Dpms 243 problem

tak

tak

Member
Have a Dpms 243 that will not eject if the bolt cover is closed.
Doesn't happen all the time. Doesn't matter how many rounds in the mag. or what brand mag. The spent brass will be about half way out and the bolt is pushing the next round into the chamber.

I'am using factory Winchester 80grn.Haven't tried any other types ammo.
I have replaced the gasblock with an adjustable. The problem was there before I switched blocks.

Hoping someone can help me with some ideas.
 
I adjusted the block all the way closed then backed it out until the bolt would stay open on the last round.
Then opened it more to see if that would help, it hasn't.

How do you know if the gas is too much?
I've haven't seen what I would call burnt powder (black dust) on unfired rounds in the mag.
 
I would try different ammo and see what happens.
If it still does it I would check your gas port diameter since it was doing it before you put the adjustable in.
Are you by chance running an extra power buffer spring?
 
I did buy it used, so not sure on the buffer and spring.
I guess I'll try another brand of ammo, same bullet. Would hate to switch, these are at every Walmart
and less than $20 a box.
 
We are just trying to determine if the ammo you have is underpowered. If it still does it then we move on to something else. If it functions fine with different ammo then the stuff at wally world is underpowered and we can open the gas port up a little and then all is good..
 
Weak extractor spring, poor fitting or damaged extractor, or over-strength ejector spring. Pretty common.

Other ammo may fix it, but if it's locking back, it's traveling plenty far, so I'm not prone to believe it's an under powered ammo issue. If it were short stroking and failing to eject, sure, but not when it's traveling full stroke - that tells me it's most likely an imbalance in your ejector and extractor. The ejector is pushing too hard and over-powering the extractor. Either the extractor is weak or doesn't have a good grip, or the ejector is too strong.

If the buffer were too heavy or the buffer spring were too strong, it'd give the same symptoms as under powered ammo - it'd short stroke and fail to eject. You have enough bolt carrier travel to lock back, so carrier/buffer weight and spring power are not excessive. Your rounds are slipping out of the extractor before the case mouth is clear of the extension, leaving you with stovepipes. That's an extractor issue, which can be caused by an over tensioned ejector spring.

They're really simple machines, the way they fail tells you what could be wrong, no mystery about it.
 
Last edited:
I had a 16 inch crack from the gas block all the way forward while shooting 855 ammo.I couldnt figure out why it was short stroking as the crack was about the 5:30 position and I didnt notice it until i was cleaning everything including the gas tube trying to figure out where a blockage to the gas system could be.... that also explained why my sand /rice bag was cut open... LOL
 
Last edited:
I haven't had time to try different ammo.
I talked to a gunsmith and he was talking about ejector, extractor also.
I'am having a hard time wrapping my head around why it doesn't do it all the time.
There's no pattern to it, but never happens with cover open. Doesn't happen every time with it closed.
I know I can just load it and leave the door open while calling, but I'am sure I would forget at some point in time maybe missing a double.
 
Kicking the door open does add a little bit of drag on the BCG, but it shouldn't ever create enough bind to cause a short stroke.

Fun test - put ONE ROUND in the chamber and an empty magazine in the well. Close the port cover. Fire one shot. Does it lock back?
 
Originally Posted By: VarminterrorKicking the door open does add a little bit of drag on the BCG, but it shouldn't ever create enough bind to cause a short stroke.

Fun test - put ONE ROUND in the chamber and an empty magazine in the well. Close the port cover. Fire one shot. Does it lock back?

I've done that.
Closed the cover after every shot.
The bolt locks back and sometimes the empty is laying half in/ half out. Sometimes the spent case is laying on the ground at my right foot, sometimes four feet away at the 3 o'clock.
More times than not with the cover closed the empty doesn't go far.

The cover seems to latch and open like any other AR15.
Bolt doesn't hang up on it when moved by hand.
 
Weak dust cover spring, doesn't open fully in time for the spent brass to clear the port, thereby knocking the brass back in....

Just a thought, and another item to investigate.
 
Originally Posted By: takHow do you know if the gun is getting too much gas?

If you tuned your gas block to just lock open, it is not getting too much gas.

Dead give aways for too much gas are case head swipe, extractor "shelf" and ejector impressions, excessive rim damage from the extractor. Ejection forward of the 3pm position, and dents mid-body on the case bodies are other signs.
 
Back
Top