Velocity Variations Between Different Chronos

[Sin-ster]

What type of deviation in FPS can you expect when comparing your personal chrony to one you'll find at a Major Match?

Have you ever been really surprised in this situation, and can't write it off to environmental conditions (i.e. temperature, elevation, etc.)?

[juan]

I use a old shooting chrony.

always seams to throw same numbers as the match chrony.

[Sarge]

I use a Pro Chrono Digital and it is generally only a PF point off at most.

[Sin-ster]

Good, that makes me feel better.

Anyone ever run into real problems with the match chrony?

[shred]

With the new USPSA Chrono rules that XRe and I wrote, it's a lot better, but still watch out for poorly or uncalibrated scales and poor ammo storage and handling.

I put a CED with screens interlaced between those of my Oehler 35 and got the same readings to within +/- 5 FPS on the same bullets.

Now if you use a Chrony or something in poor light conditions, then your readings will vary

[Joe4d]

I got pretty poor resu;ts with a shooting Chrony. But my Pro-chrono has always been right on, and I dont use any boxes, or worry about moonbeams or sun angles,

[Maksim]

just went through this with nationals.

Bought a new ProChrono Digital. Came with about 172 pf for my loads. Went to nationals, the CED M2 gave me 169.5

So while there is a difference... unless your loads are at PF.... I would not be tooo concerned.

Just dont do what I did at Area 8... went by the book and not have an exact recent chrono and the powder was slightly inverse sensitive. (WSF) went minor. 162.5

[RePete]

just went through this with nationals.

Bought a new ProChrono Digital. Came with about 172 pf for my loads. Went to nationals, the CED M2 gave me 169.5

So while there is a difference... unless your loads are at PF.... I would not be tooo concerned.

Just dont do what I did at Area 8... went by the book and not have an exact recent chrono and the powder was slightly inverse sensitive. (WSF) went minor. 162.5

Your difference maybe because the temperature/humidity/barometric pressure/altitude are different. And quit playing close to the PF line, it'll bite you in the a$$ - oh yeah, it did.

[juan]

difference also maybe bullet weight.

I always watch and see how much the pulled bullet weighed,

if Im close and they pulled a light bullet. I will have them pull another.

[Sin-ster]

Good advice from all.

My chrono is a CED, and I've been very careful with the lighting conditions and use of the screens. It's put out exactly what I've expected at every turn, if not a bit on the low side (which is a good safety net).

The bullets are MG 124 JHPs, so very consistent. I've weighed several and they're always within the SD of the scale at 124. I'll definitely keep my eye on what they're getting at the match!

The powder is the boring ol' N320, which is about as consistent as it gets from situation to situation. The match is also less than 200 miles from where I chrono, so I'm not too concerned with anything else.

The PF is 130 on the button, and I'll obsessively chrono a few dozen rounds (at random) from the "for tournament" lot across the week before the match, just to feel good about myself.

[gm iprod]

Buy a box of CCI std, Win T22, Eley anything, or RWS MAtch or better. Check you chrono against what the speed on teh box of the 22lr ammo you use says. Use a bolt gun at 10ft. This will give you a base line that you have sod all influence in.

Then you knwo if your chrono is fast and or slow.

Also as previously stated go a littel higher than you think.

I can assure you, the guy at the next match you go to will not have calibrated the chronograph. I have had the oportunity to test 4 different chronographs with the same rifle and batch of really expensive 22lr ammo by interleaving and mounting one chrono behind the other in a multiple test. We got some very good data on certain brands of chrono.

However, I also tested three new CED M2 the same way and found that they can vary by up to 10 or so fps. One especially was very much different. The next test they were near identical. Less than 2fps average across the test. I went home more confusd than when I started.

Thas when I decided to use 22lr std velocity ammo as my base point and keep records as I go.

BTW my test rifle is a shortened BSA MK2 that gives 1090fps at ten feet, when the CCI box says it is going 1070. But it is fast with everything else I ever shot out of it, and when I am not shooting it it will go 1" at 100M of sand bags. So I trust it.