New MP Blackout-design

[Spindrift]

Schultz & Larsen .30-06, 1:10 ROT. These were the PB bullets. Nuclear medicine mystery alloy, water quenched BHN about 15. Sized .310 in my Lyman 45 with my standard (soft) home-brew lube (two-stroke oil, atf, high-temp grase, lithium grease, moly grease, beeswax, a little soap, paraffin wax, a little microwax and a hint of lanolin). Never done a pound cast, so I’m pretty thin on chamber details...... The gun, lube, powder and alloy performs very well with sub-loads with shorter bullets (like the NOE 311284-clone).

The plan is to see if it will group with the powders I have available in the relevant burn range. The rifle usually shoots well with .310 bullets. If I can’t get it to group with subsonic loads (which wouldn’t be entirely unexpected), I’ll PC them and try at higher velocities.

My plan with the GC bullets, was to powder coat then, and try them at near full power. But I’ll give the GC-bullets a try in the subsonic level as well

 

[Spindrift]

At least you're back to shooting!

Ohh, finally!

Elkins, the socom looks like a great cast bullet cartridge!

 

[Ian]

Dang, Spindrift, how you're loading them ought to work just fine, I don't know what else to suggest other than PC them and seat a little deeper so they'll chamber.

 

[Ian]

Me likes the .458 too!

 

[Tomme boy]

So what is the purpose of this bullet? I don't get it. The design that is.

 

[Ian]

300 BLK subsonic bullet for 7-8 ROT AR-15s.

 

[popper]

"This is a 300 blackout specific Boolit and is designed to stack nicely in a magazine with little or no bulge." There have been several attempt to make heavy (heaviest is 247gr) subs, Taco has the best. Forget if Milhec or NOE making it.
Several have tried the wasp waist, didn't work. This one looks like a bore rider with mid section slightly smaller so only nose part 'jams' for alignment.

 

[Ian]

It is not wasp-waisted. Should have two or three gentle tapers forming a concave nose from ogive to front band, but the smallest point is the ogive. A couple swipes with a file on the guide ribs cures plastic magazines of the bulge, and Magpul has been making 300 BLK magazines for some time, I have some and they are good.

 

[Spindrift]

The apparent «wasp waist» is only a trick of the light in the photos, the nose is a complex-taper nose, like an elongated MP-SIL.

SORRY GUYS, I have mislead you. It actually IS wasp- waisted . This is more than a little embarrasing, my initial quick assessment of the bullet was a little TOO QUICK...

In my alloy, the driving bands are .312. In front of the front driving band, I get .308. It tapers to .293 (!), and the increases to .300 in the last part of the nose....

The lack of technical information on the MP web shop is more than a little annoying. Well, well; I guess I`ll just see what I can get out of the bullet, anyway. Just loaded some rounds for my next range trip- PB, and GC.

 

[Will]

I have this mold but haven’t cast with it yet. What do you think the purpose of the wasp tail design was?

That’s one thing that sucks about MP Molds. You rarely get to see a drawing of actual dimensions.

 

[popper]

bore rider with mid section slightly smaller so only nose part 'jams' for alignment.
People are having trouble with bore rider designs needing to be nose sized. This one allows a small portion of the nose to get sized. Other solution is like taco did, undersize the nose so PC will build it up. With all the inertia of the heavy IMHO the undesized part is going to bump up real fast with soft alloy. If the tip engraves the mid part will have a lot of torsion on it.

 

[Ian]

Measure the mould itself, it shouldn't be that way, at least it wasn't all those years ago when being discussed. Sometimes long, skinny bullets shrink in the middle and become wasp-waisted after cooling, refer to a lengthy article on the Mountain Molds forum titled "shrunken bullet syndrome" or something like that. 45 2.1 doesn't publish dimensional drawings but does a lot of research before arriving at a design for a certain purpose, so the buyer has to take it more or less on faith that the bullets will fit and function correctly, for example he used measurements from over 200 chamber casts to arrive at the nose shape of the 30 Silhouette and a few others, likely including this one. Then again I could be totally wrong and it IS a wasp waist design, although if it was I'd think the nose would have a significant notch for the guide rails of the AR-15 magazine, it makes no sense that Bob would design the middle of the nose to float in space for no other reason than to not touch anything.

