224 valk (factory hornady 88eldm and also fed 90gm), rainier 24" +2 barrel, superlative .875 adj gas block, jp lmos bcg and buffer, mega billet upper & lower. worked fine for 2-300 rounds including friday before the match. partially into match on saturday it stopped ejecting and i had to manually cycle the rest of the day. that evening, tyler graciously helped and swapped out his various bcg parts but same problem. readjusted block (and re-loctited) and settings and got it ejecting again. but next day it again stopped cycling for the rest of the match. can a gas block 'go bad'? with detents on the adjustment screw, doesn't seem that could just go in and out by itself. could it be the adj block, +2, and 224 valk cartridge are just too finicky together? recommendations appreciated!
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Gunsmithing gas gun turns into bolt gun
- Thread starter davsco
- Start date
mark your gas block adjustment and make sure its not rotating under recoil.
also, is your rifle lubed?.......slather that thing in oil and see if the problem persists.
also, you should try cleaning it when it stops ejecting and see if cleaning alone cured the issue........if you have a tight fitting match chamber, you might just have to clean more frequently
also, is your rifle lubed?.......slather that thing in oil and see if the problem persists.
also, you should try cleaning it when it stops ejecting and see if cleaning alone cured the issue........if you have a tight fitting match chamber, you might just have to clean more frequently
good idea to actually mark the adjustment screw, i will do that (though there are detents and it does seem to be the same length out as when it worked). yes, i well lube all my guns, and racking the slide seemed pretty easy. it was pretty clean before it stopped working (no more than 20-30 rounds after cleaning) but yeah i'll try that as well. i removed the gas tube stake pin at the gas block just now, it's been in since day 1. was going to pull the tube but haven't yet.
some phone pics attached if that helps anyone see what may be going on.
Attachments
I had dirty tight chambers fail to feed/ lock up before they would not extract..?
A quick snake run through got that squared away to continue.
Maybe something internal on the gas block clogging slowly, chip, burr, chunk trapped?
A quick snake run through got that squared away to continue.
Maybe something internal on the gas block clogging slowly, chip, burr, chunk trapped?
bolt moves from zero to a little. when i rack it manually i don't feel a bunch of tension or friction so it's not like the case or bolt/carrier is getting stuck.
in the pics you can see a bunch of carbon aft of the block on the barrel and tube so not sure if that indicates a loose or sloppy fit. i snaked the tube all the way to the block and no blockage, snaked the gas key to inside the carrier and no blockage, and the gas port in the barrel has no blockage.
How are you setting your gas block? Meaning how are you deciding where to leave the detent screw?
from all the way in (gas closed) i backed it out until it was cycling/locking back then went out a few more clicks (quarter turns). worked perfectly for 2-300 rounds then stopped working early saturday. did same process saturday evening and got it cycling again. i just can't believe the adj screw is walking with the detents, but maybe it is, i will mark it and see. also maybe despite backing it out a little more once it starts cycling i need to back it out even more so it's not on the 'edge' of working but in the middle of the threshold.
with block off the gun, i pressure sprayed it with gun scrubber (nozzle into the port). with screw all the way in (closed), the stuff sprayed back out. with screw backed out some it came out where the gas tube connects. and with the screw backed all the way out, it came out where the tube connects, and out the front where it relieves excess gas. so the block does seem to be working as designed.
I would adjust til it locks back and then open a full turn. I don't think that is your issue though if the bolt is not moving at all or moving very little.
Match grade barrels can be tricky. You look to be pushing a lot of pressure, through the block. I would use a heavy non adjustable block on a .224 I use UNIQUETEK - AR-15 GAS BLOCK ALIGNER, sometimes when I have issues, then run air through as someone already stated. If you are still in "break in" for the barrel, you will clean the chamber more frequently. Lastly, are you running a carbine or full length buffer? May sound silly, but I always check everything from to back.
I know you said you replaced various bcg parts, and I could be way off on this, but what do the gas rings on the bolt look like? Can you extend the bolt out in the bolt carrier, unlocked position, and place it on a table bolt down and it stay in the unlocked position while supporting the weight of the bolt carrier?
while they say the adjustment screw can come all the way out, i didn't figure out how to do it. with it all the way in, halfway out, and fully open i sprayed in every hole. again based on where the spray oozed out based on where the set screw was, the block seems to be open/closed as intended.
so pull the cotter pin and the firing pin and the bolt cam pin; and with the bolt in the carrier pick it up by the bolt and there should be enough friction where the carrier doesn't drop off the bolt? there is not enough friction. even if i hold it by the carrier with the bolt facing down, the bolt does drop out if i give it just a very light shake. this is a brand new jp full bcg. i tried this on another older AR and either way (hold by bolt or carrier) it's tight enough that nothing drops out.
yes they got back to me today. he was going over all the ejecting patterns and i'm like, it's not ejecting... basically said to turn it ccw from closed to full open (4.5 revs, 18 clicks iirc) and let him know what happens, and if it doesn't cycle it's not the block's fault. but he did say even if it doesn't seem to be the block, he'd help me troubleshoot.
based on above, thinking it might be the gas rings on the bolt, but no idea how they (and/or the carrier inside) could have worn so incredibly fast.
The gas rings look funny. I've never seen a JP bolt or a 6.8 bolt so I donl't know if that is normal.
Yeah sorry bout that, but the way you described above should serve the same purpose. I've seen regular gas rings go bad after a couple hundred rounds on occasion, not sure if they were just a bad set or if there were issues with the bolt carrier. I know JP rifles makes good stuff, don't have any experience with their enhanced gas rings though, and from the pictures they don't look bad, but looks can be deceiving, might try giving them a call as well, even though gas rings are pretty cheap, it'd suck having to replace them every couple hundred rounds if the bolt carrier is out of spec or something. Hope you're able to figure out what's causing the issue.
Looks like a JP one piece gas ring. So the bolt is it just clicking out of battery then back home when fired? Sounds like gas issue, my JP bolt I have here is loose in the carrier compared to my other 3 gas ring bolts. I've never used the gas block your using, does it normally blow that much gas out onto the barrel? My gas blocks don't leak that much on any of my ARs? Maybe the tube is messed up inside the block or split? Have you pulled it from the block?
I expanded the bolt picture, lots of lube.
I did not see any of the splits on the rings i was told to make sure they are staggered.
I lube my rings and use a otis bone tool to clean carbon off the bolt.
Shooting 5.56 and 300 blk rings have lasted over a thousand rounds easy.
I have let ar's get dirty enough that a round wouldn't chamber on a cold day and used fwd assist just to see if it would work.
Fired the round and the heat melted enough gunk several rounds fired, happened again at lunch after clearing chamber then reloading later.
Went ahead and fired again just to see.
Both times almost could not get bolt closed but ejected and since warm next round fed and closed the bolt.
That is a filthy pig. Lol my sons said I was over cleaning and I just wanted to see how long before ftf happened.
Conclusion was over 500 rounds all on hot days, not the same day one freezing cold day and not so much.
Can you put a standard gas block on it for a weekend? Or will that cause damage because of the 224 pressures?
I did not see any of the splits on the rings i was told to make sure they are staggered.
I lube my rings and use a otis bone tool to clean carbon off the bolt.
Shooting 5.56 and 300 blk rings have lasted over a thousand rounds easy.
I have let ar's get dirty enough that a round wouldn't chamber on a cold day and used fwd assist just to see if it would work.
Fired the round and the heat melted enough gunk several rounds fired, happened again at lunch after clearing chamber then reloading later.
Went ahead and fired again just to see.
Both times almost could not get bolt closed but ejected and since warm next round fed and closed the bolt.
That is a filthy pig. Lol my sons said I was over cleaning and I just wanted to see how long before ftf happened.
Conclusion was over 500 rounds all on hot days, not the same day one freezing cold day and not so much.
Can you put a standard gas block on it for a weekend? Or will that cause damage because of the 224 pressures?
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Superlative AGB is both a restrictive and a bleed-off gas block and by the looks of it you have it in the bleed-off settings due to the fouling marks in front of the gas block. Either that or you do not have a good gas block to barrel seal. How many clicks/rotations do you have it set from full closed? Above 4.5 rotations you start getting into the bleed-off settings. What buffer length/weight are you running?
sometimes the bolt doesn't move back at all, sometimes moves back just a little. again, new it worked fine for 2-300 rounds and then worked again for 10-20 rounds after disassembly and re-assembly and then died again.
when i was playing around with it during the match, after it stopped cycling, pretty sure i didn't perfectly re-align the gas block (didn't have reading glasses...) and that may be why we see seepage fore and aft. but it was aligned that evening and it worked for a couple of shots then and a couple of shots the next morning. the block set screws were tight every time i checked, so don't think it walking is the problem.
i did pull the gas tube from the block and didn't notice anything awry. i sprayed and scrubbed everything (barrel, block, tube, bolt, etc) so if there are some leaks or splits, it should be easy to see.
i don't remember what setting i had it on, but it was working perfectly for 2-300 rounds at whatever that setting was. haven't changed any parts since i originally assembled the gun, jp lmos bcg and matching jp rifle length buffer/spring. with it not working, after each stage i opened the block some and close the block some to see if those changes made a difference and they did not, but could account for carbon in front of the block when i may have had it turned past the 4.5 revolutions.
just dimpled for the one screw, the one closer to the chamber. yes blue loctite was used originally and when we loosened and re-tightened it. the screws were tight every time it was loosened to check it. so i don't think the block was walking.
I think that agb has tortured you enough, 30$ shot at a good day.
http://www.primaryarms.com/troy-ind...as-block-875-set-screw-style-sgas-875-00bt-00
http://www.primaryarms.com/troy-ind...as-block-875-set-screw-style-sgas-875-00bt-00
Looking at your photos I'd say you are in the bleed-off positions due to the flute showing on the adjustment screw. I would turn the adjustment screw all the way in and start unscrewing once you get reliable ejection and then turn it out one more click. If you want to keep it in bleed-off I'd screw the adjustment screw in 1-click at a time until you get it to cycle the leave it there. My guess is the AGB isn't properly aligned and the adjustment screw is on the edge of non-restrictive and bleed-off.
