.308 Buffer question

[codyusaf04]

The Jist:
Bought a DPMS .308 Recon w/ 16 inch SS HBAR. Decided I wanted a long-range contender so I bought a completely separate upper and 24 inch SS BBL, gas block, tube, etc. As well as a magpul PRS stock that I plan to keep on the lower receiver permanently. I planned to simply swap-out uppers for doing different range shooting. Started thinking about he PRS stock and the rifle length buffer tube I had to install and larger buffer etc.

Question...Since I installed the rifle-length buffer tube, spring and larger buffer with the PRS stock...will that cause problems with recoil, cycling, etc. when I go to swap back to the 16 in upper?

It won't damage the action/buffer/spring will it? Does having the different length gas system do anything to affect the action significantly to cause harm?

As you can see at the links below...the 16inch upper has the gas block located closer to the upper receiver than the 24 inch barrel does. I haven't shot the 24 inch upper yet because the new gas system was missing the gas tube roll-pin...Gotta get another one.

This link shows the 16in .308 recon.
308 RECON

This link shows the LR-308 which has the exact same-length forend, barrel, and gas block location on it that I installed on the long-range upper.
LR-308


Please advise.

 

[USMC-FURY]

You can adjust for any cycling problems with the gas block, I would definitely get a JP spring and a .308 dynacomp then say bye bye to recoil, a step further, a lightweight JP bolt (6.2 ounces) HALF THE WEIGHT of a regular BCG.

 

[ORD]

There are no "one-size-fits-all" buffer/spring combos for ARs. Anytime that you are running the same lower with multiple uppers (especially uppers with different gas system lengths such as in your case...rifle-length on the 24" vs. mid-length on the 16"), you may find it necessary to adjust the buffer weight/spring setup up/down accordingly to obtain optimum levels of function. Its possible that either one or both of your uppers may be overgassed (a pretty common issue with many factory-production large-frame ARs). If so, a heavier buffer will serve to relieve at least SOME of the overgassing symptoms, but as I've said before, its a proverbial band-aid for a sucking chest wound. The best practice for dealing with tuning the function of any DI-operated AR-platform rifle is to fine-tune the gas flow by means of an adjustable gas block. This allows you to run lighter buffer/spring weights (less reciprocating mass in any AR, especially a precision-minded one, is a GOOD thing) by tuning each upper's respective gas system for optimum functioning/cyclic rate/accuracy/etc. with the same lower components.

At the end of the day, the only way to tell if you have issues is to shoot them both on your lower and investigate for yourself. Its all hypothetical until you have the hard data from your own use of the different uppers on your one lower as to whether you have issues or not. Look for things like any failures to feed/extract/otherwise function properly, excessive recoil/blowback/etc., brass being thrown a blue country mile with damage/trickling out upon ejection/short-stroking/etc., etc. All are signs of over/under-gassing and indicative of the need for either: a) adjustable blocks on the offending upper to get to the root of and resolve the problem; or b) others mods such as heavier/lighter buffer, stiffer/weaker recoil spring, heavier/lighter carrier (whether a low-mass carrier or more weight with something like a carrier weight insert), etc.

 

[Ballista One]

You can adjust for any cycling problems with the gas block, I would definitely get a JP spring and a .308 dynacomp then say bye bye to recoil, a step further, a lightweight JP bolt (6.2 ounces) HALF THE WEIGHT of a regular BCG.

Really? Is your statement based on experience or the vast amount of time you have spent on interwebs?

 

[jasonfaz]

I would say it is just random blabber. The JP .308 BCG weighs 14.4oz, the bolt alone weighs 2.6oz, and the carrier alone weighs 10.4oz. Even JP's AR-15 platform complete BCG weighs more than that at 8.9oz.

I read that post going whaaaat the fuu? You never know who's gonna say what sometimes man...

 

[codyusaf04]

Thanks for the info guys. I'll be sure to look into your suggestions!