Gun Geek Posted January 2, 2005 Share Posted January 2, 2005 Then divide by 1,000.Bullet weight x muzzle velocity/1000=Power Factor Well, here's where a little controversy sets in. Currently in IPSC (and USPSA, I think) you do divide by 1000. In IDPA you don't. There's a thread here about the issues with that divide by 1000 (this stuff about significant digits). A scale that reads to 1/10 of a grain is good to 1 grain (you don't know if the last digit, 1/10 of a grain is correct). A chrono is good to only 10's of fps (chrono reads to 1's). Problem comes when you round - how do you report the number 164500/1000. Is it 164 or 165? Did the competitor make PF or not? I think Vince said he planned to propose a rule change to drop the divide by 1000. ========================== UPDATE: I went a found the thread about digits. The last post from Vince is that they will not drop the divide by 1000. He said they were doing something else (but I don't know what it is) http://www.brianenos.com/forums/index.php?showtopic=14304 Link to comment Share on other sites More sharing options...
Merlin Orr Posted January 2, 2005 Share Posted January 2, 2005 Then divide by 1,000.Bullet weight x muzzle velocity/1000=Power Factor Well, here's where a little controversy sets in. Currently in IPSC (and USPSA, I think) you do divide by 1000. In IDPA you don't. There's a thread here about the issues with that divide by 1000 (this stuff about significant digits). A scale that reads to 1/10 of a grain is good to 1 grain (you don't know if the last digit, 1/10 of a grain is correct). A chrono is good to only 10's of fps (chrono reads to 1's). Problem comes when you round - how do you report the number 164500/1000. Is it 164 or 165? Did the competitor make PF or not? I think Vince said he planned to propose a rule change to drop the divide by 1000. Seems pretty simple to me... 165 yes 164.9999999999 no Link to comment Share on other sites More sharing options...
Gun Geek Posted January 2, 2005 Author Share Posted January 2, 2005 Merlin's response is exactly the issue - do you round or do you truncate? About half will say round, half will say truncate. From his example above Merlin says truncate, but there are lots of good reasons why you don't truncate. Any basic physics or chemistry class would tell you that, with the measurment devices we are using, you can't get a result like 164.9999999. We can't measure that precisely, so you can't report that precisely, then you are supposed to round, now we have the argument. The tread link above goes over that pretty well. Link to comment Share on other sites More sharing options...
Merlin Orr Posted January 2, 2005 Share Posted January 2, 2005 No round ups Are you barely pregnant or nearly pregnant? Did the bullet nearly kill you are barely kill you? You can take the argument about the measurements from devices we are using and do anything you want with it. This way or the other... My reading is 124.49999 - but your instrument is not precisely calibrated and I think you should give it to me. I load to a + 5 added factor so - knock on wood - I don't worry bout it. You wanna game it - be ready to pay the price occasionally. And when you do pay - smile.... Take my opinion with a grain of salt because I don't care one way or the other - just trying to explain why I feel as I do. Link to comment Share on other sites More sharing options...
Nik Habicht Posted January 2, 2005 Share Posted January 2, 2005 According to the logic above, there should be a really simple solution: Use a scale that reads to a tenth of a grain --- and you can get an accurate grain number, right? Next use a chronograph that measure velocity to a tenth of a foot, and you're accurate to feet, right? Multiply grains x feet and divide by 1000. The resulting number needs to be equal to or greater than 125 or 165 for minor/major respectively..... Oh, yeah the chrono: My Pact Mk. IV will display velocity to a tenth of a foot..... Link to comment Share on other sites More sharing options...
shred Posted January 2, 2005 Share Posted January 2, 2005 According to the logic above, there should be a really simple solution: Use a scale that reads to a tenth of a grain --- and you can get an accurate grain number, right? Next use a chronograph that measure velocity to a tenth of a footOh, yeah the chrono: My Pact Mk. IV will display velocity to a tenth of a foot..... On loads over 1000 fps? You'll still have significant digit problems, but it's less of a problem. Of course anything that reads 124.9 over the chrono came out of the gun at at least 126 PF. Food for thought, but I'm not getting into this again. Suffice it to say the current method is analogous to using a meat cleaver to split a hair-- using a sponge as an anvil. Link to comment Share on other sites More sharing options...
zhunter Posted January 2, 2005 Share Posted January 2, 2005 I'm with Merlin, because he was so helpful today when I went to watch my first match! Shoulda stayed home tho, it seems I am going to HAVE to buy a $1800 limited gun now! Link to comment Share on other sites More sharing options...
Merlin Orr Posted January 2, 2005 Share Posted January 2, 2005 I'm with Merlin, because he was so helpful today when I went to watch my first match! Shoulda stayed home tho, it seems I am going to HAVE to buy a $1800 limited gun now! As Jay - "zhunter" is a pro golfer (PGA) I should have used the analogy - No gimmies... If it is 1/2 inch from the hole it still don't count. Link to comment Share on other sites More sharing options...
EricW Posted January 2, 2005 Share Posted January 2, 2005 Gee. I have an idea. Why not get off the dime, put that extra 0.2 gr of powder in the case and deal with massive, uncontrollable recoil that results? I'm just going head off another Power Factor Floor Limbo Contest before it ever starts. It's a minimum standard, not the goal. Link to comment Share on other sites More sharing options...
spook Posted January 3, 2005 Share Posted January 3, 2005 Gee. I have an idea. Why not get off the dime, put that extra 0.2 gr of powder in the case and deal with massive, uncontrollable recoil that results? That would be the easiest way. I shot lots of matches with 180 PF where 170 was required. There is no difference on the clock between 170.1 and 180.0. Link to comment Share on other sites More sharing options...
Larry White Posted January 3, 2005 Share Posted January 3, 2005 This is a real simple deal, 164.whatever is minor. 1 point or 9, its minor. I shoot 165s and I'll be danmed it I'm going to drive halfway across the country to shoot 1007fps(maybe) when 1050 is just a twist of the knob away. 125or 164.9999, its still minor.-----Larry Link to comment Share on other sites More sharing options...
Dead Buff Posted January 3, 2005 Share Posted January 3, 2005 Seems pretty simple to me... 165 yes 164.9999999999 no If I remember correctly Vince stated that this will be the way it is implemented in IPSC. Minor: 125.xxxx - yes; 124.xxxx - no Major: 170.xxxx - yes; 169.xxxx - no Link to comment Share on other sites More sharing options...
shred Posted January 3, 2005 Share Posted January 3, 2005 OK.. I think we all have our answers. In the kindler, gentler Rules forum rules (see above in big red letters), I'm going to close this one. If you've got something useful to add, let me know. Link to comment Share on other sites More sharing options...
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