I've been having some difficulty chrono'ing my muzzleloader. It's a roundball gun and I'm only getting readings in the 800-900 fps range and I know it should be more than twice that. My thoughts are that it's reading the patch and not the ball. Any suggestions on how far away from the muzzle to put the screens? Thanks.

You should be at about 10 yards from the screens. What is your load? Ron

Be sure to cover the front of your chrono if shooting sabots! I have broken the LCD on mine before. Louis

quote:

You should be at about 10 yards from the screens.

Ron, I'm just curious, I do all my chronographing at 10 feet, I've never heard of anyone chronographing at 10 yards.

Why do you chronograph at that distance?

[/QUOTE]
Ron, I'm just curious, I do all my chronographing at 10 feet, I've never heard of anyone chronographing at 10 yards.

Why do you chronograph at that distance?[/QUOTE]

Because the patch, sabot or wad might fly through the crono, and cause a false reading.
At 10 Yds, you will only be loosing a few FPS, and your reading will be more accurate, and your cronograph will be safer. As mentioned above, a sabot moving at 900 Fps can damage your cronograph. At 10 yards (30 feet) the sabot, wad or patch should have fallen to the ground.

I have no experience chrographing patched loads but have done hundreds of sabots and always run my chrono 10 feet away and have never experienced false readings. I guess it is possible depending on the chrony though.

My chrony has a remote read out so no worries about damage from sabots hitting it but I can't say that I've ever noticed that happening at 10 feet.

quote:

Originally posted by brianbo:
My thoughts are that it's reading the patch and not the ball.

A projectile, any projectile, crosses the first skyscreen, starting the timer. It then crosses over the second skyscreen stopping the timer. Are you intimating that your spit patches fly faster than your round balls? I find that highly unusual. At the normal placement of 10'-15' in front of the muzzle, the patch and ball should still be in unison, thus starting and stopping the timer together.

My Oehler 35 skyscreens don't even have cables 30' long; maybe 20' at most.

I chrono my Mlers at about 6 feet w/o sky screens. It reads fine every shot, but it does get powder residue on it when that close. I do it so close so the sabot will not smack the LCD. Been doing shotguns that way for a while to keep the wads from hitting the chrono.

Fired about 20 rounds from two Mlers last weekend the same way.

Good Luck

Reloader

8 to 10 feet works fine for me...Just past the smoke cloud and long before the sabot opens.

I have to use 30 feet with some big BP cartridge guns for several reasons. The timer starts when a shadow passes over the screen. This can be followed by wadding (rapidly slowing due to drag) that the chrono may think is the bullet, resulting in a longer elapsed time and thus a very slow reading. Shadows are also caused by the smoke when using BP.

Finally, and this is really strange, I've watched a high speed film of a friend firing a large bore rifle frame by frame and there is clearly a shadow that apprears on the ground in front of the barrel BEFORE the bullet exits the barrel! I assume it was caused by the air in the barrel being compressed ahead of the bullet enough to refract the sunlight and create a shadow for a fraction of a second. I don't know if that's enough to trip a chrono, but could explain some erratic readings?

I guess it depends on your powder and load. If closer works, go for it. If you a go with a longer distance, protect the chrono as others have mentioned. Don't ask me how I leaned that!

Bob

I had a problem with close in crono on MZ's so got a longer cable and have not had problems since.

I also shot thru a taugh piece of butcher paper which effectively catured all of the smoke, wad and BP residue and I doubt slowed the projectile down much but was a lot of hassle to set up.

quote:

Originally posted by madabula:
I had a problem with close in crono on MZ's so got a longer cable and have not had problems since.

I also shot thru a taugh piece of butcher paper which effectively catured all of the smoke, wad and BP residue and I doubt slowed the projectile down much but was a lot of hassle to set up.

These are a lot of great ideas. Has anyone tried covering the sensors with saran wrap like the shooting chrony folks suggest? I've never chrono'd my BP guns because of all the issues raised (but now answered) here.

I ran mine about five feet. I burned the screen and had to send it in for repair. Now I have a plexiglas cover for the readout and that works OK. I got good readings at that distance.

I have yet to get reliable/consistent results with 16-bore/5-dram black powder loads.
It could be the huge quantity of smoke - not sure.
I recently got a set of infra-red screens and some time hopefully soon, I'll run bore-rifle loads over them and see how it works out.



Cheers
Tinker

I use 15' from the muzzle to the first screen - always have, and been chronographing round ball guns without problems since 1973 - several difference machines of course. My initial Oehler sky-screens needed a protector in front, but the later ones, 1980's onwards, haven't. I'm currently using an old PACT timer as well as a Beta Master Chrony, both without trouble.
I cannot see a patch tripping a screen, as it is behind the ball and the screen is already tripped by the leading ball.

I've been chrnographing larger bores mostly, the .40 squirrel rifle being the smallest so far, but need to do my .32 soon - when it warms up - maybe April?

The odd time, you get erroneous numbers - don't let that screw with your mind, merely edit that shot and shoot again. Same thing happens when trying to chronograph a .17 bullet at 4,000fps or more. It's normal to get the odd bad reading at times.

Light defusers are necessary for me with blue skys and sunshine, but that's normal as well. Slanting sun can also give problems - again, normal.