AR Sponsor
Posted: 2/11/2012 11:56:38 AM EDT
|
Just got done building an LR-308 and I believe I need a recoil buffer spring....... My stock spring (used DPMS) is measuring just under 12 7/16 inches in length. From everything I could find, the DPMS stock spring should be 12 3/4 inches long, which is giving me a spring over 9/16 inch short.
I checked the spring, because my bolt / carrier is not going fully into battery from locked open or while shooting. This does not happen every time, but is becoming more frequent. I have used different mags and have tried it with Federal GMM 167 and 175's..... The bolt appears to be in battery and I have to push the forward assist to send the carrier the last 1/8 inch or so home. This push on the forward assist is just that, a slight push or touch, not requiring a slam. The barrel, bolt and gas block are new...... everything else was on the gun before the barrel change. It has 130 rounds on the new barrel. The build is.... DPMS Upper and Lower DPMS Carrier that came with the above JP Enterprises enhanced bolt Kreiger 24" Stainless Barrel headspaced to the new JP bolt Magpul PRS stock Enidine Hydraulic buffer Geisselle Hi Speed National Match Trigger JP Enterprises adjustable gas block Aadmount scope mount Trijicon Accupoint 5 x 20 x 50 Mil Dot Scope DPMS free float quad rail Reaper in black hyrdocoating GG&G heavy duty XDS Bipod I have been looking at the Superior Shooting Systems (Tubb) flat wire CS springs..... Anyone tried these? Or, should I just use another DPMS stock spring? Any other suggestion would be appreciated also |
|
Ok, took the upper off.... This was all checked by hand, no recoil spring.
Bolt (out of carrier) goes in and rotates no problems. Carrier has no interference with the gas tube, charging handle or any other parts and works smooth. Bolt in carrier is stiff. Rotates and can be, "flicked" out with a good, hard, flick of the wrist. Bolt in carrier (no ammo) goes in, rotates then stiffens up just before the carrier is in full battery. With just a little bit more force / push goes into battery. Same thing with a round in the chamber and with one already loaded into the bolt face. Feed ramps are aligned and smooth. This may be a combination of a new / stiff bolt and shortened recoil spring. The old spring has approximately 5,000 rounds on it. I am thinking of honing / smoothing the inside of the carrier just slightly to see if it improves..... Or, maybe a new spring and JP Carrier are in order 
|
|
Have you tried closing the BCG by hand?(with the upper open, just push the BCG into the barrel extention) Do you get the same results?
That JP bolt may be a tight fit, or it could be the cam pin binding. I would try a new spring if the 1 you are using has that many rds through it. If you get a new carrier I'll take the old one off your hands |
|
Quoted:
Out of spec bolt lugs and or barrel Ext.? I would try the spring if that does not fix it then send it back to JP. AL I don't believe so, the bolt goes into the extension, rotates into battery without a problem, both with and without ammo. It is only the last little distance that the carrier moves, is where the problem is. I am going to swap out the spring and see what happens....... The rings on the bolt do fit tight...... Maybe with some more shooting it will smooth out. |
|
Quoted:
Just got done building an LR-308 and I believe I need a recoil buffer spring....... My stock spring (used DPMS) is measuring just under 12 7/16 inches in length. From everything I could find, the DPMS stock spring should be 12 3/4 inches long, which is giving me a spring over 9/16 inch short. I checked the spring, because my bolt / carrier is not going fully into battery from locked open or while shooting. This does not happen every time, but is becoming more frequent. I have used different mags and have tried it with Federal GMM 167 and 175's..... The bolt appears to be in battery and I have to push the forward assist to send the carrier the last 1/8 inch or so home. This push on the forward assist is just that, a slight push or touch, not requiring a slam. The barrel, bolt and gas block are new...... everything else was on the gun before the barrel change. It has 130 rounds