Common SIG Sauer 516 Problems and Solutions

The introduction of the Sig Sauer 516 successfully enhanced the traditional AR-15. In many aspects, the SIG 516 was intended to be the HK416’s direct competitor.

The military and police groups indeed used it far less frequently although the SIG 516 supposedly had lower costs and less recoil. A 4-position gas regulator included with the 516 allows for less recoil and wear. Above the barrel, a short-stroke tappet system is present.

However, the most common problems with the Sig Sauer 516 are FTF/FTE, not locking on the last round, roll pin issues and not cycling properly.

After reading this article, you will know the solution to all these problems. You will also know how the users feel about this product. So stay tuned!

Features & Specifications of SIG Sauer 516:

Cartridge5.56×45mm NATO 7.62×39mm
Capacity10/20/30 rounds
Barrel Length7.7/10.6/14.6/16.1 inches.
Weight6.45/6.75/7.25/7.65 lbs.
Length (Extended Stock)27.9/ 30.6/34.9/35.8 inches.
Width2.9 inches (Patrol).
Height7.7 inches (Patrol).
SafetySafety lever on the left side.
SightsIron sights.
Common SIG sauer 516 Problems
SIG sauer 516

Common SIG Sauer 516 Problems and Solutions

The owners deal with many common SIG Sauer 516 problems. Here are some of the issues and how to solve them.

Quick Overview of the Problems and Solutions

FTF/FTETroubleshoot. Use correct magazine and ammo.
Not Locking on Last RoundTroubleshoot.
Roll Pin IssuesTroubleshoot.
Does Not Cycle ProperlyTroubleshoot. Use adverse gas setting for 55gr ammo.


After a few hours on the range, the gun might FTF frequently. It does not eject the empty casing before trying to feed a new round. You may have to manually feed the next several rounds.

The Fix:

Before firing, cleaned the bore and the feed ramps. Disassemble, clean and oil the bolt carrier, and recheck the piston settings. Apply some gun grease on the carrier along the bearing surfaces, and a small amount on the bolt.

Although the FTF is rarely due to ammo issues on the 516, 55gr Winchester FMC pushed with 25gr Varget, 69gr Sierra Match pushed with 24gr Benchmark are some combinations that work smoothly.

It is wise to try different magazines and even size the cases a little more.

2. Not Locking on Last Round:

After cycling some rounds manually, you will have failures to extract. The round seems to get stuck in the chamber. The bolt just doesn’t seem to be grabbing the round to extract.

The primary problem 516’s have is a lack of the bolt staying open after the last round when shooting certain ammo. For example the .223 in 55 gr.

The Fix:

Cut the buffer spring by taking around 1/2″ to 1.5″ (or more) off the bottom, not the top. It releases one to two pounds of pressure, depending on how much you need to cut to shoot.

This will allow the .223 ammunition with the chamber locked open. New rounds will properly feed into the chamber. Cut 1.5 inches off for severely tight springs.

Lube the bolt properly and check if it cycles properly.

3. Roll Pin Issues:

When installing a trigger guard on the 516, it is necessary to take out the roll pin. Usually, the pin does not come out and is very heavy. Taking it out might also damage the gun.

You couldn’t get the back pin to budge using a flat punch (not center punch. The front pin of the stock guard releases very easily. Its the back pin that’s hard to take out.

The Fix:

Put a little oil on both sides of the pin. Use a small allen key roughly the same diameter as the hole and a tack hammer to remove the back roll pin.

4. Does Not Cycle Properly:

After firing a few rounds, the bolt fails to fully cycle. More than one or two bullets can’t be fired before the gun jams.

With an AAC suppressor, it usually cycles flawlessly in a suppressed mode. But with the Surefire SOCOM556-RC suppressor in suppressed mode, it may fail to cycle and continually has FTEs and FTFs. It’s not getting enough gas in this mode.

Surefires and the 11.5″ BCM upper don’t cause any problems either. That, however, is a direct gas higher.

The Fix:

The 516 doesn’t like 223’s. Change the gas setting to adverse to get the BCG to cycle properly. With any 5.56m ammo, doesn’t matter if it’s only 55 grain, doesn’t matter if steel or brass, you will most likely get problems.

Usually firing 55 grain requires operating the gun at the 10-4 “adverse” gas vent position. But if you stay away from 223’s, it cycles better in normal gas setting.

In the case of suppressors, it may not be a SIG problem. Rather a suppressor problem.

User Feedback on SIG Sauer 516

Regarding LE and military use, the 516 is most likely among the top three. HK and LWRC will be the other two in this list.

It draws quite the attention too. It is entirely accurate and reliable. The 516 has a lifetime guarantee and the proprietary parts are covered. However it is extremely rare (though not impossible) that an op rod or bolt carrier would ever break.

The gas system can be altered. Compared to a 1/9 inch, the 1/7 (or 1/8) is more adaptable. Granted, there may be some 45gr that the 1/9 inch performs better with. But since the 1/9 stops at the 68/69gr and the 1/7 performs the extremely useful and desirable 75/77gr better. I would advise using either the 1/8 or 1/7 and avoiding the 1/9.

This view is shared by most users. Because it needs unlocking and unscrewing, cleaning the piston or cylinder is quite deliberate. When suppressed, the shooter is smooth and produces slightly less gas in the face.

The additional weight of the item caused by the hefty rail and brick gas block is a major drawback. Though the rifle is constructed like a tank. Overall, users generally feel good about this one and there are very few complaints.

Frequently Asked Questions (FAQs)

How can you tell if the SIG Sauer 516 a Gen 1 or Gen 2?

Gen 1 has a threaded in gas plug in the gas block and was only manufactured for a brief period of time. With Gen 2, there is no threading. A Gen 1 would require serious searching because they are rare to find.

Can you use different aftermarket rails with the 516?

If you use a barrel nut that doesn’t have sprockets/spike things, you might be able to use several different aftermarket rails.

Has the SIG Sauer 516 been discontinued?

Yes. The SIG 516 was discontinued as of 2019.


All in all, the SIG Sauer 516 is a great gun. The one word of caution I’ll provide is that, once you start using the platform, you’re reasonably likely to want to make modifications.

Therefore, starting with a more expensive gun might make you less likely to tune for what you truly want. The SIG guns also have a good resale value. So, if you ever need to sell it, you can easily do so.

The only drawback you might feel other than a few issues is the expensiveness of the product. So if you can find one, you better grab it fast.

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