What .40 P.F. do you recommend to be "safe" when chronographed

[Krag]

I just switched to using TiteGroup in my customized Springfield 4.5 XDM and am trying to work up a decent USPSA load. The best so far is a 180 gr. Remington FMJ bullet and 4.7 gr. of TiteGroup which gives an average P.F. of 180.4. Do you think this is too high for serious competition? How low would you suggest I go to be safe?

[mosher]

Average velocity minus 1 standard deviation needs to be above 165PF.

[motosapiens]

generally in the 170-175 area is enough cushion tht you don't have to stress about bad luck or a wacky chrono or getting a light bullet pulled. Anything above 175 I personally would reduce, but it really doesn't make as much of a difference as you might think. Once i discovered my splits were near identical between major and minor, I stopped worrying about and extra 3-4 pf here or there.

[Vesteroid]

I just switched to using TiteGroup in my customized Springfield 4.5 XDM and am trying to work up a decent USPSA load. The best so far is a 180 gr. Remington FMJ bullet and 4.7 gr. of TiteGroup which gives an average P.F. of 180.4. Do you think this is too high for serious competition? How low would you suggest I go to be safe?

just out of curiosity, what OAL are you loading that to?

[Hi-Power Jack]

I fire 20 rounds thru the chrono and want ALL 20 to make 165 PF (they

usually average around 173).

[Woodsk]

I try to load to ~171 stays safe and I can't really feel a difference between that and 165

[RecoilJunkie]

Mine are averaging around 170, loaded short, 4.2gr titegroup.

[enzo357]

170-172 is very safe

[zzt]

The PF you need to be safe really depends on how consistent your load is. If your SDs are high, you'll need more PF to make up for the inconsistency. If they are good, you can go lower.

For example: my Limited load chrono SDs for 10 and 20 shot strings average at SD 6.5. With SDs that good, I could shoot 167PF and the slowest bullet in the string would be 5fps faster than needed to make 165PF. However, I choose to load to 172PF. That means that the slowest bullet in the string is 36fps faster than needed. I don't really notice the difference in recoil, so I'd rather have the larger margin.

Even though the chronos are supposed to be calibrated using reference ammo, chrono technique plays a part as well. One guy at my club shaves it close. He usually gets away with it. At one match he chrono'd just under and had to shoot minor. It ruined his day. Why take the chance?

My rule of thumb is if you cannot get SDs consistently under 12, change your load. Personally, if it isn't in single digits, I'm not happy.

[Krag]

Kylelee: What pistol and length of barrel do you use?

Edited June 2, 2016 by Krag

[mach1soldier]

How consistent your bucket weight is matters quite a bit in my eyes. Plated and lead vary a few grains which can drastically affect your PF.

I always shoot for 170 average and all shots above 165 PF.

[fishsticks]

Very informative thread on this topic here:

Reloading to Meet Power Factor with Confidence!

https://r.tapatalk.com/shareLink?url=http://www.brianenos.com/forums/index.php?/topic/229005-Reloading-to-Meet-Power-Factor-with-Confidence%21&share_tid=229005&share_fid=16618&share_type=t

[Krag]

Veteroid - 1.135"

I just loaded up some with 4.3 and 4.5 grs. of TiteGroup and will chrono them tomorrow.

[jwhittin]

Here is the link. Forget about PF, what's your SD?

http://www.brianenos.com/forums/index.php?showtopic=229005

[jwhittin]

Average velocity minus 1 standard deviation needs to be above 165PF.

If you do this and use 165, your chance of failing chrono is about 44%.

[motosapiens]

Average velocity minus 1 standard deviation needs to be above 165PF.

If you do this and use 165, your chance of failing chrono is about 44%.

with the first 3 rounds. Now go calculate what the chances are for 7 rounds and report back to the group please.

[jwhittin]

Your average velocity is always determined using 3 rounds, never 7. If you fail the first attempt using 3 rounds, the 3 highest measurements are used out of 6 rounds. If you still fail to meet PF, you have a choice of using best 3 out of 7 rounds or recalc based on a new bullet weight. I much prefer to pass first time and not have to worry about it.

[PatJones]

I can't feel a change of 5 power factor. I don't flirt with the minimum required.

[teros135]

I've heard that, statistically speaking, your average chrono'd velocity should be at least two standard deviations above the PF floor. For instance, with .40 cal 180 gr, 916 is the floor for 165 PF. Your loads are chronoing with a SD of 10, so you need to be at least 936, which is a PF of 168.

For .40 major, I go for about 170-172 with SD 10 or less and all rounds reading 170 or above. (With a SD of 15, you'd want to load to 946 fps and 170 PF.)

Don't forget to WEIGH THE BULLETS. Don't just calculate from the bullet weight on the box. A bullet that's off by 1 gr translates into about 1 PF at a given velocity (at least for 180 gr at 946 fps, 147gr 9mm at 884 fps, and 124gr major at 1400 fps).

[jwhittin]

Yep, minimum 2SD. Use 2.5 or 3SD if more margin is needed.

[broadus123]

Don't forget the chronograph. Some are more accurate than others. I use competition electronics and have found it to be right on with major match chronys. I load to 172 pf to be safe. Outside temperature also affects some powder.

[motosapiens]

Your average velocity is always determined using 3 rounds, never 7. If you fail the first attempt using 3 rounds, the 3 highest measurements are used out of 6 rounds. If you still fail to meet PF, you have a choice of using best 3 out of 7 rounds or recalc based on a new bullet weight. I much prefer to pass first time and not have to worry about it.

exactly. sounds like you didn't do your homework, which was to calculate the probability of passing using your best 3 out of 7 rounds (for the sake of this exercise, we can assume that the shooter will choose to shoot rather than weigh the 7th round).

[Krag]

4.5 grs. of TiteGroup gives me an average P.F of 177.7 out of my XDm and 173.9 out of my Para 16.40. I' going with that.

[blaster113]

I'd shoot for a minimum of 172-175 pf for big matches. I've been to majors where my ammo chronoed 172pf at home then got169pf at the chrono stage

[teros135]

Yep. Mine chrono'd 175 at home & 171 at a recent L2.