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Gas System for .308 AR-Carbine or Middie?


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#1 liontribe

 
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Posted 18 February 2012 - 02:29 AM

i have a DPMS Oracle with a carbine length gas system.  is there any reason i should go to a mid-length system for my .308?  it seems to run just fine as is, but i keep reading about mid-length systems being preferable for one reason or another.  is this just internet hype or is one better than the other for our big AR rifles?

liontribe

#2 imschur

 
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Posted 18 February 2012 - 02:43 AM

Ill vote for if it aint broke dont fix it.

#3 Robocop1051

 
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Posted 18 February 2012 - 02:53 AM

I say, you wouldn't have bought an AR if you don't plan on changing it at some point.
I think you should go to a rifle length. The 308 is over gassed as it is. I know 1 or 2 guys here have 16" barrels with rifle length gas. I just ordered a 17" with rifle length gas.

If you're looking to conceal the gas block, the mid length is as short as I would recommend.

I wouldn't go to a carbine unless barrel length gave me no other option. I just switched my last AR15 over to a 14.5" mid. I'm done with carbines, at least till I can finagle a SBR.

Having Tom and I post on the same thread is like having two fat chics at a night club. It doesn't matter what song is playing, we are going to take over the dance floor.


#4 edgecrusher

 
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Posted 18 February 2012 - 03:01 AM

Ill vote for if it aint broke dont fix it.

+1 , don't feel like you have to change it, it's all personal preference unless it's giving you fits. if you decide to change, do all your research first, bounce questions off us, we'll help.
mostly though i feel if you are enjoy shooting as is leave it. it's too easy to get caught up in the kool aid.
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#5 Jgun

 
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Posted 18 February 2012 - 03:39 AM

I think that the carbine length gas system being a bad thing originated with the M4's. I have read that they were very hard on bolts because of the earlier gas pressure on the carrier effected the timing and this caused the bolt to be trying to cycle and extract the case too early, before the case pressure had diminished sufficiently. I have a mid length gas system on my 14.5" 5.56 gun and prefer it to the carbine setup. I find that the gun seems to cycle smoother and recoil is less. Now if you were to apply the same logic to the .308, I would think that the mid length gas system (or rifle length for that matter) has the potential to give you a smoother operating gun. Of course the 7.62 is not the same rd as th 5.56 so the gas impulse will not be the same.
Personally I have a 14.5" 7.62 AR with what Noveske calls a carbine gas system, But the GB is actually located in the same place that an AR 15 mid length gas block is located. I wouldn't want the gas system on my 14.5 gun to be any longer than it is for reliability reasons. That being said, a 14.5 barrel is a different animal than a 16". Barrels are expensive, If your gun runs well as is, I'd be inclined to leave the system alone. You could put a heavier buffer in it. The only reason I'd consider a different gas system type would be if you wanted to change the barrel, not to change the barrel because you want a different gas system.

#6 edgecrusher

 
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Posted 18 February 2012 - 03:56 AM

That being said, a 14.5 barrel is a different animal than a 16". Barrels are expensive, If your gun runs well as is, I'd be inclined to leave the system alone. You could put a heavier buffer in it. The only reason I'd consider a different gas system type would be if you wanted to change the barrel, not to change the barrel because you want a different gas system. want the gas system on my 14.5 gun to be any longer than it is for reliability reasons.

well said
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#7 Robocop1051

 
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Posted 18 February 2012 - 04:15 AM

The only reason I'd consider a different gas system type would be if you wanted to change the barrel, not to change the barrel because you want a different gas system.

Truer words have never been spoken. Well put.

Having Tom and I post on the same thread is like having two fat chics at a night club. It doesn't matter what song is playing, we are going to take over the dance floor.


#8 liontribe

 
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Posted 18 February 2012 - 04:28 AM

thanks for all the quick replies.  i have installed the buffer set-up from slash.  i am also thinking of going with an adjustable gas block in the near future, just in case i run into a problem with certain loads.  it is my main hunting rifle and i have only had one FTE with a round that it had no troubles with before hand.  i have a bit of tax cash coming my way.  i have been debating another rifle or just working this one over exactly as i desire.  tough call.  i have only put maybe 150 rounds through this gun with the one failure to cycle.  it isn't even broke in good yet.  i feel the need to customize everything though.  i am a knife maker and i can't leave anything as is.  :cookoo:

liontribe

#9 survivalshop

 
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Posted 18 February 2012 - 02:15 PM

Ill vote for if it aint broke dont fix it.


