Newly built AR10 doesn't cycle

[DaWhip]

I finished building a new AR10 about a month ago and put about 50 rounds through it so far. It has not ejected a round, cycled, or locked back on empty mag yet. I'm looking for any advice that anyone can offer. My gut feeling is that my lightweight bolt doesn't have enough mass to compress my buffer. I'm looking at ordering a lighter buffer spring, but thought I'd check first as it may be gas related and I can't find tube diameter info. Specs of the build are below for perusing and advice. For what it's worth, I was able to zero and take a couple of deer this year while manually cycling it, so at least it goes bang and shoots straight. It will lock back on an empty mag if cycling by hand and the bolt stops at random lengths along it's travel, but never far enough to eject the spent case.

Aero Precision M5 upper & Lower

Rubber City Armory Titanium BCG

Brownells 20" barrel, Rifle length gas w/gas block

Aero stainless gas tube, rifle length

Leapers UTG A2 Fixed stock kit for AR308 including rifle length buffer tube, buffer, & spring

 

 

 

 

[98Z5V]

7 minutes ago, DaWhip said:

I finished building a new AR10 about a month ago and put about 50 rounds through it so far. It has not ejected a round, cycled, or locked back on empty mag yet. I'm looking for any advice that anyone can offer. My gut feeling is that my lightweight bolt doesn't have enough mass to compress my buffer. I'm looking at ordering a lighter buffer spring, but thought I'd check first as it may be gas related and I can't find tube diameter info. Specs of the build are below for perusing and advice. For what it's worth, I was able to zero and take a couple of deer this year while manually cycling it, so at least it goes bang and shoots straight. It will lock back on an empty mag if cycling by hand and the bolt stops at random lengths along it's travel, but never far enough to eject the spent case.

Aero Precision M5 upper & Lower

Rubber City Armory Titanium BCG

Brownells 20" barrel, Rifle length gas w/gas block

Aero stainless gas tube, rifle length

Leapers UTG A2 Fixed stock kit for AR308 including rifle length buffer tube, buffer, & spring

Weigh that BCG, and give the weight in this thread.

Spec out that recoil system, and give the results in this thread.

That's the only way we can get somewhere here.  We're talking results like those that are detailed in this thread right here - so please read this one, before responding...

 

[98Z5V]

2 minutes ago, 98Z5V said:

Weigh that BCG, and give the weight in this thread.

Spec out that recoil system, and give the results in this thread.

@DaWhip - this is our starting point.  Doesn't mean that more info won't be required.  These two items of information are mandatory, though, with known facts, before going forward.

[DaWhip]

Thanks, I'll check it out and get back with more detail this evening

[Albroswift]

10 hours ago, 98Z5V said:

It will lock back on an empty mag if cycling by hand and the bolt stops at random lengths along it's travel, but never far enough to eject the spent case.

That doesn't hardly make sense. Please elaborate 

 

[DNP]

That’s a weird quote. It’s a quote of the OP but in 98’s name. 
 

agreed-  spill all the info you can. Pretty well lubed up?  Have you pulled the gas block to make sure you’re getting gas?  Should see some signs of carbon around the port in the barrel. Gas tube sitting proper in the upper?  (See photos in the water boarding thread). 

[Albroswift]

4 hours ago, DNP said:

quote of the OP but in 98’s name. 

I must have quoted his quote. 

[DNP]

I almost called him...didn’t sound like something he would say...figured there was some Jameson involved. 

[392heminut]

1 hour ago, Albroswift said:

I must have quoted his quote. 

Yup!

[98Z5V]

Damn, @Albroswift!   That ain't me, brother!   I don't think I could try to put those words together into one sentence...  

[billymagg]

10 hours ago, Albroswift said:

That doesn't hardly make sense. Please elaborate 

 

translation: it will lock back on an empty magazine when cycled with the charging handle...

                      when fired, the bolt hangs up on the magazine before the shell has ejected...

[98Z5V]

14 minutes ago, billymagg said:

translation: it will lock back on an empty magazine when cycled with the charging handle...

                      when fired, the bolt hangs up on the magazine before the shell has ejected...

^^^ That's pretty good, right there!   You are now assigned as his Official Interpreter!  

That's not a bad thing, either - I'm @sketch's Interpreter, and I pull part-time duty for @Cunuckgaucho when he gets going...  

