Got Juice? Posted October 1, 2012 Share Posted October 1, 2012 And if so, by how much? I live at 3300' ASL. My current load chronographs at 184PF This upcoming shoot is at 1200'ASL. What is the general concensus on how much velocity loss there is when you lose 1000 feet of altitude or better? Link to comment Share on other sites More sharing options...
a.roberts Posted October 1, 2012 Share Posted October 1, 2012 (edited) I live at around 400 feet in east Texas, shot a match in Albuquerque this weekend. I think I was 135 at home and 136 at the match. Edited October 1, 2012 by a.roberts Link to comment Share on other sites More sharing options...
Got Juice? Posted October 1, 2012 Author Share Posted October 1, 2012 I live at around 700 feet in east Texas, shot a match in Albuquerque this weekend. I think I was 135 at home and 136 at the match. What was the difference in altitude? Link to comment Share on other sites More sharing options...
a.roberts Posted October 1, 2012 Share Posted October 1, 2012 Albuquerque is right around a mile. Link to comment Share on other sites More sharing options...
Guest Posted October 1, 2012 Share Posted October 1, 2012 (edited) Since we chrono right out of the muzzle (for practical purposes 10’ is right out of the muzzle) there should be very little change, but your down range performance will change since the flight of the bullet is affected by density altitude (which effectively changes the ballistic coefficient of the bullet). Probably not a big deal for USPSA pistol shooters even at 50 yards. In theory due to less pressure at altitude there might be some very minute muzzle velocity change which probably isn’t measurable or significant. I’d be more worried about temp variations affecting powder performance. The ambient temp swings are greater at altitude. Also, gravity is less at altitude so be aware that your bullets won’t weigh as much! edit: I should add that I used to live at sea level and shoot matches at Reno and other "high" ranges and never got chrono bit but did have one near miss due to temp differences when using WW452AA, which is reverse temp sensitive. Edited October 1, 2012 by Bamboo Link to comment Share on other sites More sharing options...
Sarge Posted October 1, 2012 Share Posted October 1, 2012 And if so, by how much? I live at 3300' ASL. My current load chronographs at 184PF This upcoming shoot is at 1200'ASL. What is the general concensus on how much velocity loss there is when you lose 1000 feet of altitude or better? I think you'll be fine! Link to comment Share on other sites More sharing options...
NMBOpen Posted October 1, 2012 Share Posted October 1, 2012 (edited) Albuquerque is right around a mile. 5900' ASL at the range used for the High Desert Classic. Edited October 1, 2012 by NMBOpen Link to comment Share on other sites More sharing options...
Got Juice? Posted October 1, 2012 Author Share Posted October 1, 2012 (edited) And if so, by how much? I live at 3300' ASL. My current load chronographs at 184PF This upcoming shoot is at 1200'ASL. What is the general concensus on how much velocity loss there is when you lose 1000 feet of altitude or better? I think you'll be fine! Did some load development with the APEIRO. Starting at 4.2 Titegroup and 180gn Berrys. Major PF was achieved with 4.66gn of Titegroup. (174PF) Afterwards we took all the loads and tested for percieved and felt recoil. Drawing a straight line on a wall, videotaping the gun, and shooter. You can then pause the video and scale the muzzle rise of the gun on each load. 4.66 was the softest, but on the edge for PF in my opinion. 4.7/4.75/4.8 was snappy and rude. Which was backed up by shooters comments and corroborated with the video. 180PF 4.91gn load was a lot smoother, and the gun was much easier to control. Smoother recoil pulse, less muzzle flip, and I did not feel any harshness in my wrists (unlike the 4.7 loads) The fact that it made 185PF is almost irrelevant. Once I found a smooth controllable load that made power factor without beating me or the gun up, I decided to leave it there. Edited October 1, 2012 by Got Juice? Link to comment Share on other sites More sharing options...
Robert King Posted October 1, 2012 Share Posted October 1, 2012 It does, but not by enough to matter in my experience. My loads that were developed and loaded at sea level are no more than a couple PF different at 5,000 feet. And those small variations may have little to do with the altitude. YMMV. Link to comment Share on other sites More sharing options...
Got Juice? Posted October 1, 2012 Author Share Posted October 1, 2012 It does, but not by enough to matter in my experience. My loads that were developed and loaded at sea level are no more than a couple PF different at 5,000 feet. And those small variations may have little to do with the altitude. YMMV. Perfect. That is exactly the information I needed. I don't want to travel and then shoot standard minor. Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted October 1, 2012 Share Posted October 1, 2012 My current load chronographs at 184PF img]http://www.brianenos.com/forums/public/style_emoticons/default/surprise.gif[/img] we tested for percieved recoil. Drawing a line on a wall, videotaping the gun. You can pause the video and scale the muzzle rise of the gun on each load. 4.91gn load was smoother and much easier to control. The fact that it made 185PF is almost irrelevant. Jonathon, sounds like a real good way to measure muzzle flip and feel. Might be good idea to add one additional dimension to your measurement - the results of a timer. Pick a drill and shoot the various loads with a timer and see if there's a difference in the time necessary to shoot all A's ... One load might feel better, but take more time to shoot 20 A's Link to comment Share on other sites More sharing options...
