Buffer tube spring question.

[inkinskin]

Hey everybody.

I recently bought a Sig 516 patrol rifle in FDE. It is a beautiful rifle but it has not been performing up to par. I have been having FTE, FTF, Double feeds, jamming, and bolt not locking open on last rounds. About 50-60% of the time. I have experienced this mostly with .223 caliber rounds but also a few times with .556 also, & different types of magazines as well. I tried switching the gas setting to adverse but it didnt change it enough to make a difference. I cleaned the rifle before I shot it after I bought it just to be clear there. I have done some reading and narrowed it down to either the rifle hasn't been "broken in" or its a manufacturer defect until today where I stumbled upon a post in a blog discussing the buffer springs installed on the Sig 516 rifles. The guy was stating that the buffer springs they installed were super tight and over powered by 1 -3 lbs, making the bolt not cycle properly when running .223 rounds causing the problems I described. In theory once the buffer spring gets broken in the rifle runs fine. He stated that he had two Sig 516 rifles himself and had done a modification to the buffer spring that fixed the problems in both of his rifles. He said he cut 1/2 -1 & 1/2 " of the bottom of his buffer spring and it allowed the rifle to cycle properly and allowed the bolt to lock open every time using .223 rounds. In turn you would need another buffer spring to run .556 rounds seeming kind of silly but would be something I would do to be able to run it properly. I decided to just store it with the bolt locked open for a few days and see if that loosens the buffer spring up any. I also ran across a underpowered buffer spring by WOLFF that states is made for cycle function of .223 in AR platform rifles.

My questions are: Does anyone own a Sig 516 that has had these problems? If so can you give me any feedback as far as cause or solution? Has anyone heard or tried the spring. You WOLFF?

Any help would be much appreciated.

Thanks guys.

 

[hatt]

How many rounds have you put through it? And is it well lubed?

 

[TurboFC3S]

I don't have a Sig 516 and don't know if the factory spring is over powered, I'd have to doubt that it would be. But as cheap as buffer springs are, just buy a standard one for whichever supplier you like and give it a try.

But if it won't run with the gas wide open I'd send it back to Sig. I've sent a few guns back to Sig over the years. How it goes is you give them a call, 10 minutes later a pre-paid FedEx label will show up in your email. Print it, stick it on the box, and drop it off. 10 days later or less the gun will be back on your door fixed.

 

[MistWolf]

A Double Feed is when two or more live rounds are fed out of the magazine at the same time and the magazine is the source of your problem.

If you have an empty and a live round in the action, that's a Failure To Eject the empty case. From what you're describing, it sounds like your rifle is Short Stroking. This is the result of Underpowered Ammo or Gas Leakage or Undersized Gas Port or Something Slowing the BCG or a combination thereof.

If the action spring is too stiff, cutting it is only a stop-gap measure. Go buy the right replacement spring. They don't cost much. Cutting up to 1.5" from the spring sounds like a lot. Is the OEM spring too long?

Leaving the action open to compress the spring will not help

 

[Tirod]

The AR action, and most military guns, is designed around 1 (one) issue round - not everything the ammo makers can put together and sell. A lot of it is also for bolt guns, and in that use, the amount of powder to make the action work reliably is completely dismissed.

In the AR, you generally get a single port size tuned to the military load data, and it's not a plinker round, it's full power to punch a penetration round thru hard barriers. Not a light target or hollow point. And certainly not cheap import loads.

The 516 offers the extra settings to overcome internal powder residue and the increased friction, but if the round is loaded light already - and .223 is NOT military loaded - then it's still less than needed to cycle a gas powered self loading action.

Don't use civilian light loads in it, try it with full powered military rounds, and see how that works. Don't expect reject or overrun rounds to be full power - they didn't make spec for a reason, which is why they didn't go on the contract and were dumped on the market to recover profit.

Unlike auto shotguns, AR's don't have highly complicated gas systems to compensate for different loads. They shoot full power ammo only. Most reports of them malfunctioning come from owner's who insist otherwise and shoot light civilian loads that the maker's never intended to be run through the gun. Winchester White Box or a Russian import isn't issue ammo and won't ever be used in testing the gun for military acceptance.

