AR Sponsor
Posted: 12/11/2012 3:46:23 PM EDT
|
I just finished building a DPMS style LR 308 and I can't get the Bolt to lock open... The build is as follows:
Magpul PRS Stock (AR 10 Model) DPMS Rifle Buffer Tube JP Enterprises JPS-OSR .308 Rifle Length Spring Tried both Enidine Hydraulic .308 Rifle Buffer and Armalite AR 10 Rifle Buffer JP .308 Low Mass BCG JP Enhanced Bolt Phase 5 Tactical Extended Bolt Release v2/308 (it's like a B.A.D. Lever combined with a bolt catch for those wondering) I had read some posts where the Magpul PRS Stock screw was too long by 3/8's of an inch, so I tried backing out the screw and I still couldn't get it to lock open. I have tried with both an Armalite AR 10 Rifle Buffer and the Enidine Hydraulic .308 Rifle Buffer and it won't lock open with either. At this point I think JP could have accidentally sent me the wrong spring, or maybe it is an issue with the Low Mass BCG (this is my first low mass), or possibly the Phase 5 Tactical Extended Bolt Release? My Buffer detent is pretty stiff, but I don't think that would be the problem... If any one has any idea please let me know. It's painful to have a complete build that just won't work! I'm sure a lot of you have more experience and knowledge than I do, and I'd appreciate any help I can get. Thanks. |
| One out of ten times, if I apply a lot of pressure, I can get the catch to hold the bolt back. However, as soon as I release my hand from the bolt catch the BCG shoots forward. So no I can not lock the bolt back manually. I've inspected the bolt catch and it appears to be the same size as my other DPMS LR 308 bolt catches. At this point I think it has to be the buffer spring or the low mass BCG. |
| Will it lock back with an empty magazine? See if the Phase 5 lever is making contact with the lower receiver as you pivot it to lock the bolt back. If it does touch, this may be impeding the full motion of the bolt catch and not providing enough surface for the carrier to stop against. Do you have a standard bolt catch to compare against? |
|
Does the PRS use a screw like the A2 stock does?
If so it may be in to far and not allowing the buffer to retract completely. Try removing just the stock and with the bare tube still installed retract the bolt carrier and see if the catch will hold it. Just saw you already tried that. I agree with the poster above, try removing the aftermarket bolt release and see if that helps. |
|
What is the length of your two buffers? I have this setup but I use the DPMS rifle buffer and have no issues at all. The DPMS LR-308 rifle buffer is 5.250 inches and the standard spring is 12 7/8 inches, but if your spring is SLIGHTLY longer or shorter, that is of no concern since my spring is old and may have taken some set.
Make sure you are not using the longer AR-15 buffer because if you are, well, there's your problem. You mentioned you backed the butt screw out, but did you make sure it is the shorter A1 screw and not the A2 screw. The A2 is longer and you may not have backed it out enough? Or if you used the screw that came with it then you should be OK. ed to add: Does your spring slide freely over your buffer? I ran into a situation on an AR that when I tried to use a Wolff XP spring on a particular HB that the spring bound up on the buffer body and would not collapse around the buffer. That in affect made it seem like the spring was too long and the rifle would not function. If I used another buffer all was well, or used a spring that did not bind on the buffer all was well, but that XP spring binding on that particular buffer was a no-go and had me scratching my head for a minute or two. |
|
I'll be watching this closely. I also put together my 308 DPMS lower. It has the DPMS LR-306 upper with 24" bbl. Just for the record it shoots great, often .5 or less @ 100 yards. Anyway, I've never been able to get the bolt to stay open on the last shot and manually setting it in place only works 50% of the time. I was just about to tear it apart and look for the issue. It has about 500 rounds through it now so it is probably not a wear in issue.
Bill |
|
Try different mags. Sometimes the follower shifts forward and doesnt positively engage the bolt catch. Take any empty mag and push the follower all the way to the rear. On a closed bolt, insert the mag and rack the charging handle.
Also try this. Remove your upper and install an empty mag. Does the bolt catch raise all the way to the top or is there play? Try moving the follower around. You may have an out of spec mag well. |
| Thanks everyone for all of your help!!! Turns out the arm on the Phase 5 Tactical Extended Bolt catch was hitting my JD Machine Tech lower, and not allowing the bolt catch to pivot fully. I guess these two are not compatible. I feel like an idiot for not noticing this earlier. Again thanks. |
AR Sponsor