Proper bullet size?

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jski

jski

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I have a .30 Carbine Blackhawk and have been reloading for it for some time. Lately I ordered some 155 gr GC cast bullets from Montana Bullets Works with a .308 diameter. I measured the cylinder throats; they were all .307. But, I can easily push the bullets thru the chambers with a cleaning rod.

When I try to push a bullet into the forcing cone, it’s immediately stopped and I’d need a hammer to push in further.

Is there any reason to consider next time ordering .309 diameter bullets? I was concerned that the bullets so easily passed thru the cylinder throats.
 
It boils down to this: what should the bullet diameter be with respect to the cylinder throat diameter?
 
Shouldn’t the bullet diameter be .001” larger than the throat diameter ?
 
That is a good rule of thumb, but a good tight slip fit of the throats is best. Then of course we need our throats to be a decent match to the groove diameter, which absolutely has to be smaller than the throats, .002 being close to ideal IMHO, but more is OK. .308 groove and .310 throats with .3085 bullets would be awesome, but .308 groove with a .312 throats and .311 bullets should be ok. First trick is to know the groove diameter and throat diameter.

Or you could just size bullets for a tight slip fit of the throats and shoot them. No leading? Well, your golden and your grooves are under the bullet and throat size. Leading? Time to play with bullet hardness or mike throats slug barrel etc.
 
At one time jski, the common wisdom was to size bullets .001' larger than groove diameter. As it happens, when one shoots a lead bullet from a revolver, it will actually bulge (just a little) in the cylinder - barrel gap (from impacting the slightly smaller diameter forcing cone), then swage down to forcing cone diameter and - presuming the forcing cone isn't tighter than the bore - just continue out the muzzle.

When the bullet is notable undersized (in relation to the bore) AND very hard, one has trouble. The bullet will not 'upset' into the lands and grooves properly.
 
The problem is I’ve tried .309 cast bullets before (tho they were 115 gr) and had problems seating them in the cylinder. They would stick in the chamber throats (pun intended). Remember, these rounds are rimless and hence headspace on the case mouth. The chambers by definition have a ridge in them that narrows the chamber after that point.
 
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jski wrote:
Lately I ordered some 155 gr GC cast bullets from Montana Bullets Works with a .308 diameter.
Click to expand...

The first (an seemingly obvious) question is WHY are you attempting to shoot 155 grain bullets out of a 30 Carbine pistol?

Why are you attempting to turn your 30 Carbine Blackhawk into a 38 Special?
 
hdwhit said:
The first (an seemingly obvious) question is WHY are you attempting to shoot 155 grain bullets out of a 30 Carbine pistol?

Why are you attempting to turn your 30 Carbine Blackhawk into a 38 Special?
Click to expand...
Excellent question and I was wondering when someone would ask.

I read:
Paco’s Long Range Load
For the .30 Carbine Blackhawk
keeping mindful of the caveat: “Warning – This is a very special load and uses a bullet longer and heavier than the caliber is designed for at pressures that are probably at the top of the range for a .30 Carbine in the Ruger Blackhawk. Use this data at your own risk.”

I’m trying to duplicate their results.
 
I use a Lee .311-113gr FNGC for both a Ruger Single-7, and a BlackHawk .30Carbine (among others...)

I size to .311”. It works in everything. Based on my experience, the 155gr is unneeded. The 113gr at 1,400fps will expand and completely penetrate a deer on broadside or shallow angle shots. (Based on observed performance from a friend’s.32-20 Marlin).
The only Lee 150gr .311” FNGC (casts to 158gr) we’ve ever recovered was from a large up-state NY doe. The load was 7.5gr of Unique with unsized/un-checked bullet with tumble lube in .30/30. Bullet hit jumped deer in rear ham, recovered from under hide of far shoulder. ~45yd shot. Estimated velocity of 1,200fps.
Something for snowshoe hares!
 
I’m using:
TYPE: FN-GC
ALLOY: Linotype, BHN 22
DIAMETER RANGE: .308"
WEIGHT: 155gr
CALIBER: 308
NOSE TO CRIMP: 0.475”
​
With the chamber throats measuring .307”, if I were to use something larger than .308” diameter bullets, I’d have trouble getting the cartridges to seat properly in my Blackhawk cylinder.

As for which powder and how much, I’m using 10-11 gr of H110, possibly going as high as 12 gr max.
 
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BTW, unlike “Paco” Kelly and John Goins, aka “Beagle”, I’m looking for something that’s driving nails at or less than 50 yards.
 
Well I have two of those 30 carbine Blackhawks. I measured the twist rate and mine are 1:20 so trying to get an accurate stabilized heavy bullet is going to be a good trick IMHO. My problems with getting the rounds to chamber was that the brass did indeed grow in length depending on the number of reloads and getting crap on the seated bullet to brass joint part of the cylinder keeping them from sliding in all the way. YMMV

ETA: My 9MM and 45 ACP cylinders build up that crap and cause loading issues with lead bullets after a couple cylinders full in the Blackhawks that they work in as well.

Also the 30 carbine Automag pistol has a 1:10 twist rate and most of the 32 cal revolvers have between 1:12 and1:16 twist rate.
 
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What I would do is if you can just size like 12 or 15 and shoot'em and then take 12 or 15 bullets that are not sized and shoot them let's see what the difference is
 
I also use the Lee 113gr FNGC and swear by it. I size it to .310, but have used it at .308. Usually, I cast it from linotype, but have used quite a bit from Lyman #2.
Another bullet I use is an RCBS 88gr .32cal sized to .310. I cast it from WW+2% or Lyman #2. It works well for tin cans and bottles.
4.0gr Bullseye will go over the screens at 1100fps, and 5.0gr will send them at almost 1300fps from my 4 5/8" barrel.
Have fun,
Gene
 
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