How much can you size a bullet without hurting accuracy?

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  • Last Post 14 March 2013
Chargar posted this 08 March 2013

For many years the cast bullet mantra has been that sizing bullets more than .003 destroys accuracy. Folks who really are trying for the “bug hole” groups go to great lengths to buy or have made molds that produce bullets that require no sizing for their rifles.

But, how about the guy with a collection of military and hunting rifles that wants to shoot cast bullets and can't or won't have custom molds made for each rifle? How does sizing a bullet effect his shooting? A few years back, I decided to find out for myself.

I have a collection of about a half dozen Lyman 311291 molds of various vintages that produce bullets that vary greatly on the size of the body and nose.

I selected one of these that produced bullet .315 X .303 and another that yielded bullets .310 X .300. I also have a fine Browning Traditional Hunter single shot rifle in 30-30 that loves cast bullets and produced great groups even with the factory tang sight.

I lubed and checked 30 of the smaller bullets in a .311 size die and they were not sized during the trip.

I took the larger bullet and sized the body .310 and the nose .300.

I now had two bullets of the same design that are of the same size. One of which fit the rifle without sizing and another that required .005 sizing on the body and .003 on the nose. I very carefully inspected the bullets and discarded any that were not perfect. I also weighed each bullet, looking for any voids inside.

I loaded 30 rounds of each bullet over a known accuracy charge for my rifle and headed for the range. I set up 6 targets at 100 yards and fired 6 ten shot groups, alternating between the bullets, so any fatigue would be spread out between the two bullets.

When I was all said and done I took the targets home and set about to measure the groups. Groups ran between 1.5 and 2 MOA and when averaged, there was no significant difference between the sized and unsized bullets. In fact the sized bullet average size group was a smidge smaller.

I did do the sizing with a nose first push through die held in the top of a reloading press. I am convinced that bullets can be distorted when too much pressure is placed on the nose when sizing in a traditional machine. After the bullets are sized, I lube them in the same or .001 oversized die.

At the end of the day, I discovered that sizing bullet had no bad effect on my shooting in my rifles, so I ceased to worry about it. I do think “how” the bullets are size can make a big difference.

Anyway, that is just what I learned on still fall day at the shooting range in Corpus Christi Texas in 2007.

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John Alexander posted this 08 March 2013

Charger,

Very nice and logical set up experiment. I haven't done anything similar but breathe a little easier when I am sizing a bullet down a considerable amount.

Cast bullet shooting is full of old husband's tales and a lot of them are baloney.

You have cast some doubt on the one that any sizing is bad.

Thanks,

John

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robroy posted this 09 March 2013

I've got a 311299 that measures about .316 on the driving bands and .306 on the nose. I think it should have been stamped a 314299. My thought is to size the bands to fit the throat and the nose to just kiss the lands of a rifle yet to be aquired. I'm considering a Savage model 12 in one of the target configurations. This thread gives me hope that I can get good accuracy from such a combo.

A bit off topic, have you tried sizing noses in a push through sizer? In an appropriate distance and then out gently with a modified or improvised nose punch.

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rockquarry posted this 10 March 2013

It's refreshing to hear about someone's accomplishment in demonstrating that there is little or no susbstance to another erroneous cast bullet “axiom", one that's been perpuated forever. I suspect most of these tales are born of truth and fact, but not enough of either to really substantiate much. Continued flawed and sloppy “testing” by others, however, tends to firm things up.

From a general standpoint, and as long as it's done carefully using good equipment, I must agree with what Chargar has reported on bullet sizing.

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Chargar posted this 10 March 2013

Please note guys, that my test was not done in a bench rest rifle capable of sub MOA accuracy. With a rifle like that, results may have been different, I just don't know. There are plenty of guys here, who can speak to that issue.

I like military and sporting rifles and I like shooting cast bullets in them. I can get cast bullets to shoot as well as any jacketed bullet. For MY shooting in MY rifles, bullet sizing has ceased to be a bug-a-boo if done correctly. This makes life simpler as I can size bullets to fit individual rifle without loosing sleep over it.

I don't know if we are “myth busting” or just learning how to not make mistakes with older inferior equipment. I started casting and sizing when Lyman still made and sold the sizing dies with the sharp shoulder inside that shaved lead off bullets rather than swage them down. We have also learned that too much pressure on the nose of a bullet in sizing will deform or bend it. Using this old equipment, the .003 limit might not be a myth, just information that has not been updated to match current knowledge.

We own a huge debt to those cast bullet shooters that have bone on before us. Much of what the did is still producing excellent results today. 311284, 311291 and other Barlow Ideal designs are still crackerjack bullet more than 100 years later.

