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300 Blkout 1st range test

Discussion in 'Gunsmithing and Repairs' started by Zero19, Sep 14, 2019.

  1. Zero19

    Zero19 Member

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    Took my 300 blackout 10.5 inch to the range today and had a couple issues. Trip was to tune the gas block running subs. Process- 1 round per mag until the BCG locked to the rear. Setup - Carbine gas/ Seekins adjustable gas block/ Sig M400 BCG, Barrel is 10.5 purchased from Classic Firearms as "us manufactured" but when asked said Bear Creek Arsenal

    1. After chambering a round, the bcg & charging handle became next to impossible to extract the round. I had to use the bench to knock it loose if I wanted to eject/extract the live round. This didn't happen on every round though...Im struggling to figure out what could have caused this.

    2. After several different sub loads and gas block almost completely open the BCG would only lock back on an empty mag if I ran super sonics. I figured this was due to the buffer which is an H2. Though im not ruling out issues with the BCG

    Any suggestions on a different buffer to try and reasons why the BCG lock up would have happened?
     
  2. Blue68f100

    Blue68f100 Member

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    Have you checked the head spacing on the chamber?

    Are you shooting factory Sub's are handloads? The reason I ask is if the bullet is jammed into the lands or the shoulder has not been pushed back far enough you will have a press fit when the BCG is home.
     
  3. Zero19

    Zero19 Member

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    I used a foster set of GO/No go Gauges which it passed the test. I just received an email from Bear Creek saying to use PTG gauges as its more accurate to their match grade chamber but also saying that if I used foster set I wouldn't get any different result which was a bit confusing. What was weird about it was it only did it in groups of 2, then would work freely as it should for 2-4 rounds then jam up 2 times in a row. There wasn't anything that stood out as to what would have caused it, no marks on the casings or bullets, no new or stand out marks on the barrel, feed ramp, bcg or charging handle.

    2 other guys at the range sighting in their own builds, one being a 300 blk 9inch where clueless why it would hang up like it did.

    Shooting Remington UMC 220g & Sellier & Bellot 200g.
     
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  4. Blue68f100

    Blue68f100 Member

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    I'm wondering if the barrel extension nut did not scrape off some brass/copper during feeding and caused the problem. All it takes is a spec to make a min spec chamber too tight. Check for burrs on the barrel extension nut. I de-horn all of mine before I install the barrel. Since I handload I do not like my brass gouged up. A magazine can gouge the brass too. If you have one of the chamber brushes, use it and take it with you the next time you go to the range. If it happens again, use it and see if it clears up.
     
  5. jbm

    jbm Member

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    I'm going from memory here, but I think the 300 blackout was meant to run subs WITH a suppressor and supersonic bullets WITHOUT. I don't know if you'll get enough gas pressure without it. I built mine with a 10.5" barrel, but I run a yankee hill suppressor on it with no problems. It will not run subs without the suppressor. It's overgassed with supersonic bullets (which I almost never use) and a suppressor.
     
  6. jmorris

    jmorris Member

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    If your reloads are sticking. Remove the upper and one at a time drop them into the chamber and install the BCG (don’t forget the charging handle) and snap the extractor over the rim. Is the BCG flush with the back of the upper and eject easily?

    If not try just sized cases.

    That will tell you where you need to focus your search.

    You could also try factory ammunition, if they don’t stick, it’s almost certainly your reloads that are the cause.

    If you are forming 223 brass and using a Lee die, that could be your problem. They seem to work for reloading but not forming. Don’t ask me why but I have seen it first hand.

    An adjustable gas block can only take gas away. Almost completely open and not having enough gas to operate means you should open it further.
     
  7. HankC

    HankC Member

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    Carbine gas will need 16" barrel and standard buffer to cycle unless you use a tube. If you use converted brass, many are too thick and will jam. Stick with factory brass or Lake City 223 brass.
    http://www.300blktalk.com/forum/viewtopic.php?t=88599
     
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  8. Zero19

    Zero19 Member

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    Im not using reloads. I was using UMC 220g and Sellior & Bellot 200g. I did a headspace check with a bare barrel and the other on a built upper, both passed. I opened it 100% but its still not enough to lock the bolt back on the last round. I checked my buffer and its 2.9 oz.
     
  9. Zero19

    Zero19 Member

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    Im not using reloads. I was using UMC 220g and Sellior & Bellot 200g. I did a headspace check with a bare barrel and the other on a built upper, both passed. I opened it 100% but its still not enough to lock the bolt back on the last round. I checked my buffer and its 2.9 oz.

    I know carbine gas system on a pistol build will require some fine tuning & touches to fully cycle and lock the bolt back. The build itself was more of a well lets see how this works out but it shouldn't have any issue just racking the bolt to clear the chamber.
     