Such wisdom , it gets my vote also.

I have one question , why a adj. gas block for a hunting rifle ?

The only thing it would do is restrict gas flow, not some thing you want with a hunting rifle . If your rifle doesn't function correctly with a certain type /manufacturer ammo , I would stay away from it .

Your gas system is wide open now , restricting it may cause problems .

#10 liontribe

 
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Posted 18 February 2012 - 03:25 PM

from what i have read and my experiences with AR rifles, the big .308s are many times over gassed.  with an adjustable gas block i can fine tune for a wider variety of loads.  some commercial loads are on the hot end of the spectrum and could possibly cause problems in an autoloader.  adjustable gas block would just give a wider range of choices.  i like plenty of choices.  and that is one of the fun things about AR rifles, they are like legos.  i liked legos.  <thumbsup> 

liontribe

#11 imschur

 
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Posted 18 February 2012 - 03:37 PM

I like to refer to my conversations with John Paul of JP. According to JP much of the 308 ammo was designed for bolt action rifles with no regard to semi auto funtion, reliabilty and wear. Often the pressure curve of ammo is not ideal for the semi auto and in fact most rounds do over gas the weapon. These semi's were originally designed to fire very specific military rounds.



#12 Jgun

 
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Posted 18 February 2012 - 04:16 PM

Regarding the adjustable GB's. I see that JP's now offering clamp on, steel, lowpro (how lowpro I'm not sure) gas blocks. I'm not a fan of aluminum gas blocks and as far as I know all of their adjustable GBs used to be aluminum, which was a deal breaker for me.

#13 imschur

 
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Posted 18 February 2012 - 04:28 PM

They have stainless as well. I just ordered the JPGS2B. Visit JP here.

#14 imschur

 
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Posted 18 February 2012 - 04:29 PM

the low profile is aluminium

#15 Jgun

 
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Posted 18 February 2012 - 05:26 PM

I recall seeing a ad from JP from the shot show where they had two low pro GB's pictured and I thought they were both described as being steel. But now I can't find the ad and I don't see them on thier site.

#16 liontribe

 
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Posted 19 February 2012 - 01:23 AM

that block in your link looks like just the thing.  that was my thinking as well on many of the commercial .308 loads.  they vary greatly in pressure because that is of little worry to most modern bolt guns.  i like the idea of tuning my action for my pet loads or favorite commercial fodder.  i used to be a big FAL shooter and that is a great thing about those rifles.  fully adjustable gas system.  thanks for that link.  i will be doing some not so scientific experimenting with this rifle over the summer.  i will keep everybody up to date on my tinkering results.  i am very pleased with this rifle as is, i just want to see how versatile i can make it.  thanks for all the input.

liontribe

#17 unforgiven

 
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Posted 19 February 2012 - 02:12 AM

Welcome from Indiana brother liontribe.
If you fail to plan ~ You plan to fail---Don't complicate poop ~ With complicated poop--- I will die on my feet ~ than live on my knees

#18 washguy

 
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Posted 21 February 2012 - 10:56 PM

Hi Lion!  Welcome aboard  My vote is to leave it alone...if it aint broke...just leave it alone <thumbsup>  If you just wanna spend money...start a savings piggy bank for some good optics...if ya cant see it...well you know the rest! 8)
Wash

#19 liontribe

 
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Posted 21 February 2012 - 11:09 PM

i got the optics covered.  i gotta nice little trijicon scope riding on top at the moment.  great low light scope. 

liontribe

#20 jeffreyC

 
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Posted 30 March 2012 - 07:13 PM

Put in my vote for rifle length gas system, unless it would be longer than the barrel.
Lower recoil, easier on the BCG.
"Every good and wise man should be wary lest he be deceived by sham internet quotes. " – Thomas Jefferson




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