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Chargar posted this 10 March 2013

rockquarry wrote: It's refreshing to hear about someone's accomplishment in demonstrating that there is little or no susbstance to another erroneous cast bullet “axiom", one that's been perpuated forever. I suspect most of these tales are born of truth and fact, but not enough of either to really substantiate much. Continued flawed and sloppy “testing” by others, however, tends to firm things up.

From a general standpoint, and as long as it's done carefully using good equipment, I must agree with what Chargar has reported on bullet sizing.

My nose sizing dies are custom made by Buckshot and are of two types. One is a press mounted die and the other goes in a Lyman or RCBS machine. Either way they don't have a taper in them. This leaves the issue of how far you can push the nose in without doing damage to the body. I have thought about using using Lee push through dies or Lyman/RCBS dies in a press mount set up as you suggested, but have not tried that yet. I may or may not work due to the taper in the mouth of the die. We need to find out.

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rockquarry posted this 10 March 2013

Maybe I should qualify my statement also by saying my work has not been with benchrest rifles either. While benchrest shooters' accuracy requirements are certainly more stringent, it would seem that the fundamental principles of cast bullet work would remain much the same. However, there may be specific areas where such is not the case.

Perhaps some benchrest people might care to comment on bullet sizing.

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robroy posted this 10 March 2013

Chargar: You quoted rockquarry but answered my question. Thanks. If I find those elusive round tuits I need to get a bunch of stuff out of the way I plan on finding out about the nose sizing with a press mounted die.

For now all I can do is offer guesses and opinions. So like an ... here it goes and I hope it doesn't stink too bad: If a bullet is straight, true, and fits the gun it will shoot accurately given an accurate load and a trigger nut that can keep things on target. The method used to accomplish fit doesn't matter. Plese recognize that in another age I'd have been burned for a heretic.

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axman posted this 11 March 2013

It might not apply but I've sized unlubed grooved bullets .010" for use in paper patched bullets and they shot well.

By the way I used case forming lube a Lee push thru and sized base first thru die to avoid distortion of base.

Thanks. Jim

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frnkeore posted this 11 March 2013

My experiance is different regarding resizing.

I had two issues, the first was sizing w/o lube in the grooves. Second was the bullet going off center.

The bullet was the 323471 that cast .326. I wanted to use it breech seated in my 32/40 so, I had to size it .005. I pan lube and do all my sizing nose first in a arbor press with dies that I make.

The first attempt was pushing it through a .321 die w/o lube. You could see where it push the bands back towards the grooves. Next, I pan lubed them and pushed them through, here they went off center. When you spun them in your fingers, you could see the band width change.

Sizing with the grooves full of lube keeps the bands from collapsing because the lube is incompressable and the bullet has to become longer when sized. If the bullet isn't longer after sizing, it is distorted in some way, such as the bands being pushed into the grooves.

My cure was to make the die, two sizes. The first part is about 2/3 the bullet length and as cast size. It then tapers at 1 deg to the .321 diameter.

I reamed it .321 then came back with a boring bar and cut it .326, stopped the carridge and then cut the 1 deg taper into the .321 dia. Then polished the those cuts.

There is no bore riding section on a original 323471 so, I could push it all the way through.

Frank

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noylj posted this 13 March 2013

Nobody else agrees with me, but I found any sizing produced a less accurate bullet. I have only shot as-cast bullets since about 1979.

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TRKakaCatWhisperer posted this 13 March 2013

noylj wrote: Nobody else agrees with me, but I found any sizing produced a less accurate bullet. I have only shot as-cast bullets since about 1979.

I agree, but size bullets (.45acp) to ensure they chamber.

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cityboy posted this 13 March 2013

A lot depends on how the sizing is done. In my opinion push-through sizing is less damaging; in-an-out sizing can do a lot if damage if the axes of the ram and die don't line up.

Jim

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pat i. posted this 13 March 2013

I agree.

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Chargar posted this 14 March 2013

A traditional sizing machine, can indeed have alignment problems. I only size flat nose handgun bullets in such a machine and even then use a large flat faced nose punch so the bullets can center themselves in the die.

One nice thing about the flat face punches, is one size (a large one) will work for any caliber. I took and old Lyman 45 caliber punch and turned it flat faced in the lathe. It would be simple to make one from scratch as well.

All other bullets are sized in a press mounted push through set up.

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Harp posted this 14 March 2013

I use the lyman 31108 cast diameter is .314 put it through a lee nose first to get .311 then I lube it in a lyman 450. shoots good in 30 M1 Ruger and .308 up to 1600 fps. Not after match accuracy in either of these. In the future I will lube this with Gary's tumble lube method.

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