Read this article: https://www.pewpewtactical.com/superlative-arms-gas-block-review/
The fouling in front of the gas block looks like what you have on your barrel. This is the bleed-off working. Try setting it 4.5 full rotations from full closed. This will set the AGB to the maximum amount of gas. Now turn the adjustment screw in until it stops cycling then one click out for reliability.
Read this article: https://www.pewpewtactical.com/superlative-arms-gas-block-review/
The fouling in front of the gas block looks like what you have on your barrel. This is the bleed-off working. Try setting it 4.5 full rotations from full closed. This will set the AGB to the maximum amount of gas. Now turn the adjustment screw in until it stops cycling then one click out for reliability.
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as noted above and in discussion with superlative arms, today i had the adjustment screw out 4.5 revolutions which should be full open with no bleed off. haven't found a borescope yet to verify the gas block is centered over the barrel port, but with reading glasses on and some measuring, the gas block back set screw is in the barrel's dimple and loctited. the first 2-3 rounds the cases ejected barely but it didn't catch rounds out of the mag. next couple shots it didn't eject or catch a round off the mag. again the bolt has almost zero friction inside the carrier, so thinking that is where the gas is leaking. and it gets worse as the oil on the rings gets blown off thus reducing the seal even more. thoughts? i have an email into JP to hopefully get a replacement bcg to confirm that is the issue.
I got here late but for one thing it looks to me like you have a hell of a lot of gas blowing out of the block onto the top of the barrel. Try a diferent block. And make sure the gaps on the bolt rings are stagard.
Something ive seen in the past so this might be stupid. is there any play between the upper and lower receivers? I have also seen where the bolt, somehow I couldnt figure out, catches the buffer retainer pin and stopped the bolt until it finally sheered off.
other than that, my best guess is what the other guys are saying with the gas block.
other than that, my best guess is what the other guys are saying with the gas block.
this is the mega billet matched upper and lower, no play. and when i rack it manually, feels just like all my other AR's, no unusual friction, dragging, stuck case, etc and it extracts and ejects nicely.
so i ordered another block (the non-adj Troy suggested above), +2 tube and JP is sending me another bcg to try. hopefully replacing one of these will highlight what is not working.
I’m still wondering about the gas rings. Is that a different type ring set up? Also I see zero wear in the finish on the end of the bolt which makes me wonder if it’s out of spec too small or the carrier is out of spec too big?
they said this is the newest version of their rings, out a couple of years. when i mentioned it seems to run a 'little' better after the rings are freshly oiled, they sort of agreed that suggested some sort of ring clearance issue (whether rings too small or inside carrier too large), hence them sending me another bcg to try.
I too have been fighting this battle with both my valkyrie and a year before with my grendel. I'm 90% sure it's the relationship between my jp bolt and jp carrier. In the grendel I replaced the bcg with a non JP bcg and the problem went away. Which leads me to believe the jp bcg is venting gas to easily. I've ordered a new one piece gas ring as well as new standard gas rings but haven't had time to try them yet. I also want to order a carrier that is just a standard Milspec chrome lined carrier as the problem has persisted in the valkyrie while using a non JP bolt with three gas rings but a nitrited carrier.
Thinking outloud...
Maybe the nitrited carrier is the issue because my stainless jp carrier and bolt in my 6.5 creedmoor has never had an issue...
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my valk carrier is jp's stainless. i have the jp-built ctr02 that has the black carrier and that has been 100%
so you went to a non-adjustable block? not saying your wrong, as i may have the same problem, but how can an adjustable block affect reliable ejection? i can understand if it's set at just the cusp of the rifle cycling, but if it's all the way open, doesn't it stay all the way open, so at worst you basically have a fixed block?
Still trying to figure out if the issue is with the mags or the gas block. Going to a fixed removes that from the equation for now
here's the latest. jp was nice enough to send me a replacement gas ring and carrier. swapped out the ring and in the new carrier there is a lot more friction, similar to my other various AR's. also replaced the adj block with a fixed and replaced the tube also. shot a box of ammo with no issues, and at yesterday's gas gun match, roughly 100 rounds) had zero issues. at some point guess i will put the old stuff back on piece by piece to see what component was causing the issue, but was tired of it not running and wanted to use it yesterday, so replaced everything at once. may not mess with an adjustable block again, at least for this rifle, as i stayed on target for every shot, maybe the +2 by itself gives enough recoil reduction...
Looks to me like your gas block is not sealing correctly around the gas port. Look at the barrel around the port in your pics, there should be NO carbon showing except maybe a very small circle around the port.
G
From looking at the pics, what is the contamination around the gas port ?
Shoot it without a handguard, wrap it with tissue, and see if you have a block to barrel leak.
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