Author Topic: Chronograph Readings (Read 810 times)

bumble · « **on:** October 22, 2003, 03:56:42 PM »

I don't usually have to many problems clocking a load. Sometimes the sun or the clouds or the two together give me pause. I'm curious to find out what, if any, problems you've run into trying to work with rifles that have muzzle breaks. I'm coming to the conclusion I might have to put up a sound barrier ahead of my sensors. I'd like to hear some experiences or opinions please. What are you running into?

Iowegan · « **Reply #1 on:** October 23, 2003, 02:34:37 PM »

Unless you have some new fangeled chrono, all the ones I've seen are light sensitive, not sound sensitive. The standard chronograph measurement point is 12 feet from the muzzle. If you get the chrono too close to the muzzle, it will get spoofed by the muzzle flash and gasses. The muzzle break has no influence on the chronograph.

jhalcott · « **Reply #2 on:** October 23, 2003, 02:46:22 PM »

I once recorded a vel. of 3200 fps from my super blackhawk .44 mag.
The problem was the muzzle was to close to the machine. The muzzle blast shakes the inners and gives a false reading.(shoulda read the @#$#@ instructions). It is easy to spot one of these errors.This blast CAN come from the cylinder gap,and I assume the ports on a break.I was trying to minimize movement on the bench and had the box too close to me.Chronographs are sensitive machines. jh

Duffy · « **Reply #3 on:** October 23, 2003, 07:25:52 PM »

I was told that on certain models that even static and electrical disturbance say from a storm or dry air can throw them off. Also if your mounting for the screens isn't solid and they wave around that can throw them into a tizzy too.

Blackhawk44 · « **Reply #4 on:** October 24, 2003, 09:16:46 AM »

If you will set your equipment so that the middle of the screens equals 15ft from the muzzle, you'll have few problems. Also, any equipment boxes on the bench with you need to be positioned near your side, not on the end of bench near the muzzle. Muzzlebrakes are not normally a problem since their extra gas is diverted at 90 degrees or more away from the screens. When the screens are closer to the bench, the gases from magnum handgun blast commonly causes false readings. Moving the screens farther out or a cardboard blast baffle ahead of the screens will cure that problem. Shotguns are notorious for that trick (heavy wood baffles here saves a lot of equipment).

bumble · « **Reply #5 on:** October 25, 2003, 06:32:50 AM »

Thanks for the help. Sounds like I need to move those sensors out a little further.

Donna · « **Reply #6 on:** October 27, 2003, 03:29:53 AM »

Hello bumble,

There are two areas of problems between the gun/chronograph interfaces. And both have been touched on here but let me reemphasize them.

1) The muzzle to screen interface: The muzzle flash and powder debris is traveling at a greater velocity then the bullet is after the bullet exits the muzzle, if the screens are to close to the firearm then they can be triggered by the muzzle flash and/or powder debris before the bullet reaches the screens. To solve this either move the screens farther away from the muzzle till this false triggering stops, you will need to compensate to get the true muzzle velocity. Or set up blast shield that would allow the bullet to travel through but eliminate or limit the muzzle flash and powder debris from passing through.

2) The muzzle to chronograph interface: The muzzle blast that you feel is a shock wave, the same shock wave that is produced from aerial bomb going off that you might have seen in film footage. This shock wave can disturb the electronics of the main unit. Either move the unit to another location so that the muzzle blast will not effect it, shield the unit from the blast, and/or in some cases take the cover off and pack the inside with anti-static high density Styrofoam and put the cover back on, in most cases this is the most preferred method.

I hope this helps you.

Donna :wink:

boneguru · « **Reply #7 on:** October 29, 2003, 04:42:13 PM »

I called PACT, one they said I was too close, two they said the sun was causing trouble (even with skyscreens) so now I'm mad here I have a tool to tell me how fast my loads are going but it won't tell me how fast they're going. so their suggestion was to move the screens about 10' away and turn them 90 degrees, nuts as it sounds it worked. I'm getting numbers where they are supposed to be.