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hey all. im a newbie when it comes to ar 15s. my first one is my 6.5 grendel built from ground up by myself. i recently bought a cheaper 223 wylde upper from cbc industries and i cannot get it to work. my grendel is a 20in bbl with rifle gas system adjustable gas block turned out 3/4 with a carbine buffer system. shoots like a dream. this new upper is a 20in bull barrel with rifle gas and non adjustable gas block put on the same lower. when i got it i cleaned lubed and check every thing over. loaded 10 rounds in mag and 8 out of 10 short stroked and didnt pick up next round. brought it back in took gas block off checked the ports and marked the port locations put it back on to make sure the ports were centered. took bolt back out checked gas key and gas rings and looked for any thing rubbing wrong. all looked good, took it back out loaded 1 round at a time in the mag and it still wont cycle fully. brought it back in yet again tore it down yet again. verified barrel port size and its location from the barrels shoulder, checked gas block port location from its shoulder checked for leakage and all is good. ran out of day light so will have to test it this weekend. is there any thing i can be over looking? help much apreciated thanks!
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Try an H3 buffer, which weighs the same as a rifle buffer, since you’re running RLGS. If you don’t have access to an H3, try a lower with a rifle buffer system.Member since 2011, data lost in last hack attack -
Is the gas port diameter correct?
Rough chamber? (check fired bass for "frosting")Comment
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Manually pull back the charging handing slowly and see if you feel any binding occurring as you pull back especially as near the last couple of inches. What weight buffer are you using and you didn't to happen to measure the gas port when you removed the gas block? I'd look for gas leaks around the gas block and gas tube as well, the couple of cbc uppers I've seen didn't instill confidence and the barrels looked like the came from bca.Comment
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yes i checked barrel port size and its correct. also check location of port length wise from barrel shoulder and block shoulder and all is good. i made up a dummy round chambered it and upon extraction there was resistance trying to get bolt to unlock. checked brass and shoulder had a mark on it. checked all my fired brass and they have the same mark on the shoulder just deeper. so it appears to have a rough chamber. going to run 50 rounds through it and see if it clears upComment
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also my buffer weight is 3ozComment
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Caleb, what is the twist rate, 1:8 perhaps?
And what weight of bullet are you shooting?
My 223 wyldes handles the heavier, 69-77 gr bullets and Nato spec loading pressures better than lighter weights, it is also a new barrel...
Plus, the 77 gr Federal SMK GM also shoots too softly to cycle it.
I switched to a Nato 77 gr load and voila! good cycling, shootin' and not bad groups.
Might want to check this angle in your troubleshooting.
Assuming assembly is all ok.
O btw I'm shooting a carbine stock and buffer system, still gtg on the 77 Nato's."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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Sometimes brass gouges are due not to a rough chamber but because the brass hits a sharp corner in the barrel extension on one side by the feed ramp on extraction. See the forum thread using gouging in the search box.Originally posted by caleb90 View Post
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so after much tinkering i finally got it to run. shooting factory federal and umc 55gr 223 ammo. Ended up having to tap the gas block with a brass hammer tight to the barrel shoulder, tweaked the gas tube so there was minimal contact with the gas key. thinking the main issue is cheap gas block and tube, will be ordering a new gas set upComment
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1:8 twist and shooting factory federal american eagle and umc 223 55grOriginally posted by grayfox View PostComment
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That is interesting, usually I recommend to bump the gasblock forward off the shoulder. To mimic a two-piece handguard front cup spacing, in order to line up the gas port to the hole in the gas block.Originally posted by caleb90 View PostComment
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Some of the current-market gas blocks and barrel shoulders are now being made to be placed flush...
It doesn't hurt to measure what you've got b/c of the variations.
The GB hole is also, typically much larger than the hole in the barrel, so there is some wiggle room."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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You said it was a used upper could the gas tube be fouled/blocked? Just a thought? I troubled shot a friends upper who had similar situation i had to align the gas block and put in a carbine spring and buffer to get it to run 100%Originally posted by caleb90 View PostComment
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A method I use to check gas block/barrel port alignment that works quite well. I shove a tight fitting piece of surgical tubing over the gas tube with the gas block and tube installed but not yet completly torqued, but snug. I blow air, from my mouth thru the tube while moving the gas block around. I can feel the pressure change as the alignment is least restrictive. Then I torque the block screws and check that it still feels good and feel around for any serious leaks I might need to keep an eye on until fouling seals up things real good.Comment
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The inner hole for the GB is 180 deg opposite to the rear set screw but radially aligned. Turn/rotate the GB over so set screw holes are up and measure/align the GB rear edge while the screw hole is centered to the barrel port; use a fine pencil to scribe a match line onto the barrel for that rear edge of GB. Now rotate the GB back around and align it to TDC over the GB hole using that rear-edge line.
Lots of variations on this theme making use of the set screw/GB port alignment.
With the GB rotated you can tell if it centers on the barrel port while snugged up to the shoulder or if it needs a gap to be able to center..."Down the floor, out the door, Go Brandon Go!!!!!"Comment
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