THAT is the reason someone is chopping the spring to shoot light .223 - the AMMO is the problem, and he's forcing a change on the design to satisfy his own demands. It can be done, but the unintended consequence is that when full power ammo is shot, it won't be controlled as much and the weapon might be battered by a bolt that now has less spring pressure than it should - causing things like bolt bounce and out of battery ignitions.

Those are fondly known as Kabooms. Be careful what you ask for.

 

[inkinskin]

The rifle was properly cleaned and lubed yes. Tirod, that is also what I have come to realize too. I'm gonna order the underpowered spring and and see if that helps with the lighter loads and keep them color coated and separate for when I shoot normal. I'll keep you guys updated after I get it and test it out again. Thanks for the input.

 

[d2wing]

I think the spring or buffer is the problem. I had similarity problems a few years ago with a carbine. I went to a heavier (H2) buffer as well,as extractor upgrade and that fixed it. I also tried a heavier buffer spring but that made it worse. So yes a stiff buffer spring can cause those issue. Get a lighter one. You may consider a heavier buffer.

 

[chris in va]

Unlike auto shotguns, AR's don't have highly complicated gas systems to compensate for different loads. They shoot full power ammo only

My DI S&W Sport does just fine with various handloads of various powder charges and velocities. Some eject further than others.

Sounds like the gas system is partially plugged or some tweaking is in order. I know my friend's FAL malfunctioned something fierce until he got the gas valve set just right.

Edit: Upon further Google-fu, seems the gun must be run with the 'adverse' setting when new to break it in, especially when using 55gr bullets. People report multiple FTE, FTF etc until the gas system breaks in.

 

[moxie]

I'd contact Sig before messing with it.

As Turbo noted in #3 above, they will take care of you.

I don't have a Sig, just a plain AR (CMMG) but mine will fire anything. "Full power" military loads (LC and IMI), civilian .223 loads (WW, RP, PMC, PRVI, etc.), as well as my own reloads with 55FMJBT running as slow as 2717 fps. As Chris noted above in #8 with his rifle, the only thing that changes is the ejection pattern.

A good AR should be able to reliably function with virtually any commercial 5.56 or .223 ammo available on the market, as well as decent reloads.

It sounds like you've tried the break-in procedure and the "adverse" setting but still not running right. Don't mess with it, contact Sig.

 

[hentown]

I've built a bunch of ARs. I've never had one of my ARs fail to function, regardless of the ammo that I ran through them. I don't always load hot loads, yet my ARs always work.

If the 556 is piston-driven, then I'd opine that there's a reason that the military uses d.i.!!

I do use an adjustable gas block for my .300 Blackout, as I'm loading both subsonic and supersonic rounds.

I use standard buffers and either M-16 or semi-auto AR BCGs in my builds. Never had a problem with either.

 

[shrewd]

Buy a springco white spring and you should be good.

I'd still call sig first, though

 

[hardluk1]

inkinskin You sound more like you have a gas adjustment issue . Do a simple search for sig 556 problems and most are gas adjustment related. Sigs sharp enough to build a rifle with what spring you need and buffer to work but how some one screws with the adjuster can make or break function for sure. Mine is a normal gas impingement system and using a stock spring or wolff std pressure spring with a H buffer runs well with any make 223 or 5.56 I have tried and those have a velocity spread of almost 300 fps.

 

[inkinskin]

Trust me I have done a ton of research online on multiple forums and blogs including Sig's forum. I called Sig Monday and explained the issue to them and they said it sounded like an issue with the buffer or the buffer spring. I asked them about the possibility of the spring just needing to be broken in and the rep said that is a def possibility. He recommended running it on the adverse setting when shooting .223 until the rifle is broken in. I explained to him that I was storing the rifle with the bolt opened and was going to give it another run next week to see if the cycling gets any better. He said that would be fine, and he sent me what I need to send the rifle back to them. In the meantime, I ordered the Wolff reduced power buffer spring and bought some federal 5.56 ammo for this weekend. I am first going to run some 5.56 rounds through it and document and photograph what happens. Then I will switch to .223 with the factory spring and try running it on normal gas settings, then adverse settings and take photos and document my results. Then, I will switch the factory spring for the Wolff spring and run some .223 rounds through it to see if it helps with the cycling.

At least this way, I will have everything that happens documented down to exact details for when I send it to Sig. I am hoping that it just needs broken in, and I will be able to remedy it myself, but if not I am confident Sig will make it right.

