New AR10 does not extract or cycle.

[masonb55]

I just finished my first AR10 build and took it to the range to test fire. I put about 25 rounds through it and only ONE was able to fully extract and eject. Every other round I fired would cycle the bold back about an inch and get jammed. It only ejected when I forced the charging handle back, then would have no issue chambering the next round. I'm not sure if it's a head space issue or a over/under gassed issue. I'm really not sure what the issue is. Any suggestions?

[Armed Eye Doc]

How much lube did you have on the carrier?  These tend to like lots of lube.

Beyond that, what are the details of your build?  Details are important.  A parts list with brands can help to diagnose this.  We may need measurements as well but we'll ask if needed.

[masonb55]

Its an Aero M5 upper and lower but I bought the BCG and barrel(20")from CBC industries which I am almost positive is DPMS. The buffer tube and spring are not AR10 specific but it doesn't even have the chance to compress the spring as it gets caught right after it fires. The one round that did eject on its own cycled perfectly though. I just saw Cjnut's post from yesterday and it seems like the same issue. I realigned my gas block and will super lube the carrier before I try again tomorrow. If that doesn't work then maybe I should try enlarging my gas port like Cjnut? 

[masonb55]

Its an Aero M5 upper and lower but I bought the BCG and barrel(20")from CBC industries which I am almost positive is DPMS. The buffer tube and spring are not AR10 specific but it doesn't even have the chance to compress the spring as it gets caught right after it fires. The one round that did eject on its own cycled perfectly though. I just saw Cjnut's post from yesterday and it seems like the same issue. I realigned my gas block and will super lube the carrier before I try again tomorrow. If that doesn't work then maybe I should try enlarging my gas port like Cjnut?

 

 

 

I might have figured out the problem. Gas port on he barrel is .936 and I bought a .750 gas block -__- every little thing counts

[edgecrusher]

8 minutes ago, masonb55 said:

 

I might have figured out the problem. Gas port on he barrel is .936 and I bought a .750 gas block -__- every little thing counts

That is not it. Those measurements are for the size of the barrel diameter at the block. Measure your spring and buffer as well as the buffer weight and inner depth of buffer tube please and post.

[masonb55]

 

thanks for the info, rookie mistake lol

buffer tube inner depth is about 7"

spring is 11 1/4"

buffer is 2 1/2 " and weighs 37 oz or 104.5 g

 

[masonb55]

So what was cjnut talking about with his gas port then? did he over-gas the rifle?

[98Z5V]

Start by reading through this info:

 

[masonb55]

Thank you for the information this is exactly what I was looking for. I appreciate you posting this thread.  

My gas tube looks good but measures closer to 15 1/4 than 15 1/2 so that could be the problem.

and when it comes to gas ports, I have now seen 2 people post on here with the same issue I'm having and it sounds like after having the gas port enlarged to .960 they're problem was fixed. 

I think I will just take it to a gun smith and see what he says.

BTW I'm not on here looking to complain, just learn. thanks again

[98Z5V]

7 minutes ago, masonb55 said:

Thank you for the information this is exactly what I was looking for. I appreciate you posting this thread.  

My gas tube looks good but measures closer to 15 1/4 than 15 1/2 so that could be the problem.

and when it comes to gas ports, I have now seen 2 people post on here with the same issue I'm having and it sounds like after having the gas port enlarged to .960 they're problem was fixed. 

I think I will just take it to a gun smith and see what he says.

BTW I'm not on here looking to complain, just learn. thanks again

That off-angle pic doesn't help much.  Read this thread, and get some real details on the rifle in here.  This thread is pretty (excellently) descriptive on the kind of information it takes, to diagnose someone's issue, over the internet.  You haven't stated s single thing about your gas system, besides 20" barrel, and your recoil system is far out of whack.  Read this thread, too:

 

[98Z5V]

I,myself, know that you have a rifle gas system - because of the gas tube numbers you gave.  There's alot more to it than that, though.

Oh, and most gunsmiths won't know what to do to fix this, unless you sent it to someone like ADCO.  Most crap-tastic manufacturers send your gun back to you, stating that it function just fine for a full box of amminution when they test fired it - and it gets back to you with the exact same problem.

You're in the right place, to gain the knowledge needed to fix it.  We need pretty detailed information FROM you first, though. Otherwise, it's like playing a game of Competition Darts, with a blindfold on.

Edited May 4, 2020 by 98Z5V

[masonb55]

I know they're low quality pics, my camera is messed up, but this is what I can get now. 

And yes you are right, the buffer system is too short and light. would that cause a failure to extract though? 

I don't have an accurate way to measure the gas port in the barrel but a 1/16 (.625) bit can fit but an 5\64 (.781) barely doesn't so I'm guessing its .750

I also don't have a pic of the malfunction but when fired the bolt only travels about an inch back and gets jammed. It doesn't travel far enough to try to load another round on its own. The gun only cycled properly once in about 25 rounds I put through it today and that was randomly in the middle of shooting.

 

[98Z5V]

Your gas tube is right where it needs to be.  Now, it comes down to the recoil system, and the gas port diameter.

Numbered drill bit, in the appropriate numbers/sizes, are the easiest was to measure gas port diameter, somewhat accurately.  Irwin brand numbered drill bits are available at every Ace Hardware.  You'll need a range of them, and you'll need one or two to drill and test anyway.  Research bit numbers for sizes/diameters, and get a range of the with everything between 0.070" and 0.095". 

Gotta fix that recoil system as a priority, then pop that gas port up.

[98Z5V]

3 hours ago, masonb55 said:

buffer tube inner depth is about 7"

Need more information on this part, and a definitive number.  This is where you have to start with the recoil system, OR you just buy this and be done with it.  You won't find a better deal, when you look at the prices on the individual parts.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201

 

That is IN STOCK right now, so that's someone to jump on fast.  I'm just sayin'...

[masonb55]

I kind of suspected the gas system, but had no idea the buffer differences were so drastic. I'll hop on that deal. 

Thanks again man!

[98Z5V]

7 minutes ago, masonb55 said:

I kind of suspected the gas system, but had no idea the buffer differences were so drastic. I'll hop on that deal. 

Thanks again man!

If everything about the Recoil System and the Gas System isn't balanced - then the gun doesn't run.

With that deal, you're looking at a $40 receiver extension, a $40 buffer, a $6 recoil spring, and a free castle nut and endplate.  It's a bargain, any way you slice it, even though they jumped the price up another $10.  All the parts are always made to the same standard, and work every single time.  It's WAY easier than piecing together components from reputable manufacturers, that are alot more expensive.  Especially when you count in the shipping from different manufacturers.  

Since it was in stock, I just bought another one for a spare set.  No kidding.

[98Z5V]

1 hour ago, 98Z5V said:

 

 

This piece right here that I quoted is kinda paramount - the proper information.  We never did get that from you, and you were kinda spoon-fed here.  That thread I linked above details the kind of information that is needed.  The thread I linked prior to that is the "why" on all that.  Why the recoil system and gas system needs to be balanced, to work right.

For a 20" .308 Win AR barrel with a rifle gas system and a 0.750" gas block journal size, I can pretty much tell you right now the range you need to hit for your gas port diameter, in order to make this gun right properly. If you purchase that recoil system, you'll have the proper recoil system for full functionality with any ammo that isn't pure garbage.  

[Cjnut]

With a 20" barrel your running the rifle length gas tube and you should be able to fit a 3/32 drill bit in the gas port. 3/32 is .093. That said, drilling your gas port is the last resort only when you have the rest correct. Gunsmith isn't required, just go with the bit that fits and step it up until you get a 3/32 through it. Use a good bit and a squirt of WD-40. Took me like 2 min to do mine with a hand drill. Get the correct buffer assembly, then throw an adjustable gas block on there to tune it up.

[Cjnut]

Edit: Check your port size first....If that isn't correct, no buffer set-up is going to work for you. Gotta make sure it's not an under-gassing problem first. Keep in mind also, when re-installing your gas block, all the way back to the shoulder is not always correct. I had to space my block forward of the shoulder .060 to get the port centered. If you flip the block over and line the port up with the set screw hole, this will tell you if it needs to be offset....most gas blocks place the rear set screw directly perpendicular to the gas tube inlet.

[98Z5V]

11 hours ago, Cjnut said:

.most gas blocks place the rear set screw directly perpendicular to the gas tube inlet.

All gas blocks use the rear mounting hole to drill the 0.125" hole for the port in the gas block.  Even fixed front sight bases have a hole in the bottom there - that's exactly how they drill the 0.125" block port.