[jski]

.30 Carbine Blackhawk needs to have its cylinder reamed?

I have a .30 Carbine Blackhawk and have problems with both accuracy and precision. And this is a gun renown for both. Maybe a problem with me? Maybe not?

Does the .30 Carbine Blackhawk suffer from cylinder throat issues. Exactly what is the end result from having a cylinder reamed?

 

[jski]

One other point. Since the .30 Carbine Blackhawk headspaces at the case mouth and, consequently, there's a small ledge in each chamber for this purpose, does that raise addition issues about reaming this cylinder?

 

[Iowegan]

jski, An easy way to find out if your 30 Carb cylinder needs reaming is to remove the cylinder and see if you can push a .308 cal bullet through each throat from the front. If a .308 bullet passes through with just finger pressure, your throats are just fine.

As for the case mouth stop .... the case mouth diameter is .331" and bullet diameter is .308". The chamber about .001" larger in diameter than the case (.332"). That leaves a case mouth stop about .011" wide ... what you call a "ledge". If the throats were .306", the stop (ledge) would be .012" before reaming and .011" wide after reaming. So ... the answer is ... not a problem!

 

[ditto1958]

jski, have you tried having someone else shoot your gun?

 

[opos]

I had an old model 30 Carbine Blackhawk that I loaded for...it did not have throat problems and there was a man (since deceased) that used to do reaming...he quit taking 30 carbine in as he felt they seldom needed reaming...the "push test" should answer your questions....one thing I might mention is the 30 carbine cartridge looks like a straight wall cartridge...it's not..it's tapered (roll one on a flat surface and see what it does)...with that in mind and the headspacing on the mouth of the case, case trim becomes very important...I found that a serious effort to be really accurate with case trim was a big factor in the way things shot...Fun cartridge...wear your ear protection

Here's a youtube link (not mine) about trim on the 30 carbine ...shows things pretty well with the way he does it.

https://www.youtube.com/watch?v=COWOrNkd1KY

 

[veeman]

I did have to ream my NM 30 carbine, they were very tight. I also use 32-20 brass in mine.

 

[jski]

Results from the "push test": in 4 chambers the bullet simply fell right thru the chamber; in 2 chambers in took a little pressure but then fell thru.

In all honesty, I haven't cleaned the chamber since the last 2 times I took it to the range. So those 2 slightly reluctant chamber may be mea culpa.

 

[jski]

BTW, I used one of Berry's plated .308 110 gr. bullets.

 

[Iowegan]

jski, Berry's bullets are not famous for being precision. Give your cylinder a good cleaning then try the test with a jacketed .308 bullet. My bet is ... your throats are just fine. One thing I noticed when I had my 30 Carb BH .... it favored "full power" factory ammo so I used Speer 100 or 110gr .308 cal jacketed bullets with 15 ~ 15.5 gr of W-296 powder. These loads are very accurate and are 1400~1500 fps .... way faster than you can push a Berry's plated bullet.

Most revolvers have a slow twist rate barrel. Smaller bullets demand a faster twist rate to stabilize so 30 Mi Carbine rifles have a 1:16 twist rate, however Ruger decided on a 1:20 twist rate for the 30 Carb Blackhawk. In my opinion, it should have been a much faster twist rate, but you get what you get. So ... due to the very slow 1:20 twist rate, you really need to develop a velocity of at least 1300~1400 fps if you expect good accuracy.

 

[jski]

Iowegan, riddle me this. My current plan with the .30 Carbine Blackhawk is to go in the opposite direction. To that end I purchased 200 GC, hard cast (BHN 22), .309 bullets from Montana Bullet Works. These puppies definitely do not pass the "push test". But my understanding was if you're at .308 with jacketed/plated bullets then you'll want .309 with cast bullets.

The other ingredients here are:

Starline brass,
15 gr. of H110, and
CCI small rifle mag primers.

Does this sound reasonable?