on the new barrel. The build is.... DPMS Upper and Lower DPMS Carrier that came with the above JP Enterprises enhanced bolt Kreiger 24" Stainless Barrel headspaced to the new JP bolt Magpul PRS stock Enidine Hydraulic buffer Geisselle Hi Speed National Match Trigger JP Enterprises adjustable gas block Aadmount scope mount Trijicon Accupoint 5 x 20 x 50 Mil Dot Scope DPMS free float quad rail Reaper in black hyrdocoating GG&G heavy duty XDS Bipod I have been looking at the Superior Shooting Systems (Tubb) flat wire CS springs..... Anyone tried these? Or, should I just use another DPMS stock spring? Any other suggestion would be appreciated also The buffer spring in my .308 PRS is 13.75", or 1" longer than a AR15 rifle buffer spring. I would try a real AR10 rifle spring, not the AR15 rifle spring. Just pulled my spring and checked. It's 13.5" after a few thousand rounds. Ripped from the AR10 FAQ. Rifle springs. As you can tell the AR10 is 1" longer than the AR15 spring at 13.75" 
|
|
Quoted:
Quoted:
Just got done building an LR-308 and I believe I need a recoil buffer spring....... My stock spring (used DPMS) is measuring just under 12 7/16 inches in length. From everything I could find, the DPMS stock spring should be 12 3/4 inches long, which is giving me a spring over 9/16 inch short. I checked the spring, because my bolt / carrier is not going fully into battery from locked open or while shooting. This does not happen every time, but is becoming more frequent. I have used different mags and have tried it with Federal GMM 167 and 175's..... The bolt appears to be in battery and I have to push the forward assist to send the carrier the last 1/8 inch or so home. This push on the forward assist is just that, a slight push or touch, not requiring a slam. The barrel, bolt and gas block are new...... everything else was on the gun before the barrel change. It has 130 rounds on the new barrel. The build is.... DPMS Upper and Lower DPMS Carrier that came with the above JP Enterprises enhanced bolt Kreiger 24" Stainless Barrel headspaced to the new JP bolt Magpul PRS stock Enidine Hydraulic buffer Geisselle Hi Speed National Match Trigger JP Enterprises adjustable gas block Aadmount scope mount Trijicon Accupoint 5 x 20 x 50 Mil Dot Scope DPMS free float quad rail Reaper in black hyrdocoating GG&G heavy duty XDS Bipod I have been looking at the Superior Shooting Systems (Tubb) flat wire CS springs..... Anyone tried these? Or, should I just use another DPMS stock spring? Any other suggestion would be appreciated also The buffer spring in my .308 PRS is 13.75", or 1" longer than a AR15 rifle buffer spring. I would try a real AR10 rifle spring, not the AR15 rifle spring. Just pulled my spring and checked. It's 13.5" after a few thousand rounds. Ripped from the AR10 FAQ. Rifle springs. As you can tell the AR10 is 1" longer than the AR15 spring at 13.75" http://i32.photobucket.com/albums/d37/madcratebuilder/AR10/riflebuffer.jpg That is exactly what I am going to do. I ordered a new spring this morning from Brownell's. Heavy Buffer brand, which is listed as 13.75 inches. 
|
|
Stay away from the flat wire springs, far, far away. I've done extensive testing and I recommend using ArmaLite AR10 buffer springs in all .308 ARs. Until I can talk Wolff into making .308 springs the ArmaLites are the best available. DPMS .308 springs are notoriously weak and inconsistent. And that is assuming that the assembly monkeys at DPMS installed the correct spring in the first place. I've seen several factory DPMS .308 rifles with AR15 rifle buffer springs.  Measuring the relaxed length is not an accurate way to compare/identify springs. Counting the number of coils is much better. I'm not sure how JP 'enhances' a bolt, but I always stick with OEM for ALL BCG parts, and match the barrel/extension manufacturer to the BCG. |
|
I agree headspace should always be checked especially within the 308 realm but to the OP's defense the JP bolt is made as a replacement for DPMS and other patterned rifles, no need to switch the carrier and as the OP said the barrel was headspaced to the new barrel. It sounds like the new bolt just needs some wearing, let us know how the new springs runs.
|
AR Sponsor