.30 Carbine Ruger Revolver

[Big Boomer]

Recently came by a Ruger .30 Carbine revolver. Here are the figures obtained by slugging the barrel and cylinder mouths using a Starrett micrometer to measure the slugs:

Barrel mikes at .3092 with some unexpected tightness under the barrel/frame threads. After the slug passed the muzzle moving toward the breech, it moved increasingly easy until it reached the barrel/frame threads. I can fire-lap that out, though.

Cylinder chamber mouths measure uniformly at .3096

Unfortunately, my cast boolit measures a generous .3099 and will not enter the cylinder throats.

Do I look for a smaller boolit, opt for a smaller sizer die for my Star, or open the chamber throats? This boolit is from a Lee 2-cavity mould that drops the most consistent weight of any boolit mould I have ever used. It boringly weighs boolit after boolit at 115.5 grains.

Right now I'm thinking open the cylinder throats. What would you do? Big Boomer

[Dusty Bannister]

While the alloy might make a difference, you can at least try some and see if it is a problem or not. A little interference might be a good thing if you can seat the bullet out enough to just enter that tapered portion of the cylinder. Well supported at ignition is a good thing. No need to worry until you have determined it will lead or not.

[beagle]

I was tinkering with the 31440 in the Ruger .30 Carbine Ruger and needed to seat the bullet out as far as possible and ran into this problem. I sized the first couple of bands down to .309" (nose first) and was able to accomplish what I wanted. You may try this and see if it will work before you mess with the chamber./beagle

[Big Boomer]

Thanks for the practical suggestions. I only loaded one round according to the length specs of Lyman's Handbook and it never occurred to me to seat some boolits deeper, shoot them and see what happens. Thanks. Big Boomer

[Outpost75]

A bit of thread choke where the barrel is turned into the frame is not surprising. Most of the time this can be fire-lapped out. If your bullets are only a wee bit oversized I would try shooting some as-cast, with Lee Liquid Alox and a moderate load and see how they do. My 1977 Blackhawk has .310 throats and .309 barrel and shoots best with Accurate 31-100T with 7.4 grains of AutoComp:

Ammunition__________Ruger 7-1/2”________US M1 Carbine 18”

LC44 Ball M1__________1586 fps , 20 Sd, 46 ES_______1981 fps, 20 Sd, 56 ES

Accurate 31-100T

Attachment 215044
7.4 grs. AutoComp_____1527, 11, 29__________1692, 16, 54 Most accurate REVOLVER load
14.0 grs. IMR4227_____1524, 12, 35__________1858, 13, 33

[buckshotshoey]

Could it be leading that is making that area tight to begin with?

[Ballistics in Scotland]

Thanks for the practical suggestions. I only loaded one round according to the length specs of Lyman's Handbook and it never occurred to me to seat some boolits deeper, shoot them and see what happens. Thanks. Big Boomer

It is always tricky when two distinct problems are bouncing off one another. But nothing you can do to the barrel will reduce the need to do something about the fit of bullets to throats. It is certainly worth seating a few bullets deep enough to chamber (for which the carbine round leaves plenty of length) to see if the constriction of the barrel reduces accuracy. It is indeed worth checking for local bore leading (although I think you would have recognised it), but barrel threads constricting the bore are no big surprise with Rugers. But I wouldn't go on shooting over-deep bullets. They can't be crimped, and if there is a chink around the neck, in real everyday use gritty dirt is liable to get in there.

You might find the constriction doing less harm than many would think. But if you do want to do something about it, the first 5/8in. or so of bore isn't the only part on which fire-lapping will operate. If I decided that lapping was in order, I believe I would hand-lap with a poured lead lap, inserted from the muzzle.

For the throat diameter problem, since you have the Star machine and a mould you like, a new bullet sizing die seems like the way to go for that end of things. One of the largest size that will permit

[ShooterAZ]

I would try sizing to .309 before opting for the more expensive/drastic options. Interestingly I have 3 GI M1 carbines, two of which need to be sized at .309 for reliable function. The other I size .310. Yeah I know, not a Ruger revolver, but I get no leading in any of them. Just my $.02

[DougGuy]

Send the cylinder and have the throats reamed and honed. Normally I size the 30 carbine throats to .3105" but I can go whatever diameter as long as none of the throats are larger. Ruger cylinders are fairly inconsistent due to the way Ruger changes out reamers as they wear, they only replace the worst one, now they have a new reamer cutting throats alongside two worn ones on a 3 chuck Hitachi machine, so each reamer cuts two throats and obviously the newer reamer will cut larger throats. Pretty common to need throats "dimensionally corrected" for use with cast boolits. It is an inexpensive, one time fix that works great. Send a PM for details.

