Chronographing Shot Loads

[roundball]

Chronographing Shot Loads

Out of fear of any shot spread damaging the chronograph out at 15 feet away, I want it sitting as close as possible to the muzzle but still be able to get a good reading of the passing shot charge only...maybe just 6-7 feet away”¦close enough so the OP wad will still be part of the shot column.

To try and eliminate...or at least minimize...the smoke & flame from the muzzle blast affecting the readings and/or the chronograph at that close range, I’m thinking of building a plywood barrier wall...just a section of ¼” plywood maybe 2 feet wide x 3 feet tall to have standing in between the muzzle and the chronograph with base legs so it won’t tip over, and with a small 4” square window cut at the appropriate height to shoot through...thinking that the small window will block a lot of collateral muzzle blast from reaching the chronograph...test in first before putting the chronograph behind it, etc

Does anyone have any hands on experience (or know of a reference article) about this?

 

[paulvallandigham]

I had trouble keep the shield standing upright, and not falling onto my chronograph. I guess I didn't anticipate the power of those gases, and needed a more sturdy stand for it.

I chose instead, to simply make a package of the shot, so it went over the screen in one solid, I have the screen set out at 20 feet, as I do for shooting RB over it. The added friction of the paper shot cub balances any otherwise increase in velocity that would come from the shot being kept together by the closed packet. Shotgun velocities vary a lot more from shot to shot, than can RB velocities. even shooting modern commercially made shotgun shells.

 

[mazo kid]

I guess I had never heard of anyone chrono-ing shot loads. When shooting round ball I usually put a piece of Saran wrap over the sensor to keep the crud from covering it up. Easily changed when it gets a little dirty.

 

[roundball]

I use a piece of 3" wide Scotch packing tape over the sensors...my main interest for shot loads is blocking the bulk of the muzzle blast from reaching the screens at all when I have them so close.

Since making my first post I've had the thought of running some dummy tests with sheets of flip chart paper, one sheet at a time...2 feet, 3 feet, 4', 5', 6', etc...to get an idea of how wide and far the muzzle blast expands, and to what distance it retains heavy smoke, powder particles...show any errant pellet spread that close, etc, as it moves forward. That should tell me the best distance to have the screens with the plywood wall/window right in front of them.

 

[Leonredbeard]

Roundball,
you might just pattern a few loads at 15ft to see how big a spread you get, and also where it hits with regard to your sight picture. With the patterns you are getting at yardages, you may not need to worry about hitting your screens at 15 ft.
volatpluvia

 

[roundball]

Roundball,
you might just pattern a few loads at 15ft to see how big a spread you get, and also where it hits with regard to your sight picture. With the patterns you are getting at yardages, you may not need to worry about hitting your screens at 15 ft.
volatpluvia

Could very well be...I do remember its very dense at 10 yds from past pattern testing...I can recall a fist size hole but what I can't remember is if there might have been a few stray pellets flipping out from scrubbing the bore walls.

The test shots on flip chart paper should show up anything like that...I can shoot a couple at 15' to start with like you mentioned to see what's what, and start backing up from there if I have to.

The other unknown out at 15 feet distance is if the cushion wad would have separated from the shot charge enough to wander off slightly and damage the unit.

 

[paulvallandigham]

The more important concern about the wad is will it have separated enough to give a second, SLOWER, reading as it passes over the screens. 15 feet is only 3 yards, and it should not be a problem, either way. The pattern will be larger than bore diameter, after 9 feet, but only about 1.5 times the bore diameter at that distance. You should expect to see a few pellets straying from the main mass, but only by fractions of an inch at 15 feet.

 

[Leonredbeard]

roundball,
I'll be anxious to hear how it went.
volatpluvia

 

[roundball]

roundball,
I'll be anxious to hear how it went.
volatpluvia

It'll be several weeks now as the range is closed to conduct some state pistol matches and I'm going to try and bust a crow with a .62cal Flint smoothbore the next couple Saturdays...will post results when I start testing stuff again