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How does one go about chrongraphing a shotgun. I see some ammo manufactures state velocities on the box, but how do you keep the wadding from screwing up the velocity reading.

TEX wrote:How does one go about chrongraphing a shotgun. I see some ammo manufactures state velocities on the box, but how do you keep the wadding from screwing up the velocity reading.

This is just a guess...... the wadding follows the shot charge out the barrel, and it has very little mass. So the shot charge is what the chrono picks up, and it just doesn't even see the wad...except as part of the larger mass of the shot charge. The chrono is most likely set up 10' or less in front of the muzzle, and at that distance the shot column and the wad are still one amorphous mass.

I have never gotten a good chrono reading with lead shot, stainless shot has worked well for me. The chrono works by sensing the change in lighting as the projectile crosses the windows, with that in mind I think it will measure the front of the shot column more than anything else. As for why lead shot has never given me good results I do not know, I do know that I have gotten good results with the PDX plated stuff as well.

The Annoyed Man wrote:

TEX wrote:How does one go about chrongraphing a shotgun. I see some ammo manufactures state velocities on the box, but how do you keep the wadding from screwing up the velocity reading.

This is just a guess...... the wadding follows the shot charge out the barrel, and it has very little mass. So the shot charge is what the chrono picks up, and it just doesn't even see the wad...except as part of the larger mass of the shot charge. The chrono is most likely set up 10' or less in front of the muzzle, and at that distance the shot column and the wad are still one amorphous mass.

TAM - that is a good guess. I am sure that SAAMI has a standard test method for measuring the muzzle velocity of shot shells.

I too wondered about that and there is a YouTube video

http://www.youtube.com/watch?v=dQTtMhL1E4E" onclick="window.open(this.href);return false;

to condense, they fire with the choke that they plan to use in the field at a distance of 3-4 feet and are always prepared to buy a new sensor. In this video they did not use the sun shield.

rotor wrote:I too wondered about that and there is a YouTube video

[youtube]http://youtube.com/watch?v=dQTtMhL1E4E[/youtube]

to condense, they fire with the choke that they plan to use in the field at a distance of 3-4 feet and are always prepared to buy a new sensor. In this video they did not use the sun shield.

Fixed it for you.

G.A. Heath wrote:I have never gotten a good chrono reading with lead shot, stainless shot has worked well for me. The chrono works by sensing the change in lighting as the projectile crosses the windows, with that in mind I think it will measure the front of the shot column more than anything else. As for why lead shot has never given me good results I do not know, I do know that I have gotten good results with the PDX plated stuff as well.

I never knew that. I always assumed that it sensed the mass of the object passing through the screens. Don't know why I thought that.......I just did.

The Annoyed Man wrote:

G.A. Heath wrote:I have never gotten a good chrono reading with lead shot, stainless shot has worked well for me. The chrono works by sensing the change in lighting as the projectile crosses the windows, with that in mind I think it will measure the front of the shot column more than anything else. As for why lead shot has never given me good results I do not know, I do know that I have gotten good results with the PDX plated stuff as well.

I never knew that. I always assumed that it sensed the mass of the object passing through the screens. Don't know why I thought that.......I just did.

Some of the earlier chronographs worked by the bullet breaking the continuity of an electrical current. When the projectile broke the first [metal] screen the timer started and when the bullet went through the second screen the next circuit broke and the timer stopped. If you knew the distance between the screens you can calculate the velocity. I haven't kept up with the current technology.