 

[Spindrift]

@Ian ; I found it a bitt difficult to measure the mould directly, but measurements I found indicates it actually is wasp-waisted....
Shot a few groups today, with the Schultz &. Larsen .30-06. Bullets lubed and sized .310, and not from the cull- jar this time
Two 5- shot groups with the PB bullet around 2 MOA. Still oval holes. But it might be possible to salvage this situation, 2 MOA is not disastrous for a «first date».
The GC bullets where also lubed and sized .310. Holes were oval with these as well. Universal 8,5 grs produced a 1,5 MOA group. With N32c, 10,4 grs, I pulled a shot to the left (called flier). The other four around 1 MOA (photo).
TEsted two supersonic loads, Norma 200, 23-24 grs. Just sub-2 MOA. Holes were round with this load.

The bullet might not be entirely stable at low speeds, but it still seems possible to get some accuracy out of it. This will be interesting, for me at least

 

[Ian]

If it's truly wasp-waisted like Popper said, I'm really shocked. If I had a dog in the fight I'd see about contacting the designer, but I had my doubts about this one from the start and declined his suggestion to get one along with some others of his which are well-proven. Oval holes don't always mean it won't group, as you're finding out.

 

[Spindrift]

contacting the designer

Actually, the designer contacted me by PM, on another forum with some advice (much appreciated). I´ll try to render the gist of it. The «wasp waist» is a minimal relief cut, to allow the full use of the magazine. It will bump up if you use a suitable alloy, like 20:1. Further, he suggested trying different powders, and sizing .311.

I shot some more groups with both PB and GC bullets today, in the S&L 30-06. Lately, I`ve given a «second chance» to a scope I had lying around. Now I remeber why I didn’t like it much, it is impossible to get a clear picture at 100m.

Anyway, accuracy was reproducible at 1,2-1,5 MOA with subsonic loads, still a bit oval holes. For me, shooting from prone with a hunting rifle, this is not bad. I shot a few PB-PC over the magnetospeed. Velocity with PC was exactly the same as with lubed bullets. PC next.
The coming autumn, a much awaited change in our gun laws will take effect (delayed due to covid). Them, I’ll get a Bergara take-down break-action in 300BLK (I had a plan when I bought these BLK- moulds )

 

[Ian]

Interesting Bob made them with a relief, I would have lost money on that bet. I don't understand what powder he thinks will bump the nose that far forward of the taper and still allow subsonic use without riveting the base up before the throat.

 

[Will]

Interesting Bob made them with a relief, I would have lost money on that bet. I don't understand what powder he thinks will bump the nose that far forward of the taper and still allow subsonic use without riveting the base up before the throat.

I thought the same thing. If a fast burning powder is needed to bump up the nose on initial launch you can guarantee everything behind the nose is going anywhere you allow it to.

I still haven’t cast a bullet with mine but this is not looking good. I received a shipment of SOWW lead +3% SN today. I had planned to cast some of these with this alloy.

 

[Spindrift]

Don’t despair, Will!
Remember, my use of the bullets here (in a 1:10ROT 30-06) is outside the intended use of the bullet. The fact that a little yaw is present, is no big surprise. I’m sure it will stabilize nicely in a BLK, like it was designed for.

The relief cut? Not sure it matters much. This design does not rely on nose support, it seems to have nice self-aligning properties.

And while these groups are not «Ben-groups», they’re quite good «Spindrift- groups», for a new bullet that I have shot maybe ten groups with. I still have a lot to learn in the art an science of bullet casting. The accuracy potential of this bullet is probably excellent. I really look forward to shooting it in a 1:8 ROT, some time in the future......

 

[Spindrift]

I tried some BLK-PB, coated bullets made from my new range- scrap BHN12 alloy. Still using my S&L .30-06, 1:10 ROT. Viht N32c 10,4 grs gave the best 5- shot group, at 1,1 MOA. Holes are not perfectly round, but I’m not complaining about the accuracy! One day, I must find out what this bullet and I can do from a shooting bench (and a scope that is a bit sharper than the one currently mounted). It would also be interesting to test it in expansion media.

 

[popper]

Actually may not be a stability problem but 'bent' projectile! If nose engraves, base engraves but mid doesn't then you've immediately twisted (stress) it before firing and definitely when fired. Short neck of 06 (& BO) kinda forces that.