Edited January 27, 2021 by 98Z5V

[Cunuckgaucho]

There are some days I don't even understand me... 🍻

[98Z5V]

46 minutes ago, Cunuckgaucho said:

There are some days I don't even understand me... 🍻

I think THIS sums up your last statement - and it sums up my whole life...  

 

[billymagg]

Well it seems that I will be in good company on the interpretation team... how did you enjoy your little snow? My SIL got to take his first HH-60G flight yesterday, lots of mush in the back, which of course melted, just wearing BDU's a Jacket and pair of headphones... 3 hours of "missile evasion" and a couple of thousand rounds of .50 cal expended, he stated all he could see was sky and dirt, no doubt very low, and very fast, he was rather proud that he didn't have to use a single "barf bag" of the half dozen he was handed.. Frozen and no doubt all shook up? he was on the floor, tied down in a harness to a tie down ring,  kid is a good sport, I'm proud of him... his old man is very "gunny", building 1919 30 cals up from cut ups, I'm looking forward to my first range session with those babies!

[DaWhip]

On 1/26/2021 at 9:49 PM, billymagg said:

translation: it will lock back on an empty magazine when cycled with the charging handle...

                      when fired, the bolt hangs up on the magazine before the shell has ejected...

Thanks for the translation, spot on. Busy couple of days, but I'm going through the waterboarding now, get that up soon.

[DaWhip]

Didn't get to the gas tube yet, but here's most of the rest. It was well lubed, extra well lubed while I tried to troubleshoot on the spot. I did block the chamber and blow through the barrel and the gas block/tube seems to be flowing freely for whatever that is worth. I'll see if I can get the block off tomorrow and add that info. Thanks for the help.  

Rubber City Armory Titanium BCG - 12.25oz

Brownells 20" barrel, Rifle length gas w/gas block/front sight pre-installed

Aero stainless gas tube, rifle length

Leapers UTG A2 Fixed stock kit for AR308 including:

rifle length buffer tube - 10 5/8" depth

 buffer - 5.35oz, 5.21"

 spring - 36 coils, 12 5/8"

[edgecrusher]

Just quick: 

 

Spring is not correct. That’s an AR15 spring. It should be 13 3/4”. Gas tube is too short, should make it to half way in the cam cut out. 

[98Z5V]

7 hours ago, DaWhip said:

Rubber City Armory Titanium BCG - 12.25oz

 

Leapers UTG A2 Fixed stock kit for AR308 including:

rifle length buffer tube - 10 5/8" depth

 buffer - 5.35oz, 5.21"

Common rifle buffer for .308ARs, but the receiver extension depth is about an inch TOO deep. Internal depth for a rifle receiver extension should be 9 11/16".  Please re-verify that number, and make sure it's internal depth, and not overall length...   The earlier mention of the spring is correct - wrong one.  Armalite EA1095 spring will be the one to use, and solve that issue quickly.

BCG weight...    BCG weight is reciprocating mass, just like buffer weight is.  It's weight, sitting there, that had to control the force of the .308 Win cartridge, and cycle a gas operated gun.  Normal full-mass .308AR BCGs are around 18.87 ounces (Fulton Armory .308AR chromed BCG is that example).  Though yout buffer weight is correct (close to 5.4oz), you have effectively taken 6 ounces out of that reciprocating mass, by using that lightweight 12-ish oz BCG.  That's a cycling issue, right there.

Now, you can fix this quickly, and keep using the Ti BCG in your gun, but you're gonna need one of the 10oz rifle buffers from Slash (www.heavybuffers.com).   That will get that weight back into the reciprocating mass, that you need to be there.

This isn't a Race Gun - Standard parts will work fine, at standard "specs" - for lack of a better term.  Using "specs" in a sentence with ".308ARs" is an oxymoron...  Fancy lightweight parts are just going to complicate the process of reliability, unless you're using this gun to make money on the professional 3-Gun circuit...

