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.22-5-40
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Mold base-band enlarging
Jan 4th, 2019 at 7:59am
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I have a Sabonis .32 tapered mould that breech-seats nice in my Stevens-Pope Ballard .32-40...But base band needs to be .327 dia. for no-light seal.  Needs .004" enlargement.  Who would you recommend for this work?  Thanks!
« Last Edit: Jan 4th, 2019 at 8:54am by .22-5-40 »  
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rgchristensen
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Re: Mold base-band enlarging
Reply #1 - Jan 4th, 2019 at 9:01am
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     You might try shooting it first.   With an appropriate wad placed in the breech-seater so that it ends up behind the bullet, it might work fine.  Setting the blocks up to bore out the base band can be tricky, as the cavity is not always square with the exterior of the blocks.  Doubly tricky with a tapered cavity, I'd think.  "If you improve something enough, eventually you will screw it up!"

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RGChristensen
  
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calledflyer
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Re: Mold base-band enlarging
Reply #2 - Jan 4th, 2019 at 9:35am
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Maybe seating it further would help too. It could be that it's still in the leade of some barrels and not sealed, but further up would do it.
  

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OLD TUCK
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Re: Mold base-band enlarging
Reply #3 - Jan 4th, 2019 at 9:53am
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I have over many years Bored Base bands for just the reason you have mentioned. All you need is to find a Machinist in your area with a Nine Inch South Bend Lathe with a 4 Jaw chuck. The issue of getting the Blocks properly square is a real one. My method has been to get the Mold roughly trued up with Copper or Brass shims on all four sides. Then using the four Jaw adjustment push the Mold around until you get an Indicator reading that shows Minimal run out in two places
in the cavity. Once you get that you are ready to Bore. I always ask for some bullets cast from the Alloy the guy uses. With that I can calculate what the Bore has to be brought to for the Diameter wanted. In a few cases I have found the cutoff face of the Mold NOT really square. So while it is still set up I would face off that surface by whatever it needed to give a Bullet with a square Base, usually .002-.003. I never attempt to do any more than that. I have more than a few Mold Blocks with screwed up inner conditions from trying to find my way to where change was requested. Ask me how I got them for a fun response. I only ever now do anything but the BASE. HTH Regards FITZ. OLD TUCK Smiley
  
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marlinguy
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Ballards may be weaker,
but they sure are neater!

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Re: Mold base-band enlarging
Reply #4 - Jan 4th, 2019 at 11:57am
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I've also opened up molds using a bullet cast in the mold, and valve lapping compound. I drill and tap the bullet base to accept a machine screw, and then chuck the screw/bullet up to spin it. Put lapping compound on the bullet and close the molds as I spin the bullet.
Lapping molds can be time consuming, but it's worked well for me, if the mold doesn't need a large increase in size.
  

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ledball
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Re: Mold base-band enlarging
Reply #5 - Jan 5th, 2019 at 9:57am
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You might consider having someone make you a simple “bump” die to bring the bullet to the size wanted.  Ledball
  
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OLD TUCK
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Re: Mold base-band enlarging
Reply #6 - Jan 5th, 2019 at 11:51am
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I had a friend now passed that bought a Kraut Martini with a Brezine barrel in 32-40. He got it cheap as the person he bought it from told him he could not make it shoot. It has a bright shiny perfect looking bore. Guy started shooting, Bad, Bad, Bad. So he checked the Bore. Was NOT! a .32 but a .33
caliber. So he took some of the .32 cal. bullets he had cast and pan lubed and ran them into a .33 cal. Lube die and gave them an extra pull when they were bottomed and bumped them up, they bumped right up to .33 caliber the whole length. Shot beautiful, a tack driver. When he ran into the seller the next year he told him and he the seller was bull$hit. He had gone to great lengths to get Brezine to bore that barrel. So the option of "Bumping UP" is or can be done. HTH FITZ. OLD TUCK Smiley
  
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.22-5-40
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Re: Mold base-band enlarging
Reply #7 - Jan 5th, 2019 at 12:45pm
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Thanks for replies, I have lapped base band using both coarse & fine Clover lapping compound..Have yet to have a chance to try out mould...but base band was originally .323..at the time I was trying for .324..barrel groove dia.  I did not yet know I needed .327 for seal.  I used plug gages to check dia. and stopped when a .325 was a close slip fit.  I'll have to try out mould and lap more if needed...takes a lot of time & effort...but sometimes going slow is the best and safest way.  Thanks again.
  
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Chuck V
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Re: Mold base-band enlarging
Reply #8 - Jan 8th, 2019 at 1:02pm
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Gents-
In recent years, I have used Erik Ohlen at Hollowpoint Mold Services (IIRC) in Oregon to enlarge the base band of a Lyman mold by a few thousands-  he also does a great job at removing gascheck bases.  His work is always well done, prompt, and surprisingly affordable.  Quality work by a young machinist that cares!  (541) 738-2479
Chuck
  
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marlinguy
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Re: Mold base-band enlarging
Reply #9 - Jan 8th, 2019 at 1:42pm
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Erik's hollow point conversion work is fantastic for those hunting with cast bullets! The work is perfect.
  

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uscra112
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Re: Mold base-band enlarging
Reply #10 - Jan 8th, 2019 at 7:26pm
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I once took out the gas-check shank with a chucking reamer, using the mill.  Setting up took 1/2 hour.  Cut took seconds, turning the reamer by hand.  Reamer held in a guided type tap wrench.

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Reamer cost me $20, but it also made me a sizing die into the bargain.

  
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JLouis
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Re: Mold base-band enlarging
Reply #11 - Jan 8th, 2019 at 10:07pm
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uscra112 when ordering the reamer how much over the exact size desired did you add for bullet shrinkage and what caliber and alloy was being used.
  
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uscra112
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Re: Mold base-band enlarging
Reply #12 - Jan 8th, 2019 at 10:11pm
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Since it was a .25 caliber bullet that I expected to size, I didn't even think about that.  Reamer was .259 if memory serves.
  
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