Fading rifling grooves to crown edge

beltron462 · #1 06-18-2010, 03:06 PM

Here's a question from a relative newbie to revolvers. I have a five groove .38 spl. When you look at the crown, all of the rifling grooves do not look the same size. The two towards the top are much more distinct than the other three,and the the grooves seem to fade away as you work your way around the crown. I always hear about escaping gases and what not, and was wondering if this could be problem. The gun itself seems accurate and this is coming from someone who has never shot DAO (albeit I was only 4-5 yards out). Thanks for any input.

tomcatt51 · #2 06-18-2010, 09:52 PM

Clean the muzzle well, shoot the gun and then look at the carbon/crud pattern on the crown. It should make a nice, even "star". If it doesn't the crown needs to be recut.

Pisgah · #3 06-18-2010, 09:58 PM

Quote:

Originally Posted by tomcatt51

Clean the muzzle well, shoot the gun and then look at the carbon/crud pattern on the crown. It should make a nice, even "star". If it doesn't the crown needs to be recut.

I will disagree, mildly, that it necessarily "needs to be recut". It may, but if accuracy is acceptable there is really no reason to do it. Recrowning could mess things up!

Dragon88 · #4 06-18-2010, 10:57 PM

Fussing over the crown is for target rifles. Unless you have excessive damage to your crown, which you don't have from your description, then don't worry about it. Accuracy is what matters.

tomcatt51 · #5 06-19-2010, 12:29 AM

Quote:

Originally Posted by Pisgah

I will disagree, mildly, that it necessarily "needs to be recut". It may, but if accuracy is acceptable there is really no reason to do it. Recrowning could mess things up!

True, if it shoots well enough, leave it alone. If it doesn't and the pattern is uneven it's something to do.

beltron462 · #6 06-19-2010, 10:16 AM

Thanks guys. I'm going to take it out early next week with a couple of guys who are pretty good shooters and see what they think before I do anything. Thanks again.

Alk8944 · #7 06-19-2010, 02:52 PM

beltron,

What you describe seems to be fairly common on recent small frame S&W revolvers with 1 7/8" barrels for some reason. There have been several posts asking about inconsistent groove depth. As well, and as a result of these posts, I have examined several new guns and observed this characteristic in several. These are all guns made since the rifling process has been done by EDM. It appears S&W has a problem perfectly aligning the EDM electrode in the barrel for the rifling process resulting in deeper grooves on the side the electrode was closer to, and shallower on the opposite side.

There isn't anything to be "done" to correct this except send it back to the factory to have the barrel replaced. Since it is so common it appears it falls within acceptable current standards for the company and they well may say it is acceptable. It the gun shoots acceptably you will probably have to live with it.

tomcatt51 · #8 06-19-2010, 03:05 PM

Quote:

Originally Posted by Alk8944

It appears S&W has a problem perfectly aligning the EDM electrode in the barrel for the rifling process resulting in deeper grooves on the side the electrode was closer to, and shallower on the opposite side.

That totally sucks. Obviously not a crown issue. Is this on the one piece barrels or the "shroud and liner" version?

Wayne M · #9 06-19-2010, 06:51 PM

Rotate the revolver with light at the forcing cone to illuminate the inside of the barrel to be sure the rifling is different depths as light strikes it at different points. What you're seeing could be an optical illusion; have noticed the illusion myself until more light is added. A white light will help.

beltron462 · #10 06-19-2010, 06:58 PM

Quote:

Originally Posted by Wayne M

Rotate the revolver with light at the forcing cone to illuminate the inside of the barrel to be sure the rifling is different depths as light strikes it at different points. What you're seeing could be an optical illusion; have noticed the illusion myself until more light is added. A white light will help.

Should the rifling be at different depths as it reaches the end of the barrel or should there be five even sized grooves at the crown? I guess this is my main question. There are different size grooves when they reach the crown area. Can this effect accuracy or are they just made this way. If so, I think I can let it go. Thanks for all the input guys.

tomcatt51 · #11 06-20-2010, 08:58 PM

If the crown is mis-cut you could have the appearance of uneven depth rifling. Or it could actually be uneven. Or it could be just fine and it's just how you're looking at it. First thing I'd do is see how it shoots, that is what matters most, not sitting on the couch playing with it.