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2/20/2008 1:48:39 AM EDT
Here's what I did.
I built a very nice Tack Driver and used a MagPul PRS.  I used a Rifle Length Buffer, Spring and Tube.  The barrel is a 24" Olympic Bull UltraMatch.  Everything worked perfectly.  No Problems.

Then I robbed the lower (including the Magpul PRS, Rifle length Buffer Tube and Buffer) and put a 11.5" barreled Upper on it.  

Now I have a ...... Glitch.  When I Fire a round, it ejects great and loads the next cartridge fine.  But now, After I fire the last round, the Bolt Doesn't Catch.  As if it retracts enough to grab the next round but not far enough to engage the bolt catch.

Any Idea's?

I see there is a big difference between a carbine buffer and a rifle buffer.
With a much shorter Gas tube, is it a problem to use the longer Rifle Buffer and Spring?
I cant really change the buffer tube or the Magpul PRS wont install.
2/20/2008 1:53:00 AM EDT
[#1]
did you try other mags? the rifle buffer vs carbine buffer shouldn't matter
2/20/2008 2:05:38 AM EDT
[#2]
Well CRAP NO hehe.  I could kick myself for not trying a different mag, I'll do that.

I was so puzzled that I just kept loading one more cartrige to try to figure it out.

I'll post tomorrow what I find.
2/20/2008 2:28:02 AM EDT
[#3]
ok, with that mag empty, manually lock it back to see if it will. Most problems can be contributed to the mags. When you test it, IM me and I'll help you out
2/22/2008 9:44:41 AM EDT
[#4]
Thank a ton MuRDoC.  I went to the range yesterday and everything is working perfectly now.  I would have thought there would be more quality control especially on something like a low profile gas block.  There wouldnt ever be anything between the gas block and the "stop" on the barrel that would ever change the alignment would there?  

I should have caught the problem though.  If theres one constant between my hobbies of Handloading, Rod building, and now building/modifying AR's it is Measure Once, Twice, and then again to be sure.
2/22/2008 10:16:31 AM EDT
[#5]
There must have been some off the forum discussion here. We went from not working....... to works great. What did you find as the problem and what was the correction?  Just curious should a similar problem occur with one of mine.
2/22/2008 10:49:00 AM EDT
[#6]

Quoted:
There must have been some off the forum discussion here. We went from not working....... to works great. What did you find as the problem and what was the correction?  Just curious should a similar problem occur with one of mine.


HeHe, Your right, Sorry.
MuRDoC advised me that the problem shouldn't have been with my Buffer Tube/Buffer/Buffer Spring configuration.  We ruled out any issues with magazines after finding that I could manually pull back the Charging Handle and the bolt catch would engage on all of my magazines.  The issue was possibly Short Stroke then.  

When I built the rifle I used a 16" Stainless RRA Barrel, YHM Low Profile Gas Block, and a YHM Free float tube.  When I installed the Gas Block I only worried about vertical alignment thinking that running the gas block up against the Barrel Stop (not sure of actual terminology) was the correct thing to do.  It worked on previous builds just fine.

Well, after carefully measuring I found the gas block needed to be backed off toward the end of the barrel by 0.85.

So as it was, the gas tube may have been into the receiver a bit to far as well as there may have been some pressure loss from the gas block and barrel hole not being lined up correctly.

Problem Solved
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