Author Topic: Double cavity mould & weight consistency...  (Read 2433 times)

Offline Skychief

  • Hero Member
  • *****
  • Posts: 650
Double cavity mould & weight consistency...
« on: March 31, 2010, 05:23:59 AM »
For those with double cavity moulds....how close in weight are the balls from the different cavities?

I cast some .445's tonight with my Lyman double cavity.   One group weighed ~132 grains and the other group weighed ~ 134 grains.   Is this fairly common?

northmn

  • Guest
Re: Double cavity mould & weight consistency...
« Reply #1 on: March 31, 2010, 03:04:40 PM »
Ive noticed some variation like that in casting bullets from my Lyman molds.  Some throw heavier bullets out of one end.  Whether it makes a practical difference depends on your use.  For a cap and ball revolver likely not, for a chunk gun or X sticks maybe.  The other issue is that if you weigh for consistancy a bullet from the heavier end with an air bubble might be within parameters of the light side.

DP

Offline Maven

  • Hero Member
  • *****
  • Posts: 637
Re: Double cavity mould & weight consistency...
« Reply #2 on: March 31, 2010, 09:21:14 PM »
Skychief, Regardless of whether you're casting RB's or say, .30cal. rifle bullets, there is usually some variation in the weight and occasionally diameter of the castings (assuming the alloy is constant).  Some of this can be reduced by pouring technique and maintaining a fairly constant temperature (I use a casting thermometer for this,)  You can further reduce weight variation by weighing a sample (~25 - 40), calculating the mean and standard deviation, and retain only those RB's (or other types) within that range.*  That way you can't fault the projectile for a flyer or missed shot.  Btw, I have a Shiloh .495" RB  mold whose cavities produce RB's that differ in both diameter and weight.  By way of contrast, I also have a Saeco 3 cavity mold (#315), whose droppings are remarkably consistent.


*You can be even more selective if the application is more critical, going to 1/2 a SD if you must.
Paul W. Brasky

Daryl

  • Guest
Re: Double cavity mould & weight consistency...
« Reply #3 on: April 01, 2010, 12:20:10 AM »
Guys have it right, of course - there is usuall some variation.  Only custom bored moulds will throw identical weights - they also cost more - like $125.00 and up, quickly.  Seems to me LBT moulds are garanteed for duplicate bullets.  Round ball should be easier and with the supposed press Lee uses, they should be round and equal in weight - they are neither.  Will it matter? - depends. For trail walks - probably not at all.  The larger the ball (or larger/heavier the bullet), the more defects it can have before they become an influence.
I've shot bullets given to me that looked like wadded up pieces of tinfoil or frightened lead, that plunked into sub MOA at 200 yards with iron sights and shot perfect bullets into well over MOA at 100.  It depends.

As far as the different weight being a factor, probably not much if any difference to 100 yards.  My 14 bore puts patched pure lead balls (482gr.) into 1" to 1 1/2" at 100 meters - then plunks 5 Wheel Weight balls cast from the same mould, .002" larger and weighing 466gr., & loaded with paper ctgs. into the same group without enlarging it.  Almost 20gr. lighter, .002" larger, 2 wrapps of paper for patching instead of cloth - same group.

Offline Dphariss

  • Hero Member
  • *****
  • Posts: 9751
  • Kill a Commie for your Mommy
Re: Double cavity mould & weight consistency...
« Reply #4 on: April 01, 2010, 08:31:54 PM »
For those with double cavity moulds....how close in weight are the balls from the different cavities?

I cast some .445's tonight with my Lyman double cavity.   One group weighed ~132 grains and the other group weighed ~ 134 grains.   Is this fairly common?

If this is really important put a small punch mark in the cavity, bottom is best, then sort the balls as you weigh them.

Dan
He who dares not offend cannot be honest. Thomas Paine