sizing dies and bullet diameters

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  • Last Post 05 April 2008
billwnr posted this 31 March 2008

Anyone ever check out the diameter of cast bullets after sizing them?   I have two .310 sizing dies and the after sized diameter I'm getting is a .311.  While this doesn't usually bother me it does mess with a new throating die I had made to .310.  I figure I wouldn't be able to seat the .311 bullets in a barrel throated with the new reamer.

Guess I'll have to check out my .309 and see what size it puts out.

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CB posted this 31 March 2008

Ya, I've seen that before. I've honed out Lyman sizing dies to get the diameter I want. I get to the point not to call the die a .309 or .310 or .309 1/2, but calling it my Savage die or my Remington die. I pick up used dies whenever possible just for the tweaking purposes..................'the Tweakanator' Dan

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billwnr posted this 31 March 2008

I may learn to be a “tweaker” also.

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CB posted this 31 March 2008

Ya know down in Phoenix we call the meth heads tweakers.... Just figgered you guys would want to know that..

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billwnr posted this 31 March 2008

They get called the same here in WA state.  But I'm a gun “tweaker"...that's different.:fire

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CB posted this 31 March 2008

I prefer to call it fiddlin...

Fiddlin out in the shop sounds better than I'm out in the shop tweakin.. Neighbors might think I'm out there doing something illegal...

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JimmyDee posted this 01 April 2008

Jeff Bowles wrote: I prefer to call it fiddlin...

I think the correct term is “putzing."

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CB posted this 01 April 2008

Yep that will work...

I use putzin when I aint working on anything inparticular.... Or when I got so much to do I don't know where to start, which is the case most of the time.

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billwnr posted this 01 April 2008

Jeff Bowles wrote: I prefer to call it fiddlin...

Fiddlin out in the shop sounds better than I'm out in the shop tweakin.. Neighbors might think I'm out there doing something illegal...

I forget which way the color designations go for Democratic (what I really mean is LIBERAL, LEFT LEANING, TREE HUGGING) neighborhoods but whenever my neighbors see me toting my guns to the local gun range they figure I'm doing something illegal. 

If only they knew the truth.  In my varmint hunting days I was their first line of defense in the war on pestilence.:fire

 

Back on topic, sometime later this week  I'll check out my .309 H&I dies and see what diameter bullets they produce.

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TomG posted this 02 April 2008

The more you check into things like this the more you'll realize that sizer die makers don't control their tolerances very closely.  I've found sizer dies that were a full thousanths off. It's sort of a crap shoot to try to find one that is the exact dia. you need for your alloy and throat dia. 

I always check to see what dia. I'm getting as I try to hold my  bullets to a .0002” interferance fit in the throat. 

Not only will you find the sizer die holes are not on dimension, but you'll find that  the same die will produce different diameters between hard and soft alloy. A hard alloy will sometimes give a bullet that is a thou. larger than say with wheel weights or softer.

I've made a lot of taper dies, (also called bump dies) and do a lot of fiddling around to get just the right dia. I want on the rear driving band. There is probably some spring back in the bullets when they are very hard. There is definately some stretching of the die when using Monotype or Foundry Type bullets. My theory is to shoot the hardest bullet you can and size it properly for whatever throat it is shot in.

 I used to make my bump dies out of cold rolled since it was easier on the throater reamers and then went to making them 1.25 dia. instead of 7/8” so they wouldn't stretch and make a bullet the size I wanted. If you take the threaded bushing out of a Rock Chucker press, the threaded hole is much bigger.  

Lately, whenever I needed a die of a specific size, I just set it up in my lathe and ground it to produce the dia. I needed with a tool post grinder. Eventually, after you play this game long enough, you will end up with a bunch of sizer dies so that you can usually find one that gives the dia. you want. 

Tom Gray

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billwnr posted this 02 April 2008

I used to figure it wasn't proper to expect close tolerances on an $11 H&I die.  I've been forced to revise that thinking to not expect close tolerances on an $18.50 H&I die.

I've got two things going on with my .311 H&I die (nee .310 H&I die).   One, I size bullets for my military .30/06 and my main concern is how the bullets shoot in the rifle.  I told people I size them with a .310 H&I die and don't focus on the fact that it's not really .310 diameter.

Two, is I'm now sizing bullets for a new BR barrel and the throating reamer is .310.  My concern here is I may have problems getting the (actually) .311 bullet to seat properly in a .310 throat.  Had I known the true diameter of the sized bullet I would have specified .311 for the reamer.

My backup plan is to use one of the .309 H&I dies, figuring they will actually be a bit oversize.   I'll post more on this later once the new barrel arrives and it gets  chambered.

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TomG posted this 02 April 2008

Bill,  I'd be interested in your logic behind choosing a .310” throater.  I'm assuming you're building a 30 BR benchrest gun and your barrel will have a .308” groove dia. 

Do you have any data or has anyone done any testing to show that that is the ideal size for a cast bullet in a 30 cal. barrel?

I haven't shot any cast bullet benchrest in a long time and am behind the power curve. 

Tom

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billwnr posted this 03 April 2008

My logic for picking a .310 throater is I was after a fairly precise fit between the bullet contour I'm planning on shooting and the chamber throat.

In retrospect I could have gotten the same throat angle specifying either a .310 or .311 as the starting diameter.

My basis started with my initial assumption that the bullets would come out of the H&I die at .310 and then “so why not pick xxx as the diameter......."

added on edit:

I guess I picked .310 also because I have another BR rifle that has an Ardito throat that starts at .314 and I bump the bullets up to .314 for that precise fit.

I wanted to do the same thing with this new barrel by having a throating reamer made to the finished dimensions of the bullet I planned on shooting (311679) which is a newer Ardito designed bullet that Lyman makes moulds for.

I figured if I had the throat cut to match the bullet I would be eliminating the “bump” staget to make the bullet match the throat.

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TomG posted this 03 April 2008

Bill, 

I've shot that Lyman bullet that you described.  It has the form that a lot of Don Eagan bullets had.  That being, a straight cylindrical section into a fairly fast and short tapered section and than transitioning into a straight bore ride style nose. If you look at the Eagan drawings, you will see what I mean.  I'm not at home so I can't pull a print but the taper is pretty fast in the range of 2 or 3 deg. per side. The straight cylindrical setion on the back was around .140 to .200 long which will give the base of the bullet lots of guidance if just the gas check was seated in the case.

Not too long after that design hit the market in a Lyman, I bought one and started using it. I also had a throater reamer made to the same lengths and taper as the mould. It also fit the Eagan line of AR bullets if memory serves me correctly.

I chose a freebore dia. of .309 so as to keep the bullet closer to the actual groove dia.  of the barrel.  If I recall,  know John A. shot a lot of bullets that were as big as 314” in 30 cal barrels at one time.  He also would bump up bullets to make them fit.

My latest reamers are set up so that the bullet is no more than a thou. larger than groove dia. The idea being that I would rather size the bullet down to fit the freebore in a lube sizer under well controlled conditions than have it oversize in the chamber and make it size down as it leaves the case under the stress of combustion pressure. I could keep it straight in my lube sizer when the lube sizer was properly modified. I could not gaurantee that it would stray straight when it left the case neck.

I tried bumping bullets up years ago when I was using larger freebore dia's. and I found that it was very hard to bump them all up to the same dimensions. Bumping them up did nothing for accuracy at all.  However, sizing them down can be much better contolled and more uniform results occur.

Another benefit to staying at or less than .309 is that you can use RCBS moulds that all seem to cast at that dia. in Linotype. A couple of their designs work quite well and are worth shooting.

When I started building full race BR rifles and long range rifles for my customers, I noted that jacketed bullet freebore dia's are usually held to only .0004” over groove dia. That's what got me to thinking as to why would I want to take a lead bullet that is way oversize for the bore and smash it into the throat and size it down under the stress of firing. I can't see the logic anymore in making lead bullets and throats so large when it costs no more to specify the size on custom reamers.  

I've got a 30 br reamer with a freebore dia. of .3084” and a very short throat so as to shoot 100 to 120 gr. jacketed br bullets.  The next time I chamber up a 30 cal. cast bullet barrel, I will leave it at that dia. and see how it shoots with bullets of .3086” dia. I know that .309” freebores will shoot very well from past experience.

