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Posted: 8/21/2007 11:54:21 PM EDT
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I got the DPMS .204 Ruger barrel from Brownell's. Slapped it into a RRA gun using a new RRA bolt. Took it to the range with no sites and shot 20 rds to check "function" and "break in the barrel", cleaning it every few shots. Then I put on a new Meopta 4x16 scope and headed to the range. Using a Caldwell rest I try several differnt types of ammo. Wouldn't group, wild flyers. Ok, must be a defective scope. Switched scopes. Wouldn't group, wild flyers. Ok, perhaps I didn't properly torque the barrel nut. Then, with the upper off the receiver, I put a round into the chamber, inserted the carrier and bolt into the upper and closed it on the round. As the bolt enters the barrel extension and contacts the round, I realize the bolt isn't going far enough into the extension to rotate. In fact, it appears the case rim is protruding a good .250 out of the chamber. The barrel was chambered but not to the proper depth. I wentback and look at some fired brass and sure enough there is a light ring about .250 up from the rim showing where the chamber begins. Luckily there was no bulging or other pressure signs. I can't believe the gun would function with the bolt so far out of battery. I mean, the bolt isn't able to enter the extension far enough to rotate and lock. I guess I will call Brownells in the morning. Prior to installation of the barrel I bead blasted it. I've fired probably 60 rounds through it. I wonder if they will 1. take it back 2. try to sell me a reamer or 3. tell me I'm not the first person with this problem. Perhaps I should have bought the $400 Shilen barrel with bolt from Midway. PropDoc is right (Thanks) the gun isn't firing out of battery. The round I tried to chamber with the gun apart is out of spec, even though it is a factory Hornady round. The ring on the spent brass is perhals 3/16 from the rim which is about right I guess. Other rounds will chamber properly and the bolt is closing and rotating to a lock position. As such, I'm back to square one as to why I'm getting poor accuracy and wild flyers. I've re-torqued the barrel nut and I will shoot a few more rounds after work today. Perhaps I have two scopes with problems but it seems unlikely |
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I am having a real hard time wrapping my head around this. If the 204 round was a 1/4 in out of battery, you wouldn't have a receiver left. I can assure you, a brass case WILL NOT hold in those kind of pressures. The chamber may be very tight and require the buffer and spring to "slam" the round home, but i don't think it was firing out of battery (not to mention that unless something is broken, the FP shouldn't be able to even hit the primer with the bolt 1/4 out of battery). Good luck with getting your problems resolved. Keep us updated. 
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Agreed. Many times a scope appears tight because it cannot be moved by hand, then under recoil, it will slide around nearly undetected. Use a little White Out to mark the scope in the rings, just to make sure it's not moving. Also mark the ring mounts as well, even though the cross bar should hold them in place (assuming your mounts have one) it can still move a bit. A loose scope will have you chasing your tail for a good long time. Keep us updated.
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Russ4777, Nice groups. Thanks for the words of encouragement. The scope that is/was mounted on this gun is a new Meopta Meostar 4x16 in a set of TPS rings. It is a nice piece of glass. All rings screws are torqued with a Wheeler 'FAT' wrench. Barrel has a DPMS free float tube and is set in a RRA upper/lower with 2.5lb trigger. Feeling it might be a defective scope.. I pulled it off and threw on a Simmons 6x18 Whitetail Expedition in Millett angle loc rings. I re-torqued (the shit out of) the barrel nut today using a torque wrench at lunch time and ran out after work to shoot again. Same problem. No pattern to the shots. Now, I'm not David Tubb (but I've met him) and the 10/22 I built is good for shooting aspirins at 50yds (off bags  ) so I don't think it is me.If I can get away at lunch Thursday, I'm going to try a third scope, the Millett DMS-1 off my CQB .223. After that I will either give up or just order a second barrel and try it.. I've ruled out most other variables. I keep thinking it has to be something simple but frankly there are not that many variables in an AR upper. |
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Another good suggestion, I will take a look but I did not bead blast the crown, it was masked off with tape. I also have watched the muzzle to see if I can tell that gas is diverting unevenly but can't really tell. I'm going to call a local riflesmith and see if he has a bore scope. |
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