More Size-Down Adventures

[Zeek]

Having ordered a Lee custom push-thru die in 0.258, and having opened up its entry-cone to a more gentle one, it occurred to me that this could be a neat size-down diameter for 6.5mm CBoo cores, for patching back (2X notebook paper comes) to 0.268". I had a couple of CBoos in the cold mould, so I tried putting them thru the die, prior to casting up a bunch more. This is the 160 grain NEI pill. Well, there was so much resistance that the CBoo's base obturated out and the whole darn thaaaaang just stopped dead in its tracks. I had to hammer that Boo out from the top with a steel rod and hammer.

Its as-cast band diameter is 0.268", so this was a 10-thou size-down. Have any of the rest of you run into a size-down limit? If so, what was it, in what caliber, and how did you deal with it?

One thing that bothers me about the Lee die sets is that the push-rod's top diameter is ~0.020" under bullet diameter, which causes all sorts of issues that one could avoid with a closer-fit top-of-punch diameter.
Zeek

[303Guy]

Being one for making my own stuff, but also favouring rather soft or at least malleable alloys, I would apply as much force as is required to make it go through. I also use STP as a lube. I do get a little 'feathering' around the base punch as it is smaller than the entry cone or 'throat'. I do get some tighteness due to the 'leaking' past the punch when said punch enter the tighter portion of the die. (Ummm... not actually answering your question but ... Thing is, the questions you ask are so like the things I like to know about too!)

[Zeek]

303Guy, our main problem is that we are far too observant for our own good. Perversely, that is also our strength.
Goat figure!
Zeek

[rhbrink]

Been there and done that several times, maybe you could do it in several steps? You didn't mention lube but something very slick helps softer alloy helps too. I have been sizing down some .460 black powder boolits to .445 in three steps do get some feathering at the base like 303Guy mentions but it is easy to remove also notice a big difference in pure lead compared to 20:1 which is still soft compared to WW's or most of the alloys that modern guys shoot.

[redneckdan]

I find that it really helps to polish the die. I take a dozen or so boolits and tumble them with lapping compound then size them to help remove tool marks. Before I size down a casting I tumble lube them with JPW. I size them right away, ya it is messy but it works. I've gone .490-.452 in one pass

[barrabruce]

My homemadee bodgee brother Inc size die has a slow taper to the diameter. ans a section IIRC about .3" or so ish long.
I made a "floating punch" that just fits throught the die say 1 thou clearance.
Mine has a slightly domed contour on it.

I get a dimple on the base of my bullets. Bigger for harder lead or real soft thick ones. I mostly use a gas check with out the gas check but plain base ones aint bad either.

Try some dish washing liquid for a lube.
If you get galling then clean it out with a bore brush and solvent.

At one time I was getting lead pipe about 1 or 2 thou thick in the die.
After a good tapering and polish thou it goes well.

Hope it helps
Bruce

[Zeek]

Thanks, y'awl! That gives me some things to try.

I had not run into this with larger-caliber push-thru work. However, even if that larger-diameter stuff was on the edge (close to giving trouble), like I suspectorate, then the effect SHOULD have been more easily manifested with 6.5mm CBoos, now that I stink about it (see below).

See, if you divide pixDxD/4 (cross-sectional area formula) by pixD (circumference formula), then you get a result of area-per-unit-of-circumference formula of D/4. So, for a smaller-diameter CBoo, each incremental length of circumference has less cross-sectional area to squeeze down than it would on a larger-diameter CBoo.
REVISED TO REFLECT BARRABRUCE's CORRECTION
So, it should be easier to get a mushed-out the base, when pushing it through the sizer, with a smaller-diameter CBoo because there is not as much cross sectional area resisting (the cross sectional area per unit of circumference is less, so the CBoo will have a greater tendency to mush-out). I'm glad that we're clear on that!

On that issue, I should have been more refused than confused, but Barrabruce got me straightened out. The formula makes sense even when you apply it correctly! Mah!
Zeek

[rhbrink]

Thanks, y'awl! That gives me some things to try.

I had not run into this with larger-caliber push-thru work. However, even if that larger-diameter stuff was on the edge (close to giving trouble), like I suspectorate, then the effect SHOULD have been farther on the same side with 6.5mm CBoos, so the result I got really makes no sens to me.

See, if you divide pixDxD/4 (cross-sectional area formula) by pixD (circumference formula), then you get a result of area-per-unit-of-circumference formula of D/4. So, for a smaller-diameter CBoo, each incremental length of circumference has less cross-sectional area to squeeze down than it would on a larger-diameter CBoo. So, it should be easier to do a given amount of sizing-down on a smaller-diameter CBoo not just because there is less area, total, but also because each unit of circumference has to cause a diametric reduction on less CBoo cross-sectional area than it would with the larger-caliber CBoo. Therefore, the base-slump should be LESS on a 10-thousandth size-down on a 6.5mm CBoo than that same size-down on a 30 caliber CBoo of the same alloy. I'm glad that we're clear on that!

So, at any irate, now you can see why I am even more confused about this than you may be. That's my excuse, and I'm stinkin' with it!
Zeek

HUH? I think you may be right but then again I'm not sure
Maybe the only thing I'm sure of is when something works .... sometimes.

[barrabruce]

No I thinking your wrong if I read it right.
Sure you got less lead to remove...but that lead constitutes more of the overall cylinder you are trying to remove.
eg: 10% on small dia instead of 6% on larger.
Yeah sure the bigger one should have more resistance all being equal but there not in the same proportion.

The smaller one would have a higher factor distortion thou the extrusion than a larger one.

Thats why the big 45 cal work so well. They could be so much out and still be proportional in the overall "tolerance" of the small stuff.
Get me drift????

Barra

[303Guy]

OMG! I've got a headache now! I can't be away for just a few days! Hooh boy!

Zeek, I nearly split my sides reading your post! That was good!

[Zeek]

I corrected my formula-blab (above). After thinking about Barrabruce's comment, finally, the truth floated up to the surface. Thanks for the help, Barrabruce!
Zeek