9mm Power Factor Question

[Mike in CT]

Hello,

I am a long time reloader but new to Power Factor stuff.

I am loading 9mm on my Hornady LNL and using 3.9 grains WSF on top of a 147 Montana Gold FMJ with Remington primers and a 1.169 OAL. When I chrono'd those rounds a 10 shot group gave me an average PF of 133. That was taken indoors in probably 55 degree conditions.

My question is that enough of a cushion to shoot a match outdoors with a chrono station and possible temp of 70 degrees.

The Hodgdon charts give a load of 4.0 and a velocity of 900 and mine averaged 905 fps so I am pretty close to the charts.

Follow up question, I think I chrono'd those with my 5" M&P Pro, will there be much drop off for my wife's 4.25" barrel (another M&P).

Chrono days are hard to come by so I just wanted to hear what everybody thinks and if I need to chrono the rounds through her gun to be sure to meet minimum PF or if I have enough cushion. I guess the other option would be to just bump up the load to 4.0 for more cushion.

Thanks in advance for the help,

Mike

[kevin c]

Does the load:

function flawlessly in your gun (specific to the powder charge, it cycles well)?

satisfy you as far as accuracy and "feel" go (hit the A zone all the time with a well aimed shot at 35 yards, with a recoil impulse acceptable to you)?

shoot consistently enough velocity wise so that you will make PF just about all the time (five PF points usually does it)?

If so, it's good to go in your gun.

As far as your wife's shorter gun, you will need to chrono it, bench it, and have her judge the feel of it herself. As far as velocity goes, it might be just a bit close

[Mike in CT]

Yeah, that is what I was worried about.

The load satisfies all the requirements but it looks like a chrono day for my wife's gun with the shorter barrel.

What I will probably do is load some 4.0gr rounds and check them from both guns.

Mike

[yoshidaex]

WSF is temp sensitive. The warmer it gets, the slower the velocities.

Not sure if a 15 deg delta will make a difference but keep that in mind.

In your case, I'd be concerned since it'll mean shooting minor or "Not for Score".

[Hi-Power Jack]

When I chrono'd those rounds a 10 shot group gave me an average PF of 133. That was taken indoors in probably 55 degree conditions.

enough of a cushion possible temp of 70 degrees.

I chrono'd those with my 5" M&P Pro, will there be much drop off for my wife's 4.25" barrel

Mike, three issues:

1. the shorter barrel has to be chrono'd (even two different guns with same barrels should be chrono'd separately)

2. you should chrono guns on very warm day - in the 80's (or plan of going higher than 130 pf

3. you need more than 10 shots to determine your pf;

shoot 20 rounds, and don't look at the average, look at the lowest velocities.

None of the rounds should be below 125 pf. If you have any rounds below 125 pf, bump it up again.

Alternatively, if you can't do that before a match with a chrono,

I'd definitely add 0.2 grains powder (4.1) to Make Sure.

Just what I'd do.

Good luck,

Jack

[hkguy]

i used a different powder but for info's sake, out of a USPc 9mm i was getting a 127-128 pf, with the same load i was getting a 131-133 PF out of my P30L. the shorter barrel will cause a decrease in PF.