[Wayne Smith]

BigBoomer, if you don't know from reading here you can trust Dougguy's disagnosis and fix.

[Outpost75]

Could it be leading that is making that area tight to begin with?

Leading WILL occur at the thread choke, but is a RESULT, not the cause, which is collapsing the barrel shank at the root of the thread from over-torquing the barrel in assembly.

[mehavey]

I would try sizing to .309 before opting for the more expensive/drastic options.

+1

[Larry Gibson]

+1

+1......

The couple Ruger BH 30 Carbines I played with have all shot very well with .309 sized bullets, excellent in fact. Especially with 311008 or 311316 1115 & 118 gr cast bullets over Unique.

I might add in many LC carbine cases with a .311 bullet would not chamber easily, actually some not at all. With .310 sized bullets a few required hard thumb pressure to seat. It was 35 years ago so I don't know what new Ruger BH 30 carbines chambers are like.

[Big Boomer]

Thanks for all the responses and suggestions. Info for all on this revolver - no lead to deal with because this is a new, unfired by me as yet (may have been fired at factory), Ruger revolver. Dealer in Indiana ordered some in and couldn't sell them so I had to have it shipped to my local dealer. Got a great price on this piece. I've been a reloader/boolit caster/fire-lapper since about 1975 so I've been around the track a time or two. I knew for years that someday I'd get a .30 Carbine Ruger revolver so I got the brass in spades, reloading dies, and the boolit is one I planned on shooting in my .30-06. Now I just have to make it work in this revolver or get another boolit mould. I'm thinking opening up the chamber mouths to about .310, perhaps .3105, is the way to go. I have all the paraphernalia to get that done. Big Boomer

[mehavey]

I'd shoot it first, before taking metal off...
You might be surprised.

[Artful]

Wear plugs and muffs at the same time - the freq. of 30 carbine out of a pistol just seems to drill deeper into my head than 357 or larger bores.

[woodbutcher]

Hi Artful.Either that OR load down to 32-20.And yeah,the muzzle blast on those is unreal.Not to mention the muzzle flash.
Good luck.Have fun.Be safe.
Leo

[dubber123]

I'm sorry if I missed it, but were the measured barrel slugs ones that passed all the way through the barrel? If so, you only measured the tightest portion, which in your case is the thread choke. Your bore and throat measurements are close now, and I suspect they will be even closer after the tight spot is lapped out. I generally like to be 1-2 thousandths bigger than the bore, but I do have one gun that is pretty much even up like yours, and it shoots very well too.

[Big Boomer]

dubber123: Yes, barrel slugs passed all the way through. Very tight at muzzle but increasingly easy until slug reached threaded portion of barrel/frame junction, which means thread choke. Thought I would open cylinder mouths until rounds will chamber then worry about fire-lapping out barrel/frame junction tightness. If I open cylinder mouths to .3102 that should give me a full .001 over bore groove diameter. In my experience, a lap works most effectively early, less effectively later, which should change only the barrel/thread area. Big Boomer

[Ballistics in Scotland]

Hi Artful.Either that OR load down to 32-20.And yeah,the muzzle blast on those is unreal.Not to mention the muzzle flash.
Good luck.Have fun.Be safe.
Leo

Much has been said against the .30 Carbine as a revolver round. Loads designed for the rifle (or near-rifle) are high pressure, with a slower powder than is ideal for this application, and will indeed give high muzzle blast, flash and perhaps erosion at the cylinder gap and topstrap if you shoot a lot. But I don't see why the handloader can't make it into a .32-20, or as special a .32-20 as he feels inclined.

However you might treat the one that is the subject of this thread, it sounds like it is at least within reach of being highly accurate. You can remove metal a lot more easily than put it back.