New Vaquero land/groove and diagnosis

[AggiePharmD]

Is there a consensus as to what the lands and grooves are running? I've been shooting .452 with 5 gr of Trail Boss using a commercial 'hard cast' bullet and while it isn't necessarily leading there is a residual "brownish" tint to the stainless barrel. Before anyone says "slug your barrel" know that I've tried slugging 2 different barrels with poor results. My thought on the brownish tint is that I'm not getting a good seal between barrel and bullet either due to a diameter issue or a hardness issue?

[DougGuy]

Ruger barrels are fairly consistent and right at .451" diameter of the grooves. Their issues stem mostly from undersize cylinder throats which run generally in the .450" .4505" range on recent production cylinders to as tight as .4485" - .4490" on some of the 90s production. For many years they used to gang ream cylinders 3 holes at a time and they replaced reamers as they wore so it was quite common to have cylinders with 3 different size cylinder throat diameters. For the most part these will shoot factory loaded ammo without any issues at all. It's only when the user wants to shoot cast boolits, especially hard cast (air cooled wheel weight and harder) that these dimensions need to be corrected so the gun will shoot decent groups without leading.

The other problem that seems to be hit or miss depending on when your Ruger was made, since .45 caliber is the largest bore diameter produced, and all the barrels are the same diameter on the outside, the .45 and to some extent the .44 caliber barrels are the thinnest. The part of the barrel that threads into the frame is thinner, the larger the caliber, and therefore the easiest to "crush" due to torquing the barrel into the frame. It is quite common to find "thread constrictions" on these larger bore revolvers, and if they are severe enough, they can be .003" or more smaller in the threaded part than the rest of the bore. So now you have a spot in the bore right past the forcing cone where the bore diameter is squeezed down like a wasp waist, and this will in turn size down the boolit as it passes through this part of the barrel.

Most people would slug a bore to determine if theirs is constricted, but there is an easier way. With a plastic or brass cleaning jag, and a clean shiny bore, use cloth patches to patch the jag into the bore very tightly. It should be stiff to push down the bore. Now, push the cleaning jag down the bore toward the cylinder (with the cylinder removed of course..) and if it gets tight or hard to push when it gets to the part that threads into the frame, then there is a constriction there. If it is mild, and only slightly harder to push through this area, the constriction isn't too bad and can usually be fire lapped out or simply left alone where it will eventually wear itself out with enough normal use, i.e. a few thousand rounds.

If the cleaning rod stops, and takes an enormous amount of extra effort to push it through the threaded area, the constriction is severe enough that the gun should be sent back to Ruger and let them fix it.

[AggiePharmD]

Thanks for the information. I'll try to use your patch method and report.

On a side note, I found a recovered bullet today. Would measurements or markings anywhere on said bullet provide a clue? Unfortunately I don't have a micrometer right now.

[DougGuy]

After it is fired it wouldn't be an accurate measurement of the bore since it would expand upon impact with the backstop.

One way to measure the cylinder throats, is try to put a .452" boolit into the throat from the front. If that won't fit, try with a .451" and if it don't go either, the cylinder needs to be reamed so it isn't downsizing your boolits before they even make it to the barrel. This way does not give you a numbered measurement, but it doesn't take a micrometer to tell if the cylinder is or is not causing a diameter problem, it takes a couple of boolits.