150 gr. Cast Bullets for the .30 Carbine Blackhawk

[jski]

This is basically the same question asked in a 2009 posting. But with one major difference, instead of the targeting the M1 Carbine, I'm looking at the Blackhawk. This should provide much greater margins for safety.

This stems from a conversation I had with my Nevada gunsmith (for the purposes of this conversation let's call him, Nevada Smith) who's smithing my .30 Carbine Blackhawk. We were discussing the .30 Carbine cartridge and, well, all rimless autoloader cartridges. The point he made was interesting.

Without the ability to roll crimp these cartridges, because they're headspaced on the case mouth, you're really not getting all you can from these cartridges. Simply put, the harder it is for a bullet to escape the case, the more tightly held the bullet is, the more completely the powder will burn in the chamber and barrel. And the higher the pressure level will get.

Now here's the interesting point: Nevada Smith stated that the best way to compensate for this is to load heavier bullets. Hence the premise of my question: Are 150 gr. cast bullets practical for a .30 Carbine Blackhawk?

BTW, Buffalo Bore offers a 125 gr. hard cast round for the .30 Carbine.

[MT Gianni]

Probably the best candidate would be the 311440. It has almost no nose taper so your weight would be the shortest bullet possible. No idea about reducing powder space that much.

[Outpost75]

The .30 Carbine Ruger has a one turn in 20" twist of rifling and I would not expect satisfactory results with bullets heavier than about 130 grains. I use the Accurate 31-120TG in mine with a compressed case full of IMR4227 (about 14 grains) with fine results, bullets being cast 50-50 linotype and plumber's lead (about 13 BHN) and sized .311". Nose north of crimp groove is .310" max. diameter with tolerance negative to fit cylinder throats.

Attachment 199716

If you wanted to load a heavier bullet the Accurate 31-134D, but having its diameters tweaked smaller to .310" fit the .30 M1 Carbine cylinder dimensions, rather than the larger diameters for the .32 H&R Magnum Buckeye Special, for which it was designed, would be a reasonable choice and would be as long as fits in the Ruger cylinder when seated in .30 Carbine brass. Probably won't feed in the US carbine, whereas the 31-120TG does fine there.

Attachment 199719

If you wanted to REBARREL your .30 Carbine Blackhawk to adequately stabilize heavy bullets, you would want a faster twist of rifling. In my experience a 14" twist will stabilize a 155-grain bullet subsonic from the .32 S&W Long, using a case full of IMR 4227, compressed, and the Accurate 31-155D bullet. Its .495 head length is too long to fit into the cylinder, if loaded in the .30 Carbine brass, but it works just fine in the .32 H&R Magnum, but is only marginally stable in a 16" twist and needs a bit more. My late 1960s Colt Police Positive .32 Colt New Police shoots it very accurately from its 14" twist, but, of course, this is a +P+ load I would not recommend for frequent use, having tested it only for academic curiosity.

Attachment 199720

[jski]

I believe the point Nevada Smith was making is that the work required to push the larger bullet through the barrel will require more time and hence give more time for more powder to burn.

[Outpost75]

I believe the point Nevada Smith was making is that the work required to push the larger bullet through the barrel will require more time and hence give more time for more powder to burn.

That is true, but if the barrel twist is inadequate to stabilize the heavier bullet keyholing bullets won't be very accurate.

My .30 Carbine Ruger maxes out with Accurate 31-134D sized down to .311".

[jski]

For the bullet I went with Montana Bullet Works:

308, RCBS 82019, 150gr, FN-GC
Alloy: Linotype, BHN 22
Diameter Range: .308"

I know Linotype is suboptimal here but the other choice was: MBW heat treated, BHN 22.

I must admit the Achilles heel to this experiment may be the twist rate: 1:20" RH. Not sure if this is enough the stabilize this bullet.

Surprisingly, the only other Blackhawk with a 1:20" RH twist rate is the .41 Magnum. The .45 Colt Blackhawk has a 1:16" RH twist rate.

[Outpost75]

Standard twist for the .30 Carbine is 1:20". That is the way Ruger makes them and so-stated in their catalog. I can tell you from experience, that the 1:20" twist will not stabilize the 150-grain RCBS bullet.
You can't drive it fast enough to work acceptably.

Accurate 31-134D when dimensioned to .311" bands and nose .310 with tolerance negative WILL work.

You need to pin out your cylinder throats to determine correct bullet fit. No avoiding this if you want the gun to shoot well. Groove diameter of the barrel means absolutely nothing. My Ruger .30 Carbine has .310 cylinder throats, a .308" bullet is too small and WILL lead.

Linotype alloy is unnecessary in terms of strength, because you will be limited in case capacity and won't generate enough pressure up upset the alloy. But RCBS molds being dimensioned the way they are, being based on linotype alloy, you are essentially doomed to failure. RCBS molds cast hopelessly undersized with anything other than linotype, and linotype is too hard for this application and unnecessary.

