A friend of mine has run into a perplexing problem with an old 25-20 lever action rifle that he would like to use for lever action silhouette. The rifle has had the original barrel drilled out for a Brownell's liner and rechambered in the original 25-20 caliber. The installation looks to be expertly done. The rifle shoots very well for shots 2 to 5. However, the first shot out of a cold barrel is always about 250fps slower than shots 2 to 5 and way out of the group. After the first shot the rifle spits them out at about 1800fps and will continue to do so until the rifle is cooled down for 30 minutes or more. This happens with all bullets, both cast lead and jacketed. If he waits about 30 minutes or more, the first shot is always about 250fps slower than the rest of the shots. Since we shoot silhouette with relays of 10 shots (2 five shot strings) with a wait of about 30 minutes between animals, the shooter will be at a considerable disadvantage if the first shot is always a flyer. I think most barrels show a very slight velocity loss for the first shot out of a cool barrel, but not 13.9% like this one. Does anyone have any ideas what could be causing this extreme (250fps, 13.9%) velocity loss for the first shot out of a cool gun?
Thanks,
John F. Orn
.
Thanks,
John F. Orn
.