RCBS X Die Small Base Sizer Die

[akinswi]

Anyone use this die or have used it

https://www.rcbs.com/dies-and-shell-...e/1000032.html


Thanks

[Shadow9mm]

I have the small base x-dies for 223 and 308
I also have a standard (not small base) for 30-06

Anything particular you were wanting to know about them?

[akinswi]

Originally Posted by Shadow9mm

I have the small base x-dies for 223 and 308
I also have a standard (not small base) for 30-06

Anything particular you were wanting to know about them?

Yes , Im tired of trimming 30-06 brass every time I LOAD will this reduce trimming. Will be resizing for M1

[Shadow9mm]

So it can, but there are some oddities. I called rcbs as the instructions that came with it are not super clear.

First off you can size normal or use the x feature. But the x feature is optional.

You need to keep your brass together in lots so to speak.

Steps
1 size with the die not using the x feature
2 trim short 0.010 below trim to. You should not have to trim again
3 shoot

So the first round is like normal except trimming short once you go to reload again is where the x feature can be used.

Size 1 piece from the batch/lot. At the top of the stroke lower the decapper/x feature until it fimrly touches the mouth of the case and lock it down.

Now size the rest of the batch and it should keep the necks a uniform lengh and minimize growth.

Each time you resize that batch you need to resize 1 and set the x feature then size the rest. Same with each batch/lot.

According to rcbs you should not have to trim again for the life if the brass.

So its a bit more work keeping your brass organized, depending on how much you have. But it can eliminate trimming.

I dont like trimming 0.010 shorter than trim to. Im currently testing trimming to the trim to length and seeing if i can get 2-3 firings before having to trim again

[akinswi]

Shadow,

So if recommended trim length for 30-06 is 2.484 I need to trim these back to 2.474.

Is there a reason why you couldnt start x sizing from day 1 when the brass is brand new? You trim to uniform everything first .

I ordered 500 new cases from sig sauer in 30-06 so that lot will be to MY M1 so keeping them separate is not an issue.

What im on the fence about is I usually shoot 50rds a range session do i keep shooting the same 50 until there toast then move on to the next 50 or shoot 50 until I run thru all the new brass and start all over again once they have all been once fired.

2nd concern is consistent case length, after you start using the X die

[Shadow9mm]

Assuming your virgin brass is all the same i would say yes. Measure some and make sure they are consistent. Size 1, run the x feature down and check length after sizing. As long as its at or under max you should be good to go. The rest should be the same length as the first.

But if your going to trim your virgin brass, no need to use the x feature.

[mehavey]

I'm confused as to how any particular sizer die design -- per se -- can prevent case wall stretch that occurs
upon firing with a case shoulder set back from the chamber shoulder.

Can someone explain that to me ?

The X Die doesn't shorten the length of the case: The mandrel reduces the growth caused by
the case mouth contacting the mandrel during sizing. Because of an extremely close tolerance
between the mandrel and die neck wall, the neck wall of the case does not thicken as the
case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few
thousandths of an inch, and then stabilize below the maximum case length

[Shadow9mm]

As i understand it limits growth when sizing. The mandrel contacts the case mouth limiting gowth or reducing the ammount of brass that moves. You will still get some, it just limits it and keeps it uniform. I suspect the 0.010 extra trim helps as well but supposedly you adjust the x feature each time you size each batch and it should never exceed max length for the life of the case.

[GeauxTide]

I use an X set in 308 for my M1A and Browning Mk3 DBM. I've got a regular set for my bolt guns. They reduce the BASE of the case while keeping the overall case dimensions at or below spec.

[tangolima]

It is the first time I heard of this product, so I looked it up. It sounds like a miracle, but it really isn't, if I understand it correctly.

First, let's understand why the case neck grows after resizing and why we need to trim. The shoulder is pushed back (it used to be a sin to call it that on this forum) and brass flows in neck, path of the least resistance. Neck becomes longer and requires trimming when it exceeds certain limit.

A few things we can do if we hate trimming. Cut the neck short is one. RCBS recommends 0.02" below, instead of 0.01". I myself control my rounds' head clearance to 0.004" for semi auto. Every 5 loads I find it necessary to trim about 0.005" off. 0.02" is good for 40 loads. Most brass won't last that long anyway.

Not exceeding case length limit is one thing, not having uniform case length is another. The x feature winky ding is there to put some resistance to neck growth. It further reduces brass flowing into the neck, and more importantly, it makes the growth more uniform.

Interesting concept. Will I pay for it? Probably not. I don't really hate trimming. It is part of the routine. Every 5 loads, anneal, resize, and trim. My brass can easily do 20 loads.

-TL


Sent from my SM-N960U using Tapatalk

[mehavey]

First, let's understand why the case neck grows after resizing....

The neck hasn't necessarily grown because of brass flow into the shoulder/neck.
The case itself has stretched down near the base.
(Hence eventual case separation)

I wait with bated breath how this die solves that problem.

[IMtheNRA]

Yes, the X Die works. I've been using these in .308 and .223 for at least ten-twelve years. Periodically, I run 4 or 5 cycle tests on 100-rd batches of same headstamp brass. The die works as advertised. As others pointed out, you can deactivate the anti-growth feature if you're concerned about neck thickness buildup, although I haven't seen it in any of my tests.

[mehavey]

How does it prevent case stretch at the base?

[IMtheNRA]

You'll be better off asking RCBS who, unlike me, designed and manufactured the die. The whole thread will be better off, too.

[Unclenick]

Mahavey,

It's redirection. With standard dies, the familiar course of events is a resized case leaves a bit of head clearance, and firing stretches the case at the pressure ring to expand to fill that space. When the case is resized again, entering the sizing die first contacts the sides of the fired case, squeezing them inward and elongating the case further. In this narrower-but-longer condition, as the shoulder of the case reaches the shoulder in the die, the press ram pushing the case deeper into the die causes the shoulder of the case to be extruded by the die shoulder, turning the top edge of the case wall into the bottom edge of the shoulder, and the top of the original shoulder sliding inward and mostly up into the neck, but partly inward to form the interior "donut", while the rest grows the neck length and thereby causes overall case growth.

In the X-Die, two things are different. One is that instead of the neck portion of the die being open at the end, it has a sharp shoulder that limits how long the case can get. The second is that it has a mandrel as the decapping pin stem that prevents the excess brass from flowing inward or forming an internal donut. So, Given those barriers to growth, where does the excess extruding brass go? The only place left is down into the powder space. So, while I don't own one of these dies, my expectation is that sectioning a case that has been resized in one for a number of cycles would show a sort of inverted lip or collar at the bottom of the neck where it meets the top of the shoulder, protruding downward into the case. Rather than an internal donut narrowing the neck diameter, it would have a downward donut that slightly extends the internal neck length. It's the only place left for the extruded brass to go.

[akinswi]

So In other words the law of physics apply the “Brass has to flow some where.” Nick would a mandrel stem from a Neck sizer die straighten this out or a lee collet die ?

[mehavey]

UncleNick, Many thanks for the reply. Your explanation is exactly that I had
also surmised -- neck growth is limited by confining shoulder/mouth
reformation to the forward section of the case.

