Sizing vs group size

[Will]

On page 41 of my old RCBS #1 cast bullet manual, it states "each .001 inch of sizing results in about an extra 1" of group dispersion at 100yds". Is this true or BS?

Will

[joeb33050]

BS
joe b.

[Boerrancher]

I would say BS. I have a 30-06 that slugs 305 dia, and I shoot 309 dia boolits out of it. It shoots sub MOA groups at 100 yds. I have posted a few of these groups in the past. I have a copy of the Lyman 46th ed reloading manual, in what little it said about cast boolits one would think one was wasting their time if they tried to shoot a cast boolit over 1700 fps. I take everything I read about cast boolits with a grain of salt unless it is coming from some one who has put a ton of lead down range in the form of a cast boolit.

For years I followed all of the experts' books on cast boolits and never accomplished anything better than minute of paper plate. By reading the posts from people on this board I went from Min of paper plate to sub minute of angle using cast boolits, and many of my rifles that are quite accurate with J bullets are more accurate with cast boolits. It was the people of this board that got me there, not books written by self proclaimed experts that do most of their research in a tavern and writings on the bar.

Best Wishes from the Boer Ranch,

Joe

[docone31]

Joe, ditto, ditto, ditto.
If it weren't for this forum, I would still be stuck in what I had read.
Ditto.

[mooman76]

There are too many factors to say something like that, so basically no. I don't know if it was taken out of contexet or just one case example they were using.

[Le Loup Solitaire]

I never heard of any formula relating a relationship between how much sizing is done to a bullet and the degree of accuracy at any distance. Generally a rule for sizing cast bullets is .001 over bore size, so to do that right you would have to slug/know the size of your bore to start with. Some shooters find that better accuracy is obtained by sizing bullets .002 (or more if necessary). There is no hard and fast rule. What counts or the proof is what the group looks like on the target. The shooter has to be ready to experiment with different size "sizings" in order to get the right one, pretty much the same as which powder and how much. LLS

[MtGun44]

I think the intent of the comment is to say that you may be damaging
the boolit when sizing. More sizing can mean more damage. The implication
is that unsized, as cast diameter is more likely to shoot well. Not a
bad concept, but it would depend a lot on how your sizer aligned the
boolits.

Probably not something to take to the bank, but more of a general
concept - "don't mess up your boolits by sizing them excessively"

Bill

[Pat I.]

I think it's bs but if you're gonna size a lot use a Lee push through die. But then again I think if you're gonna size at all use a Lee die.

[Shiloh]

BS
joe b.

'Nuff said!!

Shiloh

[Wayne Smith]

With the old stepped sizing dies that scraped rather than squeezed it was probably true. Now a days not true, unless you are still using one of the old stepped dies, of course.

[missionary5155]

Before I bought a 250 grain mold for 41 mag I decided one day to squeeze down .431 WW lubed boollets to .413 and see if it was feasable and IF they would shoot accurately. I first sized to .427 base first and others nose first in my Lyman 450 press .. no big deal. Next was the pass to .413. The nose first reductions centered much easier and natually ended up "hollow base" . The base first effort was a trial to get them centered and stay that way... after two tries I gave it up and sized nose first then reversed them to base first to smash flat the undersired "hollow base". The grease grooves almost dissapered and there was not a crimp groove. The bases were not the prettiest but somewhat flat. The SWC nose was gone and ressembled a WC.
They loaded normal and I crimped over the shoulder of the boolit. Out to 25 yards 20 rounds seemed to be on par with my 210 and 220 swc loads in the same Ruger Blackhawk. I did not test at 50 yrds.
I soon after ordered a 250 grain mold .41 as it just was not worth the effort.
If all I had was this capability (excessive resizing ) I would not hesitate.. but I would not do it for fun again. And .411 to .377 works about the same. I wanted to try a 200 grain in my Dan Wesson .375 Supermag... This time I had .401 and .385 as intermediate steps... but it still leaves a SHALLOW grease grove smashed up WC boolit. But they will shoot OK out to 25 yards... but what good is that.

[runfiverun]

you can lube first so the grooves don't collapse.
and this is like saying every .001 of bullet run out will add an inch to your groups.
no it don't help but if you have .020 run out your groups aren't 20" maybe 3-4 but not 20.