Foto Joe

December 10, 2013, 01:57 PM

Since I started casting about six months ago I've been working up loads for the pistol/revolver calibers that I shoot. So far things have gone pretty good considering my steep learning curve at times. One of the things that has me scratching my head is "Standard Deviation" and "Extreme Spread." For instance....

Let's take 45 Colt, loading a specific charge of TrailBoss under a 226gr LRN gives me an average velocity of 803fps, a standard deviation of 12.4fps and an extreme spread of 39.2fps, not much to complain about there especially since it also includes a 1.5" group at 15 yards. Not bad for an out of the box cowboy gun really.

Now, so as to NOT throw all that extra lead downrange (the stuff can be hard to come by) just to hit a gong or a piece of paper I've attempted to put together a load for a 164gr LRNFP. Yes, I know that if I'm not throwing the lead downrange I'm throwing powder instead but the point is I'm trying to work up a decent load for each boolit that I might load the gun with. Anyway the BEST numbers I can get are posted below and both powders basically suck when compared to the heavier boolit.

TrailBoss

MV = 959

SD = 30

ES = 88

700X

MV = 1016

SD = 23

ES = 74

In actuality, the TrailBoss load grouped pretty good at 1.5" even though it had a higher SD & ES than the 700X which grouped at 3".

Keep in mind for the purposes of this thread I'm NOT looking for powder recommendations, I have what I have and until others are available that's the way it is. What I am looking for is the relevance or shall we say what is the acceptable SD & ES for shall we say 45 Colt or 45 ACP. What's considered a good Standard Deviation basically or a good Extreme Spread for large bore low pressure handgun loads such as these.

Let's take 45 Colt, loading a specific charge of TrailBoss under a 226gr LRN gives me an average velocity of 803fps, a standard deviation of 12.4fps and an extreme spread of 39.2fps, not much to complain about there especially since it also includes a 1.5" group at 15 yards. Not bad for an out of the box cowboy gun really.

Now, so as to NOT throw all that extra lead downrange (the stuff can be hard to come by) just to hit a gong or a piece of paper I've attempted to put together a load for a 164gr LRNFP. Yes, I know that if I'm not throwing the lead downrange I'm throwing powder instead but the point is I'm trying to work up a decent load for each boolit that I might load the gun with. Anyway the BEST numbers I can get are posted below and both powders basically suck when compared to the heavier boolit.

TrailBoss

MV = 959

SD = 30

ES = 88

700X

MV = 1016

SD = 23

ES = 74

In actuality, the TrailBoss load grouped pretty good at 1.5" even though it had a higher SD & ES than the 700X which grouped at 3".

Keep in mind for the purposes of this thread I'm NOT looking for powder recommendations, I have what I have and until others are available that's the way it is. What I am looking for is the relevance or shall we say what is the acceptable SD & ES for shall we say 45 Colt or 45 ACP. What's considered a good Standard Deviation basically or a good Extreme Spread for large bore low pressure handgun loads such as these.