cgrivois Posted January 3, 2012 Share Posted January 3, 2012 How much of a difference can mixed heads stamps make with velocity? I’m getting as much as 50fps difference between highest and lowest velocity out of a 10 shot string. I dial in my powder by throwing 10 charges then get the average. After that I run 20-30 rounds through the press, 550B, and then set up charge for next load to test. I’ve also seen my OAL vary by as much as +- .003, which could be mixed head stamp related to I suppose, so Im guessing I could be getting some variance there as well. Chrono is a Pro Chrono and brand new. Should I take the time and make sure all head stamps are the same when testing loads? Link to comment Share on other sites More sharing options...
bigbear Posted January 3, 2012 Share Posted January 3, 2012 i get a variation with mixed head stamp as well so for major matches i make sure i use the same headstamp. Link to comment Share on other sites More sharing options...
Chris Keen Posted January 3, 2012 Share Posted January 3, 2012 I do the same for major matches, when the chrono can make or break your match. For local matches or practice sessions, I wouldn't worry about it. Link to comment Share on other sites More sharing options...
cgrivois Posted January 3, 2012 Author Share Posted January 3, 2012 Just plugged the numbers into my spread sheet had SD of 17 on one string 27 on another, and 22 on the last string. Another piece of info, this lot of powder shot on average 5 power factor higher than the last lot did. Shooting n320. Link to comment Share on other sites More sharing options...
mda Posted January 3, 2012 Share Posted January 3, 2012 SD of 17 is pretty good. Factory 40 S&W ammo is not much better from the what I have chronoed. Winchester white box was around 12 and Wolf was 10. MDA Link to comment Share on other sites More sharing options...
noylj Posted January 4, 2012 Share Posted January 4, 2012 You know, there is little evidence that small SD and accuracy go together. Then, you are participating in a sport where accuracy is NOT the deciding factor. Thus, you should be shooting for accuracy and not low SD and be happy with a load that feels right and is more than accurate enough. Remember, a data of 10 is the minimum for SD. Buy some factory and compare SD and accuracy with your loads. Keep in mind what your goal is for a load. I loaded a LOT of different bullets and charge weights, with one set being the same head stamp and the other being very mixed brass. After a little over 200 of these comparisons, the average group size for mixed was about 0.10" smaller than for matching headstamps. Don't chase your tail, unless you have a real reason to. Link to comment Share on other sites More sharing options...
cgrivois Posted January 4, 2012 Author Share Posted January 4, 2012 good post noylj. Im happy with the load, how it feels and acuracy. Reason for the load is to get down close to minor, which Im at 135. I was just curious about the numbers I was getting with my chrono and why I was getting them. Link to comment Share on other sites More sharing options...
PHX Posted January 5, 2012 Share Posted January 5, 2012 Noylj has it right. I also agrre with the headstamps producing different velocities. I section my brass off by headstamp in old coffe cans now. Once I have a few hundred of one brand ill use thos for a major match. Link to comment Share on other sites More sharing options...
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