2MoreChains Posted April 9, 2014 Share Posted April 9, 2014 I need to load up some sub-minor PF ammo for popper calibration. Of the 9mm bullets I have on hand my choices are 115 gr FMJ, 124 gr FMJs or 147 gr molys. Say I work up a load where all 3 are 120 PF (1043 fps for the 115s, 967 fps for the 124s and 816 fps for the 147s), would there be any difference between the three loads as far as use as calibration ammo (i.e. will the load with the 147s be more prone to knock the popper over than the 124s or 115s)? Thx Link to comment Share on other sites More sharing options...
Sarge Posted April 9, 2014 Share Posted April 9, 2014 You will probably get a bit of conflicting opinions on this ones. I personally would use the cheapest bullets. 120 is 120 is 120. Link to comment Share on other sites More sharing options...
leas327 Posted April 9, 2014 Share Posted April 9, 2014 (edited) +1 to Sarge. If I am ever the official calibration man you are going to get me with a 586 smith and Wesson with a 138gr. lead bullet I got from an estate sale. PF is PF to me. Its that or 120 PF ammo out of a bright polished 41 mag 657 Smith. I feel like calibration testing should be official, but have a little bit of flair. Edited April 9, 2014 by leas327 Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted April 9, 2014 Share Posted April 9, 2014 I'm no expert, but thought I heard it was based on a box of Walmart's 115 grain ammo?? Link to comment Share on other sites More sharing options...
ChrisW Posted April 9, 2014 Share Posted April 9, 2014 Walmart ammo is way hotter than 125PF. All calibration ammo is hand loaded and chrono tested to 120PF. This is from talking to RM's who do thousands of rounds a year. Link to comment Share on other sites More sharing options...
2MoreChains Posted April 9, 2014 Author Share Posted April 9, 2014 Thanks guys, appreciate the responses. I have load data for all three bullet weights, so will probably come down to what I have the most of, which is the 147 molys. Appendic C in the USPSA rulebook says the calibration ammo from the designated handgun should achieve a PF between 115.0 and 125.0 (I picked 120 as the mid-range), and I'll chrono ahead of time using my BHP to double check. Hey, the upside is mine will be the first shots fired that morning while everyone else is still checking in! Link to comment Share on other sites More sharing options...
Sarge Posted April 9, 2014 Share Posted April 9, 2014 Walmart ammo is way hotter than 125PF. All calibration ammo is hand loaded and chrono tested to 120PF. This is from talking to RM's who do thousands of rounds a year.it's covered in the rules too. 115-125 Link to comment Share on other sites More sharing options...
Caspian_45 Posted April 9, 2014 Share Posted April 9, 2014 Amidon uses 147 JHP ammo for calibration. I personally believe that calibration ammo should be loaded with a lighter bullet like 115 gr. That ammo would carry the less muzzle energy down range. THe 147 loads will knock over poppers that 115's at the same PF won't. YMMV Link to comment Share on other sites More sharing options...
AJE Posted April 9, 2014 Share Posted April 9, 2014 You will probably get a bit of conflicting opinions on this ones. I personally would use the cheapest bullets. 120 is 120 is 120. Power factor wise it is but not in kinetic energy. Link to comment Share on other sites More sharing options...
theycallmeingot Posted April 9, 2014 Share Posted April 9, 2014 Amidon uses 147 JHP ammo for calibration. I personally believe that calibration ammo should be loaded with a lighter bullet like 115 gr. That ammo would carry the less muzzle energy down range. THe 147 loads will knock over poppers that 115's at the same PF won't. YMMV This makes sense to me. Link to comment Share on other sites More sharing options...
Steve RA Posted April 9, 2014 Share Posted April 9, 2014 Seems to me, back in the day, that the rules called for factory 115 grain. Probably been changed 10 or 12 times since then. Link to comment Share on other sites More sharing options...
Sarge Posted April 9, 2014 Share Posted April 9, 2014 You will probably get a bit of conflicting opinions on this ones. I personally would use the cheapest bullets. 120 is 120 is 120. Power factor wise it is but not in kinetic energy. There are probably 50 discussions of this just on these forums alone. People a lot smarter than me have not been able to solve this question. Heavy slow bullets vs light fast bullets. Like I said I would shoot whats cheapest to load. Link to comment Share on other sites More sharing options...
