Can this be Possible?!

[mugsie]

I wanted to slug the barrel of my Taurus Tracker 357 magnum revolver so I went to Wal-Mart the other day and purchased a small pakage of bullet sinkers. They are just slightly larger than the diameter of the barrel so they worked perfectly. I pounded one into the barrel (it's very disconcerting pounding a lead slug the wrong way into a barrel! At one point I'm thinking What am I doing?!) and forced it all the way through. There was a nice imprint of the rifling on it when it dropped out. I measured it, both with a mic and a calipers and it measured .351! Is this possible? I size all my bullets to .358 so apparently they are squishing down pretty tightly.

Is it possible to have the barrel sized to .351? I did this twice, thinking there was something wrong in the way I did everything but it always came out the same. Could Taurus have cut a barrel undersized? Anyone else measured a .357 and had it come up short? I'm thinking it should be .357, maybe .358 or so but not 351. Whatta ya all make of this?????

[C A Plater]

If what you measured was actually bore diameter and not groove diameter, it could be just fine. It can be difficult to measure if it is an odd number of grooves and they are not opposite of each other so you get one groove and one land being off buy the depth of one side. Web site says it has 5 groove barrels so that may be what you're measuring.

[Harry O]

This is not exactly how to get an accurate slug and probably that is the reason you are getting .351".

I use soft lead round balls for muzzle loading myself. They are dead soft, they are available in a large number of diameters, and can be bought in a number of local places.

After pounding the ball into the muzzle (use a plastic hammer), you need to put a short piece of wood dowel in the back of the barrel (just barely under the bore size). This is easy in a revolver, but I have not tried it in a semi-auto. Then you take another piece of wood dowel and place it in the muzzle. What you have is two pieces of wood with a piece of lead between them. Then you pound on the wood sticking out the barrel. It expands it to full diameter. That is what you did not do. After done, remove the rear dowel and push the lead piece out with the front one. Then measure. If you have an odd number of lands, you cannot get a good measurement. Even number is easy.

[Ricochet]

One way to do it is to wrap a piece of shim stock around the slug, measure around the outside and subtract twice the thickness of the shim.

There's a method involving the use of a V-block you can Google up.

[JIMinPHX]

I usually need to grease the barrel to get the slug through it without hanging up. If you got it to go through with no lube & without great difficulty, I wonder if you got the lead to fully obturate into the grooves. Did the outside of the slug look shiny at the tops of the peaks or was it still the same dull color that it started out as?

I’ve seen oversized groove diameters, but I haven’t seen one more than a thousandth under before.

[mugsie]

The outside of the slug was nice and shiny. I had to oil up the inside of the barrel to get it through, and it took quite a lot of pounding in order to push it out the bottom (I used a breass ord slightly smaller than my barrel diameter). My son held the gun, and kept asking WHAT ARE YOU DOING?! It took some effort to get the thing through so I am sure it fully obturated (see, I can spell big words too!). Maybe it was because there's an odd number of grooves, I'll check it again tonight. In the mean time, I'm going to keep sizing to .358 and keep shooting. It was so much simplier when I was dumber!

Off to the range tonight with .358 sized SWC's. Whoopee!

[Bass Ackward]

Maybe it was because there's an odd number of grooves, I'll check it again tonight.


Ding.

[slughammer]

You can take the same slug and push it through again to get a better idea if there are any barrel restrictions.

Next thing to do would be to clean your cylinder throats and drop that slug through each one. This will give you a pretty good idea of the size relationship of the throat diameters to the groove diameter.

[405]

Ding, Ding! to BA and Ricochet :mrgreen:

BTW- you're sinker slug method sounds fine

[JIMinPHX]

Maybe it was because there's an odd number of grooves

Chances are good. You need a ring gage or something similar to measure those.

[MakeMineA10mm]

You can take the same slug and push it through again to get a better idea if there are any barrel restrictions.

Next thing to do would be to clean your cylinder throats and drop that slug through each one. This will give you a pretty good idea of the size relationship of the throat diameters to the groove diameter.

And to add onto what slughammer says, I'd suggest you size your boolits to chamber throat diameter and not to the bore diameter (as long as the chamber throats are the same size or bigger than the bore). If the throats are smaller than the bore, you need to get them opened up to optimize accuracy.