Developing 6 MM 350 yd accurate Load pt1

[vzerone]

That is the beauty of 'Bamalloy'. Sticks together and keeps on spinning. I am trying t get it up to 3100fps, we'll see

Well what about all the brouhaha by another member over that there is a rpm threshold? You and bama seem to have laid that to rest.

[OS OK]

The threshold still sticks for very good reasons...but...there's a couple of differences in this post.

*he is using a strengthened matrix Pb other casters only read about
*he obviously knows how to cast an inclusion free boolit
*he kicks it downrange with the proper speed powder
*this is spitwadding here but I would imagine that in his reloading he's very meticulous

There are always exceptions to any set of rules.

[vzerone]

The threshold still sticks for very good reasons...but...there's a couple of differences in this post.

*he is using a strengthened matrix Pb other casters only read about
*he obviously knows how to cast an inclusion free boolit
*he kicks it downrange with the proper speed powder
*this is spitwadding here but I would imagine that in his reloading he's very meticulous

There are always exceptions to any set of rules.

Why didn't those exception apply to others in the past? They did it without powder coat and different alloy. You're right about one thing, casting good bullets.

[Willbird]

Kind of a zombie thread but interesting. One thing that comes to mind is that the powder coat allows bumping noses up into the rifling more so that an unprotected bullet nose. Or for clarity, it helps prevent ill effects from the noses bumping up during the firing process.

Bill

[shortlegs]

tagged

[Phantom30]

Bama says that the bore rider design is for alignment and resultant accuracy. He also says that don't worry about the fit, obturation will push the thing to fill ever crack in the chamber, throat and bore as it pushes through the barrel. He has a recovered PC bullet with rifling imprints all the way up the bore rider section. In bolt guns all is well with these designs seated with neck tension only. I am having a problem with them be smashed by the force of chambering through the feed ramps etc., in an auto feeder LR6CM. Its not the bullet, Bamalloy is tough and hard. Still working on that, might use a lighter gas setting or buffer spring, also using a light lee factory crimp to keep the bullet from being pushed back into the casing. Lee crimps have been shown to keep the PC on the bullet as opposed to Hornady roll crimps. These are not cannalure bullets, smooth sided relatively high BC PCs

[Larry Gibson]

Very interesting quarternary alloy.......any 350 yard targets yet?

[Phantom30]

Bama has a good grouping with his 6x45 at 350 yards on display in his earlier thread with 350 yards in title. I am still working the powder load for the 6CM
Bama is good at cooking the water out of CuSO4 5H2O in his alloy pot and then grinding the crystals in. I don't have that skill yet so I rotometal it with 5.25lbs pure Pb, 1 lb super tough Babbitt for the Cu and Sn content, and 1.6lbs of super hard. Ends up 81% Pb, 11% Sn, 7% Sb, and hopefully 1% Cu. You apparently don't need that much Cu but keeping it in solution at temperatures below Cu melting point is necessary to get the tough finer matrix in the alloy. Rotometal Babbitt is an expensive route, but for experimentation acceptable. I have fired it at 2960fps which is same muzzle as factory ELD match, but I had some primer flow around the firing pin indentation so I need to back off some or pick a better powder. The bullets range between 103 to 125gr depending on which Arsenal mold variation you choose. Have been using H1000 and IMR 8208 XBR at around 1MOA 100 yards. Like the IMR it takes only 3/4s the volume in the casing. Good safety for accidental bullet push in during Chambering. I am going to try H4350 next.

[Phantom30]

The picture shows Bama's smash test of a water dropped bullet cast from Arsenal PC243-113-NR-BR-GC-AL mold and PC'd with Smoke's Bacon Grease. The mold is a PC specific design for 6mm with a 0.241 drive band, 0.0625 nose radius (NR), a 0.233 bore rider (BR) section, 0.233 gas check (GC) step and using Bamalloy to ensure a tough-hard bullet capable of auto loading (AL). As shown the PC bonds well with this alloy and increases the drive band to .244, and bore rider to .236 inches. Bama said his ballpeen hammer bounced off so he had to hammer it with a 3lb sledge. This actually is the Rotometal approximation to Bamalloy. The piece broken off and standing on edge shows an extra fine grain. Total bullet weight is 116gr. Idea is make it resilient enough to survive feed ramps and chambering without impacting concentricity. The mold casts undersize from most perspectives but this is necessary. Both cast drive band and bore rider are sized after GC is mounted and then again after PC applied. A lot of work but then the objective is a long range high speed accurate round.

[kens]

What kind of groups will that alloy hold in the 1:8 (fast ) twist at that velocity?
Got any pics of 350 yard groups?

[Phantom30]

This is Bama's shot group from old thread on this topic. The ones above will be shot in about 3 weeks or so. The target velocity is 2960 in a 1:7.75 twist

I don't want to trash Bama's thread but the picture above is a 100 yards powder load development run using the non-AL mold variants using Bamalloy. The mold designs are shown along with the target data. As expected the series climbed the target as the powder increased. The shooting was sloppy, I was more interested in the primers than the accuracy but it shows they are not all over the place. 24" 1:7.75 twist