Revolver slugging results, questions

[HenryC460]

S&W 629 44 Rem. Magnum caliber, 5-groove rifling. Haven't shot it yet.

I slugged the barrel and cylinder throats and also made Cerrosafe casts of each. The two techniques were equally easy in my hands.

I ran up against the odd groove problem on the barrel, and not being a machinist, I don't know my groove diameter really. I do have slugs, and I do know that if I just hammer a slug into the barrel, tap it out, and try it in the cylinder throats, it fits. That's good. According to that, my cylinder throats are at least as big as my barrel, and after passing through the throat, the bullets will be at least groove diameter.

End of good news. And it wasn't really great, high quality accurate good news.

If I really make sure that slug is filled out to groove diameter by drilling a hole in it and driving a drywall screw in the hole to really expand the slug, and if I use the drywall screw as my handle and pull the slug out, it does not fit into any of the cylinder mouths. It does fit nicely back in the muzzle, so it's not a delayed springiness of the lead slug. The groove diameter really is a little bigger than the cylinder mouth diameter. That's bad, I guess, since my bullets will be sized to sub-groove diameter by the cylinder mouths upon firing, and hot gases will blow by in the barrel and were all gonna die or go to jail or something.

Cerrosafe casts confirm that my cylinder throats are smaller than groove diameter. Fresh barrel casts enter cylinder throats, but at 1 hr, forget it.

What should I do?

Size to about cylinder mouth diameter (around 0.4315") and shoot the dang thing is the first thought that comes to mind. If it's accurate, no problems. If it's not, then there's the option of selling it. Darn pretty revolver. Also, I suppose the cylinder mouths could be reamed to oh-point-whatever is a little bigger than groove diameter once I figure that out.

That brings up an interesting problem. What if I finally figure out how to measure 5 grooves and my groove diameter is 0.434" (accounting for expansion of Cerrosafe)??? Then what? Sure, I could have the cylinder throats reamed out to 0.435" or so. Then I "simply" size my bullets to the new cylinder throat diameter and try shooting it again. Have I got it right so far?

Then, I need to find nonstandard moulds and nonstandard sizing dies that drop and squish 0.436" and 0.435" bullets and I should (should) have a sweet-shooting six gun.

Anybody know how to actually measure a 5-groove barrel? I've heard of using an expandable ball gauge to get bore dia. and then measuring land-to-groove on the barrel slug, subtracting the two to get groove depth, and adding groove depth to the land-to-groove measurement and call that groove diameter. That sounds pretty sound and complelling to me, but I'm not a machinist. Someone else said carefully twist that slug in the barrel to shave lead off into the bbl. grooves and get a slug that's bore diameter and you don't have to buy a ball gauge that way.

Two babies crying and wife expects help. I'd babble longer, trust me (but if I really had time, I'd edit it down and make it readable). I am guardedly pessimistic about the situation, but if the shooting test says don't worry, I'll stop worrying.

Gotta go, really.

H. C.

[felix]

HC, you worry too much. Get some boolits between 432 and 434 and use those. If the boolits are fairly hard, use a middle load in the books for starters. ... felix

[HenryC460]

Yes, I'm definitely going to shoot it and see.

If I need a good exercise in worrying, I could slug my Ruger GP-100, which I've been shooting lead bullets in since way before I knew about slugging or thought about casting (the point has always been cheapness).

It is a very accurate lead bullet shooting revolver. I'd be encouraged at this point if it gave me equally discouraging relative cylinder mouth and groove diameter measurements. Ah, to have the time to mess around with everything.

H. C.

[floodgate]

Henry:

A man named O. H. McKagen, in Virginia, has made up special micrometer systems and will mike your odd-number-groove slugs for you at no charge except postage both ways (and careful packing). I don't have his address handy (he has an article in the current CBA "Fouling Shot", but I just loaned that copy out today and it is out of reach), but he is well known here and someone will have it for you. Best to be SURE, before embarking on the cylinder mouth reaming.

floodgate

[Rick4570]

Henry, you can take some shim stock, say, .002, wrap it around the bullet and pinch the ends together, kinda like a pipe clamp, then take a measurement. Subtract the thickness of the shimstock X2, and it should give you a good idea of your slugs' measurement.
Regards

[leftiye]

Am I crazy or what? I've always measured S&W barrels by just putting a mike on the edges of two grooves (parts- HIGH SPOTS- pushed into the grooves when slugging) on the slug that were opposite each other. That means the "front" edge of one, and the "rear" edge of the other (opposite edges). If these aren't exactly opposite across the grooves, the measurements always seemed to be the correct size.

Alternatively, a digital caliper that is accurate to .0005" will actually find a place to measure directly across the grooves and measure at this same place, though maybe not as accurate (half a thou off can easily be compensated for by going a tad large as one to two thou. is acceptable overbore sizing for a boolit).

[Bass Ackward]

Am I crazy or what?


leftie,

Only cast. Medical evals are on another site. :grin:

You can get it done that way some times. Make several measurements and average in. I've roughed it and was close to actual. But there is room for error and more often than not. If I am indicating the right way, I don't concern myself. If it's close to going the other direction, I would want a "true" measurement. But maybe it doesn't have to be for Mr C if he's that close. Professor Gun will tell him right away.


Mr. " C ",

In a conference call I had with personnel at S&W, I was told that their research indicated better accuracy with smaller throat than bore dimensions. This was jacketed of coarse and they did not elaborate. When they came to this revelation I don't know. If they have implemented it , I don't know. Is yours one from that ideology?

But I had one. And by up to .003. Throats were .426 to .428. Figure that? And this was on an aluminum framed model 329. I had them opened to .4295 and they subsequently polished out another .0008. It does fine now and recoil was reduced considerably, thank God.

I say shoot it like you expect it to perform for you. If it limits you to lower velocities and softer / harder lead than you want to use, then you have a decision to make. But if S&W's statements of their research were implemented, then this is going to become a more prevalent problem in the future.

[felix]

Leftiye, if you are deemed crazy on the board next door, then so too me. Smith has been making those 5 groovers forever it seems, and I assume in the 60-40 configuration.
60% groove / 40& land. Maybe next time someone calls Smith, they can ask for the ratio they really use. There is prolly a demarcation there somewhere where the mic measurements we are making would really require the odd numbered technique to be in the ballpark. ... felix

[44man]

Don't even worry about a S&W! Never seen one that wouldn't shoot. Just match the throats or a little over if the rounds chamber OK and go shoot. Your only limitation is how much of the boolit enters the throats and if the rounds chamber. You might have to size them if too tight. S&W uses pretty tight dimensions.
If you used Cerro Safe to measure the throats and bore---IT IS WRONG! Use a pure lead slug. I bet the actual size of the throats is .4295" to .430" max and the bore will be .429".
NEVER DEPEND ON CERRO SAFE!

[leftiye]

I think all of youse guys are right. As for crazy, who cares (They're all nuts. I'm the only sane person on the panet). AND, Not to be agrumentative (ME?) - If the land to groove proportions are 60 /40, then the two grooves opposite each other are a true measure of groove diameter, as they are a true 180 degrees opposite each other at opposite edges as described. If they're 50/50, it still works, though it gets a little more dicey to measure correctly.