Same POI, 9mm Minor and Major

[roklock]

OK, not sure if this is even possible but seeing if anyone has tried this yet.  Shooting more SC than USPSA recently and would like to develop a load for minor but not have to sight in the cmore when moving from major to minor.

gun is a STI trubor, lone start comp, lightened slide.  Current load is 115 JHP over 7.8 gr WAC set at 1.168

Was wondering if trying 95 grain bullet and changing the recoil spring to 7 lb could be dialed into same POI as the major load.

Thoughts?

Thanks,

Steve

Edited September 28, 2016 by roklock

[Hi-Power Jack]

Great idea - looking forward to responses.

My "minor" and Major loads hit different places, right now - would LOVE

loads to hit same place (approximately).   

[echotango]

I shoot 7.0gr wac 121gr mg and 5.4gr  wac 115gr mg out of the same gun.  At 15-17yrds, poi it within 1".  Oal is 1.167"

I change from a 8/9# spring to a 7#. 

Edited September 28, 2016 by echotango

[theWacoKid]

When my gun was new and breaking in I found my sub-minor and major loads landed almost 6" apart.  Once the gun had a good bit of rounds on it a re-test showed poi change of less than 1".  Just try it and see.

[Hi-Power Jack]

Waco, would you mind sharing your two loads that hit an inch apart?

[theWacoKid]

Major load was 124 gr JHP over enough HS-6 to make 170-174 pf loaded around 1.165" oal.  Win SPM primer.

Minor load was 115 gr CMJ over 5.6 gr 3N37 at 1.142" oal and 125 pf.  Win SPP.

Not remotely similar.

Edited September 28, 2016 by theWacoKid

[ano]

Mine has pretty much idental POI no matter factory minor, homemade minor, 9 major etc, 160-180PF

[theWacoKid]

20 minutes ago, ano said:

Mine has pretty much idental POI no matter factory minor, homemade minor, 9 major etc, 160-180PF

I have found that to definitely be the case as long as the gun is both free and locks up tight.  If it's too tight or locks up loosely than I think the difference in slide impulse changes the lockup position enough to affect poi.

[andrewtac]

I think it should be directly related to lockup and timing.  The difference in impact if you had a single shot would be negligible at close range, based on ballistics.  Likely more to do with combination of the setup (springs, timing, comp, lockup) than the load. Maybe try to alter those things, one at a time and look for a change.

[roklock]

So, I started playing with loads...STI Trubor, 7 pound recoil spring.

the constant in the loads are PD 95 gr FMJ, OAL 1.100, SPP, WAC powder, target at 18 yards, loads were as follows, 

6.3 - avg 1301, PF 124 - ejection weak, hitting right rand
6.8 - avg 1327, PF 126 - ejection weak, hitting right rand
7.1 - avg 1421, PF 135 - ejection falling just right of right foot
7.5 - avg 1520, PF 144 - stronger ejection
7.8 - avg 1640, PF 156 - strongest ejection, 

All POI was roughly 1" lower (shooting off hand) than my major load, 115 gr PD JHP, 7.6 gr WAC, 1.168 OAL.

Thoughts on the 7.8 load and corresponding pressure?  No extractor marks, primers look good, no flowing and no cratering.  Thinking about trying this load with 8 pound recoil spring next and see how that feels.  Also thinking I will load  7.5, 7.6, 7.7, 7.8 to shoot for best group.

 

 

 

 

[jnr88]

7.5 grains of Silhouette, 124 Montana Gold JHP at 1.165, 173pf

4.4 WST, 125 SNS coated at 1.165 . Steel load.

SAME POI

[theWacoKid]

14 hours ago, roklock said:

So, I started playing with loads...STI Trubor, 7 pound recoil spring....

Down around 125 pf with compensation and/or ports I like a 6 pound variable recoil spring.  Ejection is still a little weak, but not a problem if doesn't malfunction.  This makes such a soft shooting setup.