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516 Failure to Feed

18K views 48 replies 22 participants last post by  Drago 
#1 ·
I recently bought a new 516 Patrol. After a few hours on the range I am very disappointed. FTF frequently. I load my own ammo and had a box of 50 grain to use up. From reading other postings Im not thinking it is an ammo issue.
I have other ammo to try being 60 & 65 grain but Im not sure the problems will go away.
I also have a 716 Patrol that I use my loaded ammo with and have had no issues.
I welcome advise.
Thanks
 
#2 · (Edited)
I just shot my 516 yesterday, Sunday 28-April-13, using only reloaded ammo and not a single failure of any kind, 55gr Winchester FMC pushed with 25gr Varget & 69gr Sierra Match pushed with 24gr Benchmark.
I don't know what to tell you that you don't already know. Perhaps try different magazines?? Try sizing the cases a little more?? I have found resizing & proper trimming can make a big difference. On another note: I doubt that you will get good accuracy performance with the lighter bullets. Shooting side by side targets I found the 55 grain bullets produced groups twice the size or the 69 grain bullets.
Good luck in working through the issues.

PS: I shot about 130 rounds in the 516 and another 50 in an R556, and 55 rounds in a 716.
 
#3 ·
FTF Issues

First time to the range yesterday with my brand new SIG 516. First AR15 for me. Bought the SIG based on reviews I read and SIG reputation. So, I fired only 12 rounds total. The first 5 or 6 no issues, but then failed to feed next round. Had to manually feed next several rounds. Using Winchester 5.56mm 55 grain ammo. Gas valve in postion #1, did not attemt to use position #2. Decided to stop and clean everything. We'll see next weekend if that resolves my issues.
 
#4 ·
During the break in period if you are using .223 rather than 5.56 and a grain of 55 or less I think it's recommended to set the 516 to Adverse conditions. I had a few FTF issues on my gun and when I set it to Adverse the problems went away. I only have about 60 rounds through the gun so far so I'll keep it in Adverse for a bit longer.

This is supposed to be unnecessary if you are using 5.56 (usually a bit hotter and heavier bullet) or if you are using somewhere like 65gr bullets or above. In any case, I don't mind keeping it in Adverse if necessary for a while.
 
#5 · (Edited)
My r556 does not like the stock mag: Had a total of three stove pipe ftfs. The ftfs occurred on the last one to two rounds in the mag, wherein the cartridges and the magzine follower went vertical ***!?!?? The standard gi metal mags had ZERO issues. I would recommend using mags other than the stock unit that came with the rifle. If this fails, then contact Sig for the warranty work on either the mag or the gun. Hope this helps. When it shoots and functions 100%, this rifle is deadly accurate :) I highly recommend getting magazines from other sources :)
 
#6 ·
Got to clean a new gun from Sig. They put a real heavy grease in the action for shipping. Not everybody does this so some rifles won't need an initial cleaning. But your Sig does. My buddy didn't clean his and it fired fine but the temperature was over 100deg. Not so lucky the next time he shot @ 80 deg. He cleaned and lubed it and hasn't had an FTF since.
 
#7 ·
Feed Issues Resolved

Finally got back out to the range yesterday. After a very thorough cleaning I had no issues with feeding next round. Using same ammo as before - Winchester 5.56 55gr. Also fired some Fiocci .223 77 grain. All on position #1, normal. Have not needed to use #2 adverse at all. Very glad that a good cleaning resolved my issues - at least so far.
 
#8 ·
Sig Sauer 516 Review with Problems and Issues with Shooting:

FTF, Cycling and Locking Open, Fixed, Solved with Buffer Spring





I have two Sig Sauer 516 rifles. Both had the similar problems that are posted all over the web about not firing correctly with not feeding in the new rounds (FTF), so not cycling correctly, and after the last round is shot, failing to lock the bolt open.



There have been many excellent posts about suggestions of how these issues were fixed. Some worked and others didn’t…, and many were still confused, often sending their upper or entire rifle back to Sig Sauer 1-2 times. I have analyzed many posts and my two rifles and others…, and did testing and experiments to find the exact cause of the issue and how to fix it.



Sig Sauer 516 Review with Problems and Issues with Shooting:

The Issue: Straight to the point: Buffer Spring Weight too Tight (for .223 ammo, usually not 5.56)



Some of the buffer springs are too tight from the factory and not all the springs have the same tension/weight, so that is why some fixes worked and why some rifles shoot the .223 ammo perfectly, while other rifles do not operate correctly when shooting .223 ammo and do not cycle correctly.