AJE Posted April 10, 2014 Share Posted April 10, 2014 (edited) I'm not arguing against your advice, just saying that from a physics standpoint that 120 is not equal to another 120. Practically I don't disagree. I didn't do that well in physics though. Edited April 10, 2014 by AJE Link to comment Share on other sites More sharing options...
Sarge Posted April 10, 2014 Share Posted April 10, 2014 I'm not arguing against your advice, just saying that from a physics standpoint that 120 is not equal to another 120. Practically I don't disagree. I didn't do that well in physics though. Some of these discussions got pretty deep. You know, dwell time, Hollow points impart more energy, Flat points vs round nose, graphs, charts, ambient temperature, barometric pressure, humidity,... . I just try to shoot the center of the target. They generally seem to fall most of the time. Link to comment Share on other sites More sharing options...
A63111 Posted April 10, 2014 Share Posted April 10, 2014 RO Class a few years ago said it was based on Winchester white box. Just to add to the mix. Link to comment Share on other sites More sharing options...
2MoreChains Posted April 10, 2014 Author Share Posted April 10, 2014 Can't say that I've ever chrono'd any WWB. What's it run? 115-125 PF? Link to comment Share on other sites More sharing options...
Neomet Posted April 10, 2014 Share Posted April 10, 2014 To quote some guy named Newton when was rambling on about the Second Law of Motion or some such nonsense "F=ma". Unfortunately he never went so far as to explain how much more a was needed to overcome less m during popper calibration. Thus we are left with the simple answer as noted above: Hit the center of the plate. Link to comment Share on other sites More sharing options...
Chris iliff Posted April 10, 2014 Share Posted April 10, 2014 Me, I'd give the shooter every benefit and use ammo at 115pf. We shouldn't even be using bullets for popper calibration anyway. This is about the dumbest idea. Probably left over from the days when we determined PF with steel. Geez, time to move on!! Link to comment Share on other sites More sharing options...
ChrisW Posted April 10, 2014 Share Posted April 10, 2014 It is also best to shoot the steel stages early in the morning, right after they have been calibrated. That way they do not get messed up after falling 250 times from other shooters. Link to comment Share on other sites More sharing options...
mgardner Posted April 10, 2014 Share Posted April 10, 2014 Lighter faster bullets won't knock steel over as well as slower heavier bullets at the same PF. Ask any old IMHSA shooter. Then there's the angle they address the target at, so a taller person would put different energy into the target than a shorter one. I'll get my machinist's handbook out today and play with the numbers. Until I get a headache that is. Link to comment Share on other sites More sharing options...
2MoreChains Posted April 10, 2014 Author Share Posted April 10, 2014 Lighter faster bullets won't knock steel over as well as slower heavier bullets at the same PF. Ask any old IMHSA shooter. Then there's the angle they address the target at, so a taller person would put different energy into the target than a shorter one. I'll get my machinist's handbook out today and play with the numbers. Until I get a headache that is. Good thing I am not overly tall or underly short... Its been a lot of years since Physics 101, which is why I posted the OP wondering what people's opinion was on light/fast vs heavy/slow for calibration ammo. But yeah, either way I'll be aiming for the center of the popper! Link to comment Share on other sites More sharing options...
D.Hayden Posted April 10, 2014 Share Posted April 10, 2014 Can't say that I've ever chrono'd any WWB. What's it run? 115-125 PF? I did chrono some WWW 115 a number of years ago.. out of a 92FS, it was PF 129.2 10 shots Std Dev 21 Avg FPS 1123 Max FPS 1149 Min FPS 1084 Link to comment Share on other sites More sharing options...
gm iprod Posted April 10, 2014 Share Posted April 10, 2014 Aim at the centre of the popper all you like. Does not mean they will land there. Link to comment Share on other sites More sharing options...
GTOGuy06 Posted April 10, 2014 Share Posted April 10, 2014 (edited) Something to consider on the subject:Power factor is essentially momentum... pf=mvKinetic energy=mv^2Therefor, a 115 grain bullet making 120 pf carries more kinetic energy than a 147 grain making the same power factor. So the question becomes, does a transfer in kinetic energy cause the popper to fall or does a transfer in momentum cause the popper to fall. Personally, I think the heavier the bullet, the safer you are making it to fall when it should. Edited April 10, 2014 by GTOGuy06 Link to comment Share on other sites More sharing options...
2MoreChains Posted April 10, 2014 Author Share Posted April 10, 2014 Aim at the centre of the popper all you like. Does not mean they will land there. Truth hurts...ouch! Link to comment Share on other sites More sharing options...
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