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Excessive "extreme spread"


kamikaze1a

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On 8/5/2016 at 10:41 AM, kamikaze1a said:

I finally had a chance to do additional load testing with the new plated bullets and my two go to powders. Loading for 40 major, 180gr bullet, 1.18" OAL with an Infinity. Powder charges dispensed with Dillon measure (not individually weighed) and bullets chosen at random (not weighed).

First load; 5.4gr HP38;

910, 903, 931, 869, 908, 935, 908, 942, 949, 889 - 914 average, 80 extreme spread, 24 standard deviation

muzzle dipped DOWN before each shot

Second load, 5.4gr HP38;

981, 973, 970, 981, 977, 973, 975, 953, 995, 997 - 977 average, 44 extreme spread, 12 standard deviation

muzzle raised UP before each shot

Third load, 5.4gr HP38;

911, 942, 944, 985, 920, 931, 965, 955, 946, 867

932, 910, 945, 987, 947, 981, 963, 994, 968, 919 - 945 average, 127 extreme spread, 25 standard deviation

shot normal

WST same bullet

First load 5.3gr WST;

903, 903, 927, 881, 957, 920, 859, 908, 854, 796 - 890 average, 161 extreme spread, 45 standard deviation

muzzle dipped DOWN before each shot

Second load 5.3gr WST

954, 966, 950, 908, 944, 946, 942, 951, 933, 889 - 938 average, 77 extreme spread, 23 standard deviation

muzzle raised UP before each shot

Third load 5.3gr WST;

915, 923, 900 912, 946, 938, 966, 897, 915, 953

936, 951, 934, 948, 959, 957, 941, 946, 965, 915 - 935 average, 69 extreme spread, 21 standard deviation

shot normal

These are not compressed loads but by my estimate there would be little space between bottom of the bullet and the powder charge so I am amazed at the amount of change in velocity by dropping the muzzle before the shot.

Tried WST because my other go to powder, HP38 with the new plated bullet gave me high extreme spread and standard deviation but it appears that it was not only with HP38. Shot 20 additional rounds for accuracy and both loads in spite of high ES/SD gave good accuracy. Plan to bump the WST charge up 0.1gr for additional velocity tests but I think I am going back to my previous brand of plated bullets.

stumbled across your post back in 2016, I appear to have the same issue and havent resolved the high ES/SD as well - using the same powder HP38/ win 231 - did you ever get this resolved?

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Would this be an OAL variance issue?  Or maybe a mixed case issue?  Seems weird that using the exact same load would vary that much unless your OAL is off round by round and/or you have mixed brass which is causing different internal pressures round by round. 

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2 hours ago, R1_Demon said:

Would this be an OAL variance issue?  Or maybe a mixed case issue?  Seems weird that using the exact same load would vary that much unless your OAL is off round by round and/or you have mixed brass which is causing different internal pressures round by round. 

Most likely mixed brass. OAL won't vary enough from round to round to make a huge difference.

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Nope. Just set my load to the lowest velocity while shot "normal" position. Shoot only local matches but asking chrono guy at a big match to dip the muzzle b4 each shot wouldn't fly. 

Never tested it but I think it could be a small charge with long OAL (1.2") resulting in the charge being loose. It's just a theory...

I did try a couple of strings with all the same headstamp and got similar results. 

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20 hours ago, GrumpyOne said:

Most likely mixed brass. OAL won't vary enough from round to round to make a huge difference.

 

Oh okay...so it would be my guess is when you are working up loads to try and use the same head stamp brass and keep everything as consistent as you can.  Even if you are going to use mixed brass overall in your normal loads?

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1 hour ago, R1_Demon said:

 

Oh okay...so it would be my guess is when you are working up loads to try and use the same head stamp brass and keep everything as consistent as you can.  Even if you are going to use mixed brass overall in your normal loads?

Yes. Otherwise, you really don't know what your SD or ES is.

