6mm Mini Short Mag

[LandenR6arc]

Ok so this is a stretch and a bit of just playing around. While messing about on Chat Gpt I gave it a proper asking it to create the most ballistically superior cartridge that will fit in a mini length action (Howa mini/ CZ 527) in the 6mm bore size. And it came up with one called the 6mm mini short magnum or 6mm msm. These are the theoretical specs it created:
Concept: A radically shortened, fat-body “WSM-style” case (~1.60–1.65" case length) with either a rebated rim (.445" to use Grendel bolt) or a true magnum bolt face (.532") if your mini action can be re-bolted/opened up. Seat 105–115 gr bullets to ≤ 2.30–2.35" COAL.

Sketch specs (target values)

• Option A (rebated): .445" rim, ~.530" body, 35–40° shoulder
• Option B (mag face): .532" rim, ~.550" body (bolt/lug thrust rises a lot)
• Case length: ~1.60–1.65"
• COAL: ≤ 2.35" (you’ll need custom magazine/follower)
• Capacity (gross): mid-40s to low-50s gr H₂O after seating

Potential performance (24")

• 115 gr class: ~3,050–3,150 fps possible on paper
• 105–110 gr class: ~3,150–3,250 fps

I basically want to know how possible this is, can it be created from an existing cartridge like 243 wssm, and should I build one for shits and gigs instead of a 6mm ARC. My thoughts: if I’m already going to pour money into a full custom rifle with dies and components for the ammo why not go all out? Main downside for me is no factory ammo available, and possible feeding issues. I wouldn’t mind going to a short action but want to avoid just jumping for a 6 prc or a 6 creed just because I want to be difficult on myself.

 

[sgtsmmiii]

I think a factory .243 WSSM in a Winchester WSSM short action and a fast twist barrel will pretty much get you there ( according to Nosler load data ). YMMV.

 

[roostercogburn98]

with either a rebated rim

Rebated rims suck in my opinion

 

[LandenR6arc]

Rebated rims suck in my opinion

I’m not big on their either that’s just what chat got gave me. I was thinking more in line with like a shorter 6mm prc or a 243 wssm with turned necks and a modified chamber reamer so I can run the thinner necks. Only problem is I don’t know who even produces brass for 243 wssm

 

[roostercogburn98]

Convert 325 wsm brass. May be a bunch of steps and another turnoff.

 

[Mike Casselton]

Have you even thought about the cartridge fitting the magazine of the CZ?
The Howa was previously (long time ago) chambered in the 22-250, as was the old Charles Daily/Interarms mini.

Unless you plan on shooting as a single shot, the Wizzum cartridges have zero magazine support.
With respect to the CZ, it's way too wide to fit any of their magazines.

If you truly want to go short, and fat, you'd be better off with an old Winchester that was actually built for these cartridges.

Or, build on an Origin and go single shot.

 

[LandenR6arc]

Have you even thought about the cartridge fitting the magazine of the CZ?
The Howa was previously (long time ago) chambered in the 22-250, as was the old Charles Daily/Interarms mini.

Unless you plan on shooting as a single shot, the Wizzum cartridges have zero magazine support.
With respect to the CZ, it's way too wide to fit any of their magazines.

If you truly want to go short, and fat, you'd be better off with an old Winchester that was actually built for these cartridges.

Or, build on an Origin and go single shot.

An origin short action would be plenty long enough and have lots of mag length, the wssm is quite a bit shorter than the conventional WSM. I think a 243 wssm would work in a magazine and have plenty of length im more interested in the concept cartridge as of now. I could theoretically modify a bottom metal for a mini action and modify a magazine to make the rifle work later down the line. It’s more of just a brain storming project to see what’s possible in the wildcat game.

 

[Mike Casselton]

Yeah, the Origin would work just fine.
The little, skinny CZ, not so much.
The Mini might just do it.


I'm gonna point out the obvious here. You know the WSSM isn't a wildcat, right?
Feeding was always an issue with the Wizzums.

You could stomp the performance of the 243 WSSM by just building a 6 PRC.
Load light. Load max and you have all kinds of variety.
It will also fit in the Origin.

OR, shorten the PRC brass to the length of a GT and load long and heavy projectiles.
That would be a super cool wildcat.


Too many options, too little time.

 

[LandenR6arc]

Yeah, the Origin would work just fine.
The little, skinny CZ, not so much.
The Mini might just do it.


I'm gonna point out the obvious here. You know the WSSM isn't a wildcat, right?
Feeding was always an issue with the Wizzums.

You could stomp the performance of the 243 WSSM by just building a 6 PRC.
Load light. Load max and you have all kinds of variety.
It will also fit in the Origin.

OR, shorten the PRC brass to the length of a GT and load long and heavy projectiles.
That would be a super cool wildcat.


Too many options, too little time.

I thought about the 6 prc but I was thinking it would have the same problems as the wssm with having thick necks, I would have to turn the necks to not have a ridiculous neck thickness an harder time resizing.

 

[Mike Casselton]

I thought about the 6 prc but I was thinking it would have the same problems as the wssm with having thick necks, I would have to turn the necks to not have a ridiculous neck thickness an harder time resizing.

Turning necks isn't bad if you do it in batches of 50-100.
Then you get to decide on how thick you want them.

It ain't much of a wildcat if it's easy.

 

[LandenR6arc]

Turning necks isn't bad if you do it in batches of 50-100.
Then you get to decide on how thick you want them.

It ain't much of a wildcat if it's easy.

I’ve never turned a neck before. Do you use a lathe and a regular small stock removing insert? I’m just don’t want to turn them to thin and have necks cracking, or the neck separating from the shoulder.

 

[Mike Casselton]

A regular neck turning tool like the K&M is what I use.
You turn the neck for .002-.004 loaded round clearance. Only what you need and nothing more. The tools are adjustable and you can set the stop to just kiss the shoulder.

AccurateShooter.Com has a pretty good tutorial on neck turning on their cartridge info page.

Most people try to cut too quickly and their work shows it. If you let the cutter pull itself into the work and come back out slowly, the necks look polished.

I also do a primary cut on each neck first. Then I reset the cutter height and make a final pass.

Some people use two cutters so they don't have to reset.

 

[LandenR6arc]

A regular neck turning tool like the K&M is what I use.
You turn the neck for .002-.004 loaded round clearance. Only what you need and nothing more. The tools are adjustable and you can set the stop to just kiss the shoulder.

AccurateShooter.Com has a pretty good tutorial on neck turning on their cartridge info page.

Most people try to cut too quickly and their work shows it. If you let the cutter pull itself into the work and come back out slowly, the necks look polished.

I also do a primary cut on each neck first. Then I reset the cutter height and make a final pass.

Some people use two cutters so they don't have to reset.

Thank you for the info. I’ll have to look into the 6prc being a more viable option now. It would definitely be a better vessel for the cartridge because 6.5 prc brass is actually available from good quality brass makers.

 

[Mike Casselton]

Yeah, and necking down 1/2 mm isn't something that would cause you to even think about neck turning.

Just verify which reamer the gunsmith uses and you will know what your neck clearance should be.

I'm sure someone around here could make you a couple of dummy rounds and you will know what you need from there.

 

[steve123]

No it's not worth the hassle and I know this because;
I could roll WSSM brass on a flat surface and see the run out of the neck.
The primer pockets were all over the place in depth and in other aspects.
Flash holes were horrible as in not centered and there was a lot of brass burs punched into the inside of the case which I reamed off.
I benchrest prepped all of my 243WSSM brass including neck turning and after doing all that my groups shrunk by half.
That batch of WSSM brass was very inconsistent, so much so I threw 25% away, some before I did anything and some after I did everything to it.

Yeah it was a screamer but that's about it. Really only 1 moa if that but this was in a AR. I sold it shortly afterwards then got a 6mmART40 from whitely which was such a great cartridge using Lapua brass. This brass was the opposite in quality compared to WSSM and only down 200 fps or so. Plus it shot tight for an AR, even won a night match with it.

I'm kinda sticking with normal cartridges nowadays because of the pitfalls I ran into when going for extremes. Give me a 6mmBR for normal distances and a 6.5 Saum for longer and I'm good, those are my go-to's now.

 

[4O6shootist]

The magnum 6mm for a mini action, is the 6dasher, people already doing it. They made howa minis in 450 bushmaster so you can already get one in a 478 bolt face, but others choose to open up the ppc bolt face as well.

You cannot put a magnum bolt face on a mini, so you're only real option is to start the the 284 win parent case. It has a base diameter of 0.501 yet runs a 471 rim diameter. You could basically put a dasher front end on it and likey be around 47gr powder.

You might be able to a few of these into a 450 bushmaster mag for feeding. You'd essentially have a short necked 6x47 lapua performance wise.

Your performance potential states nothing on barrel length. But this is the logical direction to maximizing a howa mini action. Don't go too far down the hole with chat gpt. I've thrown it a few curve balls that it basically said the calculations were too advanced and specific for it to solve.

 

[LandenR6arc]

The magnum 6mm for a mini action, is the 6dasher, people already doing it. They made howa minis in 450 bushmaster so you can already get one in a 478 bolt face, but others choose to open up the ppc bolt face as well.

You cannot put a magnum bolt face on a mini, so you're only real option is to start the the 284 win parent case. It has a base diameter of 0.501 yet runs a 471 rim diameter. You could basically put a dasher front end on it and likey be around 47gr powder.

You might be able to a few of these into a 450 bushmaster mag for feeding. You'd essentially have a short necked 6x47 lapua performance wise.

Your performance potential states nothing on barrel length. But this is the logical direction to maximizing a howa mini action. Don't go too far down the hole with chat gpt. I've thrown it a few curve balls that it basically said the calculations were too advanced and specific for it to solve.

Barrel length would likely be 24” or longer I’m not a short barrel fan. The mini action has some chambering in the ppc face like 6 arc and 6.5 Grendel. I would explore shooting something like this in a short action just as a proof of concept to make it easier to dial in the right bolt face as I can get a short action in any bolt face. If there was only a custom action maker that made a mini length action, is the impact 737 a mini length action. Just based on videos and pictures the ejection port looks shorter like a mini but I don’t know if the bolt length is full short action or not. Maybe they have extended bolt stops to reduce pull length?

 

[4O6shootist]

Barrel length would likely be 24” or longer I’m not a short barrel fan. The mini action has some chambering in the ppc face like 6 arc and 6.5 Grendel. I would explore shooting something like this in a short action just as a proof of concept to make it easier to dial in the right bolt face as I can get a short action in any bolt face. If there was only a custom action maker that made a mini length action, is the impact 737 a mini length action. Just based on videos and pictures the ejection port looks shorter like a mini but I don’t know if the bolt length is full short action or not. Maybe they have extended bolt stops to reduce pull length?

Negative, 737 is standard short action with a 3.050 bottom load port.

 

[LRRPF52]

In the Micro Actions like a Vixen or Howa, you won’t have enough tennon and receiver thickness for full pressure WSSM. We’ve already looked at that.

Hoop strength isn’t there. I would also wonder about lug strength. Those micro actions are meant for .222, 6mm PPC, Grendel, stuff like that.

They’re just not built for fatter, higher-pressure cartridges. Howa was able to do it in .450 Bushmaster because the SAAMI MAP is 38,500psi, nowhere near 65,000psi of the WSSM.

A good buddy of mine really likes wild-catting the WSSMs, mainly to 7mm. He used a R700 size short action with custom feed lips and magazine work. Spits out 180-195gr with extremely tight ES and SD, yielding sub-MOA groups at ~1 mile even on 20” gong. First time he grouped it at 1710yds, he put 7x 195gr EOLs into 14 1/8” CTC, 5.0fps SD.

My favorite of the factory WSSMs is the .257 cal of course. Smokes the others easily. Load it with the new VLD class of 131-135gr .257” bullets and you’ve got something. It also has a 30˚ shoulder, not a 28˚ like the .243 WSSM. I always wondered how it would do with a 40˚ shoulder and some other bores like 6.5mm and .277”. We already know what it does with 7mm.

 

[4O6shootist]

Never understood the wssm, holds 55gr capacity, so just run 243 or 6cm, don't deal with shit brass either, no funky feeding. I mean is a half inch less bolt throw that big a deal?

 

[sgtsmmiii]

My understanding of the WSSM line was to have a shorter powder column that was supposed to mimic the philosophy behind the PPC line of cartridges for enhanced accuracy and power. Unfortunately, didn't seem to work out as well as they had hoped.