  10. jmorris

    jmorris Member

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    I would focus on just one problem at a time, find and cure them in order of importance.

    This is #1 for both you and I. With factory ammunition, that’s a bad sign. Are both brands of factory ammunition locking up? If so, do you have another BCG you can try?

    Not like you have to even go to the range, if you can’t chamber and eject without it locking up, no point in moving on until that’s cured.
     
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  11. Zero19

    Zero19 Member

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    So far Ive looked up several things concerning this issue and all its done has made me want to get rid of both barrels and start fresh. Some say bear creek is fine but others wont go near them. Many issues have been found but it depends on when you got your barrel. Apparently they renamed the company due to very bad reviews ect. Found 2 post where the gun blew up due to unknow variants then several examples of poor build specs and also a lot who claim they've had no issue and extremely great accuracy...

    I did find 2 new things since my original post.. 1, The charging handle itself is scratched to all h*ll. The coating is gone in several areas & other parts have deep scratches but the upper inside itself only has 1 spot that shows wear.

    2, I looked over the brass fired and all casing have dots or scratch lines in the same spot.

    Ive talked with several gunsmiths that all want more then its worth to look/address the issue but did get some thoughts on what to do myself. 1, Heavily inspect then polish the chamber to deburr & make it function smooth. 2, take everything apart & make sure all is properly aligned. 3, ditch it completely.

    It did fire 10+ rounds, all ejected(except 1 at beginning of gas tuning) but the failure to easily eject a live round has me very concerned. Im not sure if its a headspace, barrel extension/burrs, the BCG.. honestly clueless at this point. Ive build over a dozen uppers, and a few 300 Blkout pistols but never had issues with an upper like this and none used Bear creek

    Opinions are welcomed, Ditch it or try to fix it?
     

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  12. Zero19

    Zero19 Member

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    Yes, had lock ups on both but the odd thing was how...2 would work as it should without issue then the next 2 rounds would lock hard. If there wasn't a bench at the range I wouldn't have been able to get the live round out.

    I do have a DPMS I can try, I figured sig would be a better BCG overall that's why I used it.

    Im going to use my mini cam to look at the chamber & down the bore. Then try the other bcg and a new charging handle. I just posted pics, may need to zoom in to see but the new charging handle is badly scratched and coating missing for only 10 rounds.

    If it locks up on the 2nd bcg or does damage to the 2nd new charging handle Im ditching it all and starting fresh. After some deep research Im honestly getting scared of it and wonder how it didn't blow up already
     
  13. jmorris

    jmorris Member

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    Can you take a mag full of rounds and chamber/eject all of them using the “slingshot” method of pulling the charging handle all the way to the rear, until it stops and letting go completely, so it has full force and repeat, without it locking up?
     
  14. Zero19

    Zero19 Member

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    Nope. That's when the "it happens in 2's" starts. I may get 1-3 rounds cycled fine then the next 2 lock up. It hasn't locked up on only 1 round, its always 2, then it will work fine for 2-3 rounds, then lock up again. Tried this using 3 different mag types. Im writing down a systematic approach to test tomorrow morning. Id go outside & test now with the 2nd bcg but my neighbor has her kids outside.

    Not sure if I can upload an example video or GIF of it
     
  15. jmorris

    jmorris Member

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    If it won’t cycle without actually firing, little point in going further. Put the safety on and cycle rounds with the muzzle in a safe direction. That’s all you need to do at this point.
     
  16. Zero19

    Zero19 Member

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    OK..test done & results are in.
    I tried a new BCG with a new charging handle. Had similar failures but I could rack the round out. So I then tried the Sig(old) bcg with new charging handle, same results. Then tried the old combo bcg & CH.

    The feed ramp chipped off on the left side & the other sides are extremely jagged. Im surprised my finger didn't get cut. On top of it all, now the inside of my upper is scratched & grooved very badly. There were no marks before but now the coating is scrapped off in several places with a lot of bare metal showing. There was shavings inside all over the BCG.

    Its hard to see the full extent due to the flash

    Im not sure if the bare upper is even worth saving. Its hard to see the chip with the upper still on but you can see the shavings & a slight dip on the side that broke off.

    Not sure who to contact about it, Bear Creek(they claim to have a lifetime warranty) or Classic Firearms. All parts but the bcg were purchase through Classic.

    Side note- I searched if a bent charging handle could cause these issues & found several posts about how these particular CH's are made for AIRSOFT.
     

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  17. Blue68f100

    Blue68f100 Member

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    I picked up a charging handle at one of the gun shows and found it to be out of spec. The handle was jammed tight when the BCG was closed. Which means the BCG was being held back by the charging handle. This could explain what is going on with yours since it passed the chamber gauges. As for the Barrel extension nut being damaged, send it back. I would also inspect the bolt very close for damage too. You maybe able to smooth it out with some Cartex polishing wheels, so it doesn't scrape/scratch the brass.The location should not impact feeding once cleaned up. I use the Cartex wheels to dehorn before I install the barrel to the upper.
     
  18. Jdcujo

    Jdcujo Member

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    Contact classic firearms first. Certain manufacturers go direct certain talk to the distributor.
    Personally I wont touch bca parts with a 20 ft pole.
     
  19. greyling22

    greyling22 Member

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    Assuming you get the broken parts fixed, I will briefly address the "not enough gas to lock the bold back" issue.
    First off, I'm both naturally cheap and chronically undercapitalized.

    Take a regular buffer and knock out the rollpin that holds the nylon part in at the back. pull it out and remove a weight. VIOLA! lightweight buffer. (note: that is way easier said than done. I had to drill a hole through the plastic, slide a nail through and yank on that to get mine apart)
    Take your standard carbine spring out and cut a couple coils off. And like magic! a lightweight spring. Worked great for my short stroking blackout.

    And don't listen to anyone who says "but greyling, those are milspec springs and buffer designed to work with that gun. don't change those" Those parts are designed to ensure the ar15 is overgassed when running high pressure 5.56 ammo with a 55 grain bullet out of a 16" or barrel . The moment any of those parameters change, "milspec" and "designed for" are meaningless.
     
  20. luzyfuerza

    luzyfuerza Member

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    My 300 BO pistol was short stroking with the AGB fully open using factory ammo. I opened the gas port in small steps until the gun functioned properly with the AGB about 1/3 closed.

    All it took was some numbered drill bits from Grainger.

    Just be sure to use a wooden dowel as a backer when drilling out the port.
     
  21. Zero19

    Zero19 Member

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    That's what Ive done so far but have yet to hear back. Im going to call tomorrow since they've taken their time with emailed pictures and all.
    I had no idea it was BCA as they have them listed as trustworthy "US Manufactures". It was only after I asked for further info did they refer me to BCA. I did build my pistol gas upper but am still looking into other barrels but the price is 3x what I paid for the complete upper as it sits.
     
  22. Zero19

    Zero19 Member

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    Its ok to try and save wherever possible. Ive actually been looking into all 3 options, cut spring 1 or 2 coils, drill gas port and either a custom odin buffer or any possible mods to the current carbine one I have. I figured start with the gas port but Im not sure how exactly to measure its current porting vs going bigger. its .1015 but my pistol gas port barrel is .125, Im assuming .125 is larger but I could be wrong. When comparing the carbine port does seem to be a lot bigger than the pistol GP.

    I found one forum post about buffer mods and using sand to adjust the weight just make sure its sealed extremely well once your done/satisfied with function.

    Honestly I think its all about the gas port, after a lot of research I found once people drilled it open a bit problems seemed to solve themselves. Im not fully comfortable with doing that first so I may cut 1 coil off the spring to see if that locks the bolt, if not then try addressing the gas port.

    I am getting curious about the bcg too. I found an article that said the Sig m400 Hunter had a special mod dealing with extractor to keep it locked in tighter. That may have some effect on the locking up part.
     
  23. Zero19

    Zero19 Member

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    Thanks. I didn't think about using a dowel for safety. After coming home & rechecking everything I noticed the AGB was 1 turn away from the screw falling out so it was basically completely open. I think I may cut a coil or 2 off my spring to see if that locks it back then tune the gas if that works. If it doesn't then Ill be drilling the gas block little by little.

    Any suggestions on how to get a better understanding of GP drilling & size. Its a carbine gas length that was supposedly over drilled to .1015 to ensure it was overgassed but this is a level of custom I haven't done before.
     
  24. Blue68f100

    Blue68f100 Member

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    I drill the gas ports on my mill. I use a pin gauges and parallel blocks to get the pin vertical, and aligned. Once centered and vertical I clamp every thing down. I run brass or Al rods inside to keep from damaging the rifling when I break through. I also run the rpm at 1500+ on these small number bits, and go real slow. Between the rpm and slow feed I get very little metal burrs inside the barrel. I then blow any shavings out using air then the burr is cleaned off with a bore brush and/or jag. You can tell when the burr is gone. The best way would be to use a EDM machine then you would not have any burrs at all to deal with.

    The main thing is that you need to follow the existing port. So alignment is the main thing.

    The max port size is specified on a rifle is 0.098" with a rifle length barrel, std velocity ammo. It's also the same size as the gas tube. So going larger is not going to help much unless you have a larger gas tube.

    Have you looked at the JP Enterprise VMOS bolt carrier setup? When used with their silent captured recoil setup you have a much larger range of operation.
     
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