jimbullet Posted June 17, 2017 Share Posted June 17, 2017 HI, Just getting opinions please. So I have done a load of 5.3 grains on a 180 grain projectile and the raw data is as follows: FPS 939 967 989 891 988 961 962 989 If I take the lowest three, it would not meet the required 170 PF. But if random choose each shot - it would. When I go for 5.4 grains, the power factor is already at 180PF raw data on 5.4 grain 1025 1006 1025 1019 1012 1003 1007 All test shot on 12 degrees Celsius cloudy day if that makes a difference 5 inch STI DVC Limited Your thoughts please - would you use 5.3 grains in a major match? Link to comment Share on other sites More sharing options...
tcazes Posted June 17, 2017 Share Posted June 17, 2017 Required pf for major is 165 not 170. I'd go with the more accurate load. Don't rely on just pf alone. Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 IPSC standard division is 170 PF though http://www.ipsc.org/rules/divlistP.php Link to comment Share on other sites More sharing options...
tcazes Posted June 17, 2017 Share Posted June 17, 2017 Ah my bad I should have thought that through. I shoot uspsa. You should Sat what powder you are using. If it's not temperature sensitive 5.3 may be fine. Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 My concern is if I take the lowest three of the 8 shots I fired (and I listed them in sequence above), that would fail. Or am I over thinking this and it should be fine? Link to comment Share on other sites More sharing options...
tcazes Posted June 17, 2017 Share Posted June 17, 2017 I mean yes it's close but temperature, humidity, barometric pressure, and the model of chronograph all make a difference. What failed today won't always fail next week. Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted June 17, 2017 Share Posted June 17, 2017 I like to fire 20 rounds thru the chrono, and have ALL of them meet minimum PF. That means that my Average is higher than Minimum. A sample of eight shots is a little low, for me Link to comment Share on other sites More sharing options...
3gunDQ Posted June 17, 2017 Share Posted June 17, 2017 I'd switch powder. AND I would not shoot either of those loads at a major. Link to comment Share on other sites More sharing options...
zzt Posted June 17, 2017 Share Posted June 17, 2017 I tinkered with loads until I came up with one that made 172PF with SDs in the 4 to 7 range. That puts every shot in a 10 or 20 round string well above the 165 floor. I go 7 above the floor because chrono technique at matches is not always the best. I want to have an extra margin. !77PF is what I would shoot for in IPSC. If my SDs were higher than 7, I'd go hotter. Link to comment Share on other sites More sharing options...
ChuckS Posted June 17, 2017 Share Posted June 17, 2017 5 hours ago, jimbullet said: HI, Just getting opinions please. So I have done a load of 5.3 grains on a 180 grain projectile and the raw data is as follows: FPS 939 967 989 891 988 961 962 989 If I take the lowest three, it would not meet the required 170 PF. But if random choose each shot - it would. When I go for 5.4 grains, the power factor is already at 180PF raw data on 5.4 grain 1025 1006 1025 1019 1012 1003 1007 All test shot on 12 degrees Celsius cloudy day if that makes a difference 5 inch STI DVC Limited Your thoughts please - would you use 5.3 grains in a major match? Jim, There is some wide variation between those two loads. The ES/SD on the first is 98/33.2 while the latter is 22/9.4. You need to figure out why the 5.4 gr load has 1/3 the standard deviation of the first load! Even throwing out that 891, the 5.3 SD is still 2x the 5.4 load. But in the general sense, you want to load 2 or 3 SD's above the required velocity. If your SD is 10 and your bullet is 180 gr, your load should yield 964-974 FPS. Also, be sure to check your bullet weight. There is a tendency to use the cheapest bullets around and you may find some weight variations. Weigh 20 or so bullets and calculate your SD for them and use the nominal weight minus 2 or 3 SDs to calculate your power factor when you chrono your next loads. Later, Chuck Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 5 hours ago, ChuckS said: Jim, There is some wide variation between those two loads. The ES/SD on the first is 98/33.2 while the latter is 22/9.4. You need to figure out why the 5.4 gr load has 1/3 the standard deviation of the first load! Even throwing out that 891, the 5.3 SD is still 2x the 5.4 load. But in the general sense, you want to load 2 or 3 SD's above the required velocity. If your SD is 10 and your bullet is 180 gr, your load should yield 964-974 FPS. Also, be sure to check your bullet weight. There is a tendency to use the cheapest bullets around and you may find some weight variations. Weigh 20 or so bullets and calculate your SD for them and use the nominal weight minus 2 or 3 SDs to calculate your power factor when you chrono your next loads. Later, Chuck I weighed the projectiles and they are coming at 180 gr, 179.9 and 179.8. I also tried a 5.5 grain load and the following were the results 1021 1017 1014 1016 1010 1019 the SD is smaller. What about brass - does it also make a difference - all of these test were shot with mix brass of starline, federal, winchester and WIN. 8 hours ago, 3gunDQ said: Link to comment Share on other sites More sharing options...
tcazes Posted June 17, 2017 Share Posted June 17, 2017 I'm still curious what gun or powder you are using. Haven't mentioned either yet. You havent given any details other thsb charge and velocity... Link to comment Share on other sites More sharing options...
