AR-15 ejection mystery

[Wakal]

The gun: Flattop upper, smooth sided (no forward assist or port cover). Titanium bolt carrier, GI bolt, GI firing pin. DPMS lower with JP trigger group. Oly barrel (carbine gas port), 18" with JP tank brake and free-float handguard.

The history: 3,000 rounds of Winchster white box (55 grain), no problems.

The problem: A few weeks ago, we found that when running five rounds with sedate .15 splits, the third or fourth round's empty brass will end up in the port...usually backwards but rarely sideways (just for variety, of course). Watching from behind the shooter, it seems almost as if the second piece of brass hits the first piece of brass, and the third hits the second, and the fourth hits the third enough to bounce it (the fourth) back into the ejection port. Weird.

So far: replaced the ejector, extractor, and both springs. Swapped out the bolt for another GI steel bolt. Swapped out the bolt carrier for a GI bolt carrier. Swapped out both the titanium bolt carrier and the old bolt for a new GI bolt carrier group. Replaced the extractor spring with one of the Wolff extra-power jobbies. Added one of the powerextractor bits.

And so far, no luck.

Any bright ideas from this, the acme and omega of firearms boards? I'm stumped.

Alex

[benny hill]

Just slow your splits down to around .50-.60 like mine . Problem solved.

[Wakal]

Heh! I've RO'ed you enough to know that you do NOT run .50 splits.

.45-.46

Alex

[Run n Gun]

The first thing I need to say is that I don’t know what’s causing it, but I suspect the gas system. You’ve changed everything that comes in contact with the case except the chamber it’s self. Could it be that the gas block or some other part of the system has a partial blockage?

My train of thought goes something like; a gas system that doesn’t impart the energy that it once did, while still enough to operate the action, but not enough to SNAP the brass out at its former velocity may cause the then “lazy” brass to not get out of the way in time.

As you know, 15 splits ARE sedate compared to a FA M-16.

FWIW, just a wild ass guess…

Ed

[George]

I agree with Benny.

What did the doctor tell me when I said it hurts when I do this?

Seriously, try taping something shaped like a little wedge right behind the ejection port where you see the brass marks from the empties hitting the side of the receiver (most do that). See if this can be made to deflect the brass downward, or at least somewhere else than where it is going now. If it works, glue something permanent in place.

If all else fails, try changing the rifle

After reading Run n Gun’s post, I will say change what you haven’t changed yet, in this case it would be the upper receiver which is basically the gas system as far as function goes. And yeah, bolt speed might just be down a bit. Run the bolt carrier back and forth without the bolt in it and see if the carrier key is rubbing the gas tube, if so, bend the tube until it doesn’t rub. Also look at where the gas tube leaves the gas block to see if gas is being lost there (lotsa‘ carbon).

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Regards,

Edited August 3, 2004 by George

[EricW]

Checked your buffer and spring too?

[George]

EricW has a point, the JP low mass carrier uses a different buffer/spring combo because it doesn’t need as much spring to return the lighter bolt carrier. You will not want to shoot a full weight carrier with the low mass buffer/spring and vice versa.

The gas system is still my thought.

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Regards,

[Wakal]

Ah yes, the gas tube...I just happen to have a spare 16" tube, new in the wrapper and all ready for swappin'...thanks!!!!!!!

Will report as soon as I get it to the range

Alex