Edited January 31, 2021 by 98Z5V

[billymagg]

8 hours ago, edgecrusher said:

Just quick: 

 

Spring is not correct. That’s an AR15 spring. It should be 13 3/4”. Gas tube is too short, should make it to half way in the cam cut out. 

the gas tube is too short by about 3/16's of an inch or so? So an ArmaLite gas tube to start and since he has yet to eject a single round, or lock the bolt back during firing, I'd say its possible that gas port is also still too small, but that's just my 2 cents.. "Miss Wilson" was cycling and locking back on an empty mag, but just dribbling brass out on my truck hood... I assumed the adjustable gas block needed to be opened up. Winchester 149 gr white box @ 2790 fps made that more  noticeable, opening up the gas block did not improve the situation.  So I drilled it up to 3/32's" and put the 40 coil flat wire back in it, it functions fine now that I opened up the gas port, ejection is still on the weak side, I'm very hesitant to open the port up beyond 3/32's"?  so I'm gonna order Wilson's new 37 coil flat wire buffer spring to replace my current 40 coil flat wire??

 

 

 

 

[edgecrusher]

42 minutes ago, billymagg said:

the gas tube is too short by about 3/16's of an inch or so? So an ArmaLite gas tube to start and since he has yet to eject a single round, or lock the bolt back during firing, I'd say its possible that gas port is also still too small, but that's just my 2 cents.. "Miss Wilson" was cycling and locking back on an empty mag, but just dribbling brass out on my truck hood... I assumed the adjustable gas block needed to be opened up. Winchester 149 gr white box @ 2790 fps made that more  noticeable, opening up the gas block did not improve the situation.  So I drilled it up to 3/32's" and put the 40 coil flat wire back in it, it functions fine now that I opened up the gas port, ejection is still on the weak side, I'm very hesitant to open the port up beyond 3/32's"?  so I'm gonna order Wilson's new 37 coil flat wire buffer spring to replace my current 40 coil flat wire??

 

 

 

 

Your dedication to Wilson parts may be your undoing but that’s for a separate thread 

[billymagg]

13 minutes ago, edgecrusher said:

Your dedication to Wilson parts may be your undoing but that’s for a separate thread 

Hey, they make good stuff, not cheap, I'm sure lots of their parts are made by other vendors, but the billet receivers and barrels are all machined in house. I bought one and built one, I decided to stick with as many of their parts as possible to eliminate mismatched issues.. and if I have a problem, I can PM Bill Wilson, he's been very helpful getting the "dirty little thirty" sorted out, but frankly what I've learned here on 308AR Forum has been priceless.. yourself, 98, AlbroSwift, and on down the line... this is still the best AR forum on the planet. 

for what its worth, the "Dirty Little Thirty" is running like a turbine, and yes I did have to play with it and swap a few parts, most importantly an H2 buffer, but you are right about one thing, its been rough on my checking account and credit card... now I'm gonna have to figure out what to do with those RCBS dies...

[Albroswift]

13 hours ago, billymagg said:

So I drilled it up to 3/32's"

Seems big enough that's probably not the problem. Double check the port lines up with the gasblock. I have a bore camera that works sweet for that, but there are about 900 other ways to confirm. 

[billymagg]

15 hours ago, Albroswift said:

Seems big enough that's probably not the problem. Double check the port lines up with the gasblock. I have a bore camera that works sweet for that, but there are about 900 other ways to confirm. 

I'm certain the port is lined up, if I plug the chamber and blow in the barrel it sounds like a hurricane and no restriction at all, now that I opened up the gas port to 3/32's", it was definitely undergass prior to being opened up... I put a 13 1/2" Carbine spring in today today with the 3.8oz carbine buffer that Wilson Combat runs in all their WC-10's, I'd like to run the Heavy 5.4 oz 2.50 inch buffer. that 40 coil flat wire spring will function, ejects, locks back, and feed's  fine, but the ejection is very lethargic, especially with the 149gr Winchester White box.  I  had to much azz for my gaz! Wilson has now discontinued the 40 coil flat spring and has shortened it 3 coils, they offer an AR-15 37 coil spring and a WC-10 37 coil recoil spring...

anyway, apologies to DaWhip for high jacking your thread man, how is your rifle running now?

Edited February 2, 2021 by billymagg
cut some random thoughts

[98Z5V]

Hey @billymagg - start posting the problems that YOU are having, in a completely different thread than this guy's thread.

Let's not muddy the waters here.  This guy is here, with a problem - and it's not your problem.  Put your problem in a new thread that you make, and just spill your beans - there. 

That just makes sense.  Right?...