AR Sponsor
Posted: 10/10/2010 3:10:43 PM EDT
What do you think. factory 115gr standard (non-tactical loaded) ammo ,16in, TYPE II midlength. Just to note it should not matter even if I shot tactical I should not be having this problem. |
|
I would say that its the gas system not the load. primers arnt flattened or cratered, in my experience the primer flattening will always be the first sign of pressure.
swipes are caused by the the bolt beginning to retract and turn before the chamber pressure has dropped enough, or by the raw speed and force of the bolt ejecting the round. this can happen with normal chamber pressure and an over gassed gun. |
|
Finding out if it's the ammo is one of the easiest things to check on first. Give SSA a call and ask them if they know of any problems with your lot of ammo. I recently had a problem with pressure using their 115 grain SMK load and it turns out that it was from a known bad lot. I was shooting them in a SPC II chambered gun, also. Everyone I talked to was convinced it was a problem with the barrel when it wasn't. ETA: Have you shot different ammo out of it? Do you have the same problem with that different ammo? |
|
Have you checked velocity with a chronograph?
Is the bolt brand new or close to it? Sometimes the finish on new bolts will be sticky and grab the brass making these swipe type marks. I have taken a fine wire wheel and Dremel tool an just lightly touched the parkerizing on the bolt face for larger caliber AR's to ease ejection. .308's almost NEED this done when new. This 6.8 may be need this treatment in this case. Do not remove any metal whatsoever, it will change your headspace. Simply polish the bolt face finish. Contact SSA and let them know what's going on. They may have had a production run that is over the top. They will need the lot# off the ammo carton. Another option is (make sure you have a spare) to remove the ejector and clip one coil off the ejector spring. Re-install the spring with the clipped end inserted first. Shoot the rifle again and check for pressure signs. As long as the rifle still ejects OK this may solve the problem. You have a spare replacement spring available in case this creates more issues. |
| Mild swipes as shown can be from aggressive edges on the bolt by the extractor or ejector hole. I've seen 6.8 brass in far worse shape, with bent rims and pierced, flattened primers. As suggested, back off 1/2gr if handloading and see if the swipes are still showing. You might want to try chamfering the edges in the bolt's extractor recess or the ejector hole, it may help. I turned down mine but haven't been to the range to see if it makes a difference yet. If its factory ammo, it may be a gas system or headspace issue as suggested above. Trying different loads can rule that theory out though, let us know what you find. |
|
I AM NOT SURE ABOUT THIS SO PLEASE CHECK IT OUT FOR YOURSELF.... but, I think I remember reading somewhere that SSA had some trouble with the 115 gr. load... or I should say that people who purchased the ammo had some pressure problems.
Go over to http://www.68forums.com/forums/index.php and ask about it...... include when you purchased the ammo. |
|
Quoted:
I AM NOT SURE ABOUT THIS SO PLEASE CHECK IT OUT FOR YOURSELF.... but, I think I remember reading somewhere that SSA had some trouble with the 115 gr. load... or I should say that people who purchased the ammo had some pressure problems. Go over to http://www.68forums.com/forums/index.php and ask about it...... include when you purchased the ammo. problem was with the bullet not the load, long story short, the shape of the bullet caused a ring of copper to get shaved off with each round fired. the ring stuck in the chamber and as you fired the copper built up shortening the headspace. that was with a bullet that is not made anymore. unless the ammo was bought from an individual then it cant be that issue. because he ID'd it as a std load instead of the combat load then it is most likely a current issue batch(because they didnt have that distinction when the bad bullets were out there) |
|
Quoted:
Definite pressure signs. For factory ammo, we have to look depper. Kotonics/Cardinal Armory barrel? Cardinal went out a few yrs ago. He got a bad batch of chome lined barrels that had too much chrome on them (or something to that effect)....after everything got settled, barrels replaced, refunds n whatever and the problem got figured out....he had to sell out, so he's been out of the game for a while.....fyi  But this guy shootin factory loads n havin swipes like this.....maybe CMMG had a problem as well? And thats awesome CMMG said to send it back n they'll handle it. Nothin like good support for the venders out there standin behind thier products. 
|
AR Sponsor