measuring slugs

[bigboredad]

Ok guys don't laugh to hard I have a simple question but can't seem to find the answer with all the help I've had through this board I know the answer can't be far. I know how important slugging the barrel and cylinder throats are but when it comes to measuring them I get readings that make no sense so can someone explain to a slow redneck how to properly measure a slug

[snaggdit]

Well, I'll try to help since it seems everyone is hiding on this one. The problem is if you have an odd number of grooves. Lets hope you don't and move on. When a boolit (pure lead) is driven through a barrel it is squeezed by the lands between the grooves. The result will have the large size being from flat to flat (groove to groove). I use a calipers but many warn that a dial caliper is not as accurate as a micrometer. If you have one, use that. What caliber and what readings are you getting?

[dromia]

Ken used to have some "V" blocks made by Pepe Ray for measuring 5 groove barrel slugs. They work well and have the formula stamped on the block so you don't spend time looking for piece of paper that you put away safe from the last time.

[Shiloh]

Like snaggdit said, this is best suited for a micrometer.
Calipers are adequate for most reloading measurements, but they are not accurate like micrometers.

Shiloh

[bigboredad]

I am working with calipers and 2 ruger blackhawks i slugged one barrel and was gettin readings in the 43 area a tad tight for a .45 I would think

[Ekalb2000]

bigbore,
I just (5min ago) slugged my SBH and got 433 in the smallest part of the cylinder, and 430 in the brl. So if my WV math is right, i could size to 432. But will try 431 first.
hope this helps.

edit for a big brain dump: cst WW drop at 433, cylinder is 432, brl is 431.

[madman]

Nope size it slightly over or equal to at the smallest dia of the cylinder. When the round is fired it is forced through through the smallest part of the cyl then slammed into the forcing cone on the end of the barrel. If the transition from cylinder to barrel are timed correctly and the cylinder being exactly the same size as the barrel and the boollit is centered in the case and the case wall tension is the same all away around the boolit and every primer and gain of powder it the same and fire it at the same rate you will get perfect accuracy of course it also has to be held solid in the same axis every time it is fire. But in real life that is almost impossable. Except for 44man he must be s robot this guy gets groups that I envy.

[Ekalb2000]

So start with 432?

[bigboredad]

ok lets see if I learned anything since I've been here I slugged both my .45 blackhawks first one had throats of .451 no surprise the since the revolver was made in th 90's its barrel was the surprise it was a tight .450 I tried for over a hour to get a higher reading but that's the biggest I got. My second .45 had thoats of.453 and the barrel measured .451 I the first .45 it will chamber a .454 diameter round with out a problem so if I was lazy i could just size everything to .454 and i should be good to go in both guns? thats is the question is .454 the size I need ? tia

[snaggdit]

I would go with .453. Squeezing down .004 from .454 to .450 in the barrel of your second gun is a bit much, IMHO.

[bigboredad]

yeah snaggdit thats what I started thinking about later on but what way to increase recoil I could have some strong wrist shooting hot loads out of it sized to .454 maybe some day when I grow big and strong I couldhave wrists of steel just like Elmer Kieth ha ha

[MtGun44]

You are looking for a good fit in the throat so the boolit doesn't get cockeyed in the
cyl prior to hitting the barrel. However, if the throats are substantially smaller than
the barrel, especially if you are using hard alloy, you get an undersized slug (sized
by the small throat) rattling down the larger barrel. BUT - if the alloy is soft enough,
and especially with a hollow based boolit design, the undersized boolit will expand
to fit the larger barrel and shoot well. The hard, undersized slug will lead like the
dickens in most cases. The ideal is where the throats are about .001 to .002" larger
than the barrel groove diam, and making the boolits the same as the throat diam
or about .001 larger.

Massively wrong diameters are so common on Colt Single Action Army revolvers in
.45 LC caliber that the std lead factory boolits are very soft and hollow based so that they can
adapt to these mismatches and still shoot reasonably well with little or no leading.

Bill

[bigboredad]

Thanks Mtgun44 and to all those that helped

[machinisttx]

Ken used to have some "V" blocks made by Pepe Ray for measuring 5 groove barrel slugs. They work well and have the formula stamped on the block so you don't spend time looking for piece of paper that you put away safe from the last time.

I don't know how much the V blocks are, but if one intends to do a lot of slugging for five groove barrels(S&W, I presume?), this micrometer (http://www.use-enco.com/CGI/INSRIT?PMAKA=601-2104&PMPXNO=2615145&PARTPG=INLMK32) is the proper one to use. There are other models available for three groove barrels. Starrett makes a similar tool. It should be pretty easy to find one cheaper on egay. If anyone goes that route, make sure you're getting the right one, as the one intended for measuring three flutes/grooves is a lot more common. :-D

[Ekalb2000]

Just sluged my 94. It is 432.
I might just be getting away with not sizing these 310 grainers. They are measuring out at 433 a week after cast.

[Bret4207]

You can have the finest micrometer in the world, but if you don't have a standard to check it what good does it do you? Get a standard- a precision ground hunk of metal of an EXACT size- and then you can check your mic and calipers against it. Calipers need to be checked all the time, a mic not so much.

I say this after learaning why my .308 diameter Sierra bullets were measuring .304.....

[machinisttx]

You can have the finest micrometer in the world, but if you don't have a standard to check it what good does it do you? Get a standard- a precision ground hunk of metal of an EXACT size- and then you can check your mic and calipers against it. Calipers need to be checked all the time, a mic not so much.

I say this after learaning why my .308 diameter Sierra bullets were measuring .304.....

The V anvil micrometer I linked above comes with an appropriate standard. A regular one inch micrometer doesn't need one, since you can screw it closed to check zero. Quality calipers rarely need to be checked. Other than getting dropped or smacked, they shouldn't change(calipers may if they get crap in the gear or rack).

The place I linked has both precision ground gage pins($40 or so for a set), and precision ground gage blocks. They also have micrometer standards if you need them.

[Bret4207]

IME checking with a standard, especially with everyone using the inexpensive calipers these days, is always a good idea. Yes, good quality instruments stay in adjustment longer. But you also have to remember a lot of people aren't machinists and don't know HOW to use a caliper or mic. I'm sure you've seen a noobie crank down on a mike or caliper. By having the standard they can use it to learn how to use the tool so that they get good repeatable measurements.

[dromia]

I don't know how much the V blocks are, but if one intends to do a lot of slugging for five groove barrels(S&W, I presume?), this micrometer (http://www.use-enco.com/CGI/INSRIT?PMAKA=601-2104&PMPXNO=2615145&PARTPG=INLMK32) is the proper one to use. There are other models available for three groove barrels. Starrett makes a similar tool. It should be pretty easy to find one cheaper on egay. If anyone goes that route, make sure you're getting the right one, as the one intended for measuring three flutes/grooves is a lot more common. :-D


Pepe's blocks were around $25US I seen to recall, don't know how much the ones your suggesting are as the Enco site was down when I tried the link.

I slug a lot of Enfield rifle barrels and the correct geometry "V" block makes it a doddle using my one inch micrometer.

[snaggdit]

I have worked in production woodshops and when a tape measure gets dropped and the tip bent we tossed it. Checking against a known standard is a very good idea. I have less experience in machining but have done a little (read newbee) and I do know enough that gage blocks are invaluable for setting up tooling etc.