Lapping a 44 Special Size Die

Hello,
I recently purchased a Redding 44 Special all steel die set. Although I have an RCBS 44 Mag/Spl carbide die set from 1985, I really wanted something better suited to using .432-433" cast boolits. My fave is a Lyman 429348 WC cast on the soft side.
Unfortunately, the Redding size die was way too tight! Case mouths were coming out .424", and had a pronounced shoulder similar to a 44-40. (see last pic) Using a Mitutoyo small hole gauge, the die chamber measured .440" where the case mouth would be when fully inserted.
I called Redding tech support, and while the guy understood what I wanted, he told me they couldn't help me. He suggested "just take it to a machinist".
Since the die was pretty much useless to me, I figured I'd just try lapping it myself. I've done a fair bit of lapping, generally of woodworking tools, like metal bench planes that need truing, etc.
The plan was to turn a brass lap a couple thousandths under the .440" figure to allow for the lapping compound, and if needed, turn another a bit larger. I planned to do the actual lapping by hand, with the lap attached to a spindle and clamped in a bench vise. I figured the chamber would keep the lap centered, and I could go "by feel", which would be lost if I chose to mount the lap and die in a lathe or drill press.

Here's the start, turning the brass lap:
Attachment 247251

Here's an assembled lap and spindle, with a second lap roughed in a few thousandths larger, atop my bench vise:
Attachment 247252

With the lap and spindle mounted vertically in the vise, I coated the spindle with cutting oil and a thin layer of 90x lapping compound. This is from a lapping kit sold by Lee Valley under their Veritas brand name.
Attachment 247253

It helped to wear gloves to do the turning. I got a nasty blister from the die threads and knurling on the first go.
It helps to pay attention to a slow, clockwise rotation, as well. I really didn't want the threads to loosen, and then having to force the lap out of the die.
As I went along, I periodically cleaned out the die, took some measurements, and sized a sample case.
My small hole gauge and micrometer:
Attachment 247255

Occasionally, I'd switch to a finer grit lap, to keep from deeply scratching the die. Fortunately, that turned out to not be a problem at all. I am familiar with the product, and working by hand kept the cutting from getting to aggressive.
Anyhow, the first lap eventually stopped cutting, as it was wearing down a little and the die was opening up as planned.
Cases were sizing with a mouth opening of .4265". I was pleased but wanted more. The second lap was dressed to .443" and the process repeated.
Here's where I ended up:

Attachment 247254

On the right is the first case sized using the die as is out of the box. The two cases on the left are a 44 Special and Magnum case. (I think the photo shows that the "after" cases are quite a bit smoother in appearance, too.) The case mouths are now coming out .428"-.429". Hard to say exactly, as the die chamber now has a gentle taper, mimicking that of old factory Special loads. The added benefit is being able to fine tune the sizing by adjusting the distance between the die mouth and the shell holder. For my purposes right now, the gap between shellholder and die mouth is about .125".
Using a Lyman M die with a .430"/433" expander, the case slides in with just a slight bit of resistance.

Thanks for following along on my little project!

Jim

I used ACRO adjustable brass laps for my cylinder honing until I got a Sunnen honing machine. These are great, inexpensive if you buy used from ebay. I have chucked dies in the lathe using Lee locking nuts jammed together, chucked the lap into a tailstock chuck where I can run it into the die, then back out to adjust, repeat with finer grits finally polish with some wet or dry paper.

Next time you need a lap, consider the ACRO lap, it makes life much easier at times..

http://www.acrolaps.com/

Attachment 247256

Hi Doug,
Thank you! That looks like it would be fantastic for cylinder throats.
Have you ever used that type of lap with the Lee press through bullet size dies?
I have a .357", and see they sell a .358". But, they don't have a .359" or .360".
That would be great for pre-war 38-44 Outdoorsman and Heavy Duty S&Ws.

Jim

The Acro works really good on Lee push-thru sizers because the part that does the sizing in a Lee die is only about .080" in length so it's real easy to lap to size. In fact you have to go slow with these by starting with a very fine grit or you go oversize in a heartbeat and then you can't polish out the sizing band without making it even bigger.

Lee sizers are often -.0005" below the published size to compensate for springback. I always stop .0005" under for this reason.

As I read more about the Acro laps, the more I like the idea of them.
Frankly, I was a bit disappointed with Redding tech service, not to mention the basic quality of the die itself.
It felt like a waste of money, for what they charge, and would have hesitated to put any more into it. So, I'm glad I got to do the job with materials on hand for no cost. And, I'm glad I posted the process so I could learn a lot more, and be in a better position for other jobs in the future.

Thanks!