How much out of round is acceptable?

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  • Last Post 03 February 2014
cbshtr posted this 14 December 2013

I have a single cavity Lyman 429244 mold that casts almost perfectly round. Wanting to increase production I recently bought a two cavity Ideal mold of the same number. I tried casting as it came and the bullets were .006” out of round. I then cleaned up the mold, removed any burrs and and high spots then reset the alignment pins. This time around they were .005” out of round. The cavity holes looked to be close to matching up with just a hint of stickiness when opening them so I'm sure I can't align the cavities any better. They produce well filled out bullets rather quickly so it is nice to use. My question is how out of round before losing accuracy. i should mention that the low end is .002” under what I need so I am concerned about leading. I will be using these in my Redhawk and possibly my Marlin 444. Comments are greatly appreciated since I don't have much time if I decide to return it. Thanks.

Robert Homan

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frnkeore posted this 14 December 2013

I don't have any faith in a mold with more that .002 out of round.

.005 is to much and can lead to gas cutting. Misaligned molds can be fixed. I did a thread on repairing one of my molds that was .006 out of round.  http://www.assra.com/cgi-bin/yabb/YaBB.pl?num=1381954877

Frank

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Ken Campbell Iowa posted this 14 December 2013

pretty cool fix-it, frank ...

as a wanna-be machinist, i wonder how they screw those molds up 0.006 ...made by committee i suppose ...in 7 different machines ... sigh ..

ken yer 2 sticks m&n are on the way 1st class.

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cbshtr posted this 16 December 2013

I checked out the link that Frank posted and I believe that would probably solve the alignment problems. Trouble is I don't have the equipment to do it. I am trying one more time and if I can't get them closeted it is going back. It's a shame cause the mold spits out well filled out bullets real fast.

Robert Homan

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Ed Harris posted this 17 December 2013

For utility hunting purposes I wouldn't worry about out of roundness of less than 1% of bullet diameter. However, an out-of-square base, even by a minute amount, raises hell with accuracy.

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

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Wayne S posted this 20 December 2013

Does this also apply to molds that have been “beagled ” to intentionally increase the Dia. on the bands & nose ?

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Ed Harris posted this 21 December 2013

Wayne S wrote: Does this also apply to molds that have been “beagled ” to intentionally increase the Dia. on the bands & nose ? Yes.  That has been my experience.  It is how I came up with the 1% figure. Round moulds which are beagled then throw out of round to about the extent of the beagle. But I've found a bullet which fits and may be a wee bit out of round, shoots better than a round bullet which is too small and therefore doesn't fit.   Unless your requirements are very stringent for benchrest competition, fit is more important than roundness, within reasonable limits.  Seek moderation in all things, including moderation.

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

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pat i. posted this 21 December 2013

Ed Harris wrote:   Seek moderation in all things, including moderation. I like it!

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Ed Harris posted this 21 December 2013

I cannot take any credit for originating that wisdom. It was a favorite toast of an Irish Catholic Navy Chaplain I knew, who was prone to take a drink now and then.

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

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cbshtr posted this 21 December 2013

Getting closer to round by using a round file on the alignment holes to gently remove a little metal allowing the blocks shift in the direction they need to go while still locking up snug. Will keep you posted of my progress.

Robert Homan

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sbhg posted this 28 January 2014

Last post at a month (+/-) old, but I have a question. Since this mold is a GC, does it really make any difference if it is out of round that amount? Wouldn't it clean up somewhat when it is sized and GC seated? Surely there would be no gas cutting with a GC. Thanks some one for an answer.

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cbshtr posted this 01 February 2014

The problem is that if the low side is LESS than your targeted diameter you will probably get gas cutting even with a gas check. The gas check can't seal the gases until it seals the throat. By that time the undersized bullet is exposed to gas blowby.If it is smaller then you have the option of lapping it out to get the diameter you need but then you just increased the larger diameter. If the low side was what I  needed and the high side only 2 thousandths over then I would have never started this thread. But the extremes I had got me wondering when accuracy starts to fall off. Now if I can just get this mold lined up I will be where I need to be since the midpoint between the 2 extremes is exactly what I need. Now if the weather would just cooperate then I would be able to see I how close I am.

Robert Homan

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Scearcy posted this 03 February 2014

I know the question wasn't how to fix a bullet but rather how to cast a better one in the first place. Having said that ,I have been able to fix some fairly poor bullets with the use of a Lee push through die. I have two 311299 molds that both drop oblong bullets. I beagled both molds and then put all of the bullets through a .311 Lee die. A side benefit of this approach was that the gas checks were seated more uniformly with the use of a push through die also. The resulting bullets did not provide match winning accuracy but they were useful for any other type of shooting I might do.

While I don't like using gas checks on handgun bullets I also have been able to control leading in a couple of problematic 44 Mags by gas checking the bullets with a push through die. For what it is worth

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