.300/221 Rimmed?

[BitOfShush]

Been lurking for a while trying to pick up as much info as I can without asking a silly question... but can't seem to find out so here goes

I'm trying to work out reamer specs to make a .300/221 Rimmed out of .357 Max brass for use in a Martini Cadet rifle.

Now, I know that the .357 Max case has a head diameter of 0.379" vs the .221 Fireball's 0.376" so I want the larger head diameter to taper down to the .221 FB shoulder diameter of 0.361" and a shoulder angle of 23 deg.

Hopefully I can then use standard Redding .300/221 dies to create the brass out of trimmed .357 Max cases.

The PT&G reamer print I have been given is supposedly for a .300/221 Rimmed but differs in several (I think) important ways:

Shoulder dia is 0.3676"
Shoulder angle is 21 deg
Neck length 0.282"
Overall length from where rim meets body to end of neck is 1.340" (rim should be 0.60")
Leade (freebore) is 0.60"

I don't think this reamer has enough body taper for the Martini Cadet, which often has problems extracting fairly straight cases... even the .222 Rimmed in a Martini can stick with stout loads.

I'd like to specify the case tapers from 0.3776" to 0.361" with at least 0.10" freebore. I'd like to change the shoulder angle to 23 deg so the neck length will increase a bit to support heavy bullets.

Really appreciate any comments members may have on suitable reamer specs for a .300/221 Rimmed based on the .357 Max case... thanks

[d-mon]

Hello BitOfShush,

Here is what I would do if i where you:

I would get a few 357 remington maximum brass , maybe from different batch or brand, shot ones even better.Let say 2 or 3 of each.

Get a set of reloding dies in 30/221 like redding ones.
Trim them close to the lenght you would like to achieve
Full length resize the cases above, but with your olive assembly removed.
Then re expend the neck with a tapered olive or an expender.

Trim to the desired lenght that you want.

Send the cases to Pacific tool and gage so that they can measure them and grind a reamer for you. The chamber cut with that reamer will be slightly larger than the largest case of the batch, and you know that what ever case you will resize with these dies will work in that chamber.

As to changing the dimensions of taper, of the the body or shoulder, will involve getting some custom made reloading dies, which can be done but pushed the price up.

See what the other come up with...

But it is still an interesting project, and those martinis are so cute

Nick

[Artful]

You are aware there are already reamers and dies made for other wildcats based on 357 Max cases right?

http://www.mygunroom.com/dvgunshop/calibers.htm
quick google here
http://castboolits.gunloads.com/showthread.php?p=290416

Trim a new 357 maximum case to 1.36" and then size it with 300 Whisper die. This would give you a rimmed version of the 300 Whisper. Just use a standard 300 Whisper Reamer to chamber your 30 cal fast twist barrel - the Aussie's did a lot of this kind of stuff and Bertram even made 222 rimmed cases.
http://www.midwayusa.com/viewproduct...m_campaign=652

[d-mon]

Well Artfull,

One way or another there is still the purchase of a reamer involved.
As Pacific tool can grind what ever you want at no extra cost, it would be better to have the proper reamer with the RIM.

With a standard reamer the job can be done, but anyway you have to either build a jig or solder the martini extractor onto the barrel and cut the rim with a lathe tool.

Just my thought.
Nick

[BitOfShush]

Finally got hold of some Remington .357 Max brass, and had a bit of fun trying out different case forming methods!

Tip No 1
You MUST trim to rough length and then anneal the brass before trying any resizing of .357 Max brass in a .300/221 FLS die... the case head size is subtly larger in the .357 compared to the .221 Fireball/.223 brass (0.379" vs 0.376").

See the first image for what happens when you don't anneal the cases first... I was SO lucky the case didn't jam fast in the die



Tip No 2
Use plenty of very high quality lube... I found Redding Imperial Sizing Die Wax to be the best.

Tip No 3
It is best to use a pipe cutter when rough trimming the .357 Max brass, as it creates a nicely rolled edge... this helps the initial necking process start smoothly and evenly.

Tip No 4
Remove the expander ball before the first case sizing pass.
Start the necking process with one smooth steady motion of the press arm, then stop and lower the arm and apply more case lube before proceeding to resize the case body. There is a lot more effort required to size the body vs the neck.

Tip No 5
Insert the tapered neck sizing ball, re-lube the case and FL resize for a second pass all in one go. This time the case should move in and out of the die smoothly and without galling.

Tip No 6
Trim cases to required length in a couple of passes... I chose an overall case length of 37mm to give a much longer neck than the standard .300/221 case.
I think this will give better support to the longer 220gr-240gr jacketed projectiles as well covering some of the lube grooves in cast bullets.

The longer necked rimmed case also holds slightly more powder than the .300/221, so should squeeze a little more supersonic performance. Using Win 296 and filling right to the top of the neck, the .300/221 holds 24.7gr vs the .300/221R's 26.5gr... a difference of 1.8gr.

I'm quite pleased with the way the Rimmed Whisper turned out... just need to draw up the new reamer specs.

And as it is now a bit different from JD Jones' original, maybe it should be called the 7.62x37R

[d-mon]

Congratulation for the job.
I have seen somewhere the method you discribe ...

If you can check the concentricity and neck thickness of different cases coming from different batches, just to make sure.
You might want to turn the neck as well to get the ultimate accuracy!

Good luck with your project, you are on the right track

Nick

[Mike-Sid]

Great job! Keep us updated when you get the reamer.

[JFettig]

You mentioned supersonic performance, you might want to check into the pressures that the cases can handle. I don't think .357 max is nearly the pressure that .223 is. The cases might not be able to handle it. It might be a good idea to section the base of a .223 case and .357 max case to compare dims.

Jon

[d-mon]

Hi,
I just had a thought last night.
Definitly check the thickness of your brass at the neck.
Mine is about 0.013" to 0.015". Anymore than that and each time you are going to size down with your die and size up again with the olive, you will be overworking your brass and reduce its life expectency.
It might be worth neck turning it down.

Or you could use a redding neck sizing die with interchangeable bushing to minimize the overwork.

Nick