Read the above sentence slowly, it shows why there is a great variance on why some rifles work perfect and others do not…., I will write it again…, “not all the buffer springs have the same tension/weight.”



These buffer spring variances can greatly affect how the rifle acts when firing .223 ammo due to its low pressure. So when .223 ammo is shot, there is not enough pressure to push the bolt back far enough to load the new round and there is not enough pressure to lock the chamber open after the last round. Some of the springs are too tight from the factory for some .223 brands.



Generally, the Sig Sauer 516 shoots fine with 5.56 rounds due to the higher pressure from the 5.56 ammo, which the spring variances do not affect.



Sig Sauer 516 Review with Problems and Issues with Shooting:

How to Fix Sig Sauer 516 FTF and Chamber locking when shooting .223 ammo: (a few ways):

1. Sometimes just a good cleaning and lube makes everything glide easier
- Clean the black packing grease off the bolt, inside and out, re-grease or oil
- Remove gas seals from bolt (they are not needed and confirmed through Sig that they are not needed and simply come from the factory like that). Removing the gas seals might make things slide easier.

2. Shooting 5.56 ammo for a while until the buffer spring is broken in and looser, then switch to .223 if you want due to the cheaper cost of .223 ammo.
3. Shoot .223 ammo on the Extreme Gas setting. Using Extreme gives another 1-2 lbs of blow back pressure and will help loosen up the spring. Switch back to Normal Gas pressure after spring is looser. This works on some of the tighter springs, but not all.
4. Shooting heavier .223 ammo (above 55 gr.) works until the spring is broken in and is looser. Sometimes however, on the super tight springs, this still does not work. Use 5.56 ammo instead.
5. Leaving the chamber locked open for a day to a few weeks breaks the spring in and makes it looser, it actually loosens it up by a few pounds over time enabling to shoot .223 ammo.
6. Instant Sig Saur 516 Fix: Cut the buffer spring: Cut ½” to 1.5” (more or less) off the BOTTOM of the spring, NOT the top. Works instantly. It relieves about 1 lb to 2 lbs of pressure to allow shooting .223 ammo with correct feeding of new rounds and locking the chamber open. There have been several posts on doing this where local gunsmiths and local gun shop workers have done this, simply cutting off around half an inch to one inch off the bottom of the buffer spring. All have proven successful. Super tight springs might need 1.5 inches cut off.


Note: Things to understand when cutting the spring
1. I would only shoot .223 ammo if you cut the spring. First cut half an inch to see if that works. If not, cut more. If you decide to start shooting straight 5.56 ammo (which has a higher pressure), then replace the cut spring with a new carbine spring. A cut spring (over time) will be too loose for 5.56 ammo and “over time” could damage the piston rod components, that is why Sig Sauer will NOT cut the buffer springs because the gun is made to be efficient for 5.56 ammo.
2. Over time, with keeping the chamber open and firing rounds, the buffer spring loses strength by a few pounds of compression strength.
3. Carbine springs are only $4 to $10 to replace, so when you want the gun back to original specs or want to shoot 5.56 only, or super heavy .223 loads, simply replace the cut spring with a new carbine spring.





The Sig Sauer 516 rifles were designed to shoot thousands and thousands of the 5.56 bullets and tested FIRST with 5.56 bullets which have a greater pressure than .223 bullets and so 99% to 100% of the time the rifle will shoot fine with 5.56 bullets regardless if the buffer spring is too tight because the high pressure of the 5.56 will override the springs tighter weight.



Now…, after the Sig Sauer company tests with rifles with 5.56 bullets, they then test with the .223, which…, at the company, work fine with the rifle…, why…, because the springs by that point are broken in and are looser so the .223 bullets shoot and feed fine and locks the chamber open on the last round. That is why Sig Sauer claims no issues with the gun. Also…, there are variances of the springs…, so many of the springs are perfect to shoot .223 ammo with right out of the box, while other springs are 1-3 lbs heavier in compression weight and will not shoot .223 ammo correctly.



All it takes is 1-3 lbs of too much buffer spring weight to cause the bullet feeding issues (FTF) and chamber locking issues when using .223 ammo. Sometime the buffer spring might be only half a pound off from working correctly, so that is why a good cleaning can sometimes do the trick. That is also why some people send in their rifle to Sig and Sig cleans it and polishes and shoots it and suddenly it works, because only half pound of difference was needed to fix the issue, but other times, Sig gets the gun returned with a super tight buffer spring, does all of that, and then fires 5.56 ammo through it and there are no issues. Sig sends it back, the owner fires .223 through it and there are issues. Again…, all due to a tight buffer spring and .223 ammo having a lesser pressure compared to 5.56 ammo. There can be 5,000 psi to 25,000 psi. difference between .223 ammo and 5.56 ammo. That is why people using 5.56 ammo experience no issue with the gun.



When using .223 bullets on new springs, because .223 ammo has less pressure, some rifles will feed the new bullets fine and lock the chamber open fine (because those particular rifles happen to have looser buffer springs) while other rifles will NOT shoot the .223 ammo correctly because those springs differ with a greater tightness from the factory and the low pressure of the .223 bullet cannot override the tighter springs. The rifles with the tighter buffer springs then fail to feed new rounds (FTF) and the chamber does not lock open after the last round because the bolt is not pressed back far enough for either action to occur correctly.



I did tests on several Sig Sauer 516 buffer springs with testing the weight of the springs with being pressed back at 2” and then at 3”. Each new factory spring tested differently!!! Some were 1-3 lbs tighter at both the 2” mark and 3” compression mark that I tested them at. So there could be up to a 3lbs. difference between spring tightness.



See Below for Spring Weight differences per lbs. at 2” and 3” compression between different factory buffer springs from Sig Sauer for the Sig Sauer 516:



Note: The Sig Sauer 516 shot 5.56 ammo fine with all springs. The .223 ammo shot fine with only the looser springs. There was up to a 3 lbs difference between the various springs tested.

1. 2” compression: 6lbs and 9lbs on the various springs tested (up to a 3 lb difference)
2. 3” compression: 8lbs and 11lbs (up to a 3 lb difference)
- Again, 5.56 ammo shot fine on all springs. .223 ammo only shot fine on the looser springs.

I hope this info helps out all the people that were frustrated thinking there awesome new Sig Sauer 516 rifles were broken with failing to feed (FTF) rounds from the magazine after being shot and failing to lock the chamber open. All the trouble comes from a simple part…, a too tight of a buffer spring that makes the gun very temperamental with shooting .223 ammo. Simply break that spring in, or cut it, and all will work fine.



Overall, the Sig Sauer 516 is an awesome gun. I love it and would recommend it. Sig Sauer company just needs to fine tune some quality control and testing.
 
#9 ·
Note: The Sig Sauer 516 shot 5.56 ammo fine with all springs. The .223 ammo shot fine with only the looser springs. There was up to a 3 lbs difference between the various springs tested.

1. 2” compression: 6lbs and 9lbs on the various springs tested (up to a 3 lb difference)
2. 3” compression: 8lbs and 11lbs (up to a 3 lb difference)
- Again, 5.56 ammo shot fine on all springs. .223 ammo only shot fine on the looser springs.

I hope this info helps out all the people that were frustrated thinking there awesome new Sig Sauer 516 rifles were broken with failing to feed (FTF) rounds from the magazine after being shot and failing to lock the chamber open. All the trouble comes from a simple part…, a too tight of a buffer spring that makes the gun very temperamental with shooting .223 ammo. Simply break that spring in, or cut it, and all will work fine.



Overall, the Sig Sauer 516 is an awesome gun. I love it and would recommend it. Sig Sauer company just needs to fine tune some quality control and testing.
Great info. Would it be possible to just buy an aftermarket spring that's within specs for the weaker .223 round? I can't figure out which ones might be in the lower range. Most of the sites just have spring length.
 
#12 ·
im not quite sure if I might have the same problem or not but the first time I shot my sig 516 I put 260 rnds through it and it worked fine then yesterday I went and put about 180 rnds and it ejected the round but didn't feed the next I had to rack it back and then it would fire off the rounds it did this a few times and aslo had it jam one in and not load all the way it also failed to lock back on last shot a couple of times but when I racked it back on the empty mag it would lock these are the same mags I used the first time and are pmags. so could it be just some of the rounds where bad or is it the gun I? I made sure it was clean and well lubed before this after I also checked the rifle and took it apart everthing seems to be in order. I would appreciate any feedback
 
#13 ·
Greetings all, new guy here. I googled, "SIG 516 ftf" and this thread was the first that popped up, and I wanted to weigh in on it. I'm a big SIG fan, and my first handgun was a P226 that I bought new a couple decades ago. My SIG stable has grown over the years and I now have several, with a P229 no-rail on order as we speak.

