Originally Posted by 4leaf4life
The difference between the readings on a virtue clock and the pulse is based on where the readings come from.
Chris from Virtue explained it to me. He said that the chronos read the fps about 2-3 inches in front of them. This is why the Pulse is a little faster as the ball is still in the barrel as apposed to just leaving the barrel, the Virtue Clock.
Just to clarify as since we discussed this on my pulse-phone I got to test out the Pulse compared to Clock. And I probably did a pretty poor job of explaining myself in the middle of the night after eating way too much at an awesome Italian place in Vienna (no, I'll never tell the name).
Depending on where you hold the the Clock it could get its reading an inch or two in front of the barrel muzzle or just at the tip of the barrel muzzle as the ball exits. This is why it's become industry standard to hold the clock a couple inches back from the barrel because the radar will pick up the ball as soon as it leaves the barrel for a "true" reading. If you hold the Clock in front of the barrel, or as often happens rest your barrel an inch or two behind the radar, it will give a slower than true reading because the ball will already have slowed down by the time its been read by the radar.
That's a long way of saying, if you put the Clock in a different place (or a different angle), it will read the velocity differently (the same is true for the various chronos out there -- big red, the little handheld thing, etc). The "true" reading would be to put the Clock an inch or two behind the barrel in a perfectly straight line, not at an angle).
That's one reason why for fields and events its good to standardize the location of where the ref holds the chrono and gun. (as an aside anyone who's ever attended my boring class on chronographs at the extravaganza would remember this...I hope)
As far as I can tell in my limited test the Pulse assumes an approximate 14" barrel. Correct me if I'm wrong here, but it seems the Pulse basically points the radar at a predetermined location in front of the barrel. So from what I've seen the results are pretty similar using a 14" barrel and the Clock. The results may vary slightly from barrel to barrel I suppose based on the porting and how quickly the ball slows down just before and after leaving the barrel... (but also keep in mind how you're holding the Clock)
But when your barrel length changes, the Pulse doesn't seem to know so it reports a velocity which will be different than any other chrono where you put your barrel right over the chrono.
Hopefully this picture makes sense of it. So if you have a shorter barrel, the ball will have slowed down a bit before the Pulse reads it.
In essence it looks something like this (substitute the in the image for a pulse...since we don't have pulse 3d files
It's why on some barrels it might read higher than some chronos (based on where you put the gun in relation to the chrono) based on how you've got the barrel in relation to the chrono, and why on some other barrels it will read slower (potentially quite a bit on the 10" barrels maybe the 12" too).
Sorry for the long post, I probably typed too much. The short version looks like this:
- Hang your barrel in behind the Clock (or any other radar) and your will have a false reading that's slower than the actual muzzle velocity. (ie you'll be shooting faster than the chrono says you are)
-Hang your barrel in a couple inches front of the Clock and you'll have an accurate muzzle velocity reading (basically have the Clock a couple inches behind your barrel)
-Shoot a 14(or approximate? this length I don't know because it depends on where the pulse scans) barrel and the Pulse will have an accurate muzzle velocity reading.
Shoot a shorter barrel and the Pulse will have a false reading that's slower than the actual muzzle velocity (ie you'll be shooting faster than the pulse says you are)
Hope that makes sense... (let me know if I'm off on the pulse/barrel length thing, that's just what I encountered in the youtube video I did earlier)