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A collection of comments and articles on the many aspects of bullet casting by various cast bullet shooters
Cast Bullets For Beginner And Expert
SECOND EDITION, 2007 - Joe Brennan
Chapter 4.1 Bullet Sizing And Bumping

Bullet sizing is the process of reducing the largest diameter of the bullet using a die and a press. Lyman makes a lubrisizer and the dies and top punches, as do RCBS and others. These presses reduce the largest diameter of the bullet, and simultaneously allow filling the lube grooves.

When a bullet is sized in a lubrisizer the smaller diameter sections are “bumped up” or made larger in diameter. As an example I have a Lyman 311291 mold that casts bullets in wheel weights with band diameter = largest diameter of .3115”/.3125” and nose diameter of .299”/.301” just in front of the first band. I lube and size these and seat gas checks in a Lyman 450 lubrisizer with minimum pressure on the handle-I’m not trying to bump up the bullet at all. After sizing/lubing/installing gas checks the bands measure .3118”/.3122” and the nose measures .3008”/.3013” just in front of the first band. Before sizing, the noses of these bullets will go into the muzzle of my 30/30 bench gun up to the forward band. After sizing, the bullet noses stop in the muzzle about 3/16” from the forward band. The small difference in dimension makes a big difference in bullet fit.

In the first Lyman Handbook of Cast Bullets there’s an article by Frank Jury (pg 21) that starts off by showing how sizing bullets to .310” resulted in dramatically smaller groups than when the bullets were sized .309”. This led me to spend a lot of money and time attempting to duplicate these results. I bought about every 30 caliber sizing die that Lyman made, but I never found accuracy varying much with .001” variations in diameter. (One thing I did find is that sizing dies had typical tolerances. A .308” die might size bullets to .3083”, a .309” die might size bullets to .3087”-both dies were within tolerances but the difference between the two was .0004” rather than the .001” that I expected. I believe that the tolerance on a nominal 308”sizing die is .3076”-.3085”)

I prefer not to size bullets, or size them as little as possible. My experience is that the bigger the bullet is, the better it shoots. I have Lyman 311299 molds that cast fairly round .314” diameter bullets that shoot very well out of about any 30-caliber gun I’ve tried them in. These shoot very well un-sized, as cast. Sized to .312”, lubricated and with gas checks seated, these bullets shoot almost as well as when shot as cast.

This big bullet premise works for most calibers I’ve cast bullets for, from .22 to .45.

I do use the lubrisizer with oversize sizing dies for seating gas checks and lubricating-not sizing (much)- some bullets.

A custom-made nose punch for a lubrisizer can be made with a large nose punch and some epoxy-using the bullet to mold the epoxy.

Some shooters recommend bullet bumping, the process of squeezing a bullet in a sizing machine in a die that is larger in diameter than the bullet as cast. Squeezing the bullet shorter makes it larger in diameter, up to the size of the die. I’ve been sizing and bumping bullets in my lubrisizer for years, and I’ve never got better accuracy from a sized or bumped bullet than from a proper diameter bullet as cast. What I have got is a Lyman 450 Lubri-sizer with the handle all brazed up because I broke it bumping bullets up in some of those oversize sizing dies.

When you buy a rifle and don’t have and can’t find a bullet big enough, bumping a slightly smaller bullet up to size may allow you to shoot the gun with reasonable accuracy until the proper mold arrives. The same may apply to sizing a bullet down, but shooting oversize bullets frequently works well.

I believe that sizing and bumping bullets can and does work when using specially designed and built dies and an appropriate press. John Ardito wrote about sizing and bumping bullets to fit his rifles, and set many records. Shooters using his methods hold many of the current records. In my opinion, only advanced cast bullet shooters using expensive dies and equipment will benefit from this.

Ken Mollohan: A legend that seems immortal says that sizing damages the accuracy potential of a bullet, and more sizing damages it even worse. There are all sorts of ‘evidence’ quoted as proof: Pope didn’t size his bullets, nor do many Schuetzen marksmen, etc, etc. And that is perfectly true. But it is also perfectly true that this legend got its start when sizing dies had sharp shoulders, and would shear lead off of the sides of the bullets, not swage them down uniformly like today’s dies do. And it was the usual case that the bullet sides were not sheared uniformly, which would indeed damage the accuracy potential of the bullet.

