Checking cylinder throat size

[LordDunsany]

I have a Ruger New Vaquero that I shoot Brin 12 LSWC sized at .358, using 5.2 gr Unique.

After removing the cylinder I can press a boolet fully through it with a fair amount of hand pressure. I can't estimate the actual force used, but it is a tight fit.

My loads are +P level and I get a modest amount of leading in the first inch or so of the barrel. It cleans up easily so is not excessive.

Are my chamber throats too tight, squeezing the boolet and not allowing it to obdurate, thereby causing leading?

What is an acceptable amount of 'tightness' when testing boolet diameter vs throat size?

 

[murf]

if you can get a lead bullet through each throat by hand, your cylinders will be the same size as those bullets. measure one with your caliper and find out the diameter. the best match-up of throat and barrel groove diameters is the throat being one thousandth greater than the barrel groove diameter.

the other question is does this load lead your throats, forcing cone, or barrel? if not, and the load is accurate, then i wouldn't worry about this.

murf

 

[Jesse Heywood]

If the bullets are too loose they almost drop through the cylinder. Too tight and you need a dowel to push them through.

Have you read this article. www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm

 

[Catpop]

Thank you Mr. Jesse Heywood for access to that great article!

 

[mdi]

When in doubt, measure. Run a ball/slug/bullet that's larger than the throat through and measure it. "Hard push through", "falls through" and "easy push through" means very little (and nothing to me) and are not measurements. Be sure of what you need and you won't know for sure much about your cylinder throats without measuring. Without facts, real measurements, it's all a WAG...

 

[oldfortyfiveauto]

Gage pins make this a lot easier. I just sent my new Redhawk back as it would not shoot much better than paper plate size at 25yds. Cylinder chambers were consistent, but I found the forcing cone area, basically where the barrel threads are about .001" tighter than the rest of the barrel. Not that unusual of situation for a revolver

 

[98Redline]

oldfourtyfiveauto hit the nail right on the head.

Most Rugers have a constriction at the forcing cone / barrel thread area. This is generally where you will see the leading accumulate on Rugers. They will often also have a mid barrel constriction under the roll mark. I would assume this to be less of a problem since Ruger moved over to laser engraving.

While your load shoots accurately now, that accuracy will drop off as the leading accumulates. Firelapping of your gun would likely get the constriction out and leave you with a nice tapered bore...perfect for shooting lead bullets.

As a side benefit, you will also find that the barrel is a snap to clean. My SuperBlackhawk Hunter will come clean with 2 patches.

 

[Catpop]

This thread has helped tremendously with my blackhawk leading issues. Thank you to all who gave input.
Question: Is Fire lapping the #1 recourse to solve this constriction issue?
Question: does fire lapping prematurely wear the barrel out?

 

[LordDunsany]

And thanks again for the link! After reinspecting my gun after today's outing I found that the barrel is still not completely broken it, and that some of what I ASSumed to be leading was actually residue from lube.

My cylinder throats are slightly undersized (tight) so I'll get a cutter and open them up a hair. Had to so this on all my Ruger 45's so not a great surprise.

Goes to show that after 50+ years of shooting and reloading, you can still learn.

Thanks!