New guy with issues

[Ozz]

Hi folks, been lurking for a while and gotten some really good info. Now that my rifle is assembled, I have a problem. I think my barrel may be faulty. Two things make me think this:

1) Standard sized forends are ~1/4 inch too long

2) Gas tube protrudes too far into the DPMS upper, preventing the BCG from locking into battery

 

I have an 16" mid-length Faxon barrel, has anyone else got any ideas?

Edited January 19, 2016 by Ozz

[shepp]

Welcome to the forum from southern Wi

[Ozz]

Thanks from southern AL

[MikedaddyH]

Welcome from AZ !

First measure :

A. Length of gas tube.

B. Length between gas block and barrel extension.

Your gas system may be set up for an Armalite rifle instead of a DPMS rifle there is about 3/8" to 7/16" difference between the two systems.  

Also look at the under side of the upper receiver with the charging handle installed ,for the position of the gas tube. It should be in the center of the circles in the upper (tool marking).

That's at start.

[Robocop1051]

Kinda need to know more about your rifle before we blame the barrel.

1. Which gas block are you using?
2. Are you using a standard Delta Ring barrel nut?
3. Was this an Armalite or DPMS pattern build?
4. Which upper receiver are you using?

[planeflyer21]

Welcome from AZ!

This issue should highlight to everyone why we harp that an AR-10 is not every .308AR.  ALl parts do NOT interchange between most subtypes.

[FaxonNathan]

Please give us a buzz and we can work to get you situation. 

We do apologize though, as we'll be hard to reach this week with everyone out at SHOT Show. We will be back with you next week when we return!

-Nathan

[Ozz]

DPMS Upper, BCG and gas block that I purchased from a friend so I have only his word to go by. The Upper is an older, high-top, slick side. Did they change any other dimensions when they lowered the top? Started with a standard delta-ring (from Brownells) and a Magpul MOE M-LOK mid-length fore-end is about 1/4" too long. Went to a low profile gas block and free-float tube, now I have a fore-end but the gas tube still prevents the bolt from seating and locking.

Barrel measures 9 inches from gas vent to underside of barrel seating ring, 8.6 inches from shoulder of gas block seat to underside of barrel seating ring. Don't have the upper handy today, will try for some pics tomorrow.

Thank you Nathan, I know you watch these forums, that's one of the reasons I ordered from Faxon.

 

[unforgiven]

Welcome from Indiana brother.

[EasyEJL]

how long does the gas tube measure, and where did you get it?

[survivalshop]

 What Caliber ?

[NTXshooter]

Welcome  from Texas.  I can't help with the gas tube but I have a Ranier barrel on my rifle and had the same problem with the MagPul fore end.  Ended up having the go with a free float tube.

[Ozz]

Thanks for all the welcomes. I'm at work but will have some pics this evening I hope. Don't know how I forgot to mention this before but my bolt catch doesn't work either...starting to think the upper is the actual problem.  Will post tonight with pics and as much info as I can.

[MikedaddyH]

Make sure you take a picture of the gas tube inside of the upper, so we can see how far it goes into the charging handle. Upside down view.

[Ozz]

Okay, I retrieved my upper and gas tube, unfortunately my gas block got ruined in the disassembly process (excess red lock-tite on the set screws required the application of heat and a hammer.) Below are some pics of the upper, barrel and gas tube.

[survivalshop]

 Well I see its a Large Frame AR . The gas Tube is definitely  too long , of course you already knew that . 

 This was asked already , but could you measure the length of the Gas Tube out of the Rifle .

Aprox. Gas Tube length for an AR :

 Pistol---  4.5"

Carbine - 7.5"

Mid.----- 9.5"

Rifle ----- 13"

Armalite lengths,

Rifle ( 308 ) ----- 15.5 "

Carbine ( 308 )--12 1/16"

super SASS Carbine ( 308 )--11"

Super SASS< Rife (308 )   ?

Mid ,( 223 )------------------ 11 3/4"

Carbine ( 223) --------------- 9 3/4 "

Rifle ( 223 ) ------------------- 15 3/16"

 National Match---------------  ?

 

  These measurements should get you close to what you have & may show you what you need .

 

AR-15 Gas System Sizes

There are four common AR-15 gas system lengths: Pistol, Carbine, Mid, and Rifle.  Each length utilizes different sized gas tubes and placement of the gas block.   Although you can use nearly any sized forearm with any length gas system, it's important to know what the lengths are if you desire a concealed gas block (under the handguard).  If you don’t know what size system you have, measure the handguard or distance to the gas block to quickly determine.  Below are the common dimensions.

Pistol-Length
Used on very short barrels, usually 10″ in length or less.  
Gas Tube Length:  Approximately 4.5”
Handguards or free-float tube Length: Generally between 3”-4” in length.  It's common to install a low profile gas block and conceal it under a carbine length free float forearm like the YHM Diamond YHM-9630-DX for more accessory space and better grip area.

Carbine-Length
Most common length gas system.  Usually found on barrel lengths from approximately 10”-18”.es of AR-15 rifles.
Gas Tube Length:  Approximately 7.5”
Handguards or free-float tube Length: Generally between 6.5”-7” in length.  For a concealed gas block look, buy a free float tube 9" or longer like the Spike's Tactical BAR 9".

Mid-Length
Commonly used on barrels from 14”-20”.  
Gas Tube Length:  Approximately 9.5”
Handguards or free-float tube Length: Generally between 8.5”-9” in length.  For a concealed gas block look, buy a free float tube 10" or longer like the Midwest Industries T10.

Rifle-Length
Found on rifles with 20" or longer barrels.
Gas Tube Length:  Approximately 13”
Handguards or free float tube length ranges from 11.5”-12” long. For a concealed gas block look, buy a free float tube 13" or longer like the Midwest Industries SS-15.

 

AR-15 Gas System Sizes

There are four common AR-15 gas system lengths: Pistol, Carbine, Mid, and Rifle.  Each length utilizes different sized gas tubes and placement of the gas block.   Although you can use nearly any sized forearm with any length gas system, it's important to know what the lengths are if you desire a concealed gas block (under the handguard).  If you don’t know what size system you have, measure the handguard or distance to the gas block to quickly determine.  Below are the common dimensions.

Pistol-Length
Used on very short barrels, usually 10″ in length or less.  
Gas Tube Length:  Approximately 4.5”
Handguards or free-float tube Length: Generally between 3”-4” in length.  It's common to install a low profile gas block and conceal it under a carbine length free float forearm like the YHM Diamond YHM-9630-DX for more accessory space and better grip area.

Carbine-Length
Most common length gas system.  Usually found on barrel lengths from approximately 10”-18”.es of AR-15 rifles.
Gas Tube Length:  Approximately 7.5”
Handguards or free-float tube Length: Generally between 6.5”-7” in length.  For a concealed gas block look, buy a free float tube 9" or longer like the Spike's Tactical BAR 9".

Mid-Length
Commonly used on barrels from 14”-20”.  
Gas Tube Length:  Approximately 9.5”
Handguards or free-float tube Length: Generally between 8.5”-9” in length.  For a concealed gas block look, buy a free float tube 10" or longer like the Midwest Industries T10.

Rifle-Length
Found on rifles with 20" or longer barrels.
Gas Tube Length:  Approximately 13”
Handguards or free float tube length ranges from 11.5”-12” long. For a concealed gas block look, buy a free float tube 13" or longer like the Midwest Industries SS-15.

 

Edited January 22, 2016 by survivalshop

[Ozz]

Survivalshop, my gas tube measures ~12 1/16" so I seem to have a carbine length Armalite tube in a mid-length DPMS 308. It seems to be maybe 1/2 inch too long. That's 1 issue tentatively resolved, I'm still bothered by the fore end fitment issue and bolt catch not functioning. I have (what I'm told by my friend is) a DPMS upper and BCG on a Palmetto State Armory lower, I know they don't always use exactly the same standards but is it usual to be so far off that the bolt catch wouldn't work?

This is my first black rifle build and I've picked up some lessons already (no more Frankenguns for me) and I appreciate all the responses to my (and others') questions.

[Robocop1051]

Switch to an Armalite or Phase5 bolt catch. You won't be dissatisfied. 

[slugger43]

Switch to an Armalite or Phase5 bolt catch. You won't be dissatisfied. 

+1

Bolt catch issues are not all that uncommon in the world of 308.  The Armalite 10-B is a good choice, but might need a little "surgery".  I had the same situation and my solution was to pick up a taller bolt catch, which I got from Mega.  No idea what model or brand name it is, but it's a tall, beefy catch that dropped in and worked perfectly.  A call to them wouldn't hurt.  

[MikedaddyH]

Switch to an Armalite or Phase5 bolt catch. You won't be dissatisfied. 

+2

The Armalite bolt catch is about a millimeter taller than the DPMS bolt catch but that is all you should need.

[survivalshop]

 PSA has proprietary component issues , its been discussed here many times . 

[shepp]

 PSA has proprietary component issues , its been discussed here many times . 

and wasn't it stated that they maybe aR-10 pattern?? I maybe mistaken

[Ozz]

Okay, have a new low-profile gas block and gas tube on order from Faxon and a bolt release from armalite. I'll update when I have the rifle put back together. Thanks for all the replies and suggestions.

[Malig8r]

Nothing new to add other than welcome to the forum from Michigan. 

[Robocop1051]

Okay, have a new low-profile gas block and gas tube on order from Faxon and a bolt release from armalite. I'll update when I have the rifle put back together. Thanks for all the replies and suggestions.

I have a strong feeling this is going to end in some pew pew bliss. Just my prediction.