This is simply not true in my experience with modern sizers that swage bullets instead of shearing them. I have swaged bullets from an ‘as cast’ diameter of 0.460” (for a 45-70) down to 0.445” (for an 11mm Mauser). In fact, Lyman once sold swaging dies for this exact purpose. And accuracy was excellent!! I would be willing to make a substantial wager that any ‘loss of accuracy ‘associated with substantial sizing (diameter reduction) will be found due to worsening of bullet fit in the throat of the rifle, not the diameter reduction per se. If you doubt it, may I suggest that you put up your favorite target load except that you use some bullets that were sized down from the next caliber up. For example, size some 8mm bullets (similar weights) to 0.311” or 0.312” (depending on what your rifle ‘likes’) and seat them into the throat the same way as your normal load. I’d be surprised if you see much, if any difference in grouping. )

How To Hone A Sizing Die

Richard Tunell

Oft times we find ourselves needing a bit more girth in a bullet to please a particular firearm. And, as sometimes happens the size we need isn't available or we don't want to pay for the custom manufacture of one. You can do this yourself and accomplish very accurate results for just a few cents worth of materials (not counting the size die) and a bit of time.

What you will need:

  • 1) A sizing die that is as close as possible to what you want.

  • 2) A length of steel rod that is close to 3/4 of the diameter of the existing die, and long enough to protrude at least 2" beyond both ends of the die.

  • 3) Wet or dry emery paper of 320, 400, and 600 grit. If you do need to remove more than a couple of thousandths you should also include 220 grit. Actually the 400 will finish the inside well enough, but hitting it with a bit of 600 sure slicks it up.

  • 4) Oil. Most any oil will do.

What you do:

The paper should be cut long enough to extend out either end of the die, almost as long as the steel rod. Wrap your starting coarsest grit paper around the steel rod a couple times and apply some oil to the paper. Insert the covered rod through the size die. With just your thumb and a

couple fingers on each end of the rod, roll it up and down your thigh (while sitting) applying only mild pressure. The reason for using a rod as large as possible is to keep from tapering the inside of the die, by having a slender rod bend under pressure. This will get your pants leg fairly well oiled up, so use old pants. Or you can staple a bit of cloth to a length of wood. Most any surface that the die can turn on is fine. I use a piece of mud flap screwed to a bit of 2x4, and clamp it in the vise, and it's a good working height.

Roll the steel rod occasionally as only a small portion of the paper is in contact with the interior of the die. You should also swap the die end for end every now and then to make sure the metal removal is as even as possible. Remember the throat of the die is tapered to admit the bullet and we're only wanting to open up the actual sizing portion of the die.

When you check your work you don't need to put the die back in the press. Just drill a hole in a board bigger than the bullet and place the die over it. Place a bullet in the die and tap it through. Remember to leave a bit of metal to remove for your polishing down to final size with the finer grit paper. The first time I did this I just took it down to where I wanted it without thinking of the finish. It works, but you do need a bit more effort to get the bullet in and out, and it just isn't the right way to do it!

Your existing plunger will still be fine in the honed out size die, unless you opened it up several thousandths. Even then it may still work fine, but you'll need to pay more attention to the lube consistency and the amount of pressure you exert on the lube reservoir.

How To Bump Bullets In The Lubricator/Sizer

   I have only used the Lyman 45 and 450 Lubricator/Sizers, but understand that the SAECO and RCBS machines will also bump bullets.

   The problem with bumping bullets in a Lyman machine is that the handle, a flimsy proposition at best, will easily break.

Ken Mollohan: The warning that Lyman handles are too flimsy for bumping, and will break is correct in my experience also. But my remedy was to weld a reinforcing strip of steel across the top of the handle above the pivot holes, which is where the handles is thinnest, and the breaks occurred. These strips were the same size and thickness as the original handles, and perhaps an inch or an inch and a quarter long. Welding was completely across the surface. This simple alteration has prevented further problems for several decades.)

Here's my Lyman 450. Note the repair/braze area where the handle broke-several times.

