9mm Velocities: Important?

[HOGRIDER]

Attempting to develop a load for the STI 4.15".  Starting with a mid-range powder weight, I'm seeing these results:

3.5g N320, 147 Zero JHP, WW Case, Fed SP Match Primer, COAL 1.125”
Temperature: 74F
Pressure: 30.1 in Hg
Bullet Weight: 147
Number of Shots: 10
Pressure: 30.1 in Hg
Bullet Weight: 147
Power Factor Average: 130
Power Factor Low: 128
Power Factor High: 131
Number of Shots: 10
Minimum: 873
Maximum: 897
Spread: 24
Average: 885
Standard Deviation: 6

 

I've been searching, with no luck, for a couple of older posts where IIRC seasoned veterans stated the 147s liked faster velocities.  But I'm just not sure...........

 

This above load felt fine, accuracy was ok.  For some reason, I think I should try 3.6g and 3.7g.  I always strive for accuracy first within 20-25yds.

 

What still has me confused is why this gun/barrel likes the faster velocities!  (See Attachment)  It's favorite load so far for accuracy has consistently been the Federal American Eagle AE9FP.  Chronos with these results:

 

AE9FP 147g. Published 1000fps Chrono @ 10’ Target @ 20 yds
Temperature: N/A
Pressure: N/A
Bullet Weight: 147
Power Factor Average: 149
Power Factor Low: 149
Power Factor High: 151
Number of Shots: 10
Minimum: 1014
Maximum: 1028
Spread: 14
Average: 1020
Standard Deviation: 5

 

Guess my biggest concern is can I develop a similarly accurate minor power factor load with my current components of N320 and Zero 147 FMJ?

 

Appreciate any and all feedback!

 

Thanks,

 

Ben
 

[nhyrum]

With n320, probably not. It's basically vv's titegroup (kinda, at least that's how I think of it) with 3n38, you could get those numbers up a bit, as it was made for 9mm with heavy bullets.

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[4n2t0]

There are too many variables. Why didn't you post a picture of the N320 group? What type of accuracy difference are we talking about? Is it a shotgun pattern? How much accuracy do you need? Bullseye? IPSC? A ransom rest is great for testing but you'll never be able to duplicate those results by hand, so why worry? The most significant accuracy gains you'll ever achieve will come from practice.

 

P.S. Generally, the faster you send them the more accurate they'll be.

 

P.P.S. Don't bother with .1gr increments, use .2gr or .3gr depending on the size of the charge window.

Edited August 19, 2020 by 4n2t0

[HOGRIDER]

There are too many variables. Why didn't you post a picture of the N320 group? What type of accuracy difference are we talking about? Is it a shotgun pattern? How much accuracy do you need? Bullseye? IPSC? A ransom rest is great for testing but you'll never be able to duplicate those results by hand, so why worry? The most significant accuracy gains you'll ever achieve will come from practice.

The primary purpose of this Chrono Session was to get a baseline of velocities since this was a new load workup.  Of course I would have noted if accuracy was acceptable for a simple bench rest setup.  And yes, I fully understand the operation of a Ransom Rest and WOULD NEVER think I could duplicate the results by hand!

 

P.S. Generally, the faster you send them the more accurate they'll be.

That's what I primarily hoped to establish with this thread.  Am also looking for feedback as to why this pistol loves to be ran in the 149+/- Power Factor Range!  

 

P.P.S. Don't bother with .1gr increments, use .2gr or .3gr depending on the size of the charge window.

 

The window for this powder/bullet combo is 3.1g - 3.9g according to Vihtavuori's most current data.  Hence my reason for starting out at 3.5g. 

 

My thinking is that pushing this combo just a bit faster may prove to be the sweet spot that will yield a minor load with (my) acceptable accuracy standards.

 

 

  

 

 

 

[mvmojo]

If it were me, I'd load up some 3.2gr and some 3.8gr and compare 'em to your 3.5gr's...

[4n2t0]

Well, it looks like you have everything covered.

 

Cheers!

Edited August 19, 2020 by 4n2t0

[Dwbsig]

This may not change a thing but I have seen accuracy improve with oal changes, I would load a few up at 1.150 oal and try it there is nothing lost by trying. I also agree with trying higher powder charges.

