been getting keyholing from what should be a pretty good load. Started with Lapua cases in 6.5 Grendel, CCI 450 primers and BLC-2 22.0 to 23.0 grains behind a Barnes TSX 120 grain BTHP solid copper.
Barrel is a 1 X 8, 3 land, polygonical, 18" long, mid-length, SS, no chrome. Checked for over-sized bore, dropped a bullet without the casing into the chamber, gently tapped it with a brass rod and removed it. Slight rifling cuts on jacket past the ogive - no grossly over-sized bore. Didn't have any #1 buck lead shot to slug the barrel to check the diameter.
At 22.0 grains the round keyholed at 50 yards. Removed the muzzle brake and checked for obstruction in the barrel, damage to the muzzle end, burrs in the lands - none found. Fired the next round with a charge of 22.5 grains BLC-2, same thing. Fired a 3rd round with a charge of 23.0 grains, same thing with signs of high pressure - flattened primers, head stamp compression. Keyholing was reduced a little with the higher charge load.
Weighed all charges individually and set bullets without a crimp using brand new Lapua cases.
Backed off to regroup and think of other reasons for keyholing. A buddy suggested starting out again with Noslers or Hornady copper jacketed bullets and see if there is a change. Haven't been able to get to the range to try this yet but I thought someone on the site might have an idea or two I could try.
Called the barrel manufacturer and he's mystified. Hasn't had a situation like this before. Gave him my load info for him to test. Waiting for word back.
Any other suggestions?
Thanks,
Gunfighter
Barrel is a 1 X 8, 3 land, polygonical, 18" long, mid-length, SS, no chrome. Checked for over-sized bore, dropped a bullet without the casing into the chamber, gently tapped it with a brass rod and removed it. Slight rifling cuts on jacket past the ogive - no grossly over-sized bore. Didn't have any #1 buck lead shot to slug the barrel to check the diameter.
At 22.0 grains the round keyholed at 50 yards. Removed the muzzle brake and checked for obstruction in the barrel, damage to the muzzle end, burrs in the lands - none found. Fired the next round with a charge of 22.5 grains BLC-2, same thing. Fired a 3rd round with a charge of 23.0 grains, same thing with signs of high pressure - flattened primers, head stamp compression. Keyholing was reduced a little with the higher charge load.
Weighed all charges individually and set bullets without a crimp using brand new Lapua cases.
Backed off to regroup and think of other reasons for keyholing. A buddy suggested starting out again with Noslers or Hornady copper jacketed bullets and see if there is a change. Haven't been able to get to the range to try this yet but I thought someone on the site might have an idea or two I could try.
Called the barrel manufacturer and he's mystified. Hasn't had a situation like this before. Gave him my load info for him to test. Waiting for word back.
Any other suggestions?
Thanks,
Gunfighter
