Making Major Power Factor

[acpie360]

I did chrono on my 45acp reloads yesterday and I noticed when the gun is clean, the first 5 - 10 shot averages may not make the 165PF.

Load data: Missouri Bullet 230gr LRN, Hodgdon HP-38 4.6gr, COL 1.25"

1st 5-shot string: Lo = 692, Hi = 713, Av = 705

2nd 5-shot string: Lo = 698, Hi = 724, Av = 710

3rd 5-shot string: Lo = 725, Hi = 761, Av = 746

All subsequent tests stabilized at Av = 746 and all Lo's were above 718-fps. So, shall I up my powder to make sure the first 10ish shots are over 718-fps (165PF)?

I have never been to any big match so I don't know how the chrono test is conducted. Would a chrono stage happen to be the first stage on a big match? Do they look the average or the lowest muzzle velocity?

Thanks.

[Hi-Power Jack]

shall I up my powder to make sure the first 10ish shots are over 718-fps (165PF)?

They look at an average of three randomly selected cartridges.

I make sure The Lowest velocity I get over my Chrono is AT LEAST 165 PF,

which means , of course, that the average PF is more like 170 - 175.

You don't want to go minor at a major (Pun intended).

[ZackJones]

I have never been to any big match so I don't know how the chrono test is conducted. Would a chrono stage happen to be the first stage on a big match? Do they look the average or the lowest muzzle velocity?

That's an odd sequence of events. The next time I chronograph some rounds I'll make sure to start with a clean pistol. To answer your question about starting a big match at the chrono station the answer is yes depending on what squad you're on. All squads have to go through the chronograph stage at some point in the match so some squad has to start there.

[TonyK]

I always start with a clean pistol and have never noticed the first batch being slower and gaining velocity as the day progressed. I would be tempted to run another test batch with your clean gun to confirm that this is a valid result for your gun and loads.

And 5 rounds seems like an awfully small number of rounds for a test. I generally don't chrono less than about 10 rounds to get an average.

[acpie360]

I think the reason the first 10ish shots are slower than the rest is due to the lead bullets I am using. Once the barrel is lubed (by the wax lube from lead bullets), the muzzle velocity stabilizes.

[67camaro]

It wasn't really implied in the original post but yes if you are competing in matches and need to make major PF I would up it a bit to make sure you are above 165 with all your rounds.