Author Topic: Adjusting cylinder throats  (Read 1662 times)

Offline Niederlander

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Adjusting cylinder throats
« on: August 21, 2017, 06:53:45 PM »
Gentlemen,
        A couple of us here have Colt style open tops that have .451 bores and .449 cylinder throats.  Has anyone opened them up to .452?  If so how did it work?  It would seem like it should help accuracy tremendously, but I'd like to hear about anyone else's results if they've done it.
"There go those Nebraskans, and all hell couldn't stop them!"

Offline Coffinmaker

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Re: Adjusting cylinder throats
« Reply #1 on: August 21, 2017, 07:27:25 PM »
I Know!!  I Know!!  Ask Me!!  Ask Me  ::)

Yep.  I've done a bunch.  Mine and my customers.  It makes quite a difference when you take the time to notice. 

A 451 or 452 bullet comes out of a 449 throat at .... yep you guessed it ... 449.  Then it goes into the barrel and just sort of skids and slides.  The bullet may "up-set" in the bore and actually pick up a spin but will wobble on the way to the target.  A 451 or 452 bullet will also be a little reluctant to pass thru a 449 throat.  Bumps chamber pressure.  SO:

Rreameing the throat will reduce immediate chamber pressure and allow the bullet to properly enter the forcing cone.  This will initially reduce felt recoil.  Since the bullet is not skipping and sliding through the bore, it reduces leading.  Since the bullet is properly sized to the bore, accuracy is improved.

I have found ALL of these things to be true and opening the throats to be very beneficial.  At 6 paces from the targets, after the buzzer goes off, you may not notice any of this.  For CAS you only need minute of pie plate accuracy.  However, it will lessen the stresses on the gun.  Get your reamer from "Manson Reamers."  DO NOT EVER turn the reamer BACKWARDS.

Offline greyhawk

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Re: Adjusting cylinder throats
« Reply #2 on: August 21, 2017, 08:50:31 PM »
Me too , Me too , Me too
I did two Cap guns - botom of groove was .462 - cylinders was .452 - we were using .454 ball - getting half or less rifling engagement - reamed the cylinders to .462 - (in a 1860 Army cylinder that dont leave much metal so just went deep enough to allow a ball in) - we got a Pedersoli ball mold in .464 size - two old cap guns that were shooting 8 inch groups with some fliers that took it out further - now shooting better that  I can hold at 25 yards (2 and a half inches on a real good day - if me eyes are working properly). Made my own reamer from a grade five HT bolt - that was way easier that I imagined - Coffinmaker thought I was crazy to attempt this (he wuz right too) but its a very satisfying result. Best part was with the bit heavier ball both of these guns are now shooting right on the tip of the front sight.   

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Re: Adjusting cylinder throats
« Reply #3 on: Today at 06:16:19 AM »

Offline Niederlander

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Re: Adjusting cylinder throats
« Reply #3 on: August 21, 2017, 09:42:41 PM »
That's what I suspected.  It makes a huge difference in cartridge guns and it seems like it should in these, too.
"There go those Nebraskans, and all hell couldn't stop them!"

 

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