Smith & Wesson Forum - View Single Post - Factory specifications and bullet diameters.

OKFC05 · 04-30-2009, 01:09 PM

In revolvers, you also have to consider the possibility of oversized cylinder throat:

QUOTE:
Revolvers

"In a revolver the throats are the areas in each cylinder chamber immediately ahead of the portion of the chamber where the brass case rests and into which the bullet projects. If the bullet is sized so that it is a gentle force fit in the throat, all else being equal, your accuracy potential will increase greatly.

Measure the throat diameters and slug the barrel. If you have a gun that has throats smaller than the groove diameter, (fortunately, an infrequent condition) there is not much hope for reasonable accuracy. From an accuracy standpoint, revolvers will not tolerate an undersize lead bullet rattling down the bore.

When you slug your barrel, note if there is a tight spot or area anywhere in the barrel. Pay particular attention to the back of the barrel where it enters the frame. A tight spot here is common and can size down your bullet. This situation can be remedied by lapping the bore.

Proper bullet fit in a revolver can do wonders. I can beat all my shooting buddies any day of the week; not because I am a better pistol shot, but because I fit all of my ammo to each particular gun - a decided advantage. I learned this way back when the Redhawk first came out. Through a series of very fortunate circumstances, I ended up with a matched set of the first year run. With their badly oversize .434" throats and using conventional ammo, the very best that I could get from them was 2" machine rest groups. By fitting bullets properly, they will now do 3/4" groups all day, even with full house loads. This dramatic improvement was realized in all my revolvers and I became a better shot overnight than I ever thought that I would be. It really is worth the effort.

Some revolver chambers have all six throats that are virtually identical, while some vary 0.0006 - 0.0007". Most hold 0.0003 - 0.0004" variation which is good enough, in my experience. Very carefully running an oversize soft slug through all six throats will give one the diameter of the smallest throat. This diameter is optimum for bullets fired in that gun.

You may very well find that your bullets shoot better with no sizing. My bullet sizer is virtually retired these past 15-20 years. Many bullets, as they fall from the mold, are already undersized for many modern production revolvers.

Tip - I fit most of my revolver bullets so that they will be a push fit into the throats and then load the cartridges so that bullets reach way out into the throats for good initial guidance; that is, with the bullet and bore axes perfectly collinear.

For those who load their rounds so that the bullets crimp at the crimp groove, rather than having them extend way out into the throat, oversize bullets, even those that are larger in diameter than the throats, can provide a definite advantage. There will be virtually no gas cutting, no matter what the bullet alloy."