WC860 in M1a

[MUSTANG]

Loaded some .308/7.62 x 51 using the RCBS 30-165-Sil Boolit for testing in one of my M1a's. Load was 41.5 Grains of WC860, with a 4.0 Grain Unique Kicker over the Primer. (Load Data and Performance Sheet is attached as a PDF).

Following is a comparison of shot strings for my .308/7.62 military ball load, and a Cast Boolit Load using the RCBS 30-165-Sil Boolit. (Click on picture to enlarge)




The five round Mil-Ball group was approximately 1.5 inches by 2.5 inches. The 9 round cast boolit group was 3.5 inches by 2.75 inches. An OK start, I'll be searching to shrink the group. Some may find it an OK group for plinking or cheap practice with a mil-surp powder load, as is. I get much smaller groups in my bolt guns with a similar load.

There is not a significant amount of Load data for the RCBS 30-165-Sil boolit; others might find this useful to develop their own start for WC860 or WC872 using the RCBS 30-165-Sil Boolit.

Mustang

[MUSTANG]

Tested some additional loads of WC860 in the M1a today. One string was with 43 Grains of WC860 on top of 4 Grains of H4895. The other String was 43 Grains of WC860 over 4 Grains of Unique.

Comparison of Groups appears in the attached photo.

[I](Tried to embed the photo here, but the system is not allowing me to do that - could be the update that is scheduled for the Cast Boolits Web Site associated with PICS).[/I


Load Data Sheets for both strings are attached as a PDF with two pages in it.


Mustang

[madsenshooter]

So a lower SD, meaning more consistent velocities, doesn't necessarily make a smaller group. Working up slowly with the kicker, while maintaining the same total charge might be interesting. Of course one will come to the point that the compressed kicker alone produces too much pressure for the alloy, or so it seemed to me, as I increased the kicker in the 6x45. Once up to the point that lead blows back on the neck of the case, game is over.

[Jim]

Many years ago, when we were still at Shooters. com, Buckshot did a good bit of testing with WC860 and posted his results. I don't remember the caliber he used, but I do remember he could not overload the cartridge. He mentioned that for every grain of powder he added, there was a steady increase of velocity.

If I'm remembering right, he said he got to the point of compressing the powder so much, he actually bulged a case to the point it wouldn't chamber.

I've been through a coupla' 8 lb jugs of 860 and found that I got my best results at a compressed charge and lighting it with a magnum primer. This is the sleepiest powder I have and usually use it to make 'bangin'' ammo. Of the three milsurp rifle powders I have, 860 has turned in the poorest results for me. Like 7383, it leaves a lot of unburnt powder in the barrel until you get it up to the pressure at which it likes to operate.

[Balkandom]

Just throwing my 2 cents in here. I know the M1a well but cast bullets poorly. I do know 860 though...it runs well in my bigger belted magnums. It is a HELLA slow burning powder. Good for a 300 or 338 WM, acceptable for an '06. outstanding for a .375 H&H, but it's really too slow to get what you need out of an M1a.

Some powders just will not do well with some cases in some guns. I think you've run into that.

[MUSTANG]

Tried a little variation on loads today. Shot 4 strings of 5 Rounds with WC860, increasing the"Kicker Charge" slightly for each.

My previous loads of WC860 in the M1A had occasions where some shots would short cycle, the brass would not fully extract/eject and pick up a new cartridge; instead when this occurred the case would extract and ride on top of the next round in the Magazine backward, and then move forward crushing the case mouth on the receiver. No short cycles were experienced with today's load variations.

Previous groups fired using 43Grains of WC860 and 3 Grain Kickers of H4895 or Unique had groups of 4" X 2.25" and 3.75" X 5.5"

Today's 5 Round groups measured:

2 .875" x 3" 8.625 sq.inches (RCBS 30-200-SP with 44 Gr. WC860 over 5 Gr. Unique)
Average Velocity 2082 & Standard Deviation of 6

2 .75" x 2.5" 6.875 sq. inches (RCBS 30-200-SP with 42 Gr. WC860 over 6 Gr. Unique)
Average Velocity 2076 & Standard Deviation of 14

5 .25" x 7.5" 39.375 sq. inches (RCBS 30-165-Sil with 44 Gr. WC860 over 5 Gr. Unique)
Average Velocity 2170 & Standard Deviation of 8

2 .5" x 5.5" 13.75 sq. inches (RCBS 30-165-Sil with 42 Gr. WC860 over 6 Gr. Unique)
Average Velocity 2225 & Standard Deviation of 14

All Cast Boolits were sized at .310 with Aluminum Gas Checks. The driving bands on the 200 & 165 boolits actually measure .309 using Air Cooled Wheel Weights in casting. The.310 sizing lubes the boolits without sizing the driving bands, but does size/seat the gas check at .310.

The RCBS .30 Cal, 200 Grain Cast Boolit performed better in the M1a than the RCBS 165 Grain Sil boolit did, particularly when comparing on a group square inch basis. I still have not achieved a level of accuracy I am looking for, although they may meet "Man of Angle" goals for some using a cheaper powder such as WC860, or similar burn rates such as WC870 or WC872.

As I move forward on WC860 in the M1A, my future efforts will focus on:

(a) Increasing the Cast Boolit Driving Band size to .311 by initially "Beagling the Mold", and lapping if that works.
(b) Increasing the "Kicker Charge" by a few grains, 1 grain at a time (While reducing WC860, cases are totally full)


Mustang