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Posted: 8/30/2004 3:59:12 PM EST
The bolt carrier and group in particular have had just under 2000 rounds through it, I've replaced chewed up firing pin retaining pins twice, and now shall I shall be putting in a 3rd FPRP (for short).

In reading the FAQ's, I still have to say WTF???

The spool dia. of the FP is .333

The bolt carrier is NON-shrouded.

And...

I'm betting on way too much contact with the hammer.

Short of replacing the bolt carrier with an M-16 carrier, any other practical ideas of a fix where I'm not needing to buy boatloads of FPRPs to replace the chewed up ones? How many rounds are these things supposed to withstand, 1k rounds per just seems silly.
Link Posted: 8/30/2004 6:03:58 PM EST
[Last Edit: 8/30/2004 6:06:18 PM EST by Tweak]
Link Posted: 8/30/2004 6:31:40 PM EST
Another possibility...
The gas pressure can leak around the tail of the bolt and push the firing pin back against it'sretaining pin. The tail of the bolt should be .250". I believe the clearance should be less than .002".

Link Posted: 8/30/2004 6:55:03 PM EST

Originally Posted By Tweak:
Your other option is to relieve the hammer where it contacts the spool of the firing pin. Does the spool of the firing pin overhang the end of the slot in the bottom of the bolt carrier?



Heya Tweak,

No, the spool of the FP doesn't overhand the end of the slot in the bottom of the carrier. BUT...

In running the edge of a piece of paper down the "ramp" at the precise angle, about mid way of the spool the paper makes contact. To me, this sure is a steep angle for which the hammer will traverse thus coming into contact mid-length of the spool.
Link Posted: 8/30/2004 7:19:03 PM EST
Link Posted: 8/30/2004 7:32:09 PM EST

Originally Posted By oldguy:
Another possibility...
The gas pressure can leak around the tail of the bolt and push the firing pin back against it'sretaining pin. The tail of the bolt should be .250". I believe the clearance should be less than .002".







The tail of the bolt when the bolt is pushed back to lock into "battery" protrudes .059 from the "notch" in illustration "A"

The distance from the beginning of the spool traversing down the FP to the "notch" when in battery is .154
Link Posted: 8/30/2004 7:34:47 PM EST

Originally Posted By Tweak:
Fully pull the bolt to the rear with the charging handle then, while holding the bolt to the rear with the charging handle, let the bolt go forward very, very slowly. Do you feel the bolt hang, or bind, at any point?



Yes, the bolt will hang slightly more than halfway down if I release it very slowly requiring that I either pull the charging handle/bolt all the way back to release normally or the use of the FA.
Link Posted: 8/30/2004 10:45:16 PM EST
Link Posted: 8/31/2004 12:20:55 AM EST

Originally Posted By Tweak:
Repeat the test but this time old the trigger to the rear the entire time. If the bolt runs smooth you need to relieve the hammer. You should see white marks in the hammer's finish where it is striking the FP.



I performed the above and, you called it, the bolt ran smooth.
Link Posted: 8/31/2004 4:12:56 AM EST
Link Posted: 8/31/2004 9:15:57 AM EST

Originally Posted By Tweak:
photos.ar15.com/ImageGallery/Attachments/DownloadAttach.asp?iImageUnq=21545

Does your hammer look like the left or right centermost one?



In the illustration, my hammer looks exactly like the left centermost labled "Bushmaster"
Link Posted: 8/31/2004 8:54:14 PM EST
Link Posted: 8/31/2004 9:21:20 PM EST

Originally Posted By Tweak:
That is the better design (from a snag standpoint) of the two so I'm going to stick with swapping to a shrouded carrier. You can relieve the upper forward corner but it can be tricky. If you take off too much you can keep the hammer from cocking. Your call.

Got a mic?

As a check pull the trigger out and run the firing pin through the trigger pin hole. Measure from the rear of the firing pin to the sear angle. Hold the jaw of the mic parallel to the sear angle not perpendicular to the body of the trigger. Post the measurement.



Tweak,

Thanks for all the info. I don't think I want to relieve the hammer, I've never even seen such an undertaking before, so, I am more apt to get a shouded bolt carrier. I had a gut feeling that I would need to go to a shrouded bolt carrier. I found a RRA "enhanced" BCG on the EE, I think I'll just break down and order one.

I appreciate all of your help and I came away learning some things I had not considered before.

Link Posted: 9/1/2004 1:25:06 AM EST
Link Posted: 10/1/2004 10:56:39 AM EST
Back to the top.

Tweak the hammer in my Armalite is just like the colt pictured above.
So what and where to relieve?
Raymond
Link Posted: 10/1/2004 10:43:05 PM EST
Link Posted: 10/2/2004 10:16:07 AM EST
Thanks Tweak.I really appreciate the help.Ive been waiting for Armalite repairs to return my calls for going on a week now trying to find out what needs to be done.So its nice to be able to find out what to do.
My hammer has a rather nasty casting mark in that area...center of the hammer...that I thought could be part of the issue.There is a very slight(bright)wear mark about where the red line is,which is also the rough pointed casting mark I mentioned.
The carrier does not bind or hang that I can tell other than when the hammer contacts the bottom of the carrier...but it must be enough contact to chew the firing pin and bend the retaining pin.
I will give that a try and see what happens.
May also get a Bushy hammer and try that if this fails.
Raymond
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