Help with chronograph data

[Bevenue]

I picked up a chronograph last week. Now need help with reading the data.

I can see I make PF(135500) with my 9mm load, but is it high enough for changing weather conditions? What about the ES and SD? What are they telling me about my loads?

Weapon: Springfield XD9 4"

Speer Gold Dot 124 +P: HI 1189, LO 1122, AVG 1162, ES 67, SD 21. 10 shot string

Montana Gold 124JHP 4.1 Titegroup: HI 1106, LO 1075, AVG 1093, ES 31, SD 11. 10 shot string

Weapon: S&W M&P340

Speer Gold Dot 125 +P: HI 808, LO 784, AVG 799, ES 24, SD 9. 5 shot string

Montana Gold 158JHP 3.5 Bullseye: HI 633, LO 591, AVG 603, ES 42, SD 19. 5 shot string

Montana Gold 158JHP 4.0 Bullseye: HI 701, LO 631, AVG 652, ES 70, SD 26. 10 shot sting

If you need any other info, let me know.

Edited September 12, 2010 by Bevenue

[Sarge]

Drop the last three digits to get 135 pf. PF is never rounded so whatever the first three digits read is your pf.

I load to 135 pf to give myself enough cushion. So I think that is a good number to shoot for.

After PF the most important number to me is SD. The lower the better. Around 10 is real good but mid teens are still acceptable to most. If you go with a good powder and bullet combination and sort your brass by headstamp and times used you can get some really low SD's. My current load was around 4 last time I chronoed.

Also, when I am doing chrono work I like to make note of the lightest loads I am getting. This way I can figure PF on them as well to make sure even if three weak loads are shot over a chrono I still should make PF.

Of course none of this means a thing unless the loads are accurate. It takes a little extra work but I put a target up at 25 yards and shoot through the chrono onto the target to check accuracy at the same time.

Edited September 12, 2010 by Sarge

[gng4life]

I agree with Sarge, good info there. On the ES, that is your "extreme spread". It tells you the difference between your slowest shot to the fastest shot. For example, your Speer GD 125: Hi 808, Lo 784 - the difference between them is 24, which is your ES.

Also, good advice on the slowest times - try to make sure you make PF with three of the slowest times!

[RePete]

Drop the last three digits to get 135 pf. PF is never rounded so whatever the first three digits read is your pf.

I load to 135 pf to give myself enough cushion. So I think that is a good number to shoot for.

After PF the most important number to me is SD. The lower the better. Around 10 is real good but mid teens are still acceptable to most. If you go with a good powder and bullet combination and sort your brass by headstamp and times used you can get some really low SD's. My current load was around 4 last time I chronoed.

Also, when I am doing chrono work I like to make note of the lightest loads I am getting. This way I can figure PF on them as well to make sure even if three weak loads are shot over a chrono I still should make PF.

Of course none of this means a thing unless the loads are accurate. It takes a little extra work but I put a target up at 25 yards and shoot through the chrono onto the target to check accuracy at the same time.

Not true if he shoots IDPA. The PF is 6 digits.

[Bevenue]

Drop the last three digits to get 135 pf. PF is never rounded so whatever the first three digits read is your pf.

I load to 135 pf to give myself enough cushion. So I think that is a good number to shoot for.

After PF the most important number to me is SD. The lower the better. Around 10 is real good but mid teens are still acceptable to most. If you go with a good powder and bullet combination and sort your brass by headstamp and times used you can get some really low SD's. My current load was around 4 last time I chronoed.

Also, when I am doing chrono work I like to make note of the lightest loads I am getting. This way I can figure PF on them as well to make sure even if three weak loads are shot over a chrono I still should make PF.

Of course none of this means a thing unless the loads are accurate. It takes a little extra work but I put a target up at 25 yards and shoot through the chrono onto the target to check accuracy at the same time.

Well I was able to erase the data off the chronograph. On my 9mm load if I take the PF of the lowest shot in the string 1075fps, I still make 133PF. So that looks like I am OK there.

On both of my 38SPL loads, I see that the ES and SD are a little higher but still about what the factory 9mm Gold Dots are. Is it OK to compare on caliber to another caliber? Will the number of shots in a string have an effect on these numbers?

[DWFAN]

IMO, the revolver will probably throw a higher variance because each chamber in the cylinder is a little different.

Make sure to try and chrono in the coldest weather you will shoot a match in, and also the hottest.

[Sarge]

If you need any other info, let me know.

What game? My info was USPSA related. As Repete pointed out there is a difference in PF for IDPA. Sorry for any confusion.

[Bevenue]

If you need any other info, let me know.

What game? My info was USPSA related. As Repete pointed out there is a difference in PF for IDPA. Sorry for any confusion.

I've mainly shot IDPA but want to try out a few USPSA matches.

The class I would be shooting in would be 125PF for both. IDPA and USPSA figure power factor the same. Just USPSA has the answer divided by 1000.

Is a 10 shot string a good number of shots or should I shoot more per string?

Edited September 12, 2010 by Bevenue

[bbbean]

Is a 10 shot string a good number of shots or should I shoot more per string?

More data is better. I typically run a 20 round string two or three times to confirm a load, plus I have the 20 round strings I rejected for being just over or under the desired PF.

BB

[Sarge]

Is a 10 shot string a good number of shots or should I shoot more per string?

More data is better. I typically run a 20 round string two or three times to confirm a load, plus I have the 20 round strings I rejected for being just over or under the desired PF.

BB

+1 Run a few 20 round strings. Also as someone else may have suggested. If possible chrono your loads in each weather season to see how your powder of choice is affected by temperature. Load what you will need for your current temps and such then test them in colder weather to see what effect it may have on your readings.

[blind bat]

I agree with everything Sarge said as a general rule. However, there are exceptions to every rule. S1000 was really ticking me off because it was giving me SD's in the 15-25 range. Tightgroup almost always runs under 10 for me. However, when I started looking at accuracy, Solo 1000 was the winner and it's cleaner than Tightgroup so that's what I run. The Solo vs TG test was performed with my Glock 34.

[G-ManBart]

Yep, low SD's don't necessarily mean better accuracy. Solo 1000 is pretty fluffy and just doesn't meter terribly well. Still, it doesn't seem to hurt it from an accuracy standpoint. R,