You would be MUCH better served by a production mold of proper dimensions to cast .310-.311" diameter from a suitable alloy such as 50-50 linotype and plumber's lead, or wheelweights +2% tin, which can be very readily obtained from Accurate, LBT, NOE or Mountain Moulds. The RCBS mold is a waste of money and source of frustration....

[jski]

I sent my Blackhawk to Nevada Smith asking if I needed to have the cylinder throats bored out any or the forcing cone enlarged. Because I tried some .309" diameter bullets and they simply wouldn't fit into the cylinder.

Nevada Smith said stick with .308" bullets, which is what I've done to date with good success.

My wife's M1 Carbine with her at the trigger is a nail driver with Montana Bullet Works:

308, RCBS 82009, 115gr, RN-GC
Linotype, BHN 22
Diameter: .308"

It's also a winner out my Blackhawk.

[jski]

I bought 100 of Montana Bullet Works finest 150 gr. .308" bullets, so I'll continue forward with my experiment. I assume the odds are against this succeeding but failure is sometimes the best teacher.

[jski]

BTW, an interesting PDF showing fastest to slowest burning powders:
Relative Burn Rates

I'm surprised to see H110 in the middle of the pack. Thought it'd be among the slower burning powders.

[Outpost75]

I bought 100 of Montana Bullet Works finest 150 gr. .308" bullets, so I'll continue forward with my experiment. I assume the odds are against this succeeding but failure is sometimes the best teacher.

The Bumblebee never studied aerodynamics at Pensacola, who knows, your gun may not have gotten the memo.

Doesn't hurt to try. Your cylinder throats ARE tight, but with bullets which FIT should shoot well.

Please report your results. My revolver, made in 1978 is different from yours and likes .310-.311 bullets, cylinder came that way.

[Larry Gibson]

Keep in mind the US milsurp spec for .30 Carbine bullets are .307 - .3075.

Larry Gibson

[reddog81]

BTW, an interesting PDF showing fastest to slowest burning powders:
Relative Burn Rates

I'm surprised to see H110 in the middle of the pack. Thought it'd be among the slower burning powders.

H110 is at the very end of the pack for handgun powders. IMR 4227 is right after it and then every other powder is a rifle powder(at least I don't recognize any of the slower powders to be handgun).

[Nueces]

Google for an article called "Paco's Long Range Load (for the Ruger 30 Carbine)", by John Goins (Beagle here). The article is in pdf form, thus easy to download.

Beagle describes his research in detail. The heaviest slug that achieved accuracy was the Lyman 311440, as mentioned above.

[jski]

Outpost75, my Blackhawk is vintage 2016. I sent Ruger a 2003 .30 Carbine Blackhawk that had issues with the cylinder locking tightly on one chamber when the gun was cocked. Their solution was to send me a brand-spanking new Blackhawk.

[Outpost75]

Outpost75, my Blackhawk is vintage 2016. I sent Ruger a 2003 .30 Carbine Blackhawk that had issues with the cylinder locking tightly on one chamber when the gun was cocked. Their solution was to send me a brand-spanking new Blackhawk.

Can't complain about that! If the .308 cylinder throats are not tighter than groove diameter, gun will shoot!

Sounds like yours is optimized for jacketed factory loads. Cast sized to proper diameter to fit cylinder should also work well.

[beagle]

I beat this one out several years ago in that article. Yes, the 311440 was the best as I recall and I had a 311440HP that I used. Another if you can find it is the 7.62X 39 130 grain RCBS. As I recall, either of the 30-150-FN bullets shot al right as well (both PB and GC'd). According to Paco's article, and I found this to be true, there is a threshold of as I recall of 1400 FPS above which, these long bullets will be accurate. Now, you're stuck with three variables: pressure, overall cartridge length and 1400 FPS. With all three bullets, we can "fudge" a little on overall length as they seat below the chamber mouth. The key is to seat them out a little and here we run into another problem, the throat. I'm almost sure Paco re-throated his as he mentioned no problems. Not wanting to do this, I sized the first ring on mine to .308" by sizing nose first only the top ring. This let me seat them out, cleared the cylinder mouth, lessened the pressure a little and still achieved the magic threshold. They're accurate up to 100 yards with no flyers detected and might make a pretty good deer load for small white tails. Dig up my article and also Paco's and read them through and have it. Be careful as you're right at the upper edge of the envelope on a lot of stuff. Pay close attention to brass as well. As I recall FC brass was thinner and gave lower pressure signs and you can use all the help you can get on this project. Seems like I used small pistol primers as well./beagle

Google for an article called "Paco's Long Range Load (for the Ruger 30 Carbine)", by John Goins (Beagle here). The article is in pdf form, thus easy to download.

Beagle describes his research in detail. The heaviest slug that achieved accuracy was the Lyman 311440, as mentioned above.

[jski]

I'm using new Starline brass for the purpose of this experiment.