JAFO Posted May 21, 2011 Share Posted May 21, 2011 I am switching from 124gr Zero FMJs to 124gr Montana Gold JHPs, and I have read that MGs typically take a few tenths more powder to drive them to the same velocity as other brands. So I made up 20 rounds using my current charge weight and OAL, and 20 rounds with the same OAL but 0.2gr hotter. I've included the 20 round data string from my previous Zero load for comparison. All data was recorded using the same ProChrono Digital. Common Data Gun: Sig 9mm P226, factory barrel Primer: Federal #100 Sm Pistol Brass: Mixed range brass (tumbled) OAL: 1.14" String Length: 20 rounds Previous Load Bullet: 124gr Zero FMJ (actual weight ~124.7gr) Powder: 4.3gr Titegroup Temp: 58 F, Clear HI: 1095 / LO: 1063 / AV: 1080 / ES: 32 / Sd: 8.0 / PF: 134 (using actual bullet weight) Test Load 1 Bullet: 124gr Montana Gold JHP (actual weight ~124.1gr) Powder: 4.3gr Titegroup Temp: 84 F, Cloudy HI: 1120 / LO: 1049 / AV: 1082 / ES: 71 / Sd: 14.9 / PF: 134 (using 124gr bullet weight) Test Load 2 Bullet: 124gr Montana Gold JHP (actual weight ~124.1gr) Powder: 4.5gr Titegroup Temp: 84 F, Cloudy HI: 1124 / LO: 1095 / AV: 1109 / ES: 29 / Sd: 8.1 / PF: 137 (using 124gr bullet weight) I suppose the temperature difference could account for the fact that the MG's had almost the exact same average velocity as the Zero's at the same charge weight. But bumping up 0.2 grains really brought the ES and Sd down while only adding 3 PF. The MG's do index on the seating die differently. I tried seating one at the same setting I used for 1.14" on the Zero's and it pushed the MG down to 1.10"! It's definitely good advice to check measurements carefully when switching components. I'll be using the 4.5gr load at a match tomorrow. Hopefully it'll work well. I'll have to do some accuracy testing to see how they look. I got the best accuracy with the Zero's at this OAL. Is that somethng that tracks more with the bullet or the gun? I did note that the max OAL (bullet touching the lands) with the Zero's was 1.17", while the MG's are out at 1.82". Link to comment Share on other sites More sharing options...
al503 Posted May 21, 2011 Share Posted May 21, 2011 What is the length of each bullet (not the entire loaded round)? If one is longer than the other and they're are loaded to the same oal, that may affect velocity as the internal case volume will be different. Link to comment Share on other sites More sharing options...
JAFO Posted May 21, 2011 Author Share Posted May 21, 2011 What is the length of each bullet (not the entire loaded round)? If one is longer than the other and they're are loaded to the same oal, that may affect velocity as the internal case volume will be different. The Zero's are about 0.01” longer. Link to comment Share on other sites More sharing options...
CocoBolo Posted May 21, 2011 Share Posted May 21, 2011 Interesting results, but when you allow for +-.1 gr from the scale and 5% error on the crono, it would account for why your results don't show that TiteGroup is reverse temp sensative. The 58 degree round should be the faster of the 3. Maybe there is some magic number on the temp when TiteGroup finds its muscle, I went to a cold major match and the Crono tilted at 189pf, from a 170 pf load at 100 degrees (40 Major). Well I didn't minor but it definately slowed me down. If you measure a zero and a MTG you will notice it is .0005 smaller in diameter and I think that is more of what causes the slow down than the jacket material. I do shoot MTG and its a good bullet just takes a pinch more powder in an open gun, never tested that in minor pf. Link to comment Share on other sites More sharing options...
Solvability Posted May 22, 2011 Share Posted May 22, 2011 I run the MG 124s in my Glock 34 with TG and can get PF with 4.1 g - I used to run a 226 and it was always slower on the Chrony than other guns of the same barrel length - always accurate though. Some folks go to a Barsto barrel in the Sig to pick up some velocity. Link to comment Share on other sites More sharing options...
G-ManBart Posted May 22, 2011 Share Posted May 22, 2011 Mixed brass is enough of a variable to totally mess with your averages. Throw in the temperature difference, and it really gets hard to say what's going on. R, Link to comment Share on other sites More sharing options...
Aircooled6racer Posted May 22, 2011 Share Posted May 22, 2011 Hello: I have not found that Tite Group is reverse sensitive The colder it gets the slower the bullet goes. It is very linear as the temps go up. The Zero's are faster bullets than the Montana Golds because of the material used. G-Man is correct again about the mixed brass The most consistant brass I have found is military brass with the same headstamp and then Starline for 9mm. One last thing is how dry your powder is. If you leave a bunch in the hopper in a damp climate that changes things also. Thanks, Eric Link to comment Share on other sites More sharing options...
RobfromME Posted June 8, 2011 Share Posted June 8, 2011 Good afternoon, JAFO, The ES and SD reported by chronographs is usually based on a 10 round string, depending on the chrono. That's really too small a statistical sample to get a reliable SD. That's certainly the norm, though, but from an engineering standpoint you need a lot larger sample. I've had two strings of the same exact load fired one after the other with noticeable differences in SD even though each charge was weighed, same case, etc. I was bored one day and wanted to see what would happen so that's why I did that exercise. And as before, my two strings are hardly a good sized sample! Didn't mean to get off track...just thought I'd toss it out there for conversation. Warmest regards, Rob Link to comment Share on other sites More sharing options...
gng4life Posted June 8, 2011 Share Posted June 8, 2011 (edited) Good afternoon, JAFO, The ES and SD reported by chronographs is usually based on a 10 round string, depending on the chrono. That's really too small a statistical sample to get a reliable SD. That's certainly the norm, though, but from an engineering standpoint you need a lot larger sample. I've had two strings of the same exact load fired one after the other with noticeable differences in SD even though each charge was weighed, same case, etc. I was bored one day and wanted to see what would happen so that's why I did that exercise. And as before, my two strings are hardly a good sized sample! Didn't mean to get off track...just thought I'd toss it out there for conversation. Warmest regards, Rob Yes, the CED Millennium needs at least five shots before it will calculate the SD. I would go with 20 - 30 round test groups and multiples of them. When I'm going to a big match, I take about 20 3-round test groups. Why you ask? Well, when you go to a big match, what do they do? They shoot three rounds, average, and get your PF. I want to make sure that I'm making the PF with only three rounds every time. Remember in statistics, the sample size should be proportionate to the population size (depending on level of accuracy/confidence) using the standard formulas or tables. If the population size was 20 and the sample is 10, I'm sure most would agree that it would be sufficient. It's all relative. I also don't mean to get off track but we have to keep tabs of the big picture. Edited June 8, 2011 by gng4life Link to comment Share on other sites More sharing options...
JAFO Posted June 10, 2011 Author Share Posted June 10, 2011 All the above test strings were 20 rounds each. Link to comment Share on other sites More sharing options...
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