CHRONO NUMBERS

[glc]

Could someone shed some light on this for me. This is all new to me.

I chrono'ed my first reloads and the numbers are not very consistent. I might add these are the first rounds shot out of my G23 G4. The chronograph is a brand new CE ProChrono.

1st mag: 789,814,826,794,796,848,825 849,811,785,822,835,822.

For some reason only nine recorded on the second mag: 827,797,820,787,829,807,785,783,819.

I used Hodgdon's numbers. I'm assuming if they're number is avg.velocity,which is 872,I'm way off that,or do you take those numbers lightly.

778 avg.

66 Ex. spread

20.32 Std Dev. (MS Excel)

Resized Win nickel .40 S&W cases

Berry 180 gr plated flat point

4.4 gr Win 231

OAL 1.125 (all measure right on the money)

Win SPP

Very light crimp. Just enough to get rid of bell.

Very sunny day.

Thanks for any replies

Greg

[jnr88]

Hi Greg,

Assuming the bullets and cases were essentialy the same the only variable is the amount of powder your equipment throws. I have a Dillon 550 and 650 and do not find the powder throws very consistant on occasion. You might want to weigh some individual loads and chrono again. The other possibility is chrono error. The problems with sunlight and chronograpgraph accracy are well known. Here is a link to an article you may find useful. frfrogspad.com/chrono.htm. Good luck.

[45 Raven]

Are Hodgdon's numbers for a 180 grain plated bullet, or a jacketed bullet?

[wgj3]

There are so many variables it's not even funny. Different barrels from two identical guns may chrono a little differently. Add in other factors like slightly different barrels lengths, slightly different bullets, temp, etc., and you have some big swings. The figures in the books are only accurate that exact load in the exact firearm that was used to test it.

[wgj3]

Just looked back and you lose a bit of velocity in the shorter barrels for sure.

[Poppa Bear]

Coming out of a 23 your barrel is likely an inch or so shorter than their test barrel.

[glc]

Hi Greg,

Assuming the bullets and cases were essentialy the same the only variable is the amount of powder your equipment throws. I have a Dillon 550 and 650 and do not find the powder throws very consistant on occasion. You might want to weigh some individual loads and chrono again. The other possibility is chrono error. The problems with sunlight and chronograpgraph accracy are well known. Here is a link to an article you may find useful. frfrogspad.com/chrono.htm. Good luck.

I also have a 550B. Being they were my first reloads, I did infact check about every fifth charge,and it was always on the money. From what you stated about the sun,and from what I've been reading,that may have been the problem. Maybe I'll wait for a cloudy day and check again.

Thanks for the reply.

Greg

[glc]

Are Hodgdon's numbers for a 180 grain plated bullet, or a jacketed bullet?

Plated bullets.

Greg

[glc]

There are so many variables it's not even funny. Different barrels from two identical guns may chrono a little differently. Add in other factors like slightly different barrels lengths, slightly different bullets, temp, etc., and you have some big swings. The figures in the books are only accurate that exact load in the exact firearm that was used to test it.

Thanks! I didn't know that.

Greg

[glc]

Coming out of a 23 your barrel is likely an inch or so shorter than their test barrel.

Thanks guys. Learning as I go.

Greg

[jnr88]

Greg,

The gun, bullets , brass and powder ,if equal, should have produced very close results. It isn't important what length the barrel is or the bullet type. Your ammunition was produced identically. I think the chrono may be the culprit.

Jim

[xdnok]

Perhaps the sun is effecting your chrono, I have seen some off the wall numbers out of mine and added a large sunshade (cardboard) to the top and the numbers improved. For the most consistent results at a major match, they put the chrono in a box to avoid inconsistent results.

[Hi-Power Jack]

GLC, your average velocity, unless I made a mistake, is 812 fps for a 146 PF.

I'd use your low velocity (783 fps) for a 141 PF.

The range is a little high, but I've seen it before - not a real problem in

my estimate.

My guess is that everything is working as it should - the powder charge and

the chrono, both.

If you're trying to make Minor, you can adjust down a bit.

If you're trying to make Major, you have to bump it up quite a bit.

[Biloxi23]

I think the guys that mentioned the sunlight are correct. I have notice that on very bright days, my CED give squirrelly readings. We have several awnings over concrete pads at my home range and I found I get the most consistent readings when placing the chrono under the awning. The last major I shot (MS Classic 2013), I chronoed all three shots within 5 fps of what I had checked the loads at.

[glc]

Thanks guys.

I still have quite a few rounds from this batch.

I'm going to see if the readings are more consistent on a cloudy day.

jnr88 thanks for that link.

Greg

Edited September 28, 2013 by glc

[glc]

I was able to check my numbers again with an overcast day.

Happy to say,they were much more consistent. 806,811,814,814,834,823,847,817,822,836,831,834,844.

One other thing. Are factory loads usually pretty hot?

I wanted to see how different the factory stuff was. I put six rounds of American Eagle 165 gr. FMJ in a mag just to see.

Holy cow!! 1109,1111,1119,1105,1137,1112.

Greg

Edited November 2, 2013 by glc

[Biloxi23]

I re-read your original post and noted that you are shooting a Glock 23, with a 4" barrel. That may be where you are missing velocity. Most semi auto tables list .40 as being test fired from a 5" barrel. Also, I have a shooting buddy with the same CED as mine, and his is consistently like 50 fps slower than mine, even when set up end to end.

[glc]

I re-read your original post and noted that you are shooting a Glock 23, with a 4" barrel. That may be where you are missing velocity. Most semi auto tables list .40 as being test fired from a 5" barrel. Also, I have a shooting buddy with the same CED as mine, and his is consistently like 50 fps slower than mine, even when set up end to end.

Yes,after reading a lot of the posts,I see why published fps,and actual fps will most likely always be different. I'm not expecting to get anything near the Hodgdon average,but I'm happy that my most recent numbers are far more consistent than the first ones. From now on I'll always chrono on sunless days.

Greg