Hypothetical loading question

[vaquero]

I don't own a chronograph, so I can only use info posted on loading data sites.  My Hodgdon loading data info. using Winchester WST powder and a 200gr. LSWC bullet in a 45 acp. the following.    Min load 4.4 gr, 830 fps.    Max load 5.1gr, 910 fps.  that is an 80 fps difference in velocity between min and max loads also a 7/10 of a grain of powder difference.  If you took the 80 fps. divided it by 7, that would equal about 11.43 fps, per 1/10 gr. of powder.  Now if I wanted to add 2/10gr. of powder from min. load of 4.4 it would be a load of 4.6 grs, 2/10 gr. would, (In the theory) add approx. 22.86 fps to the min load velocity for a velocity of approx. 853 fps.  I wish I have a chrono to test this theory out.  I know, there are a lot of variables, and most loading fps statements are far from being true.  But it was raining today, and I was bored.

[Garrison Joe]

When the velocity versus powder weight "curve" is flat (if you graph it out on paper or a spreadhseet graphing package), then "interpolating" between the two end points of known weights and velocities gives you a good estimate of an intermediate powder/velocity result.

 

Extrapolating beyond the end points of measured data is much more risky.  And, smokeless powder rarely has a linear weight to velocity relationship - it tends to be progressive, and the velocity starts trending upward from being linear as you add more powder.  Until you blow up a gun!

 

But, the biggest variation (and fallacy in trying to go from published loading data to what happens in your gun without actual range testing) is that YOUR gun won't hold the same velocities as ANY OTHER test gun.  There WILL be some differences, due to chamber dimensions, barrel dimensions, type of brass, lube on your bullet, minor differences in seating depth, and tons of other variables.

 

So, it's usually best to find a pal with a chronograph and test your load in YOUR gun, especially if you plan to be hugging the cliff edge at the low end of the allowed power factor (PF) range. 

 

But, if you just ask here, we can tell you from experience that almost everyone shooting a 200 grain bullet from .45 auto with WST in their 5" barrel 1911 will be shooting a load of 4.7 grains of WST, or slightly higher.  That will make 165 to 170 PF in most guns.  In mine, it is repeatedly 167, 168, or 169 every time I or a big match director chronos my loads.

 

4.6 grains in my guns typically only makes 155 PF.  That is TOO CLOSE to the minimum (150) for me to ever bet the results of a match on being able to stay on the good side of the PF line.  So, I shoot a 4.7 grain load.

 

Good luck, GJ

 

 

 

[Happy Jack]

I agree with Joe. I've used WST in 45ACP for MANY years. The go-to powder in my opinion and many others. 4.7 should be reliable with a 200grain bullet. I only use 230 grain bullets in 45ACP and have used 4.6grains for many years. MY pistols are tight and the 230grain with 4.6 of WST makes PF 160 + - 2 year around. So my guns shoot a bit different than Joe's so I need 4.8 with a 200 grain bullet to make 160-165. Load 4.7 and 4.8 and when you get to a chrono see what the results are. Do NOT try to hug the lower power floor. The pistols were originaly designed for a PF above 170 so going too low will not only cause malfunctions unless the pistol is re-sprung but will result in a MDQ for scoring if you don't make minimum PF.

[vaquero]

Thanks Jack and Joe, the problem that I seem to have is, I was loading 4.8 of WST behind the 200gr. LSWC, and everything works fine, but the empty cases show signs of excessive pressure, as the primers seem to be flattened some.    I thought I would try loading 4.6gr. and see if the problem cures itself.

[Goatneck]

  WST Powder is a good choice.  I use WST in  many different guns with great results.  Your loading data is what we use for Wild Bunch.  My chrony velocities are less than your data but not that far apart.  You are on the right track good luck and good shooting.............