Measuring a 5 groove slug

[hammer58]

Hey guys, can anyone give me any hints on measuring a 5 groove slug? I have recently started casting my own boolits for a Ruger SP101 .357 with a 4" barrel. I am using wheel weights for the lead and a Lee tumble lube mold. I used some soft lead stick on weights with my Lee mold, STP and a hardwood dowel to make the slugs, and they came out fine. But I can't figure out how to get the outside and inside measurements of the slug since there are 5 grooves.

I have heard that with the tumble lube mold you don't even need to size the boolits. But sometimes the boolits aren't round so I would like to size them all just for uniformity.

Any suggestions?

[Catshooter]

Wrap the slug with some stiffish paper, measure, subtract twice the thickness of the paper.

Don't really have to size any boolit if it doesn't need it.

Welcome to the forum too.


Cat

[Charlie Two Tracks]

What do your boolits mic out at? Have you measured the cylinder throats yet? It is very hard to measure the bore of an SP-101 in my opinion. If the boolis are dropping at .358 or .359 you should be good to go. If you have a problem with leading, then worry about the measurements. If it shoots great, you smile a lot and cast a bunch! Welcome

[hammer58]

I've had some inconsistencies with the size of the boolits from the mold. Some measure .358, some .360 and are not round. I'm sure this is due to rookie operator error, so I wanted to size them to make them more uniform. However, at a load of 6.0 grains of HP-36 with the 158 grain boolits, I get just a little leading after 50 rounds but nothing that is difficult to clean.
I have not measured the throats yet. What should they mic out at?

Thanks for your advise guys! I am really enjoying this new hobby!

[JeffinNZ]

Reading Glen Fryxell's book he recommens measuring the throat of the cylinder and matching a boolit. Forget the groove.

[hammer58]

Thanks for the advise guys! Looks like I have some more work to do (Darn it ;)) I'll get back to you after I get these steps done...

[nhrifle]

Good advice on measuring the throat. The only way to measure odd-number grooved barrels to any degree of precision if with a v-micrometer. Darn things come with a heck of a price tag though!

[dilly]

Let me know how it turns out. I have a very similar setup. I think the same revolver and very likely the same mold and I have had some leading problems. It's on my to-do list but I haven't resolved everything yet.

[Pepe Ray]

As NHRifle said the appropriate mikes are for those with DEEP pockets.
BUT
Our own 45nut has "V"bloks for sale, made specifically for measuring 5 groove slugs.
Help yourself as well as our site. Give Ken a jingle.
Pepe Ray

[Blammer]

someone had an "angle" block and a formula to help with it and it was fairly cheap, anyone remember that?

[Tom Myers]

A while back, a member of this forum with the handle of Legion came up with the idea of fastening together 3 rods with a consistent diameter of about 0.3125" ( does not have to be exactly that diameter, just has to be uniform) then placing the 5 groove slug on the bundle of rods and measuring the distance from the top of the slug to the bottom of the lower rod in the bundle.

He submitted a formula that would calculate the diameter of the slug using the radius of the rods and the measured height of the stack and slug.

http://www.tmtpages.com/LinkSkyImages/forum_images/5groovesketch.png
a is the measured length.*
r1 is half the rod diameter.*
r2 is half the slug diameter


I used some algebra to make the formula a little simpler and then drew up a sketch to detail the arrangement of the rods and the measurements needed to plug into the formula.

For what it's worth, here is what I can find concerning the procedure.

Hope this helps.

http://www.tmtpages.com/LinkSkyImages/forum_images/5grooveRods.png

Let r = the diameter divided by 2 of the rods that are fastened together into a stack.
let a = the distance from the top of the slug to the bottom of the stack.
let z = the square root of 3 = ( 1.732 )
let d = the diameter of the slug.

Then

d= ( a - r - r*z )² / ( a - r*z)

substituting 1.732 back in for z, we get

d = ( a - 2.732*r )² / ( a - 1.732*r )


http://www.tmtpages.com/LinkSkyImages/forum_images/new-5%20groove%20dia.jpg

[Jim Flinchbaugh]

by the time your boolit leaves the case, the throat or the barrel will make it round, and size it all in one operation. Make it fit the throat
and enjoy :)
(unless your Ruger suffers form the thread choke and front sight base choke syndrome, like my redhawk did)

[hammer58]

Ok, so I slugged the throat of the cylinders and they came out to exactly .358. What diameter do I need to size my cast boolits to, considering that they are just wheel weights at a BHN of about 14? (I had a friend check the BHN for me)

BTW Tom, Nobody told me I was going to have to do any algebra! :???:

[Blammer]

.359 or .360 is my suggestion.

[hammer58]

Blammer, Midway is only showing a .356, .357, and .358 sizers for the tumble lube. So I guess .358? I tried to measure them as catshooter suggested in post #2 and best I could tell, the grooved slug measured .357.

[Pepe Ray]

Could someone please explain to me why it seems that everyone is determined to ignore Homer Powleys efforts.63554

[Pepe Ray]

Perhaps "simple" is not considered as being reliable?63555

Please explain to this confused old man.
Pepe Ray

[451whitworth]

Could someone please explain to me why it seems that everyone is determined to ignore Homer Powleys efforts.63554

that's the way i've always done it. I saw that exact picture in an old Gun Digest from the '70's

[.22-10-45]

Hello, Pepe Ray..It seems precision mechanical skill is fast going the way of the dino.'s in this country! I saw it starting over 40 years ago in High School from the smirks and looking down the nose at guys who went into machine tool training classes..never mind we have probably made much more over the years than the college guys stuck in their cubicals. No more young guys going into apprentiships..no more skilled jobs to go to! I wonder how this country would have fared in WW2 if we were in the state we are in today?..who is going to build the "arsenal of democracy" for tomorrows world war?

[Tom Myers]

BTW Tom, Nobody told me I was going to have to do any algebra! :???:

Hammer,

The algebra has allready been done. All that is left is simple arithmetic.

Measure the diameter of a rod and divide by 2 and call that value R (radius)
Measure the height of the stack and the slug and call that value B

Next, take that number R and multiply it by 2.732 then subtract the product from number A to get a number called B
Now thake that number B and multiply it times itself to get another number called C
Again, take that number R and, this time, multiply it by 1.732 and subtract the product from number A to get a number called E
Finaly, divide the number E into the number B to get the number called D
D is the diameter of the slug.

See, nothing more than subtracting, multiplying and dividing. Not even any addition.

This procedure is just a way of making and utilizing a poor man's V block. The last one that I considered buying was just a little pricey

[10x]

I have a V block and a micrometer.
I take an unfired .308 bullet and measure it to confirm it is .308.
Then place it in the V block and measure it with the V block, then I subtract 0.308 from that total measurement.
I measure a 5 groove bullet in the V block and subtract the "value" of the V block determined in the line above this one.
The difference is the groove diameter of the slug.
Or have I been doing it wrong?

[Pepe Ray]

10X
right or wrong depends on the angle of the "V" in your gage.
If it's 108* your golden. 90's or others will give inaccurate measurements.
See Powleys work in this thread.
Pepe Ray WHOOPS!! There is a formular used with a predetermined constant.

Oh 4377!!
I give up!!!!

[hammer58]

Tom, The crack about the algebra was a joke. It is something I might hear from some of my students.

As soon as I can round up something to use for the rods I'll give this a try and get back to you.

Thanks for your help!

[Tom Myers]

I have a V block and a micrometer.
I take an unfired .308 bullet and measure it to confirm it is .308.
Then place it in the V block and measure it with the V block, then I subtract 0.308 from that total measurement.
I measure a 5 groove bullet in the V block and subtract the "value" of the V block determined in the line above this one.
The difference is the groove diameter of the slug.
Or have I been doing it wrong?

10x,

The different diameters will contact the v-block at different heights so that probably isn't working as accurately as need be .

If you v-block has a value stamped on it then you will only need to measure the distance from top to bottom and then subtract the value stamped on the v-block then multiply the result by 0.89445.

If no value has been determined for the block and the angle is indeed an included angle of 72 degrees, you can determine the value for the block like this.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20block.png

To find the value "C" that will work with a certain v-block, place a rod or bullet with a known diameter in the v-block and, using a MICROMETER, carefully measure the distance A.

Calculate the value B by multiplying the diameter of the rod or bullet by 1.118.

Next subtract the value B from the value A to get the value C.

C is the value that should be used for that certain v-block.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20blockII.png

Now, to determine the diameter of a slug with an odd number of grooves.

Place the slug in the block and, with a micrometer (not a pair of calipers like the image shows), carefully measure A.

Next subtract the value C to arrive at the value B.

Now multiply B times 0.8945 (or divide by 1.118) to get the diameter of the slug.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20blockIII.png

Hope this helps.

[10x]

10x,

The different diameters will contact the v-block at different heights so that probably isn't working as accurately as need be .

If you v-block has a value stamped on it then you will only need to measure the distance from top to bottom and then subtract the value stamped on the v-block then multiply the result by 0.89445.

If no value has been determined for the block and the angle is indeed an included angle of 72 degrees, you can determine the value for the block like this.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20block.png

To find the value "C" that will work with a certain v-block, place a rod or bullet with a known diameter in the v-block and, using a MICROMETER, carefully measure the distance A.

Calculate the value B by multiplying the diameter of the rod or bullet by 1.118.

Next subtract the value B from the value A to get the value C.

C is the value that should be used for that certain v-block.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20blockII.png

Now, to determine the diameter of a slug with an odd number of grooves.

Place the slug in the block and, with a micrometer (not a pair of calipers like the image shows), carefully measure A.

Next subtract the value C to arrive at the value B.

Now multiply B times 0.8945 (or divide by 1.118) to get the diameter of the slug.

http://www.tmtpages.com/LinkSkyImages/forum_images/Vblock/5%20groove%20v%20blockIII.png

Hope this helps.

Thank you for the explanation.

[Blammer]

I finally found it on my computer. The picture I was looking for. Of course it's already been stated but here it is anyways.

http://i54.photobucket.com/albums/g81/blammer8mm/Vblock_zps3e6a5bbc.jpg (http://s54.photobucket.com/user/blammer8mm/media/Vblock_zps3e6a5bbc.jpg.html)

[alamogunr]

I finally found it on my computer. The picture I was looking for. Of course it's already been stated but here it is anyways.

http://i54.photobucket.com/albums/g81/blammer8mm/Vblock_zps3e6a5bbc.jpg (http://s54.photobucket.com/user/blammer8mm/media/Vblock_zps3e6a5bbc.jpg.html)

I've got that exact picture on my computer along with the instructions since I can't read the handwritten instructions in the picture. I got the V block from a member whose name I can't remember. I always think I will record information like names and dates but somehow even if I do, I forget where they are.

Do you remember his name, Blammer?