Chronographing Loads

[Bent Sight]

Has anyone used a chronograph to measure the muzzle velocity of different charge weights shooting a round patch ball load? How far does the patch travel with the round ball before it separates from the ball?

I set the chronograph at 15 feet from the muzzle when testing and developing center fire loads. Any closer and the muzzle blast from a black powder rifle might skew the results. I would like to avoid hitting the chronograph with a high speed patch.

Anyone have any experience with this?

 

[BrownBear]

I put mine at 15', but I also put a clear plexiglass shield in front of the chrono to protect it. Never seen any sign of a hit, but never had any trouble either.

 

[Bent Sight]

Plexiglass is a good idea. I'll have to scare a piece up.

I want to gather velocity numbers so I can calculate hold overs at different charge weights for shooting at distances beyond 100 yards. At some point I want to see just how far I can shoot 10" steel with patch round ball loads.

 

[Billnpatti]

My experience has been that my patches land anywhere from 10 to 15 yards from my muzzle. When I chronograph my loads, I place my chronograph about 10 yards in front of my muzzle and aim very carefully so as not to hit any part of my chronograph with the ball. I have a program that adjusts for the distance from my muzzle to the chronograph to give a calculated muzzle velocity. The patch is not a problem so long as it does not pass through the chronograph screens. If it passes through the screens, it often, but not always, messes up the readings. The patch does not have enough mass to be a problem if it accidently hits your chronograph at that distance. Usually, at 10 yards, it may hit the legs of the tripod on which the chronograph is sitting but it does not have enough energy to even shake the chronograph.

 

[Spikebuck]

How far does the patch travel with the round ball before it separates from the ball?

Watching slow motion videos, all that I have seen show the patch separating from the ball almost immediately. Now, the patch continues to fly forward, but it is separated quickly.

My chrono also has a plexiglass shield in front to protect the unit.

Mike

 

[curator]

Plexiglas or Lexan shield over the face of the Chronograph will prevent unburned powder grains and sparks from pitting it. Also, consider some kind of transparent cover for the electronic "eyes." I found that powder granules and carbon dust would accumulate on them when shooting black powder loads. Better yet, consider the "Magnetospeed" that mounts on the barrel. No sky screens and can't get shot if you install it correctly http://www.magnetospeed.com/

 

[Maven]

If you have a Shooting Chrony brand chronograph, you may still be able to get 1/8" thick clear "plastic" shields which cover both the display and light sensors.

 

[George]

I have a CED Millennium brand chronograph, and the sensors are shielded inside the units which hold the sky screens. The display is wired but remote. You can certainly damage the sensing units by shooting a bullet through them, but BP debris, smoke, patches and such can't hurt them. No shields necessary.



Spence

 

[hanshi]

I have an Oehler chronograph. I set the screens up about 15' from the gun muzzle. I'll occasionally chronograph the loads I use - often been using for years - just out of curiosity and sometimes get surprised. I find all the patches 30' to 40' from the firing line.

 

[Griz44Mag]

MAGNETOSPEED -

Nothing to hit, never misses a reading because of flying patches either....

Griz

 

[Herb]

I have worn out an Oehler 35P, had it rebuilt, and have badly damaged all the supports and sun shields with patches. I armor the uprights with tin, and glue the chips back in the overhead piece. Also shield the sensors, mounted on the bar and supporting the uprights, with wood. Set it out to the length of the cables, about 15 feet. Patches can badly damage chronograph screens. I have shot tens of thousands of rounds through my chronograph. http://www.muzzleloadingforum.com/fusionbb/showpost.php?post/1650113/

 

[Bent Sight]

I have a Competition Electronics chronograph that I have been using for years. There are no cables running to it; it stands alone on a tripod when I measure velocities.

I picked up a 18" x 24" piece of plexi-glass this morning. I am considering cutting a 6" hole in the middle of the plexi-glass and positioning it between the muzzle and chronograph.

 

[AlanG]

I have never had a problem with patches hitting or causing any damage at 15' from the muzzle. I've shot PRB's from .32 to .58 over a chrono with no problems over the years.

Pretty sure patches separate from ball really fast. Round ball ballistics are pretty poor, but I'm willing to bet the ballistic coefficient of a bare patch is even worse.

 

[hawkeye2]

I have a Shooting Chrony brand chronograph which I regard as an excellent chronograph for the money but have never fired a patched round through it so I can't be much help there. I got the optional plexi shields with it and am glad I did. For my very first round through it I had set the unit a little too high, easy to do, and I hit it dead center :shocked2: ! Fortunately I was shooting a Daisy BB gun and didn't hurt it thanks to the shields. BTW the Daisy was the most consistent thing I have ever fired through it at 325 fps. I usually set it about 10 feet from the muzzle and haven't had problems from the smoke or fouling.

 

[Bent Sight]

I chronographed loads today. I stapled a piece of cardboard to the table holding the chronograph so it protected the display. I fired a total of 15 shots at 15' away from the chronograph and did not see any powder residue or patch marks on the cardboard or chronograph.

What was interesting was that the bigger the powder charge the smaller the extreme spread. I fired CCI # 11 caps and Thompson Center .490" round balls with CVA pre-lubed patches that were allegedly 0.015" thick.

Results for 80g of Pyrodex were: High Velocity-1585 fps, Low Velocity-1522 fps, Average Velocity-1553 fps, Extreme Spread-63 fps and Standard Deviation-23 fps.

I used a thick line of white hold and fired a 5 shot group at 50 meters at dusk with two called high fliers. The group measured 1-1/4" Wide x 2-1/4" High, so I think I am on the right track for load development. I haven't figured out how to post pictures yet or I would.