slugging a barrel

[dangerranger]

Im looking to buy a bullit mold for the BC 4570, and thought Id slug the barrel just to see that I was getting the right size. I dropped a wooden dowel down bore. its about 5" shorter than the bore. then a 440 round ball [soft lead]. and finally a short wodden dowel on top. a couple smaks with a mallet and then carefully pushed it out the muzzle. what came out suprised me. it has 8 lands , fairly shallow, but when I measure it am I suposed to measure it accross the gruves [widest measure]or the lands [narrowest]?

narrowest measurement is .4495 and widest measures .456

the other thing is the rifling gruves seem rough, is this something that will smooth out over time?

first time slugging any barrel and not shure of what to expect. DR

[PawPaw]

Welcome to slugging barrels.

The slug you're holding in your hands is a mirror image of the bore.  The high spots on the slug are the grooves in the barrel.  Measure it across the grooves.  Your wide measurement of 0.456 sounds about right.  Use a cast bullet at least 0.001 larger than the groove diameter and you should be fine.  Most bullet molds for that caliber throw a bullet that is about 0.459, depending on the alloy you use.  I've got a couple of molds and after the bullets are cast, I run them though a Lee 0.459 sizer.

Eight lands and grooves with shallow grooves tells me that you've got a microgroove barrel.  It's no big deal and many of us have microgroove barrels in the .45-70 and they shoot cast bullets just fine.

The grooves seem rough?  Maybe so.  If it's a new barrel, then it might be rough.  They'll smooth out with use, or you can polish it.  Look in the FAQs.  I believe there's something in there on polishing barrels.

[bikerbeans]

If  you click on the banner for LBT you can read their information on how to do chamber casts, and barrel slugs.  Also, they have a procedure to fire polish your bore with lead slugs and a polishing compound.  I haven't tried LBT's products yet but plan to in the near future on a one of my 45 cal rifles. 

BB

[Catshooter45]

Four five six sounds kinda small to me.  Exactly what did you measure the slug with?  Are you sure you upset the slug fully?  My .45-70 is a .4585.  Yours could be a six, just seems a little small, that's all.


Cat

[dangerranger]

I am shure it was compleately upset. it was a nice even ring all the way around. I expected to see .457-.458 but with deeper gruves. DR

[briannmilewis]

...I haven't tried LBT's products yet but plan to in the near future on a one of my 45 cal rifles.  

BB

Hey BB: There's just something a little wicked in having the other guy be the guinea pig eh?

[bikerbeans]

Brian,

I don't mind being the test pilot, one of my favorite phrases is "hey ya'll watch this"!    I don't think someone is blazing new ground with LBT they have been around for a bit.


BB

[dangerranger]

its been too hot to go out and shoot, so I hand lapped the bore. a friend had abrasives in 1,000 1800,and 2400 grit. I did notice it was tightest just back of the muzzle. Ill try slugging again and this time push it out through the chamber. one thing I did notice was that a cleaning patch runs so much smoother now. DR

[briannmilewis]

Brian,

I don't mind being the test pilot, one of my favorite phrases is "hey ya'll watch this"!    I don't think someone is blazing new ground with LBT they have been around for a bit.


BB

BB - Just had to yank your chain a bit!