General discussion > Gunmaking tools and techniques- metal shaping
Cutting Sight Slots by Hand and Fitting Sights
Herb:
I fitted a new taller sight (file the sight, not the notch) to lower the point of impact. This is a sight I like, all cast steel, .295" high. Order number 35009 from Muzzle Loader Builders Supply. It is .065" taller than the first sight, which lowers the muzzle and therefore the group.
I shot today in 94 degree heat to check the sight and the effect of holding the rifle at different places on the front rest. There is photo distortion here, there is only about 1/4" cast off in the stock. The photo makes it look crooked.
I shot the same as last time, front rod pipe resting on the cradle. Next group was with the rifle rested behind the entry pipe (it shot lower), but my powder measure slipped. Discovered that after the first shot on the third target and reset the measure at 70 grains. This was a new can of powder, too, maybe slightly slower. I used a mid rod pipe rest on this target. Bottom center target was with 80 grains of Goex 2F and the same mid rod pipe rest. Don't know why shot #3 was high, but I found one patch that was badly holed, probably this one. I can tap the front sight slightly to center the group laterally, but will not file the sight down until I decide what powder charge I want to shoot.
Herb:
This is a composite of the four groups I shot, with three different rest positions on the forend (to see what difference that would make), and 70 and 80 grain charges. They were expected to shoot to different points of impact. They average about one inch left.
From this chart, a 32 inch sight radius (this rifle) and a one inch sight correction shows that I needed to tap one sight .019" over to center the group. To move center right, tap rear sight right or front sight left. Also, I decided to shoot 80 grains so I filed the front sight down .035" to raise the group two inches. Then I removed the front sight to reshape it and the rear to draw file the barrel. I tapped them back about centered, but not zeroed. I need to take them off again to brown the parts.
On today's test, they were not zeroed laterally. Today I used a cleaning patch dampened with my cleaning solution on the jag as I seated each ball, and cleaned the bore well after each group. Notice from target 4 of 7/13 (center bottom) to the same load on the lower left, the velocity is 51 fps lower, apparently as a result of wiping the bore. The 120 grain target on lower right, my chrono screens were not lined up correctly first shot and the proof channel didn't read, so a 4 shot mean.
I then shot at 100 yards, first 3 groups with the blade at top of the rear sight hole, to raise the impact. I can't see the top of the sight sharply, hence large groups.
On the right side group, I tapped the front sight left to center the group and aimed with the post in the center of the rear hole, as at 50 yards. My cheek took a battering from the 120 grain loads, and I held my face away from the stock for the last (20th!) 120 grain load. That shot hit about 6 1/2" left. But I proved to me that this sight works.
Notice that with a clean bore, four of the five groups had the first shot quite a bit slower. The velocities with 70, 80 and 120 grains of Goex 2F agree very closely with Lymans Black Powder Handbook and Loading Manual, volume 2, page 210, even though I have a 42" barrel and they used a 32" barrel. The three, 5-shot groups with 120 grains averaged 1995, 1976 and 2010 fps, but that is how things go. I don't know why two shots were so fast.
Herb:
I see I made a mistake. That was only the 15th shot with 120 grains that was too much for my cheek.
Herb:
Lyman's Black Powder Handbook (first edition, 1992) has external ballistic charts, showing the bullet path through the air. The 2nd edition (2001) does not have this data. Here is the path for a .495 roundball at 2000 fps (.490 is the same):
50 yards was zero. 75 yards, -.91". 100 yards, -3.11"
My zero (8/1, target 2) was 1.7" high at 50 yards. Relatively, this added 1.5 times that amount at 75 yards, or 2.55", and twice that at 100 yards, or 3.4". Adjusting Lyman's trajectory with this path, my trajectory was 1.7" high at 50 yards, 2.55" minus .91" or 1.64" high at 75, and 3.4" minus 3.11" or plus .29" at 100 yards. My five shots on the right side average .33" high, which is just sheer dumb luck. It was just chance that I tapped the front sight enough by guess for this zero, and I did not know where that group would center. Nobody should think I did this by calculation. But this shows how high velocity and proper sighting can flatten the trajectory, at least out to 100 yards. Ain't it fun?
David R. Pennington:
I can definitly see potential on that round notch sight. Looks like I'm going to be cutting some new sights, I want to try it.
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