Thanks again for the input guys. I will keep my progress posted.

 

[DRYHUMOR]

In my experience, springs wear out, they don't break in.

Just sayin....

You might make sure there is no crud in the gas system, make sure the BCG is well oiled, add a light wipe of oil to the spring as well.

 

[inkinskin]

Ok, as soon as I posted my last reply my spring showed up. I took out my rifle and disassembled it and inspected every piece. No blockage in the piston system, bcg is well lubed, everything looks fine as before. Now my first tip off that something was wrong with this rifle out of the box is the bolt would not lock open with an empty mag without me physically engaging the bolt latch to hold it open. This was before I shot it of coarse, and I thought that was weird because every other AR I have had has locked open with an empty mag without a problem.

So I took out the factory buffer spring and put in the Wolff underpowered spring. I put the rifle back together, put in an empty mag, racked the bolt back and presto!! The bolt locked open without any manipulation. This gives me confidence this will eliminate my problem with shooting .223 ammunition. I am keeping the factory spring in it for now and storing it with the bolt locked open to continue to wear the tension down.

I am still heading to the range this weekend to do my testing but I am pretty confident my problem will be solved. Wish me luck!

 

[Mohave-Tec]

Good luck. I am curious how it turns out.

 

[inkinskin]

Ok, made it to the range today. Started with 5.56 ammo with the regular spring, ran 2-30 round mags and no failures or issues and bolt locked open. Switched to .223 ammo. 1st mag 4th shot FTE, switched to adverse setting, finished mag with no issues but bolt would not lock open. Tried a second mag of .223 and 3rd shot still on adverse experienced another FTE. Tried to finish the mag and experienced 3 more FTE, A FTF and bolt wouldn't lock open on last round.

I then switched to the Wolff reduced power spring, and ran 5 different 30 round mags of .223 brass and steel through it like a champ. No FTE, no FTF, and bolt locked open every time the mag was empty. It also sounds smoother than the factory spring when the action cycles.

The Wolff spring fixed all of my issues. I am convinced of two things, 1. Sig shipped me a buffer tube spring that is 3-5 lbs heavier than normal that will only cycle 5.56 rounds with the heavier load, & 2. The rifle needs a good break in period just like new firearms, but maybe a little more than usual.

In conclusion, I am very happy with my 516. The accuracy is awesome, it is lightweight for a piston gun, and the FDE is pretty to the eye. I just had to buy a different spring until I can get the factory one properly broken in with 5.56 rounds. I am also considering buying just a regular $5 carbine buffer spring and see if the pressure is close to my factory spring. I am worried if the factory spring is just too powerful if it will ever get broken in enough to run .223 without issues.

Does anyone know what the pressure should be on a regular carbine length buffer tube spring?

Thanks everyone.

 

[moxie]

A spring shouldn't really get "broken in." It either works or it doesn't. Toss it and stick with the reduced power spring. If it functions with everything, you're good to go.

All this fiddling with adverse setting and such gives me the hives. The adverse setting is supposed to be, according to Sig, for short stroking or fouling. Should be able to pull the trigger and go bang, every time, no matter what ammo you are feeding it. If it's not doing this, I still recommend you call Sig and consult with them.

 

[inkinskin]

I did call Sig and they recommended to use the Adverse setting when shooting .223 rounds during the break in period.

 

[Mohave-Tec]

What the hell is an adverse setting?

 

[moxie]

The Sig 516 owners manual, page 27, would indicate otherwise. And it doesn't reference anything about a break-in period. Your buffer spring should not need breaking in at all. It either works or it doesn't.

 

[moxie]

Mohave, simply go to the Sig website. Find the owners manual for the 516. Therein, behold, an explanation of the Sig's gas operation, including an explanation of terms. Voila! No need to get testy.

 

[CharlieDeltaJuliet]

Call Sig.. I have a 516. It's buffer spring, if anything is lighter than my other AR's including another piston AR. It runs like a sewing machine in a Hong Kong sweat shop. Call Sig, they will fix it. This is the first I have heard about it.

 

[SilentScream]

Call Sig first more than likely your ammo is the culprit. However there may be a mechanical issue, that if you start screwing with changing parts out may nix any chance of a warranty fix. Get hold of Sig first.