Continuing my firearms education


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Warren
December 18, 2004, 03:19 AM
I have a few more questions to pester y'all with.

From this review (http://www.shootingtimes.com/handgun_reviews/rgrRH/) I pull the following quote....

And its accuracy with .45 Colt loads will surprise you; its chambers are specced to a tight .479-inch diameter instead of the sloppy .488-inch diameter that is SAAMI-standard for chamber diameters on .45 Colt-only guns.

So having tighter chambers increases accuracy, but does it cause a problem somewhere else like being able reload the gun fast?

I read an article by John Linebaugh that said that tighter chambers meant less stress on the brass and thus reloading the cases was a lot easier and the cases lasted longer. Have you found this to be true?

And what is chamfering? I gather it is some sort of widening of a tube. If you have tight chambers and then have them chamfered does that mean you have destroyed the value of the tight chambers?

Thank you,

As always I am Here2Learn

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rust collector
December 18, 2004, 10:07 AM
.22 match rifles have smaller chamber dimensions. Since reloading isn't a factor, the reason must be accuracy. Less slop = better concentricity perhaps.

Unfortunately, a certain amount of leeway is required to accommodate oversize, dirty or recycled rounds. Hence, some barrels use a Bentz chamber which is a compromise between SAAMI and match dimensions. It promises a little better accuracy with only a little less potential reliability issue.

So the review's premise is correct up to a point. If you can't burn some stock ammo because it doesn't fit the chamber or the gun will possibly by used for self defense, a tight chamber might not be a source of joy.

mete
December 18, 2004, 11:43 AM
Chamfering of the cases is done with a chamfering tool and it puts a chamfer [cuts a 45 degree bevel] on the inside of the case mouth .Chamfer only about 1/2 the thickness of the case wall. The bullet will seat easier thus reducing the amount of belling of the case mouth necessary.

pignock
December 19, 2004, 10:21 AM
Ummm..... there are a lot of people on this board more qualified to answer your question than I but I'll give it a shot :)

Tight Chambers
Tight chambers aid in accuracy (especially in a revolver) because there is less room for the cartridge to move around during ignition.

Keep in mind how a revolver works: A chamber is rotated to align with the barrel, the firing pin ignites the primer, and the expanding gasses propel the bullet out of the cartridge, through the cylinder gap, into the forcing cone, and down the barrel.

The more closely everything is aligned with the ideal path of the bullet, the more likely the bullet will go where you aim.

In a custom revolver - like a Linebaugh - the cylinder is line bored. This means the chamber holes are cut into the cylinder while the cylinder is in the gun. The way they do this is to make all the locking cuts on the cylinder, install it in the frame, put the frame in a jig and drill/ream the cylinder holes through the barrel hole (the barrel is uninstalled of course). Line boring ensures that all of the cylinders are concentrically aligned with the barrel.

When near perfect concentricity is combined with tight chambers, the bullet is guided to the rifling with a minimum of disturbance.

In a regular production gun (from say, S&W, Ruger, Taurus, etc.) the cylinders are bored separately and the installed - a less costly, and only slightly less accurate due to tight machining tolerances - way of lining things up. Most revolver makers don't do this because of the extra expense and expertise needed. As far as I know, only Freedom Arms makes their guns this way. Also, production guns have looser chambers because the manufacturer is more concerned with making guns that work with a wider variety of ammo. A custom gun maker, like Linebaugh, can make and market his tight (and expensive) revolvers to a very select clientele who are aware of the limitations and benefits of a tighter than SAAMI spec’d gun. He fits them by hand and only makes a few hundred a year (at most). A manufacturer ensures his thousands of revolvers work for his thousands of customers using any ammo that falls within SAAMI specs..

Cylinder Chamfering

Custom revolver makers and gunsmiths chamfer the back end (where the cartridge goes in) of revolver chambers to aid in the loading of the cylinder. Think of it as a kind of funnel - it’s a lot easier to pour water into a soda bottle from a pitcher with a funnel.

The chamfering done on revolver cylinders just breaks the edge of the cylinder. If you look at a hole drilled straight into thick metal, you’ll notice the edge (shoulder) of the hole has a 90 degree angle. If you take the drill bit used to drill the hole and turn it upside down so that the flat, non-cutting end of the bit faces the hole, you can push the bit into the hole, but it takes some fiddling to line up the bit with the hole. If you then take a larger drill bit and drill out the hole just enough to break the edge of the shoulder, your upside down drill bit goes into the hole much easier because you‘re trying to stick it into a larger opening. The drill bit still fits tightly into the hole you drilled because all of the hole (except the very end) is still the same size as your drill bit, but the end you stick the bit into is bigger so it goes in easier.

The cylinder chamfer doesn’t affect all the special aligning already done to each cylinder because the cylinder holes are already aligned with the barrel and all that is added is a tiny little funnel to the tail end of the cylinder. Also, the chamfer is added where the brass cartridge is thickest (look at a cross-section of a cartridge) so it doesn’t effect the strength of the cartridge.

Tamara
December 19, 2004, 10:24 AM
And what is chamfering? I gather it is some sort of widening of a tube. If you have tight chambers and then have them chamfered does that mean you have destroyed the value of the tight chambers?

To see if I can restate what others have already said: Chamfering revolver chambers simply involves putting a slight bevel on the edge of the charge holes, thus aiding loading.

pignock
December 19, 2004, 10:32 AM
Like I said, a lot of people on this board more qualified to answer your question than I.

And much better at getting ideas across as well.

Warren
December 19, 2004, 08:35 PM
Thank you all for the replies.

Pignock, you did great. No worries, Eh?

How much more accuracy would you say a line bored revolver has over a mass market revolver?

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