Newbie BP and chronograph question

[Legionnaire]

Hi, all.  New to the forum, and new to black powder.  Not new to shooting, though.  Here's my question: when I chronograph loads for my various BP handguns, how far should the chronograph be from the muzzle?  I generally set at ten feet for all my smokeless guns and that has worked fine.  But I wonder about black powder muzzle blast, subsonic rounds, and flying wads.  So for those of you who chronograph BP cap'n ball revolvers, at what distance do you set you chronograph?  Thanks!

[wildman1]

Use the same distances that you do for smokeless, however you may want to cover the lenses with clear plastic or Saran Wrap to keep them clean. If you think that your readings are inconsistant or not right shoot through paper before the chrono, MAKE SURE you don't shoot your Chrono, this will keep the smoke from giving you false readings. Good Luck. WM

[Ranch 13]

15ft minimum 20 ft is better.

[Montana Slim]

15ft minimum 20 ft is better.

Thats more like it...and it will be somewhat dependant on the firearm/load you are using.....a Dragoon revolver with full load will give erratic results at a distance my 1860's chrony perfectly... Keep a clean rag handy to wipe things down. I also omit my usual "lube" when testing C&B pistols.

Slim

[Mako]

Use the same distances that you do for smokeless, however you may want to cover the lenses with clear plastic or Saran Wrap to keep them clean. If you think that your readings are inconsistant or not right shoot through paper before the chrono, MAKE SURE you don't shoot your Chrono, this will keep the smoke from giving you false readings. Good Luck. WM

Good advice, but I don't think your lenses will smoke up. You may get erroneous readings and the saran wrap won't protect anything from burning grains of powder.  Put ashield like Wildman suggested in front of the chronograph a piece of cardboard about two feet in front of the first screen and just shoot through it.  I have a IPSC target holder and I just use an option target or a piece of cardboard cut to fit it and it works fine.  I use a sheet of 1/4" plywood in the holder with a 4 inch hole in it for shotguns.  Well...it started out 4".

~Mako

[wildman1]

I use 3 "steps" for handguns and for rifles I use either 10 or 12 "steps" when using BP. I have had to clean the lube off of the front of the Chrony when I didn't use the SW. Guess I should have clarified that I extend the SW down over the front of it. At distances of 10 to 12 steps I think all of the fire is gone from the BP as I have never melted holes in the SW. I have also used clear plastic from packing cartons etc. Those distances are probably triple (or close to that) of what is recommended in the Chrony inst.  WM

[Legionnaire]

Thanks, all.  I've been shooting at the manufacturer's recommended 3 meters.  Results have not been erratic, but "interesting," to say the least.  Here's a table of data from my Uberti Walker.  You'll see why I ask the question:

These data are the results of two days shooting; it was 10 degrees warmer day two.  The data from day one are in black, day two in blue, and the aggregate (AG) data for each charge weight are shown in red (calculated across all 18 individual shots).   Powder was Goex FFFg, CCI #10 caps.  Loads up to 55 grains were loaded powder, lubed wad, .454 caliber ball--no filler.  Couldn't fit a wad in with 60 grains of powder, so those were loaded powder, ball, T/C Bore Butter seal.  I should note that between every cylinder, I pulled the cylinder from the frame and used a dry nylon bore brush to knock fouling out of each chamber; I also ran a bore brush and a dry patch through the bore.  In the table below, "String" is the order in which the cylinder was shot across the two days of data.  I rounded the spread for convenience.

String, Grains, Average (fps), Spread, Std Dev.
1, 35, 700, 210, 76.9 (excluded from aggregate data)

6, 35, 1019, 36, 13.5
10, 35, 1009, 51, 18.6
11, 35, 1034, 53, 22.5
AG 35, 1021, 91, 20.5

2, 40, 1100, 40, 16.0
7, 40, 1082, 64, 22.9
12, 40, 1077, 75, 27.1
AG 40, 1086, 76, 23.4

3, 45, 1125, 62, 26.2
8, 45, 1134, 69, 28.6
13, 45, 1132, 56, 18.6
AG 45, 1132, 77, 23.7

4, 50, 1173, 58, 23.6
9, 50, 1156, 47, 17.6
14, 50, 1163, 44, 14.6
AG 50, 1164, 70, 19.2

5, 55, 1188, 81, 28.9
15, 55, 1196, 60, 22.4
16, 55, 1161, 71, 26.8
AG 55, 1181, 91, 28.9

17, 60, 1271, 28, 11.0
18, 60, 1308, 53, 21.2
19, 60, 1313, 39, 16.6
AG 60, 1298, 73, 24.9

Interestingly, the average velocity gains with loads that included a wad were as follows:

35 to 40 grains = 65 fps
40 to 45 grains = 46 fps
45 to 50 grains = 32 fps
50 to 55 grains = 17 fps

However, the velocity gain from 55 to 60 grains loading the ball directly on top of the powder and then sealing the cylinder with Bore Butter ...

55 to 60 grains = 117 fps!

That's an odd pattern, and I'm looking for a theory that might explain it, including whether or not I have the chorograph set too close.  I'll back it up some next time.  Looks like I have more experimenting to do!