Got Juice? Posted October 2, 2012 Author Share Posted October 2, 2012 My current load chronographs at 184PF img]http://www.brianenos.com/forums/public/style_emoticons/default/surprise.gif[/img] we tested for percieved recoil. Drawing a line on a wall, videotaping the gun. You can pause the video and scale the muzzle rise of the gun on each load. 4.91gn load was smoother and much easier to control. The fact that it made 185PF is almost irrelevant. Jonathon, sounds like a real good way to measure muzzle flip and feel. Might be good idea to add one additional dimension to your measurement - the results of a timer. Pick a drill and shoot the various loads with a timer and see if there's a difference in the time necessary to shoot all A's ... One load might feel better, but take more time to shoot 20 A's Fantastic Idea!!!. Yes, I did try a target, and the results bear out the 'feeling of recoil' (but I did not bring my shot timer) it was a good experiment, and something new that I learned. Loading for power factor is a poor way to judge the overall performance of the loading for your gun. Sometimes you need data that you can 'see' from an outside perspective. I would have thought pistol less sensetive than my rifles for load. I discovered that is only half-true. While the overall accuracy of a rifle changes greatly with minute increments of powder, a pistol does not change accuracy to the same degree. However, the pistol does some really nasty gyrations when subjected to a load it does not 'like' Examples, are snappy muzzle, slide feels like it is 'hammering' instead of gliding smoothly (probably true), impact on wrist joints of strong hand (yes i know not the gripping hand) become sharper and more pronounced as shock, having to use more weak hand grip pressure to control the gun (that 4.7 loading was total crap!) So, I guess I can only conclude that loading until your gun feels good is the only true metric. Yes, you still have to achieve a certain power factor, however you must be comfortable to shoot accurately, which might involve changing recoil springs, altering the loading etc. In the end, I finished with a 1 piece SS Guiderod, and the main spring from the recoil master, and a thin shock buffer. Combined with the 4.9 load, the gun settles down remarkably well without the feeling that you are 'pressuring' the gun down and back on target. And after talking to a gunsmith (I am a 2011 Virgin) His thoughts also back up my findings, that loading to a power factor is a bit too simplistic when actually having to perform with the gun. Live and learn. So, the gun is happy with 185PF..... I can live with that, and shoot it quite decently for my skill level. Link to comment Share on other sites More sharing options...
FightFireJay Posted October 2, 2012 Share Posted October 2, 2012 Assuming that your video taped experiment wasn't too heavily influenced by the human variable... I have to wonder if your results have something to do with spring harmonics. Valve springs in an engine to funny things at certain RPMs... I have to wonder if something similar is happening here. As the spring starts to compress it will also "vibrate" or have an oscillation go from front to back and then back to front and so on. If that oscillation is "in time" with the slide racking the end of its travel (or possibly "out of time") I wonder if it would cause that much of a felt difference. Maybe someday someone will put a camera inside the dust cover of different guns to see things like this..... Link to comment Share on other sites More sharing options...
tagacali Posted September 22, 2013 Share Posted September 22, 2013 Does it really go up? I know depending on the powder that you use, the weather could change your power factor but I just wanted to make sure the the elevation of the location could also affect the PF to increase. Thanks! Link to comment Share on other sites More sharing options...
a.roberts Posted September 22, 2013 Share Posted September 22, 2013 http://www.brianenos.com/forums/index.php?showtopic=160320 Link to comment Share on other sites More sharing options...
Reshoot Posted September 22, 2013 Share Posted September 22, 2013 No difference in my power factor, from prone to standing Link to comment Share on other sites More sharing options...
sperman Posted September 23, 2013 Share Posted September 23, 2013 Topics Merged. Link to comment Share on other sites More sharing options...
RePete Posted September 23, 2013 Share Posted September 23, 2013 The velocity will be lower at the lower altitude due to the increase in air density. As stated you'll be fine. The problem comes when you load close to the line. I DQ'd a good friend who at a match, and a week earlier passed chrono. Temp 95 deg F with about 10% humidity. At this match the temp was 95 deg F and 95% humidity. He went from 166PF to 162PF. Link to comment Share on other sites More sharing options...
sperman Posted September 23, 2013 Share Posted September 23, 2013 Why did you DQ him? He should have been scored minor, nothing more. Link to comment Share on other sites More sharing options...
RePete Posted September 23, 2013 Share Posted September 23, 2013 Why did you DQ him? He should have been scored minor, nothing more. It was IDPA and not USPSA/IPSC. No major/minor. Link to comment Share on other sites More sharing options...
sperman Posted September 23, 2013 Share Posted September 23, 2013 Gotcha. I was obviously thinking USPSA. Link to comment Share on other sites More sharing options...
RePete Posted September 23, 2013 Share Posted September 23, 2013 No sweat. He did, however, get to shoot the whole match because I had to use his revolver. With the new rulebook that would allow to shoot for no score. Link to comment Share on other sites More sharing options...
Got Juice? Posted September 24, 2013 Author Share Posted September 24, 2013 Threadsurrection time. I found a new Titegroup loading that my gun just loves (and so do I) Measuring a Vomit-inducing 197 PF, it's enough to make an RO wish he double plugged, but oh well. 180gn Berry's 5.2 TG, CCI SRP's OAL of 1.152 What a laser, and smooooooth. After some Border gaurds saw mw shoot, they snubbed IPSC rounds as 'target ammo'. They saw how smooth the gun was and they assumed (wrongly) that they were powder puff loads. So, I let them shoot my gun. That only served to reinforce their misconception as it is so smooth to shoot. So I did the only thing I could think of to prove that IPSC/USPSA are anything but weak. I had them choose a mag off my belt, and we loaded 10 rounds in their S&W MP. Wow. The results were dramatic. The first round fired through their pistol and the officer said a bad F word. Then I tried my loading in his gun. OUCH! Poor thing felt like it was going to kersplode. He suggested that we not shoot another round like that through his gun. Yep.... ULASC time. Link to comment Share on other sites More sharing options...
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