For at least a hundred years, the common wisdom has been not to size a rifle bullet more than .003. Squeeze it down more than 3 thou and you degrade the accuracy of the bullet.

Is this just a shooters myth/old husbands tail that has been passed on from generation to generation or does it have a basis in fact? Anybody have any experience to prove or disprove this notion?

Depends upon the bullet and the alloy. I work in as pure lead as possible and am able to size from .457 to .451 with great results, accuracy-wise. This is for use in muzzleloaders. Sub MOA from such a bullet.

Chargar, I have found that the same Lyman 314299 which gives very good accuracy in my No. 4 Lee Enfield when sized .314" is outstandingly accurate in my NRA Sporter Springfield when sized .310". There was a gun writer (Bob Milek?) who sized .429" bullets to .410" and .410" bullets to .357". He reported excellent accuracy in .41 Magnum and .357 Magnum revolvers. I can't remember what he did to keep the lube grooves from closing up. HTH, curmudgeon

I suspect the .003 is historical in nature. Not that many years ago it was hard to get a sizer that was "in-line". With the ram and size die out of allignment, the more you sized, the more you damaged the boolit. With todays equipment and ability to control dimensional variations, I suspect that the .003 can pretty much be ignored. On the other hand, with all of the moulds and mould makers, it shouldn';t be too difficult to get a mould that will cast what you want so the only thing you have to do is lube it. So far, I've been able to cast boolits (rifle and peestol) and lube with a die > boolit as cast diameter (ex. 35-200 sized in a .360 die...no bullet sizing per se, but everything gets lubed.)and get very good results. FWIW Piilgrim

I've been experimenting with a Lyman #457191, a 300 gr. boolit for the 45-60 and 45-90. Damn thing casts out at exactly .457", regardless of alloy. I can get .459" by Beaglizing the thing, but I have been sizing it to .454" for use in a Winchester 94 in .45LC. preliminary testing seems to want to shoot well with the vrtical bing in the .75 to1.0" range. The horizontal is more like about 6-7 inches as the trigger pull on the thing is horrendous. (Off the scale on my RCBS trigger pull scale which goes to 8 pounds.)
Paul B.

Chargar, Since I needed a better CB than 314299 for my Arg. Mau., I followed Buckshot's (aka Whitworth) and took a previously sized & lubed .324" CB and sized it to .314" in a Lee die. I reduced it another .001" in a Lyman die and found such CB's, an LBT design and Buckshot's long, heavy 8mm design, worked at least as well as CB's sized only a few thousandths. The trick is to first fill the lube grooves with bullet lube (well, duh!) and then resize. You'll also need a strong press and bench. In short, if done concentrically, such radical resizing doesn't hurt a bit. ...Maven

You shock me beyond words Chargar. I know you've been around the block.

But, just on the odd chance you're serious, rest assured all you really need to know about that is
one word, namely, LOVERIN!!!!!!!!!!!!!!!!!!!!!!!! For once all them gooves mit modern lubes can be used. You too can lose 10k in a single day and still be slick and accurate! kid jethrow