SR4759 and Powder Measures

[Matt Anthony]

Please be cautioned on using SR4759 in any powder measure if you are not weighing every charge. Due to the size of the powder dimensionally, you could very well over charge a case or under charge it and not know it. This happened to me on using cast bullet loads in 30-06 and upon checking the loads in the loading blocks with a light, I found some cases were visually not correct. Upon re-weighing those cases I found that they had more and some had less of a powder charges.
I am using the RCBS UNIFLOW unit and it seems that due to the powder dimension, powder can hang up at times. Even though you are using the exact same pressure when working the measure, powder can and will hang up due to it's dimension.
Upon weighing the charges, there was a 10 grain difference and let me tell you that after firing one of these cartridges, my shoulder told me there was something wrong. The powder is a cylinder tube of sorts and can cake up in the measure, so please be mindful of what could happen if you don't get the correct measure. It sure was a eye opener for me!
Matt

Information

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[Gun Surfer]

I used to use it all the time when I reloaded 45-70. You are correct in that you have to weigh the charges, at least I did.

[Curator]

The minor weight differences you get with IMR4759 and a powder measure should not be a problem. However some powder measures (Lyman 55?) allow the coarse powder to "bridge" and allow some of the charge to hang up inside the measure allowing for a "squib". The next charge will usually dislodge it and weigh somewhat more than you had expected to include a serious overload. My RCBS doesn't have this problem, nor do the Lee graduated scoops.

[ireload2]

I use a lot of SR4759 and I weigh it with an AMT/Lyman Autoscale.
The Autoscale is a beam balance with a pair of powdered tricklers.
It works great on large kernel powders.

[MEHavey]

On the other hand, I just went down to the basement and scooped out 10 loads with my trusty Lee dippers (the yellow set with a dozen dippers).

For a classic 400gr 45-70 load using ~21-22gr SR4759, the 1.9cc dipper gave me 21.53gr average/0.15gr StdDev

For a powder like 4759 and a cartridge like the 45-70, that's a 10 indistinguisable loads at 45-70 ranges.

(For 25 years I've used 1.0cc/4759 as the starter charge for a duplex load under 90gr of 1F black in a .45 x 3-1/4 Sharps.)