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Well, I did buy 500 cases of mixed brass and I did sort the head stamps already.  Most were Winchester and Federal, but I did get some onesies and twosies out of the bunch.  Well, obviously there isn't much I can do about those as I can't make up a separate load for those cases.  Some I had up to five cases per head stamp, but most were more than that per head stamp.  However, even if I have ten cases per head stamp and I make up a separate load for them, I'm going to be shooting off that load anyway for testing.  So, I guess it would be kind of pointless to setup a load for those ten separate cases, no?

 

Obviously I would use the Winchester and Federal to work up my loads, but I'm not just going to throw the onesies and twosies head stamped brass away.  That's my point.  I'm guessing once I have my loads setup that I want to shoot/use, then I'll just have to use these "extra" brass anyway with the loads I came up with with the Win/Federal cases and hope they make PF or I guess I could use them as practice ammo.  I think out of my total mix, I came up with 10-15 head stamps.  So, it seems nuts to try and come up with 10-15 "loads", one for each type of head stamp.  :surprise:

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6 hours ago, RaylanGivens said:

I think they mean to use the same headstamp brass to determine what your SD and EX parameters are...  Not to use 15 different loads...

 

Thats what I figured. Just use one head stamp for load testing and not a separate test load for each different head stamp I have. 

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  • 2 weeks later...

How consistent is your oal?  Are you using the same head stamp?  

 

I was loading my 40 at 1.20.  However I was getting a large velocity spread.  I changed my oal to 1.185 and my velocity spread came down to 10fps+\-.   I chambered Several rounds and then measured their oal.  The oal's were all shorter after clambering.  I think at that length, there wasn't enough purchase on the projectile.  

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On 7/13/2017 at 2:34 PM, Aric said:

How consistent is your oal?  Are you using the same head stamp?  

 

I was loading my 40 at 1.20.  However I was getting a large velocity spread.  I changed my oal to 1.185 and my velocity spread came down to 10fps+\-.   I chambered Several rounds and then measured their oal.  The oal's were all shorter after clambering.  I think at that length, there wasn't enough purchase on the projectile.  

interesting - my oal off the press does give me slightly different OAL from 1.158 (which is what it was meant to be set up to) to as long as 1.170; randomly when all stages of the press is full.

 

I tried to put only one case and get it through the entire 4 stages of the press before putting another and this is when I get more consistent OAL exactly to what it was meant to be at 1.158. The press is an SDB, scratching my head as to why and how to solve that.....

 

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1 hour ago, jimbullet said:

interesting - my oal off the press does give me slightly different OAL from 1.158 (which is what it was meant to be set up to) to as long as 1.170; randomly when all stages of the press is full.

 

I tried to put only one case and get it through the entire 4 stages of the press before putting another and this is when I get more consistent OAL exactly to what it was meant to be at 1.158. The press is an SDB, scratching my head as to why and how to solve that.....

 

When I am done loading, I stop leaving brass in each station.  That way when I start loading again I don't have shorter arounds until all the stations are loaded.  

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  • 2 months later...

I don't have a SD, but a 550. I have determined that having a case in each station during reloading will have a direct effect on the consistency of the OAL. So I start out with maintenance brass, and new brass into the sizing station, and as I come to the end of my reloading, I finish with my maintenance brass.  My maintenance brass is defective, but same head stamp as my shooting brass. This is what I setup my tool heads with, and start and finish my reloading with.

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I buy 40sw brass 3000 at a time.  I don't sort headstamps.  They come cleaned and polished, so I just load them that way.  I use Alliant e3 powder, because it is the most consistent I've found.  My 172PF load has SDs for 10 shot strings in the 4.83 to 7.15 range.  Mostly they clusten it the 5-6 range.  So mixed headstamp loading is not a cause of extreme variation.

 

BTW, I load to 1.126" because my TS requires that, and both 2011s have no trouble feeding that OAL.

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