Optimal Weight for supersonic 300 Blackout?

[Moonie]

I like Lancer mags, had issues with PMAG's with the big 245/247gr boolits, I understand the newer gen3 mags work better with them.

[Michael J. Spangler]

OK some more updates. So I seated some bullets to a "normal" length and shot them last night with good results function wise.
I did not test for accuracy or even shoot on paper.
I did get leading from about 1/2 way down the bore to the muzzle.
My guess is that the alloy is too soft and is skidding, once it goes a ways down the barrel it's lost most of its hi-tek coating and leads like crazy.
So back to the drawing board.

I'll be casting some harder bullets this time around. I think I'll be done with the 311365 and try my hand at the Lee 309-150f now.

I do have some 180 grain spire points cast hard, with some blue lube and gas checks on them. I might load some of them next for giggles

[Texas by God]

A member here provided some NOE 170 RN that I'm going to try with 296 powder and see how things shake out. They are full nose profile so I expect deep seating will be a must.
Best, Thomas.

[popper]

i didn't have any luck with HiTek in the BO as yet. I'm running the 31-142C PCd in the rifle. I got decent results with 31-172C PB and 31-184C GC in the BO pistol. Actually got these for the 30/30. Did decent @ 50 with a scope and @10 with R.D. & SeeAll. Unfortunately the handguard keeps coming off from the bolt slam. Sort of mucks up accuracy tests - fire a couple then push it back on. Top end loads for the weight, BLL as lube. SA marked are SeeAll but couldn't get check weld so just 'guessed'. Riser should come in Monday, just figure the pistol is a 50yd gun anyway. Alloy is pretty soft 'mystery' metal I've been playing with, probably <1% Sb.
Attachment 190386Attachment 190388

[Michael J. Spangler]

That's pretty soft.

I think i need a harder alloy.

What are the rest of you running for alloy?

I'm going to empty the pot and fill it with 2/3/95 ish alloy that I have. Should make for a hard bullet after water dropping from the last hi-tek coating

[flyingrhino]

The lee 155 has been a good performer in everything I've put it in. If your having trouble keeping it on the target, check your size to make sure it's big enough ans your alloy is hard enough.

I agree. I push these to 1900 fps and have excellent accuracy. That's 3 shots at 50 yards. 17 grs IMR 4227, clipon wheel weights. Sized to .309

[Grayone]

Ok so here are some results with the 311365.
As suggested I was setting them with a driving band 2/3 of the way exposed. Hoping to get close to the rifling and gain accuracy. I have had some issues with feeding which I thought was due to the gas system being carbine and the adjustable block adjusted 60% open to run smooth and flat with my J word loads.
Well I tweeted my loads a little hotter and still had issues. Upon finally loading some mags near full I found that the cartridges were binding a bit and hard to load. After some inspection I noticed that the full diameter of the 311365 was riding on the guide grooves at the front of the magazine that would normally keep the 5.56 cartridges staggered properly to allow proper operation and advancing or double stack cartridges. Well with a damn near straight case and a 30 caliber bullet seated long they tend to rub on said grooves and drag.
The bolt would operate and close before the next cartridge would advance in the magazine. Once I was down to 3 or 4 cartridges it would stop binding and cycle fine. Now and then the bolt would catch halfway on an advancing cartridge and jam.

So after slowly single shotting my way through 100 rounds I quit for the night. Tonight I loaded 5 dummies to the crimp groove. I'm guessing about .100" shorter than what I was previously loading.
I loaded them into the magazine without any drag or binding. Even when pushing them down haphazardly to simulate a fuller magazine there was binding at all.

Good news is that this bullet is still shorter than a 208 amax which has a ton of data available. So I should be able to creep up on amax data and not be playing on the hairy end of pressures due to deeper seating bullets raising pressure.

Lets ts see how it works next week.

I also grabbed a lee 309-150-f in hopes of making that my go to bullet. I think the 311-155 is a better design for the short necked cartridge but it lacks the flat point which would be better on game.
Guess we will see how the 150-f works.

Very interested in your results with this boolit in the 300BO.

[Michael J. Spangler]

I’ll have to dig back into my notes

[imashooter2]

I’ve had good luck with the Lee C312-155-2R sized to .310 with White Label Carnauba Red in Lancer magazines.

The C309-150-F fed, but was gouged by the locking lugs pretty heavily.

[popper]

BO AR carbine, 145gr @ 50 yds, about 2k fps. Alloy is PCd ACWW equal. Middle is 30/30 that did well with same PB bullet.

[P Flados]

I have spent a lot of time working with the 300 BO and cast with most results being very disappointing. My son and I currently have two uppers in this cartridge and we have a couple of barrels that were pulled after nothing but frustration with cast. Most of my loads have been WC 680, but I have recently been trying some H110. Note that they all shot ok with j words.

I worked with the Lee 150 and Lee 170 a bunch but never got satisfied with feeding in an AR. We have used a number of different magazines including modified P-Mags, 350L magazines and a 300 BO specific P-Mag. I also did feed ramp improvements that helped other bullets but not the flat point Lee stuff.

I eventually made my own custom BO specific 156 NLG bullet. The profile is based on a bunch of dummy testing to find a shape that would feed best in an AR with the least amount of damage to the nose. In actual shooing it feeds great and shoots decent. However it does result in lead residue buildup in the bolt. This is due to the plain based that gets gas cutting of the the base as it passes the pressure port. I am pretty sure this gas cutting is not consistent one round to the next and it results in less accuracy.

I then got a Lee CTL312-160-2R mold (they drop at 165) so I could try gas checks in the BO. I have been distracted (I got into primer reloading) and have not really finished working up loads with these bullets. I think they will shoot at least as good as my custom 156, but early testing did not seem to indicate that any improvement would be much. I have tried seating the checks before and after PC. They do feed pretty good.

I really want 2 MOA, but may have to settle for 4 MOA.


Custom 156:


Lee CTL312-160-2R:

[1006]

I have not tried cast in my 300. Primarily, because of the twist rate, and my aversion to discovering lead to be cleaned out of my barrel-I just do not want to mess with it in this caliber, or in an AR.

I have experimented with copper plated Swaged 30-30 bullets, and they flew apart at velocities 1850 and greater. They are, however, very accurate up to 1850fps with Alliant 2400.
The experiment left me preferring slower heavier bullets when cast or plated is used.

I am using 17.2 LilGun and a Federal Small Rifle primer with a Hornady 150 fmj Boat Tail: getting 2005fps with good 100yard accuracy in a 16inch AR.

I have used the same load with a Fiocchi Small rifle primer; the speed dropped off by 50fps (1955fps).

If I were shooting cast bullets I would go up to 170 grains, due to the 1/8 twist that I have.