Sprue "shaver" or base "truer"?

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  • Last Post 29 October 2014
Pentz posted this 23 October 2014

Did a search but may not have had the correct search term. I made the cardinal mistake of picking up a digital scale ;).  Now I discover my bullet weights vary principally due to the sprue scar on the base of my bullets.  So, inviting scorn or ridicule, is there an accessory or device designed to shave off a little sprue scar from the bullet base? 

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TRKakaCatWhisperer posted this 23 October 2014

There is one person around here that grinds the sprue cutter edge to right-much square and sharp - uses a return stroke with a little pressure to shear the whole base square.

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onondaga posted this 23 October 2014

http://castbulletassoc.org/view_user.php?id=7960>Pentz

Sorted for match grade cast bullets means 1% by weight. Closer weight matching than 1% does not make groups smaller with cast bullets.

Good casting skill will do that. The best method controlling bullet weight within 1% for me is timing so I can open sprue cutter with  a gloved hand pushing down and opening up the cutter plate leaving a smooth cut with no chunking of sprue hole lead due to opening at the wrong time. Traditional tapping with a wooden billet to open cutter plates allows a poor fitting cutter plate to work cutting high or low depending on how you strike. That sends bullet weights all over the place.

It takes a practiced skill to glove hand open a mold and that is NOT an easy skill to develop. There is no tool that will do this.

Keeping pot temp stable is also important. I use a PID temp controller and only drop sprues into the pot when starting a new batch. This keeps temp pretty constant also helps bullet weight consistency.

Knowing how to check cutter plate fit when hot and adjusting if necessary will also help.

Dont pick a random number that you think your bulllet weights should be matched within. 1% is the match standard. So if your bullets average 250 grains for example, all bullets weighing plus or minus 1.25 grains from the average 250 grains are match grade matched because 2.5 grains is 1% of 250 grains and midway of 2.5 grains is 1.25 grains.

Gary

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gpidaho posted this 23 October 2014

Saw a  nice little homemade gadget over on the Boolits forum.  A block of hardwood with a file let in with a router, and another smaller block used as a slide, with the appropriate size hole drilled to accept the bullet and hold it plumb I'm going to make one and give it a try.  GP       

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Longone posted this 23 October 2014

You have a link for that gadget ? Or maybe some pics of your finished product.

Longone

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Pentz posted this 23 October 2014

I was using one of Pat's PIDs and my weights vary between 199.1 and 200.4, or 1.3 gr. That is less than 1% so maybe much ado about nothing aside from getting gas checks square. I too am interested in the base truing gizmo, tho.

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corerf posted this 23 October 2014

TRK wrote: There is one person around here that grinds the sprue cutter edge to right-much square and sharp - uses a return stroke with a little pressure to shear the whole base square.

Thats a really great idea.

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joeb33050 posted this 23 October 2014

The “cut the sprue-move the sprue plate back so the hole is not over the bullet base but the sprue plate is over the bullet base-whack the sprue plate to flatten the lump” method, which I invented. After casting and opening the sprue plate, close the sprue plate such that the plate and not the hole is over the bump, and give the top of the sprue plate a good whack with the yellow plastic mallet. This will mash the bump down and make it go away. file:///C:/Users/JOEB33~1/AppData/Local/Temp/msoclip1/01/clipimage003.jpg file:///C:/Users/JOEB33~1/AppData/Local/Temp/msoclip1/01/clipimage004.jpg               Several good shooters have criticized this method, adamantly warning of mold damage and sprue plate bending. (None have reported actually trying the method.) I just, January 2009, completed four sessions, casting about 900 314299s, and there is no damage to the mold or bend in the sprue plate. So it works for me, and may work for you. 

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corerf posted this 23 October 2014

Hmmmm. Ive read that somewhere Joe, Cast Bullet Handbook? I think so. That method is familiar, but maybe I read it here on the forum. Either way.

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gpidaho posted this 23 October 2014

Sorry Longone, looked and couldn't find thread again. I will try to post pic when I get mine made. As close as I can describe it the end view of the blocks is a large mortise and tenon joint with a file let in flush in the center of the tenon. The upper block end view the mortise. from the top view there would be a row of holes to fit the bullets and hold them square against the file when drilled down through the top of the block into center of the mortise. then just lightly hold down the nose of the bullet and slide top block over bottom block. Hope that's all clear as mud. LOL  GP

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Tom Acheson posted this 24 October 2014

Maybe not germain here but someone asked about taking the “flash” off the edge of the base of a bullet so he could get the gas check started. I suggested a light “trimming” by using a case mouth deburring tool. One maybe two light turns and a very slight bevel is made and the gas check starts. Might also work for a plain base bullet that won't be sized.

FWIW

Tom

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Brodie posted this 24 October 2014

N.O.E. sells aset of tools to 1. hold the bullet and 2. to remove the flash.  They look like they would be great for removing the flash that sticks on the bases of my .225 bullets, and makes getting the gas checks on a real Bear. Brodie

B.E.Brickey

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Ed Harris posted this 24 October 2014

It is real easy to get distracted measuring with micrometers while cutting with axes. A 1% weight variation is good. If you are not getting good groups your have some other problem. Correct casting technique, sprue plate adjustment and careful visual inspection alone are adequate for all, but the most severe competition requirements.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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Ken Campbell Iowa posted this 24 October 2014

mixing micrometers with axes ... heh i love that.

at the other end, i did catch an employee setting up my 3d tracer mill with a yardstick. i loved that too ... heck a good story is a lifetime investment.

moderation in all things.

ken

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Brodie posted this 24 October 2014

Just don't try to drive tacks with a sledge hammer or break rocks with a tack hammer. Brodie

B.E.Brickey

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Pentz posted this 25 October 2014

Thanks to all. I'll pay attention to my sprue plate technique next cast. Still have not mastered the gloved hand technique - need to consult sensei....

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Pentz posted this 25 October 2014

Just wanted to write that digging through some old issues of Black Powder Cartridge News (Sept. 2010 Issue #69:38) yielded a very helpful article by Bob Glodt “Diagnosing Bullet Mould and Casting Problems". Think this one has me squared away.

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cove posted this 28 October 2014

Pentz I have had good results using the sprue wrench I wrote about in a recent FS. Can't remember issue number, but it's the one with the 38 hollow base wascutter mold on the cover. Using the wrench, I cut the sprue very slowly while the sprue is still hot(within a second or two after the sprue frosts over). I mostly use 20-1 alloy , but have had equal success with numerous other alloys. Using this method, after a little trial and error, I get no tearout and a smooth base. Hope this information is helpful. Cove

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cheatermk3 posted this 29 October 2014

Pentz, Holding the handles together. put your filled mould down on whatever you dump your castings on, push the sprueplate down gently onto the top of the mould whilst turning it to cut your sprue.

You'll get the hang of it pretty quick I'd guess.

MM

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Pigslayer posted this 29 October 2014

We're just sending lead bullets downrange fellas. Not building a piano! Holding to 1% is pretty darn good! Splitting hairs probably won't make any difference.

Pat

If someone else had of done to me what I did to myself . . . I'd have killed him. Humility is an asset. Heh - heh.

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