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BRIARPATCH
01-24-2009, 11:07 PM
:-? :confused: :roll:
Howdy from another newbie,
I'm being bitten severely by the BOOLIT casting bug recently and while I've learned much from reading both on this and other forums dealing with the subject and in written material, I still find that the more I learn, the more I realize I don't know.........or at least don't understand.
I'm still at the stage of deciding if casting is going to be worth the investment in equipment. I've also decided that the AMOUNT of shooting I do is not the only criteria to use in making that decision because being a tinkerer by nature I believe I'm about to take the plunge even if it may be for only 100 rounds a month or so.
But to get to the question of my post title, in my RCBS cast bullet Manual it says on page 41, "Experience has shown that each .001 inch of sizing results in about an extra inch of group dispersion at 100 yds. "
I"m wondering how many of you concur with this statement and/or have found through experience that it's true.
It also says however on page 25 that "Cast bullets should be sized prior to loading to insure roundness, proper diameter and uniformity of diameter".
This is a little like readin' in the Good Book ain't it?
A couple more sizing questions while we're on the subject......I've read that sizing bullets also reducing the hardness particularly in the area of the bands. Does it affect it enough to change the BHN any significant amount?
And last, (for now) how many thousandths max should one attempt to reduce the diameter of a cast bullet by sizing?

mikenbarb
01-24-2009, 11:32 PM
Briarpatch, Welcome!
The first thing I would do is to slug your barrel so you know what diameter your bore is and then you will know what to size your boolits to. If your bore slugs out to .309 then use .309 diameter boolits etc, etc. A sizing die will take a minimal amount of BHN out of a boolit and not much to worry about as long as your initial BHN hardness is pretty high. I like to use a Lyman #2 alloy for my rifle boolits with GC's. Yes a .001 variance in diameter can make a big difference downrange because if the boolit diameter is too small it wont grab the rifling properly and will strip off the lands and if its too large it will squish too much in the barrel giving you an erratic boolit and could create high pressures that may be unsafe. Im sure others will have much to add but keep reading. Lyman makes an awesome cast manual that you may want to check out. Their the oldest and best in the cast boolit industry in my opinion. Good luck.

felix
01-24-2009, 11:35 PM
What you have read is true because the objective is to make the boolit exactly match the throat of the barrel with next to zero tolerance with perfectly set up dies (sizing/swaging/whaterver). Because perfect dies can cost the price of the barrel in the first place, we decide against that to make do with what we can muster up cheaply. That is where the errors come in. Therefore, the best thing we can do is cast as large as will be accepted by the chamber neck and let the barrel (throat) do the sizing. If you size the boolit and shoot within a day, the gun won't notice any alloy change. ... felix

oso
01-24-2009, 11:39 PM
I don't plan on reducing the boolit diameter when sizing (I use a size die a thou over) for lubing and seating gas checks. My minimal sizing did reduce my group dispersion compared to heavily sized boolits. Running 'em all through the the sizer will catch the off spec culls that get by the eyeball. Sizing can work soften heat treated boolts if deformation occurs. I size without deforming the same day I quench, before full hardening occurs. For me the limiting factor in sizing hard alloys is what my shoulder can stand, which isn't much any more.

Boerrancher
01-25-2009, 09:39 AM
I try to as Felix stated, make everything match as closely as I can get it to the gun if I am shooting for accuracy and or for hunting. I shoot some of my boolits unsized. I just tumble lubed them, let them dry and load. These that I don't size I only use in plinking loads, and I keep them separate from my other boolits.

Best wishes from the Boer Ranch,

Joe

Bret4207
01-25-2009, 10:19 AM
In simple terms the barrel will do the final sizing. You can slug and size as much as you want, but if the boolit obturates as it leaves the case all your work is for nothing. Same for roundness, you can make the boolit round, but if it starts off center in the chamber it means nothing. Like Felix said, in a boolit designed to sit in the throat size to that throat and call it good.

I don't mean to be a wet blanket, but here's my view- As long as the boolit will chamber you're good unless you have a drastically oversize chamber and even then if your load bumps that boolit (obturation) it's going to be fatter than it started. IMO better to use a fat boolit, let it lightly contact the leade if possible and shoot and be happy. Getting a boolit that fits the gun is more important than anything else and the fired boolit being sized by the barrel is the final arbiter on that subject. I size to get the loaded round to fit the gun and prefer them a trifle "fat" for the previously mentioned reasons. The exceptions would be auto loaders or certain guns with little camming power. You need to be able to get the loaded round to chamber every time, so sometimes you have to size down an extra thou or 2.

I picked up on all this from Al Miller in a Handloader article years ago and tried unsized boolits. Al was right and they worked great. When Lee Mule Snot came along a lot of problems were solved. Give it a try.

montana_charlie
01-25-2009, 01:01 PM
Getting a boolit that fits the gun is more important than anything else...
And that is the truest thing anybody can say about 'sizing' a cast bullet.

A bullet that has been modified in a sizing die is no longer (quite) the same bullet that dropped from the mould. That is why the market exists for 'custom moulds' that throw 'standard designs'.

You can buy three Postell moulds from Lyman and cast with them. The products will look the same, but will not BE the same. One may have a band diameter of .457" (their minimum for that design). The other two may measure .459", but their nose diameters will vary...like .447" and .450". One of the three will work better in a given rifle than the other two...because it 'fits' the gun better. You only had to buy three $50 moulds to find one that works pretty well in your rifle.
The one you chose to use may be well-finished and bullets may drop out easily...or not.

You can step up in price to NEI to get the same design. It's still an off-the-shelf mould, but it will probably cast at .460" (or slightly more) and NEI is willing to 'fiddle' with it a little if you need that done. So, for (about) $90 you can have an aluminum mould that is probably finished well enough for bullets to drop easily, and mailing it back and forth a time or two could result in a bullet that your rifle likes real well.

Or...you could order a Postell mould from a 'custom maker' like Steve Brooks or Paul Jones. They both stock that popular design.
However, they will want to know the exact size needed to fit your chamber...and they will want to know what alloy you intend to use.

Jones likes to work from a chamber cast, and Brooks has an ordering page that allows you to insert the dimensions you have determined to be correct from measurements you took from a chamber cast.

Both will send a mould that casts like a dream...and if the...as cast...bullet doesn't match the specified dimensions, it will be 'made good'.

In all three scenarios, the final cost of 'a mould that works' is about $150.
But the last one gives you the kind of fit that Bret4207 was alluding to.

The alternative is take whatever you can find cheap...and 'bump it up' or run it through sizers until it 'comes close'.

BTW...none of the above applies to revolvers or autoloaders...

CM

runfiverun
01-25-2009, 01:14 PM
now that he is pretty confused.....
you can also take your lyman mold and change your alloy and make larger and smaller boolits.
which your gun might ,or not, lke even more.
then there is spring-back of an alloy,and lube changes and g/c annealing.
if you wanna "tinker" you are at the right place.

BRIARPATCH
01-25-2009, 05:50 PM
Well, perhaps not confused but definitely with more options to consider. I need something to get my mind off the stuff the daily news bombards us with as of late and this oughta do the trick. I think I'll get to sleep quicker now pondering whether that bore slug was accurate and if I should get a custom mold or one right off the shelf rather than will I regain what I lost in my 401k in time to retire at 62 or 70.
At least we can have some control over our boolit size. As for the news, well I think a man would be better off to just say his prayers every night and take the boob tube to the dump next trip.
Thanks for all the response and please by all means keep it coming. I'll keep lurking and will post and let y'all know how it goes. [smilie=6:

leftiye
01-25-2009, 05:59 PM
Haven't watched the news for years. Don't watch commercials either. They're about the same.

montana_charlie
01-25-2009, 06:33 PM
I'm still at the stage of deciding if casting is going to be worth the investment in equipment. I've also decided that the AMOUNT of shooting I do is not the only criteria to use in making that decision because being a tinkerer by nature I believe I'm about to take the plunge even if it may be for only 100 rounds a month or so.
The size of the investment can seem unrealistic when comparing the cost of a custom mould with a Lee of the same design. It all depends on what your goals are...when shooting that 100 rounds per month.
CM

I think I'll get to sleep quicker now pondering whether that bore slug was accurate and if I should get a custom mold or one right off the shelf
You haven't said what kind of firearm you want to feed, but if it's a rifle (or singleshot pistol) I would try a few pre-cast bullet designs...just to get an idea of what it seems to like.

CM