Thoughts on cyl throat reaming .45 Colt Kirst Konverter

[LaneP]

First thanks for all the extremely helpful replies on my Uberti Walker thread (sheared frame alignment pin). Happily it is all back together and now just awaiting an opportunity to get to the range.

On this thread, I'm looking at my Uberti 3rd Dragoon that I've fitted with a Kirst Konverter in .45 Colt. I purchased a Lee 452-255-RF mold to use with it. This tosses a flat nose, 255 grain bullet and when cast in pure lead drops at .4525".

I pan lubed these in SPG then loaded them (as dropped, no sizing) over 35 grains FFg using a 3' drop tube. Due to using mixed brass, every so often a bullet would seat a hair short of the crimp groove, and those rounds would not fully chamber in the Kirst cylinder. I had to go back to the press and seat those rounds deeper.

This led me to slugging the cylinder throats of the Kirst. The Kirst throats measure in at .4515", and therein is the issue. I know...should have done all that before loading any

So now I'm pondering whether to resort to sizing bullets for the Kirst at .451" or just ream the throats out to .4525". Advantage to reaming is I can shoot the bullets as dropped, and most .45 caliber commercial cast bullets are sized to .452".

The reamer I'm looking at on Brownell's is backordered and would be a one time expense of approximately $90 give or take (comes with one pilot and I would have to see if I already have a t-handle that would fit or if that will add to the expense).

Now I have throat reamed 1911 barrels, but I've never tackled a revolver cylinder, so that would be another first for me. Image below shows the Lee 255 grain RF bullet after tapping it through the Kirst throat.

Thoughts? Am I overlooking anything? Thanks everyone.

 

[LaneP]

Follow up here. I went ahead and ordered the cylinder throat reamer from Brownell's. I was motivated by pushing a test bullet through a Lee .451" sizer die and the bullet was still tight enough passing through the Kirst cylinder throat that it swaged some lead aft of the heel in the process of pushing it through. The Manson reamer will cut the throats to .4525" and let me use the Lee 255 grain cast flat point shoot as dropped, as well as helping with bullet seating depth latitude.

I'd rather let the bullets pass somewhat easily through the cylinder, then get swaged by the barrel throat than have them swaged immediately out of the case mouth. This is based on as much research as I have found not only recently but going back a number of years. I don't know what the slope of the barrel throat is but it's of sufficient angle that a bullet nose will start in it without any issues.

I briefly considered sizing down to .450" but that would distort the grease grooves of this bullet unreasonably. I think I'm going to be okay with this plan, especially as this revolver will only be fed a diet of SPG lubed, dead soft lead 255 grain bullets over black powder.

 

[arcticap]

Just curious, how does the reamer fit in with the dimensions of the forcing cone and the barrel?
Will the new tolerance be increasing pressures or does everything measure up to being okay by matching up dimension wise with the bore and forcing cone?

 

[LaneP]

Just curious, how does the reamer fit in with the dimensions of the forcing cone and the barrel?
Will the new tolerance be increasing pressures or does everything measure up to being okay by matching up dimension wise with the bore and forcing cone?

I certainly gave that much thought before ordering this reamer and admit I'm negligent in not having slugged this bore, but I am confident there will be no problems based on a few factors.

My first thought was how these guns typically load as percussion revolvers, usually using a .454" or .457" round ball. When loading one of today's Uberti .44 caliber models, all mine shave a very thin ring of lead using .454", and a slightly larger ring using .457". Prior to installing the Kirst cylinder I used only .457" lead balls in this revolver with excellent results.

So I believe a soft lead .452" bullet will be right there where it needs to be to properly fill the bore, but not swage in the cylinder throat before getting to the barrel throat.

In fact I would be somewhat concerned about pressure spiking at the cylinder throat if using smokeless cowboy loads, despite the reduced loading, as I believe these universally use bullets around .452" in diameter.

Of course I am not an authority or final word on the subject, this is just a conclusion drawn from experience with other revolver loadings and research concerning the relationship of bullet to both the cylinder throat and barrel groove diameter.

Below is the Uberti 3rd with its percussion cylinder. It really liked the mid-40 grains 3F loading and a .457" ball.

 

[skeeterfogger]

Think I would slug the barrel first. Make sure it might be best prudent to size the projectile. Possibly there is a critical reason Krist made the cylinder bore for that frame its size.

 

[LaneP]

Think I would slug the barrel first. Make sure it might be best prudent to size the projectile. Possibly there is a critical reason Krist made the cylinder bore for that frame its size.

That's undeniably good advice and I will do that. In fact since making my previous post I planned on doing it tomorrow after work, if I can find some dowel rod around here anywhere.

 

[LaneP]

That's undeniably good advice and I will do that. In fact since making my previous post I planned on doing it tomorrow after work, if I can find some dowel rod around here anywhere.

Okay, couldn't wait. I found exactly where my dowel was (that rarely happens ) and tapped a Lee 255 grain bullet breech to muzzle. The largest measurement my caliper could find was .4525". These bullets coincidentally are .4525" out of the mold. The bullet was a good snug fit. I think I'm good. With upsetting in the barrel throat, I believe the fit will be near perfect.

Before reaming anything, how's it shoot? Pure lead is awfully elastic. It may size down to .4515 through the cylinder mouths but it will almost certainly obturate out to fill the barrel grooves. I'd shoot it a lot before doing any reaming...

I started all this before even getting it to the range. I know, crazy, but over decades of reloading for smokeless revolvers and fitting cast bullets to cylinder throats (this is the first time I will be doing the opposite), I just got on this track before touching off a single loaded cartridge.

It's just me but I wouldn't be comfortable with such a tight fitting relationship between the bullet diameter and cylinder throat. I was going to size the bullets down to throat diameter but grease groove distortion stopped that from being a solution I wanted to pursue. Anyway, I'll report back how she performs once all is said and done.

 

[woodnbow]

In the future, prior to purchasing a reamer you might consider a rental from a company called 4D Reamer Rentals. They have most every tool you need to work on these revolvers. Reasonably priced too.

 

[skeeterfogger]

Now that you have bore measurement you might give krist a call. It could be possible to have received a cylinder the is slightly out of specs. Or as your info it's all an OAL issue and there is nothing wrong. Considering your saying it's occasional and have to re crimp I would believe the OAL is it.

 

[StrawHat]

A fellow on another forum has all the readers and performs this service for those who want it.

PM for details if you want them.

Kevin