I've read JZhouse's excellent reply on a couple threads now, but I wanted to update it with my own experience, which is not quite the same. I have a new SIG 516 that I've been having the same problems with, bolt only locking back every so often on an empty mag, ejecting the round but not feeding the new one, etc.

Here's the difference between my experience and his, 5.56mm ammo does NOT function better in my SIG, in fact in some cases it functions worse than .223. Since this issue started I've used various magazines to rule them out....USGI 20 and 30 rounders, Magpul P-mag 20 and 30 rounders (both Gen 2 and Gen 3). The magazine had no effect on the outcome (equally bad with all).

Ammo...The issue persisted with Winchester WB .223 55 grain, 75 grain Hornady TAP in .223, and Winchester Ranger 64 grain 5.56mm, and 77 grain Black Hills OTM in 5.56mm. Strangely enough, the Black Hills 5.56mm 77 grain OTM suffered the issue worse than any other ammo (and NO, this is not a misprint, I know BH comes in 77 grain .223, but this is the factory new 5.56mm (civilian Mk 262 Mod 1)). Surprisingly, the 75 grain Hornady TAP in .223 suffered the least issues. So to summarize ammo, 5.56mm is not more reliable in my SIG 516. All ammo types were fired on both "normal" and "adverse condition". Every now and again I could get 2 or 3 rounds to fire in a row under adverse setting, but typically even that required racking every round.

Now on to other troubleshoots...

I changed out my SIG 516 buffer tube with a Magpul UBR. I kept the original SIG "H" buffer and spring, as per Magpul's instructions. I also installed a Geissele SSA-E trigger. Now here's the kicker...the issue has nothing to do with any lower receiver components (at least in my case). How do I know this? I placed my SIG lower on a Colt 6940 upper and it ran like a top. All mags and all ammo functioned flawlessly. I then put my SIG piston upper on my Colt 6940 lower (with a well worn in spring)...the issue returned, with my gun being a "bolt action AR" for all intents and purposes.

So at least in my case, the buffer assembly is not the problem, as the failures persisted even with a Colt lower. I called SIG this morning and they emailed me a shipping label. I'll report back when I hear back from SIG or get my rifle back from them.
 
#14 ·
Lots of posts with suggestions. I didn't read all of the responses, but others have said to use no less than 62 grain 5.56 to break in rifle. Supposed to help with higher pressures. After break in period rifle should cycle anything you put in it. I don't use much 5.56 62 grain, but I have used it. I have used 50 grain hp at range with no issues. I have about 500-600 rounds through my 516. No issues except with one 55 grain steel case Tulammo HP FTF.
 
#16 ·
I wanted to update this thread with new info from my own personal experience (not internet rumor:lol:). The buffer springs/ buffer, and buffer tube, and good lubrication make be the fix for most of the short stroking issues, but not all...and not in my case. Anyone else having this issue with their SIG 516 I can't recommend enough to simply send it back to SIG and let them fix it. Cutting off some of my spring, or some such nonsense would not have worked in my case:

The issue is resolved. I am very impressed with SIG's customer service. They paid for shipping both ways, they did not care one bit that I'd installed numerous aftermarket parts, including stock, trigger, buffer tube, etc. They sent the gun back promptly and it is working flawlessly. I just got back from the range. It fed everything from good match grade 5.56mm ammo to crappy plinking 223 ammo. Every round fed perfectly, every magazine worked great, and the BCG locked to the rear at the end of every magazine.

The note included from SIG's gunsmith said, "Replaced the gas valve to get more flow. Test fired Winchester 5.56mm M855 and Speer Gold Dot .223 64 gr. and had no malfunctions through two full mags."

The gas valve is indeed new. It is a different style than I've seen in any photos, it is not the newer rounded one and not the square edge earlier version. So evidently they are now on their third evolution of the gas valve.

So to summarize...a good lubrication job or a more worn in buffer spring may work for many folks, but it won't work for all. If you're having issues with a new 516, give SIG a chance to fix it.
 
#19 ·
Thanks for the pics. That is different, especially the piston end. I can't tell if any difference on the block, other than it doesn't have a bayonet lug, which they seemed to have dropped in the last few months, but the loop on the end of the piston is not like any of the previous versions I've seen. Glad they seem to have it worked out. My Gen2 had a few FTF/FTE early on, but none after 120~ rds through the gun.
 
#20 ·
The gas block itself is the same one that was on my gun when I bought it. I think this style of block has been around for at least a year, if not longer, based on other photos I've seen. But I agree, the valve itself (or at least the adjustment loop) is different than the previous two versions.
 