Edited August 19, 2020 by Dwbsig

[DryHeat]

Hogrider

Your list of variables has only 2 variables easy to work with. The assumption being you want to use that powder, case, bullet, primer. I make up 20 shot strings and vary the powder .1gr up and .1gr down, check the std.  dev and see if it moves and if it does move did it improve or get worse. If the powder charge causes the std. dev to get worse up or down then you were at the best spot with that powder. Repeat the process with COAL, depending on your bullet seater and how tight the range +- on length, then look for the change in std. dev, try to see if it's working for or against you. I have had a few loads that were very good with a higher std. dev, but mostly the other way. The better the std. dev the better the load. I hope this maybe helps you see an approach. Good luck.

[Joe4d]

Barrel twist could make a difference. Havent kept up with things but at one time quite a few 9mm's would keyhole 147's unless they were loaded up to 1000 fps.. Which kinda defeats the purpose of loading minor pf ammo. Did it in a couple of 9mm's I had. Ended up going to 135's. 
Another thought , Id bump up anyways. If you do some reading you'll see most folks running a little higher power factor in order to give themselves a bigger margin of error at the chrono station.

[stick]

Have you tried to reverse engineer the load?  Pull the bullet, measure the powder and develop a similar load.  The other snag might be determining what powder they use.

[4n2t0]

3 hours ago, stick said:

The other snag might be determining what powder they use.

 

lol.

[HOGRIDER]

Thanks for all the feedback/replies!

 

My game plan is to chrono/test a few rounds at 3.6, 3.7, and 3.8g using the N320.  Since 3.9 is the published max, I feel if I need to explore higher velocities/power factors, I'll have to try a different powder.  Or break down and try some 124g/125g FMJs.  Since I have several thousand 147g Zeros and Coated lead, I hope to find that sweet spot for both.

 

Of course, I also have COAL to play with.  Trying to standardize with 1.125" since the STI loved the American Eagles at that length; but could always go longer.  I'm sure the STI would tolerate 1.150" if necessary.

 

Again, thanks for everyone's replies!

 

 

[HOGRIDER]

On 8/20/2020 at 4:07 AM, stick said:

Have you tried to reverse engineer the load?  Pull the bullet, measure the powder and develop a similar load.  The other snag might be determining what powder they use.

stick:

I definitely thought about that..........however, I doubt that Federal or any of the other major ammo manufacturers are using over the counter powder such as what's available to us!  From what I've read, they primarily use powders that are custom blended on a commercial basis..........

 

Thanks!

[Rich406]

1 hour ago, HOGRIDER said:

stick:

I definitely thought about that..........however, I doubt that Federal or any of the other major ammo manufacturers are using over the counter powder such as what's available to us!  From what I've read, they primarily use powders that are custom blended on a commercial basis..........

 

Thanks!

I read somewhere that federal uses sport pistol powder in their syntech bullets. 

[CZ85Combat]

 Your pistol shoot good groups in a ransom rest at the higher PF,  but in your hand the recoil from that higher 149 PF load will result in larger groups and slower shot to shot times. The balancing act is to find a load that shoots the best group with your hand for the type of shooting you are going to be doing(Target vs bullseye vs USPSA).  If you are shooting any of the action pistol games you don't need 1.5" groups. You will score higher with the 2"-2.5" group(129pf load) that lets you shoot faster splits with good enough accuracy for the game you are playing. Generally in pistols you will get better groups with lighter bullets as they are loaded to higher velocities. 

[HOGRIDER]

7 hours ago, CZ85Combat said:

 Your pistol shoot good groups in a ransom rest at the higher PF,  but in your hand the recoil from that higher 149 PF load will result in larger groups and slower shot to shot times. The balancing act is to find a load that shoots the best group with your hand for the type of shooting you are going to be doing(Target vs bullseye vs USPSA).  If you are shooting any of the action pistol games you don't need 1.5" groups. You will score higher with the 2"-2.5" group(129pf load) that lets you shoot faster splits with good enough accuracy for the game you are playing. Generally in pistols you will get better groups with lighter bullets as they are loaded to higher velocities. 

Thanks for your feedback!