Hello all, Im new to the board and I had a question. Ive had my DSA ZM4 since december. Ive fired everything from crap plinking round to federal ammo out of it. Probably in the ball park of 1000 rnds. The last time I took it out though I was solely firing high grade ammunition (I cant remember the name at the moment) but I was getting an ejection problem every 10-20 rnds. As the bolt woudl cycle to the rear and pick up a new round it was catching the spent casing in between the new round and the top of the chamber with the bolt pinching everything forward. So now Im stuck with a new round dented and halfway into the chamber, and a spent casing stuck halfway out of the ejection port. At first I figured it was just the gas rings, but I inspected them and they were fine. The weapon was also very clean, as I clean it thouroughly after every shoot. Any idea on how to fix this problem. Im admitadly a bit concerned at having a realatively new rifle from a reputable company malfunctioning on me, now to mention the extra wear this has put on the weapon itself. It came with the D ring for the extractor aswell.

Flashbang_E4T.....interesting weapon for just plinking.

As you probably know, the ZM4 has some novel features that make this a versatile weapon. The 1st thing I would check is the barrel locking mechanism. Do you have another barrel to swap out? Is the barrel locking mechanism on each barrel or integral with the receiver?

One other thing is the extractor itself. The extractor on this weapon is beefed up, and shouldn't be causing problems, so the issue could be with the shell casings themselves. You indicated that you used some cheap ammo in it, and by all appearances the weapon functioned well until you swapped to match-grade ammo. One possibility is that the cheap ammo casings left a build-up on the extractor itself? Was the cheap ammo casing made of a different material than the match grade? Do you have access to any mil-spec 5.56? Have you checked the extractor spring itself? Is the extractor spring seated correctly when re-assembled? Does the extractor pin show any unusual wear pattern after being cleaned? Is it a tight fit?

Only other comment I have on your issue, as the cheap ammo worked flawlessly, I'd recommend switching back to it for both economy and functionality sake.

Usta get this all the time firing blanks in the M-16 with the MILES laser system.

Those dirty blanks fouled the extractor and barrel...some pock-marks down the barrels.

I'd sure listen to Gunney... and maybe get another barrel/extractor for using the good stuff.

Maybe get better cleaning solvent. Use an RBC
like Hoppe’s number 9.

http://www.armalite.com/library/techNotes/tnote29.htm

Make sure you pop your magazine good to seat your rounds, then try using better grade ammo.
The only other problem might be your extractor, but unlikely. Make sure you always tap your forward assist charging handle sharply, to insure it is home. Let me know what you find out. Jim

You don't need to switch barrels because of the few rounds that have been fired through it. The only time you need to switch them out is around 50K-60K rounds. Yes Gunny the extractor is probly bad but also is it happening with one mag. or all of them?

I own a bushy and the same thing happened to me when I started using winchester fmj's. Like you, every 10-20 rounds would do the same. I switched back to the federal I was previously using with no problems. I figured it was the win brass. It may just be that batch or brand of ammo that your gun just doesn't like.

barrel locking mechanism is what I asked him to check. you know, is the barrel locked down completely? 1/2 a mill is enough to offset everything.