FN 57 Threaded barrel?

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Where did you find it? Looks like Jarvis is still making them. I’ve always been tempted by a suppressed five seven but I just don’t like shooting suppressed pistols very much.

do you know if the five seven will need a recoil booster to function correctly?

this should probably be in the NFA discussion.

Dan
 
The fiveseven appears to need a recoil booster. But the full power, silencer fired brass appears to stretch more than the same rounds with no silencer.
 
MachIVshooter: What is a good safe weight to avoid accelerated wear and ensure reliability?

Thanks,

Dan
 
MachIVshooter: What is a good safe weight to avoid accelerated wear and ensure reliability?

Thanks,

Dan

You will never avoid it with the design of the pistol, but the lighter the can, the lower the impact.

The Five-seveN uses an interesting delay system that's like a hybrid between lever delay and short recoil; more recoil in function, as there's no mechanical disadvantage created by the lever as with a true lever delay, but unlike normal short recoil systems, the Five-seveN barrel is not really locked to the slide. It's somewhat difficult to explain the operation without visual aids, can't exactly liken it to other, more familiar systems. It essentially accomplished what roller delayed systems do, but with a moving barrel and no rollers.

At any rate,, the more mass there is attached to the barrel, the more inertia, and therefore the more stress on the lever "fingers" trying to hold the breech (mostly) closed.

5.7 rated rimfire cans are probably the safest bet. I have a fully stainless 8 ounce prototype model that's purpose built for the Five-seveN / Ruger 57, but I don't know when I'll be able to make them in quantity.

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MachIVshooter: Thank you for the response. I appreciate your explanation of how the five seven works. I could never really figure out how the locking system functions on that gun.

couple more quick questions:

- Are the parts that experience accelerated wear in the five seven easily replaceable parts or are you permanently damaging your gun?

- How about the new Ruger? Is it a better design to suppress than the FN? How does it lock up?

I appreciate your time!

Dan
 
- Are the parts that experience accelerated wear in the five seven easily replaceable parts or are you permanently damaging your gun?

Wear should mostly be on the lever (cam) part. I'm not sure how available or easily replaced that piece is, though.

How about the new Ruger? Is it a better design to suppress than the FN? How does it lock up?

The mechanism is very similar. I personally like the Ruger better and would have chosen it even if the FN were the cheaper gun, but I don't know that I'd rate one as a better host than the other from a mechanical/durability standpoint.
 
I hand loaded 55gr subsonics to go easy on the gun. It seems over boosted for factory 40gr ammo. Or at least the gemtech SFN seems over boosted on factory ammo.
 
Listed below are some (not all) modified blowback actions

categorized with my nomenclature – makes sense to GONRA anyhow…


gas buffered blowback” – late WW II German Volkstrum 7.92x33 rifles,

9mm HK P7 pistol, South African Vector pistol (recalled?).

Believe some poor soul tried this in a 12 ga. shotgun design too. Yikes!!!


delayed blowback” – Remington 51 pistol and their new R-51 pistols

are only common examples in US.

Blowback starts up, stops, restarts and finishes the selfloading cycle.


retarded blowback” – examