DPMS .308 16" Bbl with Standard Stock?

[acgeorge]

I have been doing a lot of reading about .308 rifle and carbine stocks, buffers, and springs. But nothing that  answers my question.Does anyone have any experience with using a standard rifle stock with a DPMS .308 16" Barrel w/carbine gas system? Does the buffer weight need to be modified? Is it safe to do?

 

 

[survivalshop]

 You can Put any stock on you want, on any length Barreled AR Rifle , as long as you use the Proper Components along with it .

 

Edited August 21, 2017 by survivalshop

[MrPaul]

Rifle length buffer tube needs a rifle length buffer and buffer spring and carbine tubes use a carbine spring and buffer.  Gas tube length doesn't affect anything but i would use an adjustable gas block to make sure you don't end up over gassed. 

[98Z5V]

1 hour ago, MrPaul said:

Rifle length buffer tube needs a rifle length buffer and buffer spring and carbine tubes use a carbine spring and buffer.  Gas tube length doesn't affect anything but i would use an adjustable gas block to make sure you don't end up over gassed. 

I don't have an adjustable gas block on any AR I own, and I've got a few.  Adjustable gas blocks are the love-child of the 3-gun competitors, to tune recoil to exactly what they want for their pet competition load.  They are not necessary in the least to the average person, unless that rifle is making you money in competitions.  They might make a small improvement, but it's not gonna be a game-changer.

My $0.02.

[acgeorge]

I finally finish my 308 build. First trip to the range, will not cycle. It will fire, extract, eject but not go back far enough to strip the next round from the magazine. Once in a while it would load the next round, mostly not. Recommendations?

1. Live Free Armory matched upper and lower, DPMS compatible, high profile.

2. Bushmaster 16" 1:10 Barrel, dimpled for gas block set screws

3. DPMS GII Cancellation Brake

4. DPMS Low profile gas block and tube

5. DPMS lower parts kit

6. UTG A2 308 stock assembly (spring .077" wire dia x 36 coils, 12.25 OAL) (Buffer 5.3 oz, 5.2" OAL)

7. DPMS Gen 1 Bolt Carrier Assy

 

[jtallen83]

 Don't hold out on us now.

Did you lube the crap out of it?

How many rounds fired?

Pictures of the gas tube end in the upper will rule that issue in or out. Sounds like it is short on gas a bit but 20 more rounds and some lube may see it running good, these things like to run wet at the start.

[survivalshop]

 Are there any marks on the inside of the Lower Receiver , where the BCG enters the Receiver Extension ? 

 Can you manually engage the Bolt Stop ?
 Wilh an empty Mag inserted into the Rifle , will the Bolt Stop engage the Bolt Face ?

 

 

 Formerly Part #: 308-BS-10B

.308 Standard Buffer Spring Length - 12 3/4'', 39 coils.

 

Buffer Length: 5 1/4"
  

 

*Note* 

 

The DPMS LR-308 platform rifles use a proprietary recoil buffer and spring; although similar looking these parts are not interchangeable with standard AR-15 rifles 

 

FOR GEN 1 RIFLES ONLY 
  

Edited September 17, 2017 by survivalshop

[acgeorge]

It wasn't dripping lube, but I thought I lubed it well.

Only fired 20 rds, only two cycled the next round.

Here is a pic of the gas tube protrusion into the upper. Does this look right? Got the gas tube and block from DPMS at Camp Perry, in July.

[acgeorge]

The gas key doesn't hit the upper, buffer length wont allow it.

With an empty mag I can manually engage bolt catch, however, not on last round fired.

Buffer weight/length and spring seem to be in line with "Slashes Big Buffer Table", or close.

The buffer spring seems stiff?

Edited September 17, 2017 by acgeorge

[jtallen83]

18 minutes ago, acgeorge said:

It wasn't dripping lube, but I thought I lubed it well.

Only fired 20 rds, only two cycled the next round.

Here is a pic of the gas tube protrusion into the upper. Does this look right? Got the gas tube and block from DPMS at Camp Perry, in July.

Gas tube looks short to me. This is a carbine length gas system correct? You shouldn't have to break in a rifle but more lube, a little dripping won't hurt, and more rounds might get it going.

[acgeorge]

Yup, carbine length. I understand gas tubes are the same for 223 and 308? Like I said, I bought it at the DPMS building at Perry, with most of the other parts except the receivers. I have extra carbine and mid-length gas tubes, I'll see how they compare.

 

[Boot_Scraper]

23 minutes ago, acgeorge said:

Yup, carbine length. I understand gas tubes are the same for 223 and 308? Like I said, I bought it at the DPMS building at Perry, with most of the other parts except the receivers. I have extra carbine and mid-length gas tubes, I'll see how they compare.

 

Gas tube looks short. Check out this thread. Gas tube . From what I've read, sometimes the short tube works, sometimes it doesn't. I had to get one from Armalite. 

[jtallen83]

The trend seems to have manufacturers tweaking the port location on barrels for the 308 so it's all bets off these days. Just finished a build that had the gas tube end way past the midpoint, I was surprised it didn't bottom out.

[acgeorge]

 

Beantown"s gas tube looks about the same, his is factory?

[survivalshop]

  Some rifles will work with a shorter protrusion into the Gas Key , some will not . Depends on a couple factors , Carbine Gas length has the best chance to work this way , because of Gas pressure at that length , but that depends on the Gas Port size in the Barrel , so like was said ,its a crap shoot with different manufacturers .

  Your Protrusion into the Upper Receiver with a Carbine length gas Tube is on the short side , not much in the way of another size to replace it with . Make sure the Port Holes of the Barrel & Gas Block are not restricted in any way . Check Gas Port size in Barrel .

 Unfortunitly  because of a lot of these rifles being built , have many different manufacturers of Components in them & may need longer break in time , tolerance stacking may be effecting some builds . 

  The Gas Block may also be the issue , could be set up wrong for the Gas Tube , hard to say .

  0.77" for the Spring diameter seems a little thick , I will have to look at my notes , but I think most are 0.72 " dia..

  You say the Bolt Catch will not engage with an empty mag , with out you forcing the Catch ?

 

DPMS LR 308 Gas Tube & /AR 15/16M4

 

  Pistol             6-5/8

  Carbine          9-3/4

  Mid-Length  11-3/4

  Rifle             15-1/4

 

 

 

 

Armalite lengths,

Rifle ( 308 ) ----- 15.5 "

Mid length 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---------------  ?

 

[Boot_Scraper]

@acgeorge

I swapped the barrel on my PA-10 and found my existing tube to be short on the new barrel. On my quest for knowledge, I came across the following thread.

 

 @98Z5V is WAY more "loquacious" than myself and he does a fine job of ironing it out right here, I think.:

On 4/12/2017 at 11:09 PM, 98Z5V said:

I just re-read this whole thread, and didn't see a reference in your thread here, OP, about that gunsmith and his comments.  That's me mixing up information and threads, on the exact same subject.  That must have been another person in the last couple weeks, with that gunsmith.  We made a recommendation to the guy, based on what he was telling us, and the pics revealed the short gas tube.  Immediate recommendation to replace it with the Armalite gas tube, check operation, and see how the problem was.  Pick off the easy target, and see how it goes, you know, fix the obvious.  He goes and tells his gunsmith that bit of info, and the gunsmith tells him that's not even an issue, and it won't change anything.

Well, I say BS on that gunsmith, and here's why...

It's come up that the carrier key sits further back on the 308AR than it does on an AR15 - it's in the exact same place from the front of the carrier back to the front of the key, but that 308AR bolt is alot bigger than an AR15 bolt, and when the bolts are seated in the carrier, in the firing position, that key is further back on a 308AR.

That's issue #1.

Next, Armalite vs. DPMS (and AR15) gas systems.  Why Armalite gas tubes are longer than standard AR15 gas tubes (and DPMS_based LR308 parts), I have no idea. Why DPMS uses AR15 gas tube lengths for 308ARs, I have no idea...  However, I DO know that Armalite knows their shiit, and they have a scientific, tested, proven reason for making AR-10 gas tubes longer.  Whatever reason that is, you can know that it's a good one.  Pat Raley could tell us all about it, I'm positive.

That's issue #2.

Next, that carrier key overlaps the end of that protruding gas tube, and it's for an exact distance/measurement.  It's THAT WAY so the bolt carrier receives the proper amount of gas, for the proper amount of time, in order to properly cycle the semi-automatic weapon.  Once that bolt carrier assembly has made enough rearward travel, it disengages from the end of that gas tube, and the remaining gas is discharged directly into the (now open) upper receiver.  It's the excess gas you see coming out of the ejection port when your buddy fires his weapon...

That is issue #3.

Now, that leaves us here - with a gas tube that is NOT the proper length, and it's short by 3/16", that bolt carrier is NOT receiving the proper amount of gas, for the proper amount of time, and it's not fully cycling that bolt carrier assembly with the proper amount of force that it was designed for.  It might cycle, but it's NOT going to cycle as it was designed to do...  THAT cannot be argued.  It's science and math.  Done.

Now, this isn't aimed at you, OP - this thread is just a target of opportunity to explain it.  You are on the right track.

I hope that other poster reads this, then prints it, and gives a copy of it to his "gunsmith." 

Thus endeth the sermon...

 

[acgeorge]

My bad! The gas system is MID-length 11.75"

The bolt catch does work correctly manually, just not on the last round.

I have an original DPMS 308 CAR stock assembly. I will install it and try again, this weekend. Although, I prefer the fixed A2 stock.

Since the barrel is Bushmaster, are there any nuances? I don't think Bushmaster is making the 308 anymore.  

[survivalshop]

The Armalite AR 10 ( 308 ) Mid Length Carbine Gas tube will give you a longer Gas tube for more protrusion into the gas key . Don't think the Carbine system will help , unless that Rifle Buffer Spring is not correct in some way . Ya never know though . The Gas Tube is available from ---

https://dsgarms.com/arm10007005

Armalite lengths,

Rifle ( 308 ) ----- 15.5 "

Mid length 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---------------  ?

Edited September 18, 2017 by survivalshop

[acgeorge]

After seeing Beantown's factory DPMS, I'm less concerned with the gas tube protrusion length, even though it looks odd. The only other odd characteristic is the stiffness of the buffer spring. I ordered a DPMS 308 rifle buffer spring. Between this and the DPMS CAR stock assembly I already have; I will be able to test a few things at the next range trip.

[survivalshop]

     As I posted above , there are a couple of factors of why on rifle will work with the Gas tube protrusion as in your Rifle , but that spring may also be suspect , one thing at a time . The 308 has a lot of power for cycling , but some rifles will not cycle properly with the Gas tube into the Carrier Key that short , just keep that in mind .

  I looked at my notes on spring wire diameter & I have 0.71-72" , so if yours is 0.77" & only has 36 coils , it may proprietary in nature .

[acgeorge]

Goon news, success at the range. The DPMS LR308 Rifle length spring did the trick. Just got back from the range, not one failure. Put some DPMS Mangonel iron sights on it and had it sighted in after 10 rounds. The rear peep seems a bit large, but ok. The DPMS Cancellation brake is interesting, I think it works really well. Now, I need a low power optic, maybe 4x or 5x.

[survivalshop]

  Thats great !