ChuckS Posted June 17, 2017 Share Posted June 17, 2017 1 hour ago, jimbullet said: I weighed the projectiles and they are coming at 180 gr, 179.9 and 179.8. I also tried a 5.5 grain load and the following were the results 1021 1017 1014 1016 1010 1019 the SD is smaller. What about brass - does it also make a difference - all of these test were shot with mix brass of starline, federal, winchester and WIN. Brass case volume differences can matter. Try to stick to one head stamp to eliminate that for now. The 5.5 load looks very consistent. Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 (edited) 59 minutes ago, tcazes said: I'm still curious what gun or powder you are using. Haven't mentioned either yet. You havent given any details other thsb charge and velocity... STI DVC Limited 40 Win231 powder Edited June 17, 2017 by jimbullet Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 (edited) 10 minutes ago, ChuckS said: Brass case volume differences can matter. Try to stick to one head stamp to eliminate that for now. The 5.5 load looks very consistent. The 5.5 grain load test was also of mix brass though so I am not sure why the high SD still on the lower loads. The 5.5 grain is giving me above 180PF so I dont want to go and use this Edited June 17, 2017 by jimbullet Link to comment Share on other sites More sharing options...
Steve RA Posted June 17, 2017 Share Posted June 17, 2017 Pick out 20 pieces of brass of the same make and try the 5.4 load again. Also check which is more accurate at 25yds, use a Ransom if you have one or a sturdy bench with whatever rest works best for you and see what you get. As long as you exceed what ever power factor you are going for then the loads accuracy potential is the most important thing. Link to comment Share on other sites More sharing options...
jimbullet Posted June 17, 2017 Author Share Posted June 17, 2017 9 minutes ago, Steve RA said: Pick out 20 pieces of brass of the same make and try the 5.4 load again. Also check which is more accurate at 25yds, use a Ransom if you have one or a sturdy bench with whatever rest works best for you and see what you get. As long as you exceed what ever power factor you are going for then the loads accuracy potential is the most important thing. Thanks Steve, I will try to do a ransom rest test but so far what I have found is this: The 5.5 grain appears accurate as it is consistently hitting steel out at 15 yards (6-7 inch diameter steel) - not a proper gauge but this is what I had so far The 5.3 grain appears to be shooting lower as I had to put a slightly higher point of aim. One thing I just noticed bringing out the caliper is that my OAL is inconsistent! Measuring 1.159, 1.160, 1.163, 1.167 spreads. - might be a contributor to the variances I am getting? Link to comment Share on other sites More sharing options...
Steve RA Posted June 17, 2017 Share Posted June 17, 2017 Several possible reasons for that: Could be the mixed brass, if the wall thickness varies then the resistance to seating the bullet will also vary, causing some difference in the OAL. Not knowing what you are using for a press, one possibility is that the shell plate isn't tight enough, allowing some degree of tilt which mixed with the first reason could cause the problem. Another could be that the diameter of the bullets varies which would have some bearing on the OAL length. I'd guess it's more the first reason which is why you should try the "one brand of brass" test. Link to comment Share on other sites More sharing options...
jimbullet Posted June 18, 2017 Author Share Posted June 18, 2017 ok thanks, will load some on a single brand brass - im using square deal. will check out how that goes. Link to comment Share on other sites More sharing options...
jimbullet Posted July 1, 2017 Author Share Posted July 1, 2017 more testing - Used the same brass brand - Winchester and same brand primer Fiocchi and my raw velocities are as follows: 962 1001 962 992 953 938 992 982 988 990 986 960 918 966 So far two of the shots would have failed 170PF from what I can see but the average would allow it to pass at PF 174. I cant figure out what could be causing the high deviation from a low 9118 fps to a high of 1001 fps. The two things I can think of is maybe due to dirty brass? I have used brass which I have reloaded twice already without going to the tumbler. Or it could be the inconsistent OAL. I measured the OAL on all the ammo I used today and OAL is differing from 1.159 to 1.168. Any thoughts, suggestions? I am thinking it should be adequate to meet the 170PF or should I take that extra safety margin and increase my load by 0.1 grains which will drive this to a 180 PF. Link to comment Share on other sites More sharing options...
IDescribe Posted July 2, 2017 Share Posted July 2, 2017 What type of bullets are they? 180gr what? Link to comment Share on other sites More sharing options...
jimbullet Posted July 4, 2017 Author Share Posted July 4, 2017 On 7/2/2017 at 4:29 PM, IDescribe said: What type of bullets are they? 180gr what? 180 gr RNFP - they are fully jacketed projectiles. Link to comment Share on other sites More sharing options...
IDescribe Posted July 4, 2017 Share Posted July 4, 2017 10 hours ago, jimbullet said: 180 gr RNFP - they are fully jacketed projectiles. Made by whom? Link to comment Share on other sites More sharing options...
zzt Posted July 11, 2017 Share Posted July 11, 2017 jim, there may be a couple of different reasons for the variations. First, the SDB does not have the most consistent powder measure in the world, and it IS sensitive to press operation. If the powder doesn't bridge and you operate the press smoothly, there should not be as much variation. Second, it may be improper chrono use. The most accurate reasing is goint to be along the long axis of the machine and parallel over the windows. ANY variation WILL affect the reading. It is amazing how much a little teeny offset can make in the velocity recorded. Link to comment Share on other sites More sharing options...
jimbullet Posted July 15, 2017 Author Share Posted July 15, 2017 On 7/12/2017 at 9:09 AM, zzt said: jim, there may be a couple of different reasons for the variations. First, the SDB does not have the most consistent powder measure in the world, and it IS sensitive to press operation. If the powder doesn't bridge and you operate the press smoothly, there should not be as much variation. Second, it may be improper chrono use. The most accurate reasing is goint to be along the long axis of the machine and parallel over the windows. ANY variation WILL affect the reading. It is amazing how much a little teeny offset can make in the velocity recorded. I didnt know that about the SDB.... sensitive in what way - vibration on the bench top - powder not trickling down? I havent thought about the chrono as well, interesting - thanks for this input and I may try to place more accurate shots into it. Link to comment Share on other sites More sharing options...
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