Barrel slugging

[sharpshooter79]

Howdy Folks,
I am getting into casting my own bullets and I need some help. I want to cast for my .357 but I need to slug my barrel to determine what bullet size. How do you slug a barrel? Do gas checks help improve accuracy? What is a good mold for a Ruger 357? Any advice would help. Thanks!

[cbrick]

sharpshooter79, welcome to the forum.

First, I'll assume your Ruger is a revolver. You need to slug your throats and size the bullets to a mild snug fit there. If the revovler is correctly dimensioned (not all are) your bore will slug at the same dimension or a just a tick smaller.

Clean the cylinder and the bore, lightly oil both. Use a soft lead slug (fishing weights of proper size work) and tap it through all of the throats and the bore. Use a different lead slug for each. Use a micrometer to measure the slugs. I cast bullets from stick-on wheel weights and use those for bore and cylinder slugs.

What bullet is a good bullet would depend on what you plan to use it for. There are numerous good bullets for this caliber so it would be tough to recommend one without knowing more about your type of shooting, velocity goals etc.

Rick

[Buckshot]

...............Yup, use fishing sinkers. Get as close to size as you can buy. If a tad small a visit by pliers, the vise, or the swinging press (hammer) will fatten them up. While you're out buying sinkers get a length of 5/16" hardwood dowel to drive'em through.

As Cbrick mentioned the 2 prime revolter dimensions (cylinder mouth - bbl groove) as a good example of a bad one is (for a 45) a .449" chamber mouth and a .451" groove. If it's a Ruger they'll ya it's "Within Specs" :-)

..................Buckshot

[fourarmed]

Here's what I do. Clean the chamber mouths, and check them with pin gauges. You may not have enough guns to warrant buying a set, (I got a set that goes from .25" to .50" by thousandths from ENCO for $50 or $60.) but maybe you know a machinist who has a set. Clean the bore, and oil or grease lightly. Drive a slightly oversize slug all the way through. Cut a piece of dowel about a half inch shorter than the distance from the breech face to the muzzle. Drop it down the barrel, then start another slug after it. When it hits the end of the dowel, give it a couple of taps to expand it. Push it back out the muzzle by prying the breech end of the dowel. This way you get a measure at the muzzle and at the tightest spot - usually where it screws into the frame.

Incidentally, if the barrel is tighter at the frame, you have a couple of options. 1) You can fire lap the bore. 2) A machinist/gunsmith friend told me this one: Take the barrel off, and relieve the shoulder .001" where it contacts the frame. Then screw it back on using red or green Loctite. Turn it to the exact same position as before. He says the constriction is caused by that last .001" crush fit.

[Bass Ackward]

He says the constriction is caused by that last .001" crush fit.



Fourarmed,

I say you can crush .002. Problem is that you don't know where the crush will show up.

I mean that compression at the shoulder doesn't guarantee that it will show up as a constriction in the bore or a chamber. Some of the constriction can be stress in the steel or in the threads themselves, so relieving the shoulder will do nothing to help that.

Bottom line is that you need to diagnose the cause or you are guessing.


Sharpshooter,

The simple answer is yes. GCs do improve accuracy. What they do is protect the base from abuse that you create either through powder selection or pressure range of operation. So they offer .... flexibility in load development.

If you get more .... "accurate" loads to choose from, then odds are one of those will be clearly more accurate than the rest.

Lyman 358156 and 14 to 16 grains of 2400 depending on bullet hardness and if you can hold it.

[sharpshooter79]

Howdy Folks,
Thanks for the help. I was on Midway's looking at Lyman moulds, I noticed that some are "SWC gas check" and others are "SWC" only. What is the difference?

Yep, my 357 is a GP-100 revolver. Just out of curiosity what is the purpose of measuring chamber throats and what is a 357 usually measure? Got my 5/16" dowel and I'll get my sinkers tomorrow. I live in Wyoming and I carry my gun for varmints and such. I usually use the 158 gr Gold dot hollow point from Speer but I like the idea of being able to make my own stuff (self sufficiency).


Thanks for the help again folks!

[cbrick]

Just out of curiosity what is the purpose of measuring chamber throats and what is a 357 usually measure? Thanks for the help again folks!

If bullets are sized larger than the throats it's possible to shave lead as they pass through. Even if your gun doesn't lead up the cylinder because of over size bullets it sure won't do anything for accuracy (or pressure).

What you want is for the front driving band to seal the throat as the bullet begins moving and leaves the case. As it moves further along and the front driving band engages the forcing cone the rear driving band of the bullet is still in the throat and still sealing the gas pressure behind it (no blow by in the throat). As the rest of the bullet enters the forcing cone and bore it is sealing off the bore. Blow by is why you don't want a bore larger than the throats but sadly many revolvers are. If yours is the only practical fix is for a competent smith to ream the throats, then size the bullets to the new throat size.

A big plus of a mild snug fit in the throats in addition to no blow by is a bullet lined up with the bore and no slop or play. It's as lined up and straight on with the bore as the dimensions of your revolver will allow.

Bullet seals the throats, bullet is lined up with the bore . . . life is good :-D.

Rick

[scrapcan]

SharpShooter79,

Where are you at in this fair state? Their are a few of us on the board.

[fourarmed]

I say you can crush .002. Problem is that you don't know where the crush will show up.

I mean that compression at the shoulder doesn't guarantee that it will show up as a constriction in the bore or a chamber. Some of the constriction can be stress in the steel or in the threads themselves, so relieving the shoulder will do nothing to help that.
************************************************** **
Bass, I haven't installed a lot of revolver barrels as my friend has, but I know that steel is incompressible. If you push it aside somewhere, that metal has to show up somewhere else. Strain is proportional to stress. That is Hooke's Law. Certainly some of the metal will be displaced outward - increasing the OD of the barrel and frame - but some is bound to be displaced inward as well.

The guy I'm talking about has built a lot of revolvers of the PPC type, and he sets his barrels up hand tight using Loctite on the threads. He never gets constrictions at the frame, and they never come loose until you heat them to 300 degrees or more. Now you can argue that these are new barrels rather than takeoffs. I won't disagree with you that a barrel that has been set up with TOO MUCH crush might permanently deform. In that case, relieving the shoulder and reinstalling certainly wouldn't remove all the displaced metal. Where that limit comes, I couldn't say.

[sharpshooter79]

Howdy Folks,
Slugged my barrel when I got home from work. Bullet measures .354" after slugging which seems a little too small. I don't think I am measuring right. It seems that the rifling marks in the lead may be throwing my measurements off. Anybody slugged a gp-100 before and had the same measurement?
I was looking at molds and I have heard good things about the Lee 158 gr RNFP mold. Anybody out there use this mold? I am on a limited income :-D so I might have to go with the Lee to start with. Also can a gas check be put on a bullet cast from a non gas check mold?
Manleyjt, I live in the Sheridan area, just moved here 2 months ago. I am originally from Louisiana, moved to Oregon 3 years ago. Hated it there due to the liberalism, So I took a job here in Sheridan. My wife and I like it a lot, we got lucky and are renting a place on a ranch.
I want to thank everyone for the help again!

[Bass Ackward]

I was looking at molds and I have heard good things about the Lee 158 gr RNFP mold. Anybody out there use this mold? I am on a limited income :-D so I might have to go with the Lee to start with. Also can a gas check be put on a bullet cast from a non gas check mold?
!

SS,

You can't put a GC on a non GC mold unless you have special dies or a monsterously big hammer. :grin:

You also can't measure something with a normal set of mics if the same object isn't directly across from it. So you can use the search function at the top of the home page to search for "Slugging" and get a bunch of threads that will tell you different ways of .... getting .... closer.

I do use the Lee 158 RNFP as do many others. But I don't push it. Does best for me if I sortta treat it like a wadcutter. Otherwise it goes bang is all I can say.