Cylinder Throat Size

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Aug 18, 2009
SE Pennsylvania
I'm wondering what the ideal throat size is for my Blackhawk .41 magnum. I mean that not only in theory but from a practical standpoint.

First, a little background. I've owned and shot this revolver for a little over 20 years and have never really thought much about throat size. I have always used either a 220gr. Keith SWC or Sierra JHC bullets, both sized .410. My supply of Keith 220's has finally been exhausted so I purchased some 215 gr. SWC's sized .411 .

Now, to be fair, one chamber has always seemed more prone to high pressure but I've always been able to push the Keith's pretty fast with no real signs of pressure or leading. Using the 215 gr. bullets at a less than maximum charge I am getting severely flattened primers and sticky extraction (pound it out with a stick on the "problem" chamber).

I can push the Sierra bullets and LBT WFNGC sized .410 through each chamber throat no problem, although the one chamber is noticeably tighter. The 215 gr. sized .411 won't go, no way, no how.

It seems obvious I have a throat issue with the one chamber in particular. BTW, in looking at the cylinder, there is an "X" engraved next to the chamber that is tight. I bought this revolver brand new so I know the "X" came from the factory. I wonder if someone noticed the throat was tight and it just never got fixed?

But I digress, what throat size should I be looking at? It seems that the "tight" chamber should be the same as the other five, that's a no brainer. Should all the throats be opened up to accept .411 bullets? If so, what effect will that have when shooting bullets sized .410? Should I only use bullets sized .410?

This revolver has always been very accurate and I don't want to do anything to compromise that. What is the "ideal" throat diameter for this revolver?

Sugar River

Aug 25, 2008
S Florida
I bought a 41 BH about 25 yrs ago and it became my go to field gun. Jacketed accuracy was good but cast bullets were hit or miss. :wink:

I finally got around to measuring throats this spring and lo and behold, they were between 408 and 409. Had them opened up to 411 by CAS and the improvement is startling. I would go with 411 throats and 410 or 411 cast bullets and be very happy.



Apr 10, 2005
If you already got a tight chamber, and you're already pounding the brass out of the chamber, going up in bullet diameter will surely call for reducing whatever load you were a bunch.

Your cast bullet size should be .0005-.001 over the bore size of your gun. After you determine that, adjust your throats accordingly.
Once you get the gun shaped-up, I'll bet that you'll find that you won't need a GC bullet. Leastways, not as long as the alloy is matched to the pressure of the ammo, and you got's the proper lube.

There's a guy here on the Forum who can fix your throat problems at a fair price. His name escapes me at the moment but hang on....I'm sure someone will jump in soon to help with that part.

Good luck on your project.