Several months ago, ok eight months ago I purchased an MSAR 556. I really liked the bullpup design and it seemed to handle very nicely. Ok for the first time ever I took it to the range and immediately had problems. The rifle failed to feed about ten times and when I ejected the casing I found the bullet had been pushed back into the casing. I put about sixty round through it before I said heck with it. However, to be fair the last twelve rounds fed and cycled fine. I tried three different magazines, all MSAR manufactured and had the same result. It might be that the rifle was new. I mean it was really tight. Do you think firing more would loosen it up and solve the problem or does it need to visit a gunsmith?

I would say fire some 5.56 and allow some 200 rounds for break-in.  Mine works great with XM193, but sometimes jams with commerical .223 loads. I think I need to adjust the gas regulator, but just like you, I only own the STG-556 for a few months. I am still getting used to it.

Clean and lubricate your rifle.  There may be an issue with where the magazine is seated. Don't Karate chop the mag into the stock just push it until you hear and feel that click and then pull to make sure it is seated. Run 5.56x45mm on the "H" setting for the first 200 rounds.  If the same issue continues contact MSAR as this problem has been seen before and is fixable by them.  

Thanks for the replies, I'll check the gas setting and put another hundred rounds through it.

What kind of ammo were you using?  Did you clean and lubricate the rifle beforehand?

Yes, it was cleaned just before shooting. It was new so it was already very clean. I used my departments Federal 62 grain soft point ammunition. What gas setting should I use?

Could the softpoint be the problem?

It seems to me that others have had teething problems with soft points as well. IIRC

You should run it on the "H" setting for a couple hundred rounds.

I had problems with 62 grain PRVI soft points.    No problems at all with 55 grain FMJ.

Well, I appreciate all the help you guys provided. I bought 500 rounds of the 556 WINCHESTER Q3131 ammo and put it on the "H" setting and three hundred rounds later not a hicupp. It now runs great, I couldn't be more pleased.

One final question, It loves the Q3131 ammo, is there any reason to put it back on the standard gas setting?

Sure after a couple hundred rounds you should be fine running it on the standard setting.

Fire about 200-250 rounds of xm193 and you shall have no more problems..

JFYI, I ran about 500 rounds of XM193 through my MSAR STG-556 and now run nothing but PMC Bronze and haven't had any problems at all so far and have the gas setting on "S".

I did have some magazine issues but those have since been resolved.

As others have mentioned, feed about 200-300 rounds of full-power 5.56 ammo through it. This will break-in the system and work the bugs out. The same problems happened with my E4 on its initial outing as well. I was using .223 factory reloads. I had problems on both gas settings. Upon advise from MSAR, I ran 300 rounds of XM193 through it and all the problems disappeared. It's been very reliable ever since. Regards.

PMC Bronze is GTG. Good stuff, good price. My STG loves it.

Glad to hear that your rifle is working better. After that many rounds you really should be able to set it back to the standard S setting. I am really surprised to find so many people having to put it on the H setting when new for so long. When I got mine I didn't have to-in fact I don't think I have ever put it on H ever. Then again I was shooting pretty good ammo from the get go. The only problem I originally had with my E4 was it FTF a couple of rounds in the beginning-but I am chalking that up to the weaker fiocchi .223 ammo I tried through it in the beginning. I can pretty much feed it anything and it will chew it up and spit it out. I have to admit I have pretty lucky with my E4 in not having a lot of the problems others have been facing...

Happy shooting-and don't forget there is a rule here that you must post up pics or it doesn't exist. Tomac hasn't been around to remind the new peeps of this. Welcome to the brotherhood!