Toymaker
04-06-2014, 12:32 PM
A week ago I took out my Creedmore Rigby to check the sight settings for an upcoming competition. It uses a .452, 535 grain FN bullet. I'd cast 500 bullets last October in preparation for this year's shooting season. I was very happy with the results at 50 yards - Three overlapping holes in a "V" just a tad high of center. At 75 yards the results were similar - Again three shot overlapping group, but the "V" was inverted. It was about an inch high of center. However, at 100 yards I couldn't find a hole. Front sight was secure, tang sight was secure, nipple wasn't blown out .... finally got two rounds on paper - they key-holed.
Once home I cleaned the heck out of the rifle, even cleaned for leading. Found nothing. THEN I realized I'd had 6 bullets left over from last year which I'd used at 50 and 75 yards, but used the new bullets at 100 yards. I grabbed the Saeco tester and checked a couple of the new bullets - BHN 7. Looked around and found a wrinkled old bullet in the re-melt can - BHN 5. All I can think of is that I put some hard alloy ingots in my pure lead casting pot. Dumb, dumb, dumb.
So I cranked up the pot, cast a test bullet (the test bullet came out BHN 7 as I suspected.), dumped the lead into ingots, labeled them and put them away. Then I loaded the pot with known pure lead and cast a test bullet and 200 bullets. This test bullet came out BHN 5.
Yesterday I got to the range to check things out. Everything worked out exactly right. The 50 and 75 yard 5 shot groups duplicated the 3 shot groups from the week before. The 100 yards hits did not key-hole - Success #1. The 5 shot group was about 1 inch wide and 1/2 inch high, sitting about 2 inches high of center. Success #2. The hits being a little high is a good thing because the competition distances are 50, 75 and 100 meters.
My theory - I use a light powder charge of 45 grains FFFg so I can shoot without a shoulder pad and facial bruises. I get excellent groups with 65 grains FFg, but look like I've been in a bar fight after a 10 shot relay. Because of the light charge I need a dead soft bullet to get enough expansion (obduration) in the bore to seal it. The BHN 7 bullets weren't sealing, gas escaped, the bullets lost velocity or never had it, and began to yaw giving the key-holes.
Combined with the Spring equinox, Earth/Mars junction, and two close pass asteroids the impurities in the harder bullets caused them to be pulled out of their trajectory and destabilized. That's my story and I'm sticking to it - - but I'll listen to yours.:lol:
Once home I cleaned the heck out of the rifle, even cleaned for leading. Found nothing. THEN I realized I'd had 6 bullets left over from last year which I'd used at 50 and 75 yards, but used the new bullets at 100 yards. I grabbed the Saeco tester and checked a couple of the new bullets - BHN 7. Looked around and found a wrinkled old bullet in the re-melt can - BHN 5. All I can think of is that I put some hard alloy ingots in my pure lead casting pot. Dumb, dumb, dumb.
So I cranked up the pot, cast a test bullet (the test bullet came out BHN 7 as I suspected.), dumped the lead into ingots, labeled them and put them away. Then I loaded the pot with known pure lead and cast a test bullet and 200 bullets. This test bullet came out BHN 5.
Yesterday I got to the range to check things out. Everything worked out exactly right. The 50 and 75 yard 5 shot groups duplicated the 3 shot groups from the week before. The 100 yards hits did not key-hole - Success #1. The 5 shot group was about 1 inch wide and 1/2 inch high, sitting about 2 inches high of center. Success #2. The hits being a little high is a good thing because the competition distances are 50, 75 and 100 meters.
My theory - I use a light powder charge of 45 grains FFFg so I can shoot without a shoulder pad and facial bruises. I get excellent groups with 65 grains FFg, but look like I've been in a bar fight after a 10 shot relay. Because of the light charge I need a dead soft bullet to get enough expansion (obduration) in the bore to seal it. The BHN 7 bullets weren't sealing, gas escaped, the bullets lost velocity or never had it, and began to yaw giving the key-holes.
Combined with the Spring equinox, Earth/Mars junction, and two close pass asteroids the impurities in the harder bullets caused them to be pulled out of their trajectory and destabilized. That's my story and I'm sticking to it - - but I'll listen to yours.:lol: