swage die finishing with taper.

[Mauser 98K]

has anyone else had the problem where a die is perfect in every aspect b4 heat treating and afterwards the cavity is tapered? i reamed a die today and polished it a little b4 heat treating it and everything checked out, after i heat treated and did the quench the die has a taper to it where it gets bigger as you go towards the opening and the bullets are coming out tapered.. supposed to be another .308 die but the bullets it is making is tapering from the front of the flat at about .307 and .309 at the rear.. i guess that is why they make laps that you use after the heat treating..

[clodhopper]

I haven't made any die yet, but wonder if you heated the opening end first.

The bullets might shoot okay.

[NoZombies]

What was your heat treating process? What steel for the dies?

[country gent]

On most precision parts we made we left .010-.015 stock and ground after heat treating annealing was done. This took care of any size changes and or warping that occurred. SOme parts were even cryogenically treated to stress relieve and normalize them before grinding. On tooling ( angle plates vee blocks cubes and such) we would grind it in then use it for 6 months to a year and lightly grind it back to dead nuts. After this second grinding they maintained the accuracy for years of use.

Oil hardening steels tend to grow with heattreating, water hardening can be pretty stable or grow a little, Air hardening can be fairly stable but a few grades may shrink on heat treating. Heat treat, quench, stock, annealing, and how its heated quenched all affect this

[Kevin8888]

I prefer A2 steel for this type of application, I haven't made any swage dies yet, but I'm a machinist by trade and have made other types of forming dies and of the metals I've worked with I find A2 and premium branded equivalents work exceptionally well with excellent stability when treated correctly.

[BT Sniper]

I use carbide reamers to cut die after heat treat.

[yeahbub]

If the steel you used expands on heat treat, the die will be largest where the most stock has been removed, hence, the larger opening. Up where the ogive is, less steel has been removed and ID is closer to what it was before heat treat. I have a .30 cal C-H swage die with the same problem, .308 at the start of the ogive and .3095 at the entry, but it works well as a source for paper patching cores. I suppose I could lap it out .309 for most of it's length and I might one day, but for now it's useful as is.

It's been a while since I had access to good lathes and mills - dang shame.

[Mauser 98K]

that is what i figured it was doing as when the metal is hot the structure is expanded and when quenched the part that is thinner quenches faster and is able to lock in the new structure faster thus less shrinkage is allowed making the hole bigger.. i got one die that is the one i normally use that did really well after it was quenched.. it was stepped where it was thicker at the top and a step was cut about half way up where it plugged into the die plate on my other press. i guess that allowed the bottom section to quench faster than it normally would and the top part and bottom part were closer after i polished..

BT.. id like some carbide reamers. im using drill rod for mine right now and i don't really have a way to grind the flutes in the carbide.

but the material i was using was 1 inch annealed rod from a hydraulic cylinder as i got access to a lot of it for next to nothing.. cuts like butter in its annealed state but heat treats up harder than a file with a water quench from 1,550*F.. im thinking it is 1045 as that is what is normally used for hydraulic rod but 1050 has also been used.. but i was more or less just bringing the die up to 1,550*F letting it soak for about 30min-45min and then bunging it in water with a stirring motion..

[Mauser 98K]

ok. i found that the taper of the bullet is not going to be that big a problem. even though the finished bullet is around .309 at the very end of the base it seems to swage down to exactly .308 when it is seated in my RCBS dies. i seated a few in some empty resized cases to observe what they would do and pulled with inertial puller and they all seemed to swage down that little bit when seated so im not gonna worry about it too much. im using a real thin jacket (around 0.020in) and it is more of a full length gas check than the commercial jackets and i guess that makes it easy to size it down during the seating process.. also makes them go to pieces when they hit something too..