Do I have a chrono problem?

[Amici]

I chrono'd a series of loads yesterday, using my Crony chronograph. The charges ranged from 5.5 through 5.9 grains of WST under a 200 grain LRNFP bullet. Note that the high end of the range is supposedly beyond the max load shown on some charts.

Notwithstanding the supposedly high charges, my highest velocity was a mere 830 FPS; most were in the low to mid 700's. While I did get a few 'error' codes on certain shots, I did not get a general error message from the chrony.

I had the chrony in the shade with the sunscreens in place.


SO - is there a problem with:

1. The chrony itself,

2. How I set it up,

3. The battery, or

4. Were the loads actually THAT slow?

 

[Amici]

I chrono'd a series of loads yesterday, using my Crony chronograph. The charges ranged from 5.5 through 5.9 grains of WST under a 200 grain LRNFP bullet. Note that the high end of the range is supposedly beyond the max load shown on some charts.

Notwithstanding the supposedly high charges, my highest velocity was a mere 830 FPS; most were in the low to mid 700's. While I did get a few 'error' codes on certain shots, I did not get a general error message from the chrony.

I had the chrony in the shade with the sunscreens in place.


SO - is there a problem with:

1. The chrony itself,

2. How I set it up,

3. The battery, or

4. Were the loads actually THAT slow?

 

[Cary]

What gun and caliber is it? The length of the barrel would be good as well.
Cary

 

[moosedog]

Sounds like your shooting a 44 or 45 pistol round. I'm thinking 45 acp.
Those loads actually sound like they would be in the ball park for a 5 to 6 gr charge of that powder.

 

[H Richard]

If that's a .45 ACP your loading, better make sure you have a shock buff in place. I load 5.3 gr WST behind 200 gr SWC cast, with Fed primers, and get 939 fps over my chrony.

 

[pinkymingeo]

Looking at Hodgdon's website, what you're getting doesn't seem unreasonable. Their numbers, which aren't very high with WST in any case, are always subtanitally inflated. If you want velocity with 200gr bullets in 45acp, try AA7. I have no trouble getting 1100fps in a 5" barrel.

 

[Amici]

I load 5.3 gr WST behind 200 gr SWC cast, with Fed primers, and get 939 fps over my chrony.

Hence my query.


I want 850 FPS to make major. At least one of my tested loads should make that, yet none did.

 

[jjones33]

Send a high velocity rifle round or two over your chronograph and make sure it is where is supposed to be. You should also make sure the chrono is opened completely and not stopped by the tripod or tripod mount. Double checking that it is level to your shooting plane is very important also. If it is tilted from front to back it will give you a misleading reading.

 

[Skip Sackett]

This whole question is just a continuation of another topic just not pertinent to this caliber. In our discussion of "THE LOAD" it was reasoned that we were over-pressuring our firearms because we exceeded the maximum load according to Hodgdon's data.

Their website lists as maximum 5.1gr of WST under a LSWC with a pressure of 19,900psi and a velocity of 910fps. Here is my question to you. Did you develop that pressure if you didn't attain that velocity?

I submit for discussion that you did not. You will not attain that pressure until you achieve that velocity, but with my opinion and $5 you can get a real nice cup of coffee from Starbucks!

I happen to like WST powder for plinker loads. Usually around 4.5gr under the same bullet. I have shot all the way down to 3.5gr of WST with a 200gr LSWC for an AVG. velocity of 660fps. When I take that up to 4.5gr the AVG velocity goes up to 807fps.

What I shoot in competition is 5.2gr AA#2 and that gives me 810fps. It can be increased to a maximum charge of 5.8gr.

If it were me, I would take a know velocity round and run it over my chronograph to see what it says. Usually you can get some "calibrated" 22LR ammo. Many of the forum members do that here.


FWIW

 

[pinkymingeo]

Hodgdon uses a 10" pressure barrel for most of their handgun data. My guess is that 19.9K with 10" (and no leakage) to work with will accelerate that 200gr bullet to a higher velocity than 19.9K with 4-5" to work with. It's the primary reason their performance data are so unrealistic. Since Hodgdon claims a max of 910fps with WST, I'd expect low 800's on a good day.

 

[Skip Sackett]

Good point.

 

[Wheelgunner840]

If it were me, I would take a know velocity round and run it over my chronograph to see what it says. Usually you can get some "calibrated" 22LR ammo. Many of the forum members do that here.

+1

That's a good way to calibrate your Chrony.

WG840

 

[Steve C]

SO - is there a problem with:

1. The chrony itself,

2. How I set it up,

3. The battery, or

4. Were the loads actually THAT slow?

Most likely the chrono is correct and "4" is right.

Higher pressure doesn't necessarily yield higher velocity. You see that with pressure figures where slower powder produces much higher velocity at lower pressures than fast powder. Eventually with a fast powder which WST is relatively fast being between Bullseye and W231 in burn rate, you will get extremely marginal increases and perhaps even decreases in velocity for each 1/10 gr increase in charge but much higher pressure.

Most manuals list the maximum charge at which pressures remain consistent, after which subsequent increases in charge result in erratic pressures or high pressure spikes generally delivering declining accuracy.

The other major factors in measured velocities are:

1. The barrel length and the particular pistol. Some pistols just shoot slower, and shorter barrels normally produce lower velocities.

2. Ammo shot at higher ambient temperatures and higher elevations will travel faster than lower temperatures and lower elevations.

3. Component mix. I've had 49 fps difference in average velocity (733 vrs 782 fps) with 2 38spl loads using the same bullet but with different powder charge, cases and primers fired from the same 2" Colt DS on the same day. The slower load had 2/10ths MORE Unique in Winchester cases and CCI500 primer while the faster load came from PMC cases and Winchester primes using less powder. The particular component mix made almost a +7% difference in velocity with LESS powder. Your particular component mix may not be optimal for velocity.

 

[Trigger-Time]

If the chrono is correct.

The barrel bore ID maybe a little over sized or bullets a little underd sized.

Are you shooting a pistol or revolver?

Have you ever sluged the barrel to know it's dia?
Do you know what dia. the bullets are?

Gary

 

[AzShooter]

Check your distance to the chronography. It should be about 10 to 12 feet. Too close and you will have the muzzle blast fowl up your data reading.

Shoot your loads 4 to six inches over the sky screen. Too close causes reading fluxuations and too high will give error signals.

Test at the highest temperature you expect to use the ammo. This doesn't help at this time of year but when you have data you like make sure you chrono it again in the summer.

 

[Wyatt Earp]

Originally posted by Amici:
I had the chrony in the shade with the sunscreens in place.

The instructions that came with my Shooting Chrony say that is a mistake. The sunscreens are supposed to be used only when the chronograph is exposed to direct sunlight. In the shade or under an overcast, the shades are not to be used.

I don't know if that has the effect you are seeing, but it surely can't be helping if the light contrast is insufficient when the bullet passes over the sensors.