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Posted: 12/22/2012 7:27:01 AM EDT
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Back in January, I started a SBR build. This is the fourth AR I have built. I used the following parts:
RRA 10.5 1/7 barrel Spikes stripped lower RRA LPK w/ NM 2 Stage trigger Standard Mil Spec Buffer tube, spring, and buffer Spikes Micro gas block and gas tube (carbine length) MOE furniture YHM Diamond spectre length rail I initially had problems with functioning. I was using Wolf. I changed to Federal XM193, and still had issues. It wasn't fully ejecting the spent case, but was attempting to insert another. I fired about 200 rounds just making sure that it wasn't just needing to be broken in. It continued to malfunction about two in three rounds. I opened up the gas port on the barrel a bit to about 0.62, and continued to malfunction but did improve slightly. I then opened it up to 0.093 and it started functioning really well, comparatively. It still has the same malfunction about one round per ten, but the other issue I've noticed is that it doesn't lock back on the last round. I checked it yesterday, and it is ejecting to about two o'clock. I have been told to try heavier bullets, but I can't do that, because I use it as my patrol rifle, and I have to use the issued ammo (Hornady TAP 55g). Does anyone have any idea what could be going on? Any help will be greatly appreciated! Thanks! |
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Quoted:
Have you checked the gas key on the carrier and that your gas block is correctly lined up with the gas port on the barrel? If you want to try heavier ammo, just get a box or two and use it at the range, then switch back to your issued ammo. I have checked the gas key. I will try heavier ammo. But, if it works, how could I make it work with 55g? |
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Quoted:
Is the gas block pinned or is it a screw/clamp? If it is off just a fraction, it can cause short stroking I did check the block yesterday. it was less than a sixteenth of an inch to the left, but was still totally covering the gas port. I have since corrected it, but it's still not running right. |
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load a single round into a mag, charge and fire for effect.
If the bolt locks back on the empty mag, then you have an extraction problem with the extractor slipping off the rim and a #60 O ring around the extractor spring should fix that. If the bolt does not lock back, then you have a stroke problem, and chances are it someone where in your gas system, or just related to a tighter/rougher chamber that is not going to get along with steel case ammo until the chamber has self polished out through live fire. |
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Quoted:
load a single round into a mag, charge and fire for effect. If the bolt locks back on the empty mag, then you have an extraction problem with the extractor slipping off the rim and a #60 O ring around the extractor spring should fix that. If the bolt does not lock back, then you have a stroke problem, and chances are it someone where in your gas system, or just related to a tighter/rougher chamber that is not going to get along with steel case ammo until the chamber has self polished out through live fire. That's exactly what I spent several hours doing yesterday. It ejects, still at approx 2 o'clock, but does not lock back. I have ordered an adjustable gas block to make sure it's not over-gassing. I would be scared to death to drill out the gas port any more being that it's already at .093. I've seen a couple of places that have said that ejecting at 12-3 o'clock is due to over-gassing, but I've also seen places that say that a 10.5 inch barrel needs at least a 0.093 port. I don't know what to believe about it. I guess I'll wait for the gas block to come in and see what happens. Until then, I'll just enjoy looking at my $1000, $200 tax stamp paid, single shot. 
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10.5" barrel is going to be finicky at hell.
See if someone can lone you a H-3 buffer to check if you are over gassed (if the rig runs with the heaver buffer, then the system is over gasses. If the heaver buffer just makes the problem worse, they you are under gasses, and need to check the entire gas system before even thinking about enlarging the barrel gas port. |
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Quoted:
10.5" barrel is going to be finicky at hell. See if someone can lone you a H-3 buffer to check if you are over gassed (if the rig runs with the heaver buffer, then the system is over gasses. If the heaver buffer just makes the problem worse, they you are under gasses, and need to check the entire gas system before even thinking about enlarging the barrel gas port. I'll try that. I did try a H2 buffer that I borrowed from a buddy (Spikes T2) but I'll try the H3. I'm also going to wait for my adjustable gas block before making any other drastic moves. |
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Finally got it running right! I got a Spikes T3 heavy buffer and an adjustable gas block. I turned the gas down a bit, added the T3, and put a o ring around the extractor spring and she runs like a dream! Needless to say, I'm as giddy as a schoolgirl right now.
Only one question remains...should I worry about inconsistent ejection trajectory? I tried it out with three different ammos: Wolf .223 55g FMJ, Guatemalan military surplus 5.56, and Hornady TAP 55g. With all three ammos, it varied from 2 to 4 o'clock ejection. Should I worry or just be happy with it as is(keeping in mind this is a duty gun, my life or that of someone else may depend on it one day)? |
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