Harry O
10-04-2009, 07:39 PM
I did a test today. It was testing a "new" 41LC bullet against one I previously tested. The first one (which I have lots of data on since it was my first bullet mould for the 41LC) is a Rapine hollow-base 386185 mould that casts at 188gr with 40:1 lead/tin. The second one (which I fired today) is a modified Rapine 386185 mould. It has a shorter hollow-base-pin and it casts a 218gr bullet with 40:1. There are no other differences other than a very slight difference in length. It is difficult to tell the difference between the two unless you put them side-by-side.
I have loaded the 188gr bullet with 17gr of Swiss 3F BP and a small-pistol magnum primer. The accuracy was not bad, considering the OD of the bullet is 0.386" and the groove diameter of the barrel is 0.400". It was not quite as accurate as ONE of the heel-base bullets I tried, but close. It was equal or better in accuracy than any of the other heel-base bullets I tried.
I loaded the new 218gr bullet with 16gr of Swiss 3F BP and a small-pistol magnum primer. The 1gr less of BP was to keep the amount of compression with both bullets about the same. I shot 10 groups of 6 shots each from a benchrest at 15 yards (the same distance I tested my earlier bullets). Bore and chamber cleaning was done between groups. The groups from the heavier bullet are between 1/4 and 1/3 smaller than those of the lighter bullet. Overall average is almost exactly 30% smaller. In fact, the accuracy of the heavier hollow-base bullet is essentially equal to the most accurate heel-base bullet I have.
I would be interested on theories on why the heavier bullet is more accurate. I am not complaining. I am just trying to understand. Here is more information on the previous tests.
http://harryo.sixshootercommunity.org/
I have loaded the 188gr bullet with 17gr of Swiss 3F BP and a small-pistol magnum primer. The accuracy was not bad, considering the OD of the bullet is 0.386" and the groove diameter of the barrel is 0.400". It was not quite as accurate as ONE of the heel-base bullets I tried, but close. It was equal or better in accuracy than any of the other heel-base bullets I tried.
I loaded the new 218gr bullet with 16gr of Swiss 3F BP and a small-pistol magnum primer. The 1gr less of BP was to keep the amount of compression with both bullets about the same. I shot 10 groups of 6 shots each from a benchrest at 15 yards (the same distance I tested my earlier bullets). Bore and chamber cleaning was done between groups. The groups from the heavier bullet are between 1/4 and 1/3 smaller than those of the lighter bullet. Overall average is almost exactly 30% smaller. In fact, the accuracy of the heavier hollow-base bullet is essentially equal to the most accurate heel-base bullet I have.
I would be interested on theories on why the heavier bullet is more accurate. I am not complaining. I am just trying to understand. Here is more information on the previous tests.
http://harryo.sixshootercommunity.org/