Looking for AR builders, a little help please

[Cannonman]

Not sure if anyone asked... Did you build the upper yourself, or did you get a pre-assembled upper?

If pre-assembled: Did it come with the BCG or did you buy that separate?

Can you freely and easily move the BCG into and out of battery with your hand/charging handle? I wouldn't even worry about the lower until we make sure the upper is sorted. Keep it simple and ensure proper function before we complicate it any more than necessary.

I did put the upper together myself. I bought the BCG separate

You never answered whether it would go into battery with no ammo. If that gas tube is the wrong application and too long like it appears, it probably will not go into battery as it is bottoming out in gas key. You need to get the right length gas tube for the application. To be totally blunt it is apparent you got in over your head and do not have the proper understanding of the components involved and how they interact. My suggestion at this point is to involve someone directly who has experience with this type of build and get it sorted out correctly. I also suggest not building for someone else until you have many successful builds of your own under your belt.

Sure and I agree. Where I am is in a small community. As it is, I've got more experience than those around me. The ten or so AR15 that all worked gave me a false sense of ability. There was a Co. about 100 miles from here that gave an AR15 armorer's course. We put AR15's together and took them apart for a couple of days. No problem shooting or AR10's. If I have to buy a new AR10 for this guy, a good friend of mine since retiring here, I'd be glad to. I want to learn some how and I'm open to suggestions.
. Thanks

 

[PNWPrepper]

If you're not careful when buying parts for an AR10, you could buy incompatible parts. As someone stated. The two biggest "specs" are DPMS and Armalite. If you have a DPMS barrel and an armalite upper or the other way around, this could also lead to problems feeding. I'm no expert on AR10s, but I wouldn't be surprised if this is your problem if it's not an incorrect fast tube length, and/or the bullet isn't feeding properly because of incompatible parts, therefore it's throwing the BCG off its normal path and causing the gas key to hit the gas tube on the side and not lined up perfectly. Try taking your bolt out of the carrier, and see what happens if you try to close it. Is the gas tube preventing the BCG from making it all the way to the front of the chamber? This would mean the gas tube is too long. Or did you get the BCG fully closed? This to me would mean you might have incompatible parts.

 

[Cannonman]

The gas tube in the green receiver is the correct length. It ends at about the center of the cam key cut-out ("D" shaped, left side from shooters perspective). The light colored receiver actually has the wrong gas tube (too short) and would be prone to short stroking if the gas port was properly sized, but if it ain't broke... . FYI, the circular hole next to the barrel extension is where the T-slot cutter is inserted to mill the charging handle slots. The green receiver gas tube alignment along the x-axis (left-right in pic) doesn't look that far off. I can't tell about the z-axis (up-down). If the tube has a burr, clean it up and try without a cartridge as osprey recommended.
It really needs to be headspaced no matter what. Headspace gauges aren't cheap, and from what I hear, they are hard to find these days. If you know how to strip a bolt, many gunsmiths will check headspace for free or cheap. If they have to strip the bolt, it's usually shop minimum. Stripping a 308 bolt is much more difficult than a AR15, especially double ejector HP bolts, and a bolt jig is usually required.

Edit to add: The gas tube length in the light colored receiver is very typical of using DPMS gas tubes with an Armalite barrel.

Thanks you Sir. The bolt I bought to go with the green upper does go into battery and dry fires without problem. When i change the bolt with the one from the Black Rain .308 it jams. I think that is where the "nick" I came from in the green upper. The Black Rain runs without problem. So, pardon my ignorance but
1. why would the bolt I bought need headspaced if the other works?
2. why does the Black Rain bolt jam if the other does not?
Thanks to all for putting up with me. If there were a gunsmith within a 100 miles I try that. Either way. Your input is highly valued.

 

[Cannonman]

If you're not careful when buying parts for an AR10, you could buy incompatible parts. As someone stated. The two biggest "specs" are DPMS and Armalite. If you have a DPMS barrel and an armalite upper or the other way around, this could also lead to problems feeding. I'm no expert on AR10s, but I wouldn't be surprised if this is your problem if it's not an incorrect fast tube length, and/or the bullet isn't feeding properly because of incompatible parts, therefore it's throwing the BCG off its normal path and causing the gas key to hit the gas tube on the side and not lined up perfectly. Try taking your bolt out of the carrier, and see what happens if you try to close it. Is the gas tube preventing the BCG from making it all the way to the front of the chamber? This would mean the gas tube is too long. Or did you get the BCG fully closed? This to me would mean you might have incompatible parts.

Thanks Sir. The bolt goes into battery without a round chambered. Or I can charge the bolt and dryfire over and over without a feeling drag or odd sounds. The bolt from the .308 that runs is nicking the green upper. This bolt will not go into battery. Any ideas you might have would be most welcomed. The last gunsmith that was within 100 miles charged me to take the sites off a Glock. He managed to bend the slide. I was sending the slide in to have it customized. The company told me of the problem and stated that they could "bend" it back. From the outside the gun looks great. When you take the slide off it looks like a crazy person took a Dermal tool to it in a fit of rage. So as of now, I can't tell you guys how much I appreciated your input.

 

[PNWPrepper]

What fully closed vs not fully closed looks like on a working AR15.

 

[Cannonman]

What fully closed vs not fully closed looks like on a working AR15.

View attachment 827781 View attachment 827782

Hey thanks, I'm going to check in just a moment. Question till then, will the upper mate with the lower if not fully closed? Thanks for the effort and help.

 

[Mr Smith]

Okay here's something to check...On one of my .308 uppers I built: the gas tube wasn't exactly to spec and didn't want to allow my carrier to close as the tube didn't fit inside the gas key. I ended up having to sand the gas tube a bit before it would fit inside the key and allow the bolt to close and lock into battery. May be something to look at. Make sure the gas tube fits inside of the gas key. if it doesn't then its either not aligned properly, or it's a little too large and not fitting properly.

 

[Cannonman]

Okay here's something to check...On one of my .308 uppers I built: the gas tube wasn't exactly to spec and didn't want to allow my carrier to close as the tube didn't fit inside the gas key. I ended up having to sand the gas tube a bit before it would fit inside the key and allow the bolt to close and lock into battery. May be something to look at. Make sure the gas tube fits inside of the gas key. if it doesn't then its either not aligned properly, or it's a little too large and not fitting properly.

If I can get these pics to load I think that might help. Hope to be back shortly. And thanks!

 

[Cannonman]

Sorry, but I can't get phone service where I am. However, the bolt "seems" to go fully forward and then "cams" over. Locking it in place? I'll keep working on the pics. Thanks for staying with me guys.

 

[Cannonman]

Here's the bolt going forward and then "caming" over to the left. This seems to me to be fully in battery?

 

[Cannonman]

Would you guys please look at the difference in length of this cut. The silver one is the one that works. I just put a rod in above the gas tube and blacked out the area of the cut. Then put the rod in the green upper and noticed the difference. Does anyone know why or if this matters? Thx

 

[Cannonman]

Okay here's something to check...On one of my .308 uppers I built: the gas tube wasn't exactly to spec and didn't want to allow my carrier to close as the tube didn't fit inside the gas key. I ended up having to sand the gas tube a bit before it would fit inside the key and allow the bolt to close and lock into battery. May be something to look at. Make sure the gas tube fits inside of the gas key. if it doesn't then its either not aligned properly, or it's a little too large and not fitting properly.

Thx. I checked the ends and the tube looks fine. The bolt slides over it without any noticeable hitch.

 

[Cannonman]

If you're not careful when buying parts for an AR10, you could buy incompatible parts. As someone stated. The two biggest "specs" are DPMS and Armalite. If you have a DPMS barrel and an armalite upper or the other way around, this could also lead to problems feeding. I'm no expert on AR10s, but I wouldn't be surprised if this is your problem if it's not an incorrect fast tube length, and/or the bullet isn't feeding properly because of incompatible parts, therefore it's throwing the BCG off its normal path and causing the gas key to hit the gas tube on the side and not lined up perfectly. Try taking your bolt out of the carrier, and see what happens if you try to close it. Is the gas tube preventing the BCG from making it all the way to the front of the chamber? This would mean the gas tube is too long. Or did you get the BCG fully closed? This to me would mean you might have incompatible parts.

Thx, Would you please take a moment to look at the last pics I put up? Is this an example of an Amalite vs DPMS?

 

[Cannonman]

Here is a list I compiled some time ago but should still be accurate. This is not 100% complete. Using Armalite AR10 length gas tubes in DPMS pattern barrels can prevent the BCG from going into battery.

DPMS LR-308 Gas Tube (also AR15):

Pistol 6-5/8 - 6-3/4
Carbine 9-3/4 - 9-7/8
Mid-Length 11-3/4 - 11-7/8
Intermediate 13-3/4
Rifle 15-1/8 - 15-1/4
Rifle+2 17-1/8


Armalite Gas Tube:

Super SASS Carbine (308) 11"
Mid length Carbine (308) 12 1/16"
Rifle (308) 15-1/2 "
Carbine (223) 9-3/4 "
Mid (223) 11-3/4"
Rifle (223) 15-3/16"


Oddballs:

Wilson Combat Match Grade Intermediate 13 1/4"
Knight's Armament SR-15 Mod 1. Mid-Length 13"


There are a couple of Mfg's who make DPMS patterned barrels/extensions and drill the gas ports at Armalite lengths (Fulton Armory Criterion).

Thanks for the help. I'm getting a bit of everything and It's starting to make less sense. If you would, please take a moment of your time to look at the last pics i posted. If you see something I'm missing I'd be most thankful you.

 

[Cannonman]

I have an Anderson AM-10 that was purchased new as a complete rifle. My local FFL ordered it directly from Anderson. This is the only AR style rifle that I did not assemble myself. The bolt would go into battery with no ammo but not with a live round (factory, not a reload). I was puzzled because I assumed that the rifle had been test fired before it left Anderson. My first thought was that it may have been a head space problem so had the gunsmith at the local range check it out. The problem turned out to be two O-rings around the extractor spring. He removed the extra O-right and it functioned correctly. Not suggesting that this is your problem but just to let you know that things like this happen.

Thanks, The first round out of a mag loads and shoots. It's the next round that won't go completely into battery. Well, sometimes the second round will and the third won't.

 

[DirectDrive]

Thx. I checked the ends and the tube looks fine. The bolt gas key slides over it without any noticeable hitch.

In one of your pics it looks like either the carrier or gas key is making contact with the top of the receiver.

Good trouble-shooting is doing/checking one thing at time.
That way you can track what's going on.

So you have a BCG that works 100% in the rifle, right ?
OK.
Now take suspect bolt and install it in the "known good" carrier.
Check this assembly in your rifle.
If OK, then now we know that Carrier #1 and Bolt #2 work.

Now take Bolt #1 and install it in Carrier #2
Check this assembly in your rifle.

You do it that way.
You might find that there is something wrong with Carrier #2
It could be the way the gas key is machined.

Earlier in this thread, I suggested taking the bare carriers and see if they would go all the way to the "in battery" position.
This is another simple check to do.

 

[Cannonman]

In one of your pics it looks like either the carrier or gas key is making contact with the top of the receiver.

Good trouble-shooting is doing/checking one thing at time.
That way you can track what's going on.

So you have a BCG that works 100% in the rifle, right ?
OK.
Now take suspect bolt and install it in the "known good" carrier.
Check this assembly in your rifle.
If OK, then now we know that Carrier #1 and Bolt #2 work.

Now take Bolt #1 and install it in Carrier #2
Check this assembly in your rifle.

You do it that way.
You might find that there is something wrong with Carrier #2
It could be the way the gas key is machined.

Earlier in this thread, I suggested taking the bare carriers and see if they would go all the way to the "in battery" position.
This is another simple check to do.

The bolt that works in the green upper is the one that seems to go into battery and cam over. The one that runs fine in the silver upper runs fine in the silver upper but jams in the green. I hope this makes sense and I'm not driving you crazy. It's just making me a bit nuts trying to figure out why it won't cycle or why a bolt that works in one jams in another.

If you're not careful when buying parts for an AR10, you could buy incompatible parts. As someone stated. The two biggest "specs" are DPMS and Armalite. If you have a DPMS barrel and an armalite upper or the other way around, this could also lead to problems feeding. I'm no expert on AR10s, but I wouldn't be surprised if this is your problem if it's not an incorrect fast tube length, and/or the bullet isn't feeding properly because of incompatible parts, therefore it's throwing the BCG off its normal path and causing the gas key to hit the gas tube on the side and not lined up perfectly. Try taking your bolt out of the carrier, and see what happens if you try to close it. Is the gas tube preventing the BCG from making it all the way to the front of the chamber? This would mean the gas tube is too long. Or did you get the BCG fully closed? This to me would mean you might have incompatible parts.

Do you know how I might be able to tell if this is the case? Thanks!

 

[Cannonman]

pull the gas block off with tube and see if the bolt goes all the way. what type of gas system you running?

Sorry for not getting back sooner. I've been trying to absorb everything and try anything. I'm not in the league of many here but I love to learn. What do mean by "type of gas system"? And thank you.

 

[Ops]

Not sure what im looking at but none of my gas tubes stick out that far.

 

[DirectDrive]

Sorry for not getting back sooner. I've been trying to absorb everything and try anything. I'm not in the league of many here but I love to learn. What do mean by "type of gas system"? And thank you.

I explained this once before in this thread...
There are two types..

1) Direct Impingement
$10 phrase for gas is directed via a tube to the carrier key which in turn runs the bolt.
It's been established via your pics that you has this, the most common system.

2) Piston
Gas operates a piston which in turn operates a rod that actuates the BCG