30 cal Carbine Cylinder throat

After reading a recent post about cylinder throats I checked the throats on my 30 cal Blackhawk. Have had problems in the past with bullet seating. Different seating depths for different throats. In the past I just seated all the bullets deep and fired away. On trying cast bullets the problem intensified. My jacketed bullets are .308 in dia. checked with a Micrometer and my cast bullets are .309 dia. Some of the cast bullets will not allow the case to enter the cylinder far enough so the cylinder will turn. Thus even deeper seating.
I took a fresh .308 dia 180 gr. bullet for ease of handling and tried dropping it thru the cylinders. A long story short, The .308dia bullet fell thru 3 throats, finger pressure on 2 and one would need some force, hammer etc. Should all the throats be the same and how would I accomplish this Thanks Hope I wasn't to long winded

I suggest checking throat size with gage pins, ream with .308" reamer. I have found burrs on my .357 cylinders that stopped .357" bullets from slipping thru. I reamed with .358" reamer. I could feel it just cutting a burr out of the way. I know reaming throats on my .45's helped leading and accuracy.

The most important part of a cylinder is having the throats all even with each other. Uneven throats cause variations in pressure, which affects the recoil of the gun in the shooter's hands. Basically tighter throats will develop more pressure than loose throats, this can open groups significantly. Having them all honed to the same size and within .0002" of each other cures the problem usually. Occasionally I will see a Ruger cylinder with uneven chambers behind the throats. These can be brought more into uniform dimensions with a finishing reamer. Ruger usually uses a machine with multiple cutters to ream cylinders and they replace the reamers as they wear. The problem is they wait until the reamers have no more life left and they only replace the one that is too small to use any more, now you have one new reamer and two others in various stages of wear, and these cut throats and chambers of different dimensions.

Pretty typical, this is just one of the ways they keep production costs down to make the product more affordable.

Tooling for this is expensive if you buy a piloted reamer and all the pilots, I can offer professional results at a very attractive price point.

If you want to send a PM I am sure I can take care of your cylinder issues.

Doug. Do you ream 30 carb. cyl. throats?
Thank you Eric

I can ream them and hone them with the Sunnen hone or I can use just the Sunnen hone and size them to whatever size we choose.

So how would I go about getting my cylinder to you, whats the process. Would you match the tight chambers to the loose ones etc. I would like to use as stated originally .308 jacketed and .309 cast lead.

Send a PM and I will give you details for shipping, cost, etc. Turnaround is usually less than a week.

Let's see what the throats pin out at, see what the largest throat measures and go from there. I can match them to the largest throat, usually half thou over the largest throat. It's difficult to match an already finite size, but when they get real close, I like to take all of the throats a round or two with real fine stones to "feel" how close they are with the hone, and also to insure they are all round. I would at least want to touch down in the largest throat and see if it is even, and round, and it may grow a tiny bit larger in the process but they all come out even once finished. I try to have them within .0002" of each other.

If they can be all finished at .3095" ~ .3098" that would work well for sizing to .309"

If the largest throat is already greater than .309" and they can be finished at .310" ~ .3105" that will still work, in a perfect world the bullet needs to be .001" to .002" over groove diameter of the bore, and the throats in order to deliver the bullet to the barrel without altering it, need to be .0005" to .001" larger than bullet diameter.

Jacketed will still shoot well because they have a soft core inside the jacket, and with the pressure the 30 Carbine develops on firing, the jacketed bullets will easily obturate or bump up to fill the throats so you would still have a good seal in the barrel.

Thank you Doug. I'll get back to you.
Eric

Doug My Blackhawk 30cal cylinder is on the way to you for honing the throats. Personal Check included, If you see any hard carbon deposits please remove and I will Remit. Could not send a PM keeps telling me I am sending to 2 many recipiants.

Hah okay! Thanks!

"All's well that ends well" DougGuy honed my cylinder throats and all my fitting problems are gone. Will have a shooting report Friday. Thanks Doug

Thom's cylinder was typiclal of many Ruger cylinders where they use multiple reamers in a gang ream operation. It had one throat .310" and the rest were .309" and .308" so there is no way this one would shoot all the chambers to the same point of aim. The fact that I use a Sunnen hone in conjunction with the many various reamers I use, was the ticket for this cylinder. I wanted to match all the throats and hold them as close as possible to the largest one. It is necessary to even them all out by feel and measuring them along the way with pin gages, and feeling the difference in drag on the pin gages is the secret to knowing when they are all even.

The largest throat only grew by half a thousandth, which is pretty good. You can't only hone 5, you have to at least touch down with the hone and remove the bluing to see if the throat is indeed round which some are not but once the hone cleaned it up and verified that it was round, it's easy to match the others to it if you know what you are doing with the Sunnen hone. It's tricky at times but all of Thom's throats came out at .3105" and I am certain it will show a very noticeable difference in group sizes..

You are quite welcome, sir!!

A shooting report. The cylinder worked flawlessly, all loads fit. Best part, home cast lead 100 gas check bullets, 3" groups at 25 yards. Will be a hellava carry revolver for hiking. The lead bullet load is 12 grs Lil Gun work up if you try it. Its the Lee 30 cal mold. Thanks Doug

Which Lee 30 cal mold? MidwayUSA shows 8 of them.

Rounded Flat nose Gas check, 113 gr I think will have to check the catalog Lee Mould No. C309-113F

Are you using a lubrisizer to seat your gas checks or Lee's pass through sizer die?

Lyman 450 Lubrisizor , lubes and gas checks at the same time. After cylinder honing no more issues and 3 " groups at 25yards from my Ruger
. Jacketed bullets have even smaller groups