undersize & overweight

[wiley]

Last year I started casting for the first time, and turned out some pretty good pistol boolits for my .38/.357. Boolit weight and diameter were right on the money. Had very few problems and decent accuracy.

This year I am tackling rifle boolits (.308 180 grain spire point, RCBS mould), and having no success. Actually the boolits I have cast so far look very good. The problem is that the weight is somewhat erratic, up to a 3 grain variance in weight. Is this normal? It seems a bit more than I had anticipated. The biggest problem is the diameter. My first batch I cast out of wheel weights & range lead, mixed 50/50. They were undersized, so I threw them back in the pot. The next batch I mixed wheel weights and lead shot 50/50 (thinking the antimony would make them a bit harder and help the diameter problem. I also added some tin for help with fillout. wrong..... still under size. They mic at .308 - .3085. Seems they should be at least .309

What should I try next? More antimony shot and less wheel weight? All suggestions are welcome!

[Willbird]

I guess we really do not know what dia your mold will cast if it fills perfectly. The weight variance sort of indicates you may have erratic fillout. I know when getting a mold dialed in the bullets can look KINDA good.............then you try one more trick and BOOM they look REALLY REALLY good.

You did not say if you are using a dipper, or bottom pouring...but just the other day I saw exactly what I described above when trying to get a new mold to work from the bottom with mostly pure lead.....then tried the dipper....the dipper bullets made the "kinda good" bullets look not so good :-). I turned up the hot plate a bit I was pre heating the mold with and then the bottom pour bullets looked real good too.



Bill

[wiley]

I was using a SAECO bottom pour.

[cbrick]

What does your bore slug at?

What temp are you casting at? Wide weight variations can sometimes be helped with a more consistent casting temp, both the pot and the mould. Higher casting temps causes the boolit to shrink a bit more when cooling so if your only looking for a few tenths of a thousands casting at no more than 700 degrees could help.

That is the same mould I use for my 308 and it casts WW+ 2% tin just a tick under .309" or right around .3088". It shoots 2" groups @ 200 meters from the bench whenever I can do my part but my bore slugs .3077".

Rick

[runfiverun]

what makes you think they need to be larger than your bore??
if yours is 308 then i'd say they are the correct diameter.
you just need to figure what your mold needs for a full fill out.
venting?different pour, heat, tin.
could be the weather too, some molds like high humidity for their best performance.

[KYCaster]

Lets be realistic here Wiley. If you're turning out boolits from say 180 to 183 grains, that's less than + or - 1% of total weight. While a smaller weight variance is a nice goal, I doubt very much if you'll ever be able to see the difference at the target.

I think your diameter is a much more important issue here. Depending on what kind of shot you have you may not be adding any apperciable ammount of Sb to your alloy. Even "Magnum" shot at 5-6% would only raise your Sb marginally with very little effect on diameter.

By "Beagleing" your mold you can easily gain .001 to .002 in dia to see if that improves your results. If that proves to be helpful then lapping the mold to a larger dia would be my next step.

Looking back at your OP, you don't say that you've actually loaded any of your boolits. Without results for comparison you have no way of knowing if any changes you make actually provide any improvement. Try what you have before you pass judgement, you may be surprised.

Jerry

[mooman76]

For rifle bullets I would b using at least straight WWS. If you are using range lead it can be very incosistant and it sounds like you are using quite a bit of different lead in your recipes. That could be your inconsistancy. You are usuing a 308 bullet mould, that is what the specs are.

[243winxb]

Use magnum shot with 6% antimony + some tin. Go hotter for more even weight.
Bullet Sizes & Weights – How to Vary Them




The bullet diameters and weights presented in this list
are based on the use of Taracorp’s Lawrence Magnum
bullet alloy (2% tin, 6% antimony, 1/4% arsenic,
91.75% lead).
Bullet diameters and weights will vary considerably
depending on the lead casting alloy used. This variation
can be as much as 1/2% on the diameter, and 8% on
the weight among the most commonly used casting
alloys. For example, a .358-158 grain bullet might
show a diameter variation of .002", and a 13 grain difference
in weight.
Of the most commonly used alloys, wheel weights (.5%
tin, 4% antimony, 95% lead) will produce bullets having
the smallest diameter and heaviest weight, with
such bullets running approximately .3% smaller in
diameter and 3% heavier than bullets cast with
Taracorp's metal. Linotype will produce bullets with the
largest diameter and lightest weights. This alloy will
produce bullets approximately 1/10% larger and 3%
lighter than Taracorp. Other alloys of tin and antimony,
with antimony content above 5%, will produce bullets
with diameters and weights falling between those cast
from wheel weights and linotype.
Alloys containing little or no antimony will cast considerably
smaller than wheel weights and in some cases
will produce bullets too small for adequate sizing.
Within the limitations given above, the weight and
diameter of a cast bullet can be adjusted by varying the
alloy’s antimony content.
The size and weight of bullets of a given alloy will also
vary according to casting temperature. Higher temperatures
will result in greater shrinkage as the bullet
cools, thereby producing a slightly smaller and lighter
bullet than one cast of the same alloy at a lower temperature Cast Bullets