The ADJUSTING SCREW adjusts how far down the bullet can be pushed in the sizing die by the TOP PUNCH. Note that the TOP PUNCH fits into the sizing die and into the NUT.

I use the NUT; it fits inside the SIZING DIE LOCK NUT; to stop the downward motion of the ram and TOP PUNCH. Then I adjust the ADJUSTING SCREW to limit the downward movement of the bullet in the sizing die. When the bullet is all the way down, and there's space between the ram and NUT, further pressure on the handle mashes the bullet shorter and bigger in diameter. Other and better arrangements are made by those more mechanically inclined than I.

Bumping the nose:

The example is the Lyman 311299 bullet, with a bore-riding nose that should be about .300", and a set of three bands over .308" in diameter. I'm assuming here a 30-caliber barrel of .300" bore and .308" groove.

My 311299 molds produce bullets with varying nose diameters and bands over .312" that are sized .312" in a Lyman 450.

In the process of sizing and lubing the bullets, with no undue pressure on the handle of the 450, bullet noses increase one thousandth of an inch minimum. They get bumped up. By fiddling with the lubricator/sizer and increasing the pressure on the handle, it is easy to increase the nose diameter of the bullet by three to four thousandths of an inch. Somewhere around four thousandths of an inch the nose starts to bend into a banana shape, and/or the handle of the machine breaks.

With bullets under .312" band diameter, sizing normally, without undue pressure on the handle increases band diameter at least one thousandth of an inch. All my 30 caliber molds make bullets that have the base bands "shined up" in the lubricator/sizer.

Bumping the bands:

This Lyman 319289 bullet has bands of constant diameter. Let's assume that the bullet is .321" in diameter, and we want it larger. Run it through a .323" sizing die, and make sure that all the lube grooves are filled. Then set the lubricator/sizer and force the handle down to expand the bullet to sizer diameter, .323". Again, three to four thousandths of an inch is the maximum increase in diameter before the nose gets to looking funny or the handle breaks.

I have bumped many bullets using conventional sizing dies in the Lyman 450, calibers from 22 to 45, and never increased accuracy. Others have had great success.

I like the Lyman 311299 and 314299 bullets, and have worked with them a lot. Here's a picture of the 311299, the 314299 looks exactly the same. This story is about the 314299. I have been working with a Winchester M54 rifle in 30/30, casting bullets in 25:1 lead: tin and linotype. The nose of the bullets measure .3032"-.3036", and cast in either of the alloys the nose is lightly engraved when the cartridge is chambered. With 25:1 and bullets sized .312", a cartridge overall length of 2.895" chambers in the gun, mashing that front band into the throat. With linotype and bullets sized .312", that front band stops the cartridge from chambering at an overall length greater than 2.865"-it won't be mashed in. So I sized bullets of both alloys down to .309" in search of a longer overall length for the linotype bullet, and for accuracy in general. The linotype bullets easily chambered at 2.895" overall length, but the 25:1 cartridges had the bullets pushed way back into the cases when I attempted to chamber a couple.

Now, after sizing to .312", the bullet noses grew from .3032"-.3036" to .3040"-.3045". But, after sizing to .309", the 25:1 soft bullet noses had bumped up to .306"-.3092", the bullet jammed in the rifling when chambered and was pushed back into the cartridge case. The linotype bullet noses were still about .305" and chambered with no problem.

I'm telling this story to illustrate the notion that sizing bullets can change dimensions of the nose enough to affect how the bullet fits in the gun, and the maximum overall length. And that alloys of different hardness are affected differently by sizing and bumping, and that hardness affects how easily the bullet is engraved by the rifling. Change the sizing diameter and other things change.

I seated bullets of both alloys to 2.875" and crimped the case necks slightly to keep the bullets from being pushed into the cases, loaded them up and shot five 5 shot groups with each yesterday, 4/18/07. The 25:1 bullets averaged 1.32" groups at 100 yards, the linotype bullets averaged 1.1".



Warning: All technical data mentioned, especially handloading and bullet casting, reflect the limited experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances not necessarily reported in the article or on this web site and over which The Los Angeles Silhouette Club (LASC), this web site or the author has no control. The above has no control over the condition of your firearms or your methods, components, tools, techniques or circumstances and disclaims all and any responsibility for any person using any data mentioned.

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