Redding G-RX Carbide Push Thru Base Sizing Die

For quite some time about 80% of my .40 S&W reloads would not fit in the case gauge even though they would fit in the chamber of my gun. The base of the brass had a slight bulge that the resizing die did not address.

I ended up using an old barrel to verify my reloads were not so far out of spec that they would fail to chamber. I was always concerned that using my old barrel as a case gauge was risky because it could be the current barrel chamber was slightly smaller than the old one and I would have a problem with some small percentage of the rounds. I really wanted to build the ammo to spec and use the case gauge.

I then discovered and purchased a Redding G-RX Carbide Push Thru Base Sizing Die via Sinclair.

I had some strong hints before purchase that it wouldn’t directly work in my Dillon 550B press but I figured I could figure it out. I was correct on both accounts.

The bottom end of the pushrod did not fit in the shellholder of my press. The die itself worked fine in the 550 toolhead. But the bottle intended to be used that attached to the top of the die would not fit among the other dies of the toolhead with an available opening.

It wasn’t a perfect match because it had different threads but the neck of a Dr. Pepper bottle (Coke, Pepsi, and most other soda bottles would not have worked because they have a shorter neck) had a gradual enough taper that it would fit among the dies. I cut the bottom out and screwed it into the adapter:


I took off the shell plate and verified the stroke and alignment of the pushrod on my press were close. But I needed some method to hold the pushrod in place. I strongly considered double stick tape and actually was about to buy it at the hardware store when I saw magnets just a few feet away. I found some very thin disc magnets that looked to be about the correct size and appeared to be strong enough to handle the pressure:


These worked wonderfully:


These magnets, as the packaging says, are extremely strong and held the pushrod firmly in place.

I resized about 100 cases in a few minutes and verified the base sizing die works as advertised. I’m very pleased with the result. My only tweak will probably be to buy a toolhead just for this die so I can use the correct bottle.


5 thoughts on “Redding G-RX Carbide Push Thru Base Sizing Die

  1. Very interesting. Now, I wonder if there’s a way to push the cases up into an electric case feeder and have the case feeder supply sized cases to the next step in the reloading process (which would require an extra station on the press, assuming the push through die has no way to decap and reprime the fired case). I’m assuming that there’s not a way to decap and reprime with the push through sizing die, and if that’s true, why not use a single stage press for this?

    Or, a semi-automated two-station press (initial size/decap/reprime, then push-through resize to remove the bulge. If that would work, might there be room on station 3 of the 550 for the original plastic bottle, with the regular sizing die at station 1, the push through die at station 3 and the other two spots on the tool head empty? Or, am I missing something?

    Thinking about it some more, if the two die arrangement above works, it should be possible to add a semi-rigid tube (or formed metal chute) to the top of the push through die and have the cases delivered to a tray or bin on the bench top. In that instance, the push through die could occupy station two on the 550, unless it’s more convenient to use station 3.

  2. This reminds me of my issue with a rifle having excessive head space. I questioned whether I should resize brass to spec, or size it only a few thou shorter than as-fired from that chamber. If I size to spec each time, and upon each firing the brass is expanded more than usual due to the headspace, I’m simply working the brass more than necessary. Nothing to be gained there unless I intend to use the ammo in more than one rifle, is there?

    This question would seem to apply to your situation also.

    While I marvel at your ingenuity in assembling the press, I wonder what was the specific need. Why not use your current barrel as a case guage?

  3. @Homer, If I had a single stage press I would use it for this. You are correct that decap/priming cannot be done with this die. The 550 had four stations and all are needed for normal reloading of .40 S&W. I could combine decap and push through resizing but that doesn’t really gain anything in the overall process.

    @Lyle, I use whatever brass I pick up at the range. Not just what I have fired. So the brass really needs to resized.

    It’s a pain to remove the barrel and it also means I can never “loan” a few rounds to a friend in need without worrying if they will problems getting it to chamber.

    Plus I’m have a bit of an OCD streak which is constantly whispering to me that if I’m going to making ammo I should make it to spec.

  4. Yes, a single stage press dedicated to this process is in order. Check Craig’s List… A lot of guys who panicked during the ammo shortage of 2008-9 and bought reloading gear are dumping it now after discovering they haven’t either time, aptitude for or love of the process- I’ve got several nice presses for cheap this way. BTW, have you looked at the Lee “bulge buster”? Does pretty much the same thing.

  5. I run 40sw on my dillon 650, had issues too until I used an undersized lee die for sizing from EGW

    also I use an egw case gauge (7 round) and have found that since 40 is a straight-wall case you can put the rounds in backwards (bullet up) and it works well and all rounds that fit fire in every gun I’ve tried them in.
    some bullets won’t go fully into a case gauge the correct way but will backwards and they always load and fire without issue, just something you could try.

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