light oil spay (Rem Oil?) on the spring and buffer and reassemble. In the "old days" we used WD 40 for almost everything. Also, inspect the gas port hole in the barrel.
 
#15 ·
With the Gas Valve and Pushrod removed, you can see the barrel's port hole as you look into the Gas Valve bore. The expelled gas exits the barrel's port hole and enters the Gas Valve chamber/bore. If you clean the rifle's bore with solvent without removing the Gas valve and Pushrod, solvent can dilute residue powder and block the port holes.
 
#18 ·
Ok I think I've inspected and recleaned everything again to the best of my ability....Gonna go to range one last time (hopefully soon) and fire some more 55gr ammo and then also try some 62gr ammo as well. If that doesn't work any better guess it's time to ship the rifle back to Sig and hopefully it comes back quickly.
 
#19 ·
What method did you use to clean the inside of the Gas Valve? A bronze brush soaked with solvent? Have you removed the carbon from the contact surfaces of the pushrod where it rides inside the Gas Valve? A light film of white lithium grease on the mating surfaces of the pushrod, the mating surfaces of the bolt carrier-to- receiver contact points, and inside the bolt bore of the bolt carrier.
 
#20 · (Edited)
For the pushrod/gas valve I just sprayed with degreaser, used a brush to scrape off carbon etc., and wiped it down. I didn't put any lube on these parts this time.

Charging handle, bcg, buffer tube, buffer spring, buffer, and a little bit around the hammer/sear...these I have lubricated with Fireclean.
 
#21 ·
I believe the buffer tube is to be run oil/grease free.

Does the bolt lock back when an empty magazine is inserted & you pull the bolt back manually?

Does the weapon cycle rounds without issue if you cycle them manually?
 
#23 ·
Hmmm, that says quite clearly (to me) that the bcg is not going far enough back when fired. So you have to visualize the process & figure out what is causing it. So with that I would want to investigate if it were me:

#1 - That the normal position gas port is drilled to the proper size (since you said adverse works 100% & there are no obstructions).

#2 - That the ammunition is of proper pressure.

I mean if it works manually pulling it back perfectly & on adverse perfectly it can only be a matter of pressure being applied to the head of the piston being insufficient....I.E. not enough pressure to overcome the action/tension in the springs. That would be restricted gas flow or insufficient gas flow. I'm no expert but physics are physics & common sense is common sense. As always, just my humble opinion.
 
#26 ·
Be sure to let us know what you or whoever fixes it finds please.
 
#27 ·
Yep I will let everyone know. I'm going to try to get to the range again soon (maybe this weekend ?!?) I'm thinking that I'll run into the same problems though even after cleaning again and trying out some 62gr ammo....Pretty sure Sig will have to fix this which they obviously should for a new $1600 rifle.
 
#28 ·
Have you called them & asked how big the port is supposed to be & measured it? It really has to be simple if the springs aren't wrong, it's clean etc.....everything you said you already covered; it has to be a gas pressure issue.
 
#30 ·
The last thing you need is heavy grease deposits between the buffer spring coils when the spring is being compressed, or a "sticky" substance adhering to the OD of the buffer when it cycles. After you inspect and clean the buffer assembly/group for the first time, there should be no reason to disassemble it again, unless of course the weapon falls into a rice paddy and gets full of water and poop.
 
#31 ·
I have pumped about 120 rounds through mine since I got it with 100% flawless operation. And I have not even shot 5.56 NATO rounds with it yet. I've used .223 55-62 and 69 grain Fiocchi and Winchester. I just clean it with Hoppes #9 and then wipe all working parts down with Outers gun wipes. That's the same stuff I use on my bolt action rifles. The Pmag that came with it works great. But it does sound like something is not right with yours.
 
#32 · (Edited)
I've put approx 120 rounds of 223/556 through mine and it has performed flawlessly with the exception of one FTF.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top