New moulds.....again!

[Spindrift]

I have a weakness for .30- cal moulds, I must admit
Two new MP- moulds were broken in today. After a (too) quick whipe with acetone, and a couple of heat cycles in the toaster oven I tried to cast some bullets. At the end of my casting session, nice bullets started to show up.

On the left, MP311-440 (a.k.a Hammer o’ Thor). Nose alternatives are large HP or flat point. HP is 150grs in my alloy, .314 driving bands and a nose taper from .303 -> .300

On the right, 311-140 («Sledgehammer»), I think it was originally designed for the .32 magnums. Available in .314 and .311- mine is .311, 4 cav. With the short penta point, they weigh 130grs in my alloy. The short pentas don’t retain the bullets while casting, so you can drop them without flipping the mould- very convenient.

Now, the fun begins!

 

[fiver]

nice.
is it just me or is MP starting to get a little carried away with the lube groove lengths?

 

[Ben]

fiver,

I'm with you , those are " honker " lube grooves.

Ben

 

[Ian]

That would be Bobby Kell, Jr. at work there.

 

[CWLONGSHOT]

I like that left one!!

 

[Spindrift]

I like it too, CW! Very curious how it will shoot, of course.
I agree, the lube grooves are generous. The MP-designs I have tried so far, have worked extremely well, though.

 

[Spindrift]

So, the «honkers» have had their fill.... hoping to shoot them this weekend. Will try them in the .308 first.

 

[Spindrift]

loaded a few cartridges for my Howa .308. When loaded to light jam fit, the Sledgehammer barely has any bullet grip. For the .308, this bullet probably works best with PC (jump tolerance). In the .30-06, the lube groove is in the neck

The «Hammer of Thor» looks more promising for the .308. We’ll see.

 

[Wasalmonslayer]

Ian is correct Mr Kell like tons of lube!
In today’s world I think those grooves might be on the large size with the high quality lubes we have either home grown or bought.

 

[Spindrift]

They certainly carry more lube than necessary. I’ll just shoot them a little and see how it works. There are other lube options I could try, of course; PC, or tumble lube only.

 

[Wasalmonslayer]

Mr Kells designs do shoot well no doubt.
I have several of them

 

[Ian]

They certainly carry more lube than necessary. I’ll just shoot them a little and see how it works. There are other lube options I could try, of course; PC, or tumble lube only.

Actually.....yes and no. If you use the alloy, the powders, and the lube formula that the designer does, they carry just enough lube. If you use a grease-enhanced lube (depending on which one), they need a whole lot less but still work fine. Where you run into problems is filling the grooves with a thick, hard, non-viscous lube which plays hoc with your bore condition (purge flyers, hydroplaning, lack of jettison/partial jettison at medium to low velocities). If you use a soft, instantly-melting lube like the original NRA formula (equal parts paraffin, Vaseline, and beeswax) and fill the main groove(s) and space above the gas check, you may have better luck than with hard, stiff, high-temperature lubes, especially at lower velocity.

SL-71B lube made with soda soap, beeswax, paraffin, microcrystalline wax, paraffin oil, and castor bean oil is soft, feathery, flows well under pressure (doesn't have to actually melt to work and flow out) is insensitive to amount applied to the bullet and works equally well with huge grooves or tiny grooves at any muzzle velocity you choose.

 

[fiver]

since we are talking about design features.
we might as well look at those angles he has on the drive bands too.

there are a lot more little nuance features to a bullet, than that looks right, how big it's gonna pour, or is the nose gonna lightly engrave.

the drive band angles and depth affect how the alloy that your rifling is gonna displace will move from one place to another.
it can also lock in little bits of lube, or create little imbalances in the weight distribution when all of that takes place.
to a lesser degree they can even affect the engraving spike and slightly modify the powder burn.

 

[Ian]

Very steep-sided lube grooves are a bitch to cast but shoot very, very well.

Many of those little features that make the difference between an ok bullet design and an outstanding one have to do with the dynamic fit more than the static fit and one has to play a little movie in their head (and understand how their particular alloy mix is going to move around and what shape the throat has to make that metal move) to see how the bullet will deform and where it does and does not have support during the engraving process.

Probably 99% of the cast bullet shooters out there today will roll their eyes at the above and say "you don't have to make it that complicated"....but sometimes you do. If you don't think you need to understand and get all this right, take your nose-rider Linotype bullet, pack some Alox lube on it and size to one thousandth larger than groove diameter, ramp it up with a starting jacketed load of IMR 4895 and tell me how that works out for you. Most of you already know the answer.

 

[Ian]

it can also lock in little bits of lube

New esoteric term: "lube staking". What happens to a hard lube ring around the bullet when the engrave tails coming off both sides of the driving bands clamp the lube into the groove. Good if it all stays, bad if only half of it stays. "It (lube) all either needs to stay or go"----Fiver.

 

[Spindrift]

I haven’t graduated to the SL-71B yet, lacking some ingredients
My home-brew is pretty soft, and has worked well with the MP311-180, and the MP312-159- which also have pretty large grooves. I’ll keep your concerns in mind, maybe I should tweak my formula a bit. But as long as it works....

Casting with the Hammer of Thor was pretty easy, despite the deep and steep groove. Just flipped it over, tapped the hinge bolt while opening and gave a gentle nudge at the HP guiding pins if needed.

An interesting feature of the «Hammer», is the displacement groove between the nose, and the front driving band. Maybe this affects the bullet’s suceptibility for hydroplaning/purge- phenomena?

When I checked the maximum COL in my .308 with the «Hammer», I got faint landmarks on the nose and marks of circular engagement on the front driving band. Which is promising, in my book

 

[Ian]

Lyman/Ideal, which originally made that basic bullet design, called that a "scraper groove", the theory being that any junk in the bore got collected there instead of being run over as they theorized an ogival nose would. I suppose it still works that way, but copper gas checks make better scrapers than lead bands.

Bob has posted his lube test many times on various internet boards over the years. If it passes his test, it will work on his bullets. He can be found at the CBA forum and if you can't find his description by reading back through his posts from the last few years, message him.

 

[Spindrift]

The initial groups in my .308 were unimpressive, 2,5-3 MOA. Only a couple of groups, yet- and plenty of room for refining.
Today, I shot some of the «Sledgehammers» in my Schultz&Larsen 30-06. «Static fit» was promising, as I saw landmarks, and signs of circumferential throat contact on the front driving band.

Shot two groups with 18-19 grs N110. Both were- unsensational, but not bad either. I think there is potential in this combination.

 

[Ian]

First I'd like to express my appreciation for how you follow up on your older threads. Reading about your shooting results is both interesting and helpful.

Do you have any beeswax, paraffin wax, and petrolatum/Vaseline? Canning paraffin and petrolatum should be easy to get. Make a small batch from equal parts and give that a try next time you get ready to have a go with the 311-440 bullet.

 

[fiver]

going the old NRA lube?