Unfortunately the base of the case appears to have still undergone irrevocable
stretch -- and the clock on case life continues its countdown.

~~~~~~

As an aside, I tend to judge growth in overall case length -- after "normal"
resizing -- to be an indicator of that base stretch/case life over time...
and now that indicator is gone.

[reynolds357]

Originally Posted by akinswi

Anyone use this die or have used it

https://www.rcbs.com/dies-and-shell-...e/1000032.html


Thanks

I have never used a small base X die, but own several sets of X dies. I like them. Work fine

[Unclenick]

Mahavey,

Yes, the pressure ring stretch continues unabated. You eliminate trimming more than once, but overall case life is as before. The only thing I know of that will extend that is to smooth and polish the inside of the chamber enough to get some sliding of the stretching brass in the area of the pressure ring to spread the stretching over a greater length of the case walls, and thus to have a smaller amount of thinning at each firing. Slamfire has done this by lubricating cases, but I have had oil and other lubricant squirt onto my glasses before, so I tend to avoid that particular method.


Akinswi,

Any forming mandrel tends to press out the internal donut, but to prevent future trimming, you need the case mouth constraint as well, which the Lee Collet Die does not provide. The next questions are how uniform are cases sized in the X-die? Do they tend to uniform neck wall thickness? I would expect so, but until I get one to play with, I won't know the details.

[akinswi]

Shadow,

I came across this review about the X die on midway

The idea is to trim your necks down to TWENTY THOUSANDS from the max length allowed instead of the usually proscribed .010" trim, and then set up the die so that the retaining mandrel bottoms out on the neck of the now newly shortened piece of brass...and then back the mandrel off about 1/2 turn or so, to let the brass expand a small amount to the normal .010 minimum trim length after the brass has once again been fired during another visit to the range. Do not readjust the mandrel again, and the neck is supposed to be blocked from lengthening any more. It has worked on my .308 brass quite well...no lengthening to the max trim length over time, and no bulging neck bases that can develop if you forget to back off that earlier described one half mandrel turn. Good luck

End of quote


Im in the boat with you that I dont want to trim my 30-06 brass to 2.474 , Instead Im going to Trim to 2.478 and follow this gentleman’s recommendation and back the mandrel off 1/2 turn to let the neck grow a bit. all my brass for my M1 are in 50rd lots, this lot is at end of life cycle 5th reloading, the case heads are getting pretty beat up so im going to try too shoot these 2 more times after using the x die. Then Toss this lot and start with new virgin brass and see how it fares

[Shadow9mm]

I bought the set and found the instructions to be unclear. So i called RCBS and asked and what i related whas how it was explained to me.

With that said you can tune how you use the die, it gives you options. I trim to the specified trim to length in the manual. After firing i size 1 piece twice. So a full size, then back up into the die and set the mandril to that length, so it should keep the growth uniform. Accepting that i may have to trim my brass twice during its life.

But it gives you options to eliminate or reduce trimming, and im all for that.

[akinswi]

How was runout? I was going to put this die in my first stage on my dillion, then use an expander mandrel on the second stage, then charge the case with powder on the third, the fourth and final stage seat the bullet.

[Marco Califo]

I have the X die for 308 and toyed with it. Honestly, when I got the Geraud trimmer, I haven't touched it since. I have shifted to 223 for volume shooting. So, I am not shooting enough 308 for it to make a difference to me. I will by 500 new Starline 308 before worrying about trimm8ng again.
I think my experience has probably been duplicated by others.

[akinswi]

So I set up The RCBS X die, these were trimmed to 2.478 (30-06) I then took a case that was trimmed to 2.484 and set the mandrel on hard stop at that length. Gave myself .006 of growth.

Now, I ran the same case in the die to set my shoulder back about 4 thousandths From about 2.035 to 2.031

The shoulder measurements came out spot on so just by pure luck I thought, I might as well check the length. To my surprise the case length shrunk from 2.478 to 2.464.

I ran a second case same exact thing happened the case overall length shrunk to 2.464

Can someone explain to me what is happening?

I dropped these in the case gauge and no issues, The brass had to flow somewhere im assuming it went outward

[Unclenick]

Unusual. It suggests the die is a bit wider than your other sizing die. Measure shoulder diameter and case diameter just ahead of the pressure ring out in front of the head. Die tolerances are a couple of thousandths, and fattening that much over the body length could produce shortening by lowering the neck together with the shoulder.