distance of chronograph from muzzle

[farshot]

Has anyone ever measured the difference in velocity if your chronograph is say 5 feet from your muzzle to say 15 feet?

Im placing mine at about 15 feet now because muzzle blast kept knocking the thing around.

Just wondering if I am getting accurate (or close enough) readings for muzzle velocity to compare to manuals etc.

 

[HKMark23]

Has anyone ever measured the difference in velocity if your chronograph is say 5 feet from your muzzle to say 15 feet?

Im placing mine at about 15 feet now because muzzle blast kept knocking the thing around.

Just wondering if I am getting accurate (or close enough) readings for muzzle velocity to compare to manuals etc.

5 feet = too close, MB can affect readings.

10 feet = minimum IMHO, should be optimal for pistol.

15 feet = good, particularly for rifle, you won't suffer deterioration in V that is in any way significant. Given all the other variables, this is splitting hairs into quarters.

Hope this helps.

 

[grijim]

I run my Chrony 10 From the end of the barrel.

Grijim

 

[A&Shuntr]

15 feet is ideal

 

[srt4u2nv]

10ft min add distance to that as you increase the size of the boomer your running through the chrony.

 

[ykkid]

There are formulas to work the instrumental velocity back to the muzzle, based on observed velocity and ballistic coefficient at that velocity. Totally meaningless if you are comparing one load to another, as long as you use the same set up each time. And in terms of external ballistics, even more meaningless, as the difference will fall below typical shot to shot variation.

 

[rnbra-shooter]

Some ballistics programs accept "instrumental velocity" as input (which is the velocity you measure from your chronograph), and back-calculate the muzzle velocity. Typical muzzle-to-chrono distances are 15 feet, though sometimes it can be done a fair bit closer, and sometimes a fair bit farther (I think the US Army used to measure at 78 feet?).

Instead of measuring with your chrono at 5' at 15', you could also run a ballistics program, and see what velocity it predicts at these distances. From that you can decide whether this is a worthwhile factor to consider, or if it is negligible for your purposes.

 

[Dirtdigger]

12' to 15'

Im placing mine at about 15 feet now because muzzle blast kept knocking the thing around.

Or I blow the reflectors off.

Derek

 

[Cocked&Locked]

as long as it's AHEAD of the muzzle and not IN FRONT OF the muzzle, your on the right trak

 

[Ganderite]

I found that closer than 15 feet I would get more errors. Muzzle blast, maybe?