[KMac]

I rolled the dice on an ebay 45 ACP cylinder for my Blackhawk 45 colt revolver and got really lucky. It was .0015" too long so I honed the front hub until it fit in the frame. The chamber to barrel alignment was perfect as was the lockup.
The issue I need opinions on is that the barrel cylinder gap is .003". Hoping not to need to remove material from front face, is this too tight? I realize that fouling would affect rotation sooner, but are there any other issues?

 

[Iowegan]

KMac, No offence but it sure helps to know how to fit a cylinder. You could have taken a little off the ratchet column and ended up with a perfect fit.

.004"~.008" is the most desirable B/C gap spec. I actually like .006" when dealing with lead bullets. .003" will work ... at least for a while. If endshake increases ...like it always does, your cylinder face will likely be rubbing on the rear of the barrel .... especially if you shoot lead bullets that tend to crud up the cylinder face. The good news is ... you can install a thin shim washer between the frame and front of the cylinder to move the cylinder to the rear a little. No need to do it now ... wait for endshake to increase ... unless of course your cylinder starts dragging on the barrel.

 

[KMac]

Thank you sir! I was told by a local "gun smith" not to remove from the ratchet. You live and learn. Should have asked you first. But at least it is shooting great now and shoots to the same point of aim as the colt cylinder.
Thank you again!!!!

 

[bwinters]

Live and learn as they say.

 

[Iowegan]

KMac, Just for a future reference ... taking metal from the ratchet column is typically more forgiving than taking metal from the front. The ratchet column controls headspace which ideally is between .008" and .012". You can easily get by with .006" headspace and still have enough room where the case heads don't rub against the recoil shield.

When I fit a cylinder such yours, I start by installing the factory cylinder, measure the B/C gap then start making comparison measurements on the new cylinder. There's three issues ...the length of the cylinder body, the length of the ratchet column, and the length of the gas ring (front of cylinder hub). You really can't change the length of the body but it must be considered before you start removing metal. Once you figure out if you have to take metal off the front, rear, or both, you do so very carefully. Ideally, the cylinder should have about .002" endshake .... just barely loose enough where you can swap cylinder without needing a shoehorn. I try to go for a .006" B/C gap ... if I can. Sometimes the geometry of the cylinder just won't permit the optimum B/C gap without sacrificing somewhere else.

One thing nice about a tight B/C gap ... you won't loose quite as much velocity. The estimate is ... 1.5% velocity loss for each .001" of B/C gap, based on an unvented barrel (think Thompson Center pistol with the same barrel length). With a .003 " B/C gap, you will loose about 4 1/2% ... so if your bullet's velocity should be 900 fps in an unvented barrel, it will actually be about 860 fps in your Blackhawk. This is about half as much as you typically loose (9%) with a .006" B/C gap. A bad thing about a tight B/C gap is ... the thin gap tends to focus exiting pressure and flame cut the top strap more. Normally this won't bother a thing ... just a cosmetic blemish.

 

[KMac]

Thanks again for the great info. Hopefully, this will help someone else in the future. Just goes to show that we are never too old to learn something new!!

 

[buddha1percent]

K Mac the truth is unless you shoot ALOT, you are going to be fine. You will have to shoot thousands of rounds to start to wear out your Ruger
You have one of the strongest guns ever made in the whole world.
Enjoy it

 

[Hondo44]

KMac,

Bravo for taking the bull by the horns and fixing the issue by yourself!

I also would have recommended removing the .0015" from the ratchet end. However, in your case it makes such a slight difference, it's a non-issue.

Let's review: had you removed from the ratchet end instead of from the cyl gas ring, your barrel/cyl gap would be .0045" instead of .003". Not that much different and still a tight gap.

If you have rubbing of the front of the cyl on the barrel, it will be more from the rise in temperature from shooting and the expansion of the metal parts from the heat, more than from fouling. And after a cylinder or two of shooting.

But what is your bar/cyl gap with the 45 Colt cyl?

Because if you do get some rubbing with the ACP cyl after the gun gets hot, the simple way to fix it is to hone a bit off the end of the barrel. Sure, that will enlarge the gap slightly for the 45 Colt cyl. but w/o ill effect unless it's already way too large. At best, the cyl gaps with two convertible cylinders on production guns are already a compromise, so yours will be no different.

And we don't need to over think this, like buddha1percent posted above, you'll have to do a lot of shooting and with hotter loads than you're likely shooting before you even need to think about wear. Leave that for your great great grandson to worry about if and when he inherits your gun.

Let us know how it works out for you, and enjoy shooting it!

Jim

 

[KMac]

Thanks everyone! Hondo44, the BC gap with the 45 colt cyl is .004, so you are correct that if needed, barrel could be honed a couple thnds and still be in specs. Good to know I have options if issues develop. At least it wasn't too short as I have read with some extra cylinder purchases.