Tom Gray

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CB posted this 03 April 2008

Good point Tom.  Why go up to .310” freebore diameter for CBs in a barrel with a .308” groove diameter? Us Production Class shooters have to deal with .310” diameter freebores cause that is what the factory's use.  I studied PPC and BR chamber specs last winter and found they are anywhere from .0003” - .0005” over groove diameter in the freebore.

I read Harold Vaughn's book last winter and he stressed how bad it was for accuracy to distort the bullet. The least amount of distortion of the bullet entering the bore the better, especially of the base. Thanks for letting us know what diameter works for BR throats.............Dan

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TomG posted this 03 April 2008

Hi Dan, 

Dave Kiff can hit it within a tenth on diameters like the freebore on a reamer. I'd be kinda sceered to have one made any less than .0004” over groove.  The reason being that they do wear a little and if a couple of tenths wears, you can end up with a throat that is too tight for some bullets. 

I've got a 22-250 reamer with some miles on it and when I first chamber up a barrel, the V-maxes won't enter the freebore until it has a hundred or so bullets thru it.  When they finally go in with a nice slip fit, the thing really shoots.  When the reamer was new, it worked OK but if you want to do a lot of barrels with one, it's best to order it with the freebore .0005” over groove.  This particular reamer was made by Clymer years ago and I suspect they made it a little smaller than I spec'd it out at.  I don't buy reamers from them any longer but stick with Pacific precison. 

Tom

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cityboy posted this 04 April 2008

TomG wrote: I always check to see what dia. I'm getting as I try to hold my  bullets to a .0002” interferance fit in the throat.  

TomHow much of an interference fit between the bullet and neck do you use to keep the bullet from being pushed deeper into the case when it is chambered? cityboy

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TomG posted this 04 April 2008

Jim, 

I'm going to assume you are referring to how much neck tension I use.

I use only as much neck tension as is necessary to push the bullet firmly up into the throat so that it is sealed before it is fired. I seat the bullet out far enough that it pushes back into the case neck around .020” when the bolt closes into battery. When it pushes back, you are then sure it got shoved up into the freebore so that the freebore of the throat can now guide the back end of the bullet as it moves out of the case. 

I throat my guns so that only the gas check and a little more of the bullet is in the neck before I chamber it. The case is only used to introduce the bullet to the neck and not to guide it upon firing.  That job is done by the throat which is solid and lined up with the bore better than the case. 

If you get too much neck tension, your hand will get sore forcing the bolt closed and pushing the shell into the chamber. Also, it's hard on the locking lugs and they will soon gall if you force them to push the bullet in too hard.  Additionally, if you use too much neck tension, soft and medium hard bullets can be sized undersize by the neck and you lose control of you bullet dia.

Some may want to size the bullet so that is slips into the throat more easily without so much force by the bolt. To check to see if you are getting a slight interference fit in the straight cylindrical part of the throat, simply pull a round back out and examine the first driving band on the bullet and you should see a witness mark there indicating that it did seal up and size down slightly when pushed up into the throat by the case. If you don't see anything start increasing sized dia. in .0001” increments till you see the witness mark.

When you achieve a fit like this, the bullet will obturate (not obdurate) right away and seal off gasses from escaping along side of it and damaging the bullet and stripping the lube from the bullet before it enters the bore.

I once set a gun up for a man who had a slight build and small hands.  He had trouble forcing the bolt closed and got sore hands shooting a match.  I have big strong hands and it was OK for me. Everybody's mileage varies. 

This system takes advantage of the fact that the throat holds the bullet securely rather than to rely on the case neck to do it. Incidentally, I use tight neck chambers that require the case necks to be turned to .001” clearance in the neck of the chamber with a seated cast bullet. Since bullets are quite malleable, I've gotten away with zero neck clearance but I wouldn't recommend any else to try that.

Tom Gray

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CB posted this 05 April 2008

Gents

You can take what Tom says to the bank and count on it. He set up my production gun and I can say my accuracy went from 1.5 inch groups down to .600 average with some down to .350 (depending on how well the operator was functioning that given day)

He also was the fellow that built the heavy class rifle my wife now uses (I bought it used from the fellow he made it for) and I can say that she shoots well enough with it to have beaten 2 fellows that are past national champions and the fellow that won last years national championship in Heavy.

Also it works exactly like he says, at slight push on battery and away you go. It's not everything it takes, but it is a major part of it.

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