View Full Version : Chronograph can't record pistol loads.

March 7, 2011, 12:38 PM
Its an older "PACT model 1" & it has never had a problem with 30 cal rifle bullets so I've just kept & used it with complete satisfaction. I did have an issue with muzzle blast jumping the plugs once, but sitting a sandbag on the cables solved that & it only happened with a muzzle break fitted.

Then I tried using it to check some 125 Gr .357 ammo from a 6" revolver. What a disaster! it seems to be reading blast or something as the velocities vary between 300 & 2000 fps. for every cylinder fired:rolleyes:

I've tried it with & without the diffusion screens & at several different distances 10' & 15' mostly, but the problem persists.

Any clever ideas other than buying a new chronograph?

Dr. Strangelove
March 7, 2011, 06:51 PM
Boolits or bullets?

If you're shooting lead with no plating or jacket, it could be having a hard time reading bullet pass of the sensors.

March 7, 2011, 07:29 PM
Move it a little further away from the muzzle.

March 8, 2011, 03:22 AM
at several different distances 10' & 15' mostly,

I first started noticing false chronograph readings with my 357, I moved it out to 20 yards and never had a problem after. I take all my reading at 20 yards now, just in case.

March 8, 2011, 08:28 AM
Dr. Strangelove:
It failed with both plated & jacketed bullets. I haven't tried boolitt tips yet though. It is recording something, otherwise I'd not be getting readings at all or a shot number in the string.

"with & without the diffusion screens & at several different distances 10' & 15' mostly"

Do you have a conversion back for MV? I haven't seen any numbers for 20' corrected to muzzle.

March 8, 2011, 09:34 AM
I had the same issues with my 38spl loads. I read the manual *gasp* and it said this can commonly happen with subsonic rounds. The "blast wave" reaches the chrony before the bullet does, and it ends up registering or messing it up.

If you were doing full house magnum loads then I also don't doubt that the concussion could be causing issues. As suggested, move back a little more and try again.

OH... also don't forget to change the battery. If the battery is getting low it can cause funky readings as well.

March 8, 2011, 11:52 AM
Good point about the battery, thanks, I hadn't thought of that.
In theory my loads should be running about 1250 FPS, well above mach 1, but without the chrony data I can't really tell.

March 8, 2011, 05:38 PM
if you are getting strange readings with the screens over 15 feet away you other problems. I don't have any muzzle blast problems with my Oehler 33 using magnums and the screens are usually set around 6 or 7 feet.
I would change batterys & chronograph on cloudy days.

March 8, 2011, 07:04 PM
It ONLY happens with pistol bullets, both 158 Gr plated & 125 Gr JHPs, rifle bullets work fine at either 10' or 15' depending on the rifle's muzzle blast.
I don't think the problem is distance per se, or nothing would work.

March 16, 2011, 04:50 PM
Wog, try snooping around the reloading forum. They're big on chrono's over there. And +1 on moving farther away.

March 16, 2011, 04:55 PM
I'll try there, thanks.
I'm also gettinga chance to test over a different chronograph, lets see if that gives me more info. It would at least eliminate a possibility if that one had similar problems.:)

March 16, 2011, 05:07 PM
Move it back further.

March 16, 2011, 08:23 PM
I had this issue with my Pact as well. I used a second target stand with a piece of cardboard on it about 2-3 feet IN FRONT of the first screen. It blocks the blast and allows for more accurate readings.

It helps if you cut the cardboard to the same shape as the screen and supports so you can see the outline of the chronograph.

March 17, 2011, 07:17 AM
OK, I wondered about that.
I'll head to the range next time with a cardboard blast screen.