#23 ·
My first post on my first AR. Bought my SIG 516 a week ago and after about 30 rounds of .223, started having FTF issues. Did not fully understand the gas valve adjustment until after returning from range. So I did a thorough cleaning and started researching posts on possible problems. Lots of great info out there, but have to say, in my case, to operate gun in normal mode I had to run .556 ammo. I did find some federal .223 ammo with high enough pressure to properly function the bolt. However, all my other .223 ammo I had to use "adverse" position to operate without FTF. I repeated test many times with many different .223 ammo and without fail, the .223 ammo (except the Federal) would not properly operate the bolt. As soon as I went back to .556 or the .223 Federal ammo, (gas valve in norm), the gun operated perfectly. I think I will take advice from a previous post and run a few hundred rounds though it and see if the buffer spring actually loosens up any. If not maybe I will take Jedi5150 route and send it back to Sig for a new gas valve. Looks like I have an older version )rounded head), it definitely does not look like the pic from Jedi5150. Thanks to everyone, for the great input.
 
#24 ·
CWesley:

Welcome. I had some FTF/FTEs during the 1st 120~ rds with mine. I could not tell a difference in ammo on this, but the gun ran in the adverse mode with very few issues and mainly had them in normal on the first range trip. Keep us posted after you've ran more ammo through yours and good luck.
 
#25 ·
I want to bring this post back up since I am experiencing issues with my new 516 pistol version. It has a born on date of 7/25/15 purchased Mar 2016. I've finally sorted out (I think) the failure to feed issues I've had from day one. It seems to not like NATO 55gr ammo. At first I thought it was gas because running on adverse would sometimes help a bit. It will feed on normal setting 62gr 5.56 American Eagle XM855, Hornady 5.56 75gr TAP SBR, Nosler Defense .223 64 gr bonded solid base but not American Eagle 5.56 55gr. It will sometimes get the round into the chamber but then when I draw back and reset bolt it is very difficult to extract and I discover a bent and badly scratched round. I'm thinking something in the feed ramp is not liking the shape of that round although I cannot tell the difference in it and the 62gr green tip. So do I call Sig? And be without the weapon for months? Or maybe get someone to look at the ramp where I bought?
 
#27 ·
I would start by going back to the LGS if you can. Have them test it and if they can't get it to work properly demand a refund or a replacement. I have heard horror stories of people sending their 516 back and firth to Sig multiple times with no success. I had similar problems with my first 516. The gun simply would not work properly. I took it back to my LGS within a couple of weeks. They took the gun back and gave me a new one. Your gun should shoot whatever ammo you give it.

I am no longer interested in Sig AR's. I still have the replacement 516 and it works reasonably well but if I go out and shoot it a lot, say 200 rounds it will at some point have "the problems". I am actually thinking about trading it in for something else (at a huge loss I am sure) because I don't like it and I never use it anymore. I built a DI gun in 556 and that's my weapon of choice now cause it always works.
 
#29 · (Edited)
I've not heard of issues with 55g 5.56, other than challenges with dirty ammo (which I've experienced myself). I would either take it back to the lgs or send it to Sig for remedy. With the bent casings and chambering issue, I agree it looks like a feed ramp problem, and that's not going to go away on its own.
 
#30 · (Edited)
Just wanted to follow up on my P516 failure to feed issue. Sent it off to Sig on Dec. 27 after a phone conversation with documentation and some images of failed rounds damage. I must say that they at Sig are good to deal with. I was emailed when they shipped it to me and received it on Jan. 6. I noticed some polishing on the BCG at ends of 4 channels and heavy grease at the back end. Called them to check what was done and it was mentioned that the ramps were polished and honed - see pix of b4 on left after on right. Sorry for the poor image quality but trying to image barrel receiver is pretty tough. It clearly shows enlargement of feed ramps. I've since fired ~40 rounds of the ammo that was not feeding and all did so perfectly. One other thing I noticed is that when letting the bolt close lightly by holding back on the charging handle, it slides fully closed the last 1/2" much easier now. It appeared to bind previously.
 
#32 ·
This issue is still ongoing. I've recently used two different 11.5" gas uppers suppressed without any failures using the same IMI and AE M193 ammo that fails using my piston upper. I've just sent Sig an email requesting them to replace the upper. My son suggested just a bolt switch out but we forgot to try that. I've looked around for a replacement piston upper but it appears the Sig BCG is proprietary.
 
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