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9/22/2017 12:11:25 AM
Posted: 9/5/2010 9:59:24 PM EDT
I went to shoot my RRA 10.5" SBR and had some FTE problems. I recently installed a Fail Zero BCG, upgraded extractor spring, gas ring, H3 buffer, and Sprinco SBR buffer spring.

I went to the range with some buddies today and this is how the problem developed.

used GI Okay range mags with Monarch steel cased 55gr. ammo. 100% function
used GI Okay range mags with PMC IMI 193 55gr. ball ammo. FTE on 1st round
Pmag w/ steel cased Monarch 55gr 100% function
Pmag w/ PMC IMI 193 55gr. ball ammo. FTE on 1st round
Pmag w/ M855 62gr. ammo. 5 rounds then FTE

I changed back to a stock BCG from my M&P 15 = 100% function

I thought it would be a mag or ammo issue, so I put 30 rounds of the PMC in the GI mag and ran it through an H&K 416 on full auto = 100% function

I also replaced the buffer w/ an H instead of H3 buffer and got the same results with the PMC ammo.

I am leaning towards an issue with the extractor, but it seemed weird that I got better results with the steel ammo rather than the brass.

If you have had this problem before or seen anything like it, please help me out.

Link Posted: 9/5/2010 10:01:49 PM EDT
lulz at the irony of "fail zero"

Link Posted: 9/5/2010 10:09:02 PM EDT
Sounds like its not liking the m855 and the pmc some lots of those brands are know to be loaded light.

For now I would run the stock BCG and the H buffer and practice with it for a while.

When you get ready to try the other items do them one at a time so you can isolate the problem.
Maybe put up a pic of the malfunction. We will get you goin right in no time!

IM me more details if you like.

Link Posted: 9/5/2010 10:21:22 PM EDT
I did keep all the OEM parts just in case something like this happened. I am going to go this week and change out parts one at a time and see if I can isolate the problem. I think I am going to start with the bolt. I am going to put the stock bolt in the Fail Zero carrier and see what happens. I am wondering if I got the extractor spring in wrong, or if I don't need the regular instead of the upgraded extractor spring. To me, everything is pointing to an extractor problem. Also, the possibility of an out of spec part arises. If that is the case, I know Fail Zero will make it right.
Link Posted: 9/5/2010 11:08:20 PM EDT
Try a lighter buffer and stock spring first.

Link Posted: 9/6/2010 12:01:26 AM EDT
Is it short stroking or is it double feeding? I had FTE problems when I upgraded to a 5 coil extractor spring. Had a little trouble getting the extractor back in. Went to do a function check by loading and then unloading the weapon manually and the round wouldn't eject. Tore it down put the original spring back in and have have had no problems since. I've been running an H3 and Sprinco blue spring in mine. Of course the only ammo I've shot is Prvi M193 and Fed M193 PD so far. Still no problems. Have had problems with PMC in the past. Like some of the guys have said they have a bad habit of not putting enough powder in their rounds.
Link Posted: 9/6/2010 3:56:09 AM EDT
try lots of lube before replacing anything.
Link Posted: 9/6/2010 5:53:26 PM EDT
I went to the range today and tried a couple of changes on my rifle w/ the following results:

The changes I made were to put the stock extractor spring back in the Fail Zero bolt.

I got the same results as in the original post. I did examine the FTE's a little closer, and noticed that the extractor is grabbing only half of the round on the brass casings that it is failing to extract.

I then replaced the Sprinco spring with the factory RRA spring using the Fail Zero bolt. same results.

I then put in the factory BCG, and the rifle ran perfect.

I will call Fail Zero tomorrow and see if they think I could have a bad extractor. I will let you know what they say.
Link Posted: 9/6/2010 6:43:43 PM EDT
I would ask for a new bolt and extractor.
Link Posted: 9/7/2010 1:06:52 PM EDT
called Fail Zero today and talked with one of their tech guys. He said to put the rubber ring on the extractor spring and use the black spring. He also told me to check the extractor ring to make sure it was seated properly. He told me that they only tested the BCG on 14.5", 16", and 20" rifles so they did not have any raw data on how to run the BCG in an SBR.

I put the rubber O-ring around the extractor spring and re-installed it in the bolt. When I put the bolt back in the carrier, it fit noticeably tighter. I will go to the range ASAP to test it out.
Link Posted: 9/8/2010 8:44:18 PM EDT
Went to the range today and tested the latest fix. H3 buffer, SBR buffer spring, Fail Zero BCG W/ O-Ring on extractor spring, Fail Zero Hammer, Titanium firing pin.

100% functionality!!!!!!!!!!!!!!!!!!!!!!!

I did a test of 15 rounds in a P-Mag and GI style mag as follows:

5 rounds steel cased Monarch .223 55gr
5 rounds brass cased PMC XM193 55gr
5 rounds M855 Penetrator 62gr

Everything was perfect. Spent another 100 rounds of mixed ammo in P-Mags and GI mags to check the zero on my EoTech and iron sights, and it was accurate enough to pass dept. qualification standards w/ 100% accuracy.

Glad to get this figured out. I have learned alot about AR-15s in the lat few weeks by replacing hammers, extractor springs, hand guards, barrel nuts, and a few other odds and ends parts. It's been fun reconfiguring all my weapons for their intended uses. Now it's time to go shoot 'em up!

Also, thanks to the hive for helping to figure out, and fix this problem.
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