Tool to measure squareness of bullet base squareness

[Etienne Brule]

Hi,

I use to cast 540 grains Creedmoor bullet for long range black powder shooting in cal 45-90

I use tin/lead 1/20 and I weigh each bullet to be +- 0.1 grain.

I want to know if there is a tool to measure the squareness of the base of the bullet ?

Thank you

[Outpost75]

v-block and dial indicator will work, but they make regular case and bullet spinners.

[LUBEDUDE]

Boy that's an awful tiny T- Square! :grin:

Good idea for your application. Just may be a money making opportunity.

[Garyshome]

Any kind of square would do. No need to make one just for this application.

[reed1911]

How precise do you want to be? IMHO a square would be about the limit of practical use, you could set up all sorts of jigs, comparators, etc.. However, so long as the base is 90 degrees, that will be close enough. Anything more than that is not material since once it get into the bore, the more precise measurements have just gone all to hell and are unpredictable in the course of precision.

[Baja_Traveler]

Seems to me that if you are getting complete fillout of the mold, it would all be wasted effort. As soon as that round goes off any minor difference you might detect is going to be smashed into the wad and obturated to the bore.

[country gent]

Starret and several make a small die maker sqyare that will work very well. set the base of the square to the side of the bullet with the blade over the base and sook at a bright light. a couple thousandth out will show. As mentioned above a vee block on a suface plate with indicator in a hieghth gage will also work but is a lot slower. mount bullet in vee block on a stop. catch bullet base and check 4 corners, un mount and mount next. Tere are fixtures that will do this available also. Personally I would go with the square. If you have access to an optical comparator this would be the fastet. A CMM ( co ordinate measuring machine would also work and be very accurate but these are usually in the 50,000 range. If you have the surface plate sitting the bullet on its base with the square against it and turning the bullet will give good results also. Square is in both x and y plains. Once the molds are proven square they should always be square unless work is done on them

[Taylor]

Boy that's an awful tiny T- Square! :grin:

Good idea for your application. Just may be a money making opportunity.

:drinks:

[2AMMD]

Brown & Sharpe and Starrett make small machinist squares. Should be accurate for your purpose. They are NOT cheap though.
2AMMD

[Moonman]

A small SQUARE is known as a TOOLMAKER'S SQUARE to Machinists.

[bangerjim]

Yes....T&D make's squares. I regularly use my set of 4 of them to check squareness of boolits, tools, models, and all the stuff I make. Great for squaring table saw blades!


Starrett is the best......$$$$$$$$$$$$$$.. Enco sells some cheap imports.

banger

[montana_charlie]

If you have a problem that you think is caused by the base not being square, you might not have a fully filled out base.
If the base edge is rounded ... even a little ... it is probably rounded by a different amount on different sides of the bullet.
If you drag your finger across the edge of the bullet base and it feels nice and silky, the edge is rounded.

Is the corner of the base sharp enough to feel 'uncomfortable' when you drag your finger across it?

CM

[EDG]

If you want a number to quantify the squareness of the base you can use a small surface plate, a V block and
a dial test indicator.

[HNSB]

Most of the methods mentioned assume there is no taper in the boolit.
If you have taper and don't have access to a CMM or comparitor, it would be tricky to determine how square the base is to the centerline.
A surface plate and an indicator would work - if you had no runout. If you have taper and are out of round, I'm not sure how to measure accurately without a comparitor or cmm. Probably a surface plate and indicator, with index marks on the boolit and rotating it against a stop at the base would get you close.

[fguffey]

"I want to know if there is a tool to measure the square-ness of the base of the bullet ?" Then you want +/- 0.1 grain.

Sizing bullets can square up the bottom, something that does not exist: Stack two plates, drill and then taper the holes and install tapered pins for alignment 'ever time'. After installing alignments pins drill small holes through both plates, separate the plates and tap holes in in the plate that is going to be the bottom plate. In the top plate drill holds that are the correct diameter for your bullets, all the holes can be the same diameter or different diameters.

A screw in the bottom plate can be used to push the bullet up and level with the top of the holes in the top plate. Flat, square and level? Shear the bottom of the bullet that is protruding with a file, plane or very sharp scraper, a file makes a very good scraper.

Could be a problem, the +/- 0.1grain thing, but even if you do not square the bottom you could visually inspect the bottom of the bullet.

F. Guffey

[W.R.Buchanan]

The squareness is built into the mould. If you check the boolit by rotating it in a vee block with an indicator on the base you'll be able to see if your mould is good or not.

Not much you'll be able to do to change it after the boolit is dropped from the mould unless you want to put it in a lathe and face it. Then it would be square to the centerline of the boolit.

If the boolit base is NOT square to the CL of the boolit then throw the mould away and start over.

It would be difficult to imagine a mould that had a base that was angled one side to another .

I don't know how you would make such a thing, considering how moulds are made in the first place.

Randy

[Etienne Brule]

The squareness is built into the mould. If you check the boolit by rotating it in a vee block with an indicator on the base you'll be able to see if your mould is good or not.

[...]


Randy

Thank you everybody,

First, I do not assume that the squareness of the base is not right, although I want to ckeck it.

I am often wondering if the sprue plate has the right tension over the mould.

I will give a try to the indicator on the base of the bullet in a v-block to check that squareness.

Thank you

[myg30]

Face them in a lathe ? How about and RCBS bullet puller collet, put them in up side down and swipe a file across the base ?

just thinking out loud on my keyboard.

Mike

[.22-10-45]

The best "tool" I have found for square to body bullet bases is a nose-pour mould!:wink:

[Etienne Brule]

It would be difficult to imagine a mould that had a base that was angled one side to another .

I don't know how you would make such a thing, considering how moulds are made in the first place.

Randy

So, the problem was in the sprue plate... too loose ...

Thank you

[W.R.Buchanan]

Seems that could be fixed pretty easily.

Sometimes I have found that people make things into problems that really aren't problems at all if they just looked a little closer.

Randy

[MtGun44]

How would it get out of square? Neither cherry method or lathe
boring can produce a mold cavity with an asymmetric base.

Bill

[HNSB]

If the block isn't faced in the same operation as the cavity is cut, it could be out of square.

[W.R.Buchanan]

The blocks are Blanchard ground to size and matched before they are cut by the Cherry method. If they are not square they probably wouldn't fit into the fixture and close properly.

Whereas there could be situation where the blocks are not in the fixture perfectly like if a chip was under it, I think this is unlikely since anyone who is making moulds should be a decent machinist.

With the high end custom moulds the idea of an out of square base is just something you're not going to see very often. most of the CNC guys are actually cutting each half of the mould independently and if the blocks weren't perfect they simply wouldn't go back together to make a round boolit.

This operation really amazes me.

Randy

[detox]

Here is Veral Smiths trick:

To square bullet bases on both gas check and plainbase, have the lift out plug machined concave. I turned stem in cordless drill, then gound stem concave using a Dremel with small medium grit sanding drum.

Lyman or H&I sizers have a concave end machined in allready, but their stem has a looser .001 fit in die. My RCBS versions have a tighter .0005 fit.

When you size, press down at the bottom of the stroke until the liftout plug prints a ring around most of the perimeter of the bullets base. Not much force is needed for soft 20/1 alloy. You do not want to deform bullet whan doing this.

[detox]

Another method would be turning bullets in 1/2" drill press to grind bases square/true on sandpaper. Most drill presses have a built in adjustable stop for repeatability. Weigh bullets as you go.

Over thinking....