C.O.L. for 690gr South African Ball

[Pavlata]

I am going to load up some South African 690gr Ball bullets.

My Hornady Data manual gives a C.O.L. of 5.450" using the Hornady 750gr AMAX.
I have researched many different forums and I have come up with 5.420", 5.425",5.435" using different bullets from 647 API, 661 gr M-33, to the 690 gr SA ball.
I will be shooting these in both our Barrett M-99 and M107.

I read on one forum and it was mentioned that the 5.450" COL is a military spec. What are you guys using for C.O.L. for the 690gr SA ball?

Also, I read the recommendation by David of using the US869 starting point of 220gr for loading 647gr bullets. Given the increase bullet weight I will be loading (690 gr) would this still be an okay starting point or should I back off to say 215gr. I want them to be able to function properly in the M-107. The reason for the US869 is that at the time when I purchased this powder there wasn't any h50BMG available so I want to use it up first before I start using the H50. Plus I want to use the H50 for my 750 AMAX loads for the 99.

I wish my other loading manuals list the 50BMG so I could compare Data. I don't have a Barnes manual yet though and I would assume since they manufacture bullets for the 50 they would have loading data?

Thanks for your help and insight.

Pavlos

 

[Lt. Arclight]

Re: C.O.L. for 690gr South African Ball

You are going to be somewhere between 5.413" to 5.425" with ball.You need to CRIMP the case at the cannelure groove. That is going to set your overall length. The crimp is absolutely essential for accuracy (maybe 2moa if you are very lucky) with the M107,its essential,if the neck tension isn't tight enough or the crimp isn't tight,you'll have feeding issues and worst case the bullet will slide back and compress the load.

I've used US869 with 800 gr.Lapua solids with good results.But found H50BMG to be the best powder with the Amax. (start @215gr.)

US 869 is slow but you have to be careful cutting back on the charge weight since it is such a fine ball powder. 220gr. should be a good start with the Ball. Hodgdon's max loads are HOT. You can go to 256gr. with the Amax. You'll probably be using 230gr.US 869-but work up to it.

H50BMG is my favorite 50BMG powder. US869 is alittle slower but not as slow as VV20N29.

50BMG is very frustrating to work up loads. Ball,if pulled surplus-MUST be resized-even if the supplier claimed it was CH4D makes a good sizing die. New ball might get you 2moa at 500-600 yards. Amaxes at about 2800fps seems to be about right. If you want a faster projectile with a standard chamber you may want to try the Barnes solid.

Good Luck.