California varmint/lead free design - 20/5.7x28FN - discussion

[Deleted member 46119]

As you all know, California is gone/going lead free for hunting and varminting. Perhaps for target/range as well but that's not what this is about.

Rimfire lead free is unobtainable. Even if there were not a shortage due to more gun owners, there was always precious little lead free rimfire. It is all unavailable and availability looks to be a very long way off since other options for rimfire makers are in such high demand.

22 Hornet is a very viable option but the rifles it is offered in are not tickling my fancy, expensive or just not what I want. CZ 527 not what I want, Savage 25 does not excite me and Ruger 77/22 expensive.

I have been noodling with several options beyond the 22 Hornet (std or AI) and the above 3. I have a 22 Hornet contender pistol and like it but not really keen on the lead free results.

For a while, CZ and Savage had their models available in 5.7x28FN. That is more exciting to me as it is a rimless, bottleneck design. However, they don't seem to be available and I feel there are shortcomings to the .224 caliber lead free BC numbers. Factory lead free is avaialbe at ~$0.40 and reloading costs the same or lower than a 22 Hornet and lower than most lead free rimfire if you could get it.

There is a 17/5.7-28FN wildcat but there are no component 17 cal lead free bullets.

At the moment, there seems to be 3 brand/model of 20 cal lead free. vs. 7 or so for 224. I like the 20 cal offerings a little better "just because".

The 204 Ruger is overkill for what I want.

The 20-Practiclal and Tactical are a bit closer but still "too much" for my intended purposes.

There is a 20/17-Remington but I already have a 17 Remington and it's still in the overkill area.

I like the form factor of a 5.7x28FN but l I have a 223 Remington already so that doesn't fix anything.

I have been playing with a 20/5.7x28FN. I bought some brass and dies but that is as far as I've gotten because.... I am undecided on barrel and action for the project.

Looking at the stability calculators, which are of course not perfect, it seems I would do best with a 9 twist. This puts availability on the high end barrel makers as the lower end all seem to be 12 twist.

As for actions, I'm sure I can make a Mauser or Rem 783 work and both fit the price range. There will be some serious work on bolt and extractor but everything is possible with time.

It's the money I want to limit on this project. Other projects have worked exactly as intended but this one has more unknowns so I lean towards less expensive.

any comments on the 20/5.7x28FN?

any comments on twist as in can I get away with a 12twist?

 

[Deleted member 46119]

Well, maybe I should have put this in the varmint section.

I've been electronically scratching this out. The 20/5.7x28FN still fits my thoughts better.

Two design criteria not mentioned above.

Maintain +1800fps to ~300 yards
Download to subsonic, just at sea level with balistics very close to a 22LR.

Does anyone know the minimum impact velocity of the Barnes 204 caliber 26 grain Varmint Grenade?

Does anyone know the "usual" behavior of flat base bullets transitioning from supersonic to subsonic?

 

[Deleted member 46119]

Because I want to make a 22LR/lead free varminter with reloading costs of less than $0.25 per round, I also want to make the rifle in expensive (not cheap, that's for the manufacturers to do).

At the moment the candidates for donor actions are:
Remington 783
Ruger American

Both would require significant rework of the bolt, magazine and feeding.

The easiest thing for making a repeater would be to use a Ruger 77/22, CZ 452 or Savage 25 but the extra $200-300 for the action to throw away the barrel is not my favorite idea.

Though I could prove the ballistics with a single shot. Say, just getting a barrel for my Contender, eventually I would want to make a repeater than could be duplicated at a price point lower than the Ruger, CZ or Savage.

 

[HarryN]

Hi Jeff, interesting project that we all will face sooner or later.

I had read about this cartridge, but had not really studied it more seriously until this weekend because I have had big bore fever lately.

These are just some thoughts on the subject, probably to be edited later:
- Consider to neck up to 6mm rather than necking down.

As an example, my .270 win is now essentially a 100 grain bullet rifle, a .243. To get back to equivalent mass and BC, I either need a 30-06 or maybe .338 win mag.

- In some ways, the bore rider / piston ring design concepts often seen in bullets from GS custom and CEB, while technologically great, tend to make the effective bore diameter even smaller. This makes the bullet mass / length / twist problem even harder.

- Really small bores are harder to make, and just add to the sensitivity of minor variations.

- A 6mm / 5.7x28 opens the door to lots of 6mm bullet and barrel options.

 

[HarryN]

One of the comments that is made about reloading the 5.7x28 is its extreme sensitivity to power load.

It seems like this is at least partially from the use of very fast powder needed for short barrels.

In a .22 LR replacement concept and a 6mm bullet, perhaps norma 203B or 204 could work?

 

[HarryN]

As far as flat based bullets, everything I have read is that the main purpose is greater insensitivity to passing through the muzzle blast but every one of them that I have ever seen has about 1/3 the BC of what you will really want.

 

[HarryN]

Just curious, what is your strategy to hit $0.25 / per round? I don't see any copper bullets at this price point.

Maybe copper or brass doll pins?

 

[HarryN]

After some searching, it might be that your 5mm-5.7x28 is called a 5mm Shrike.

Apparently a few rimfire 580s have been center fire converted for this round after some significant effort. There is some debate about the action strength.

Another suggestion I saw on a forum was to start with a Cooper model 40, although those seem to have mixed reputations.

 

[HarryN]

There is a 5mmx.223 short which is just what you would expect it to be and has the same powder capacity of the 5mm-5.7x28.

That would solve the bolt face, powder charge, and desire for a .204. Not sure if it actually solves the "itch".

 

[HarryN]

The lowest velocity to expand copper hollow point I know of is the GS Custom HV, around 1600 fps.

There also are some frangible copper bullets.

 

[Deleted member 46119]

Just curious, what is your strategy to hit $0.25 / per round? I don't see any copper bullets at this price point.

Maybe copper or brass doll pins?

Brass is $.005 / 5 uses = $0.01
Barnes VG: $0.15 (on sale now at Midway, could be more later)
Primer: $0.05
Powder: $0.05

Total ~$0.26

The challenge is the sub sonic load. I've been noodling on this quite a bit while the central california storm passed. It would be "interesting"

Yes indeed, it is the 5mm Shrike. Thank you for that, it led me to much more information.

It appears that this is not the easy way to go. After much reading and thinking, I believe it's swimming up stream in a strong current. I could get there but not with out too much work.

For once I must concede, the rimmed case has the advantage: Change of direction. Like others, going back to the Hornet based designs.
Better primer/base support.
Actions already fitted for it.


Well, at least I didn't spend the time and money reinventing a square wheel.

Maybe a shortened Hornet to make the subsonic loads easier.

 

[HarryN]

Isn't it possible to load most anything with trail boss and a long, heavy bullet to stay subsonic? I would have expected the reduced powder charge to help.

I suppose that another path is to chop off 1/2 of the .224 weatherby case and neck it to .204. Then you could keep the tradition going.

 

[270Weatherby]

20 Vartarg 221 Fireball necked down to 20 cal
This is what I use in a Cooper for leadfree Ca

 

[Deleted member 46119]

20 Vartarg 221 Fireball necked down to 20 cal
This is what I use in a Cooper for leadfree Ca

I thought about it. Didn't excite me.

On the plus side, it is the same bolt face as a 223 and will probably feed in the same bolt action magazine.