Freakycamo Report post Posted August 20, 2018 Good morning team I have a friend that got a used 338-378 Weatherby and he went a got 2 new boxes of 338-378 Weatherby. They say (guarantee) that if you use there ammo in there gun you will get 1 ½ MOA. We got about 3-4 inch group at 100 yards. I know for a fact that it is over pressuring the bolt is sticky, the primers are flatten, one primer fell out, ejector marks on head stamp. I am thinking it’s a fouled barrel so I started to clean the copper out of it. I just don’t about 338-378 Weatherby is this common for this gun. Looking for any help I can get or suggestions. Share this post Link to post Share on other sites
452b264 Report post Posted August 20, 2018 I have owned two 300 wby, and their ammo was excellent. I never had any problems with pressure etc, and both of them shot under an inch with the last vanguard under .5 without a muzzle break. Share this post Link to post Share on other sites
win71 Report post Posted August 20, 2018 Don't believe you could foul a barrel to the point of having pressure swings a dramatic as you are experiencing. Would explain poor grouping though. I have found wby ammo to be very inconsistent with respect to pressure. Out of five boxes of factory 300 mag I had to cull over 30 casings due to loose primmer pockets. To remove that cooper try JB Non embedding bore cleaner available from Brownell's ( 800-741-0015 ) or in some of your better shooters supply shops. Start with the jar with the blue writing and finish with the jar with red writing. Nothing works better. Since you bought the rifle used, and I am assuming don't know for sure it's history, I would have the headspace checked on it as well. Good luck with your cannon at least that's what I called mine before I sold it. I just couldn't handle the recoil. Dan Share this post Link to post Share on other sites
Hoss50 Report post Posted August 20, 2018 Flinching? I know I would be unless that beast had a BIG brake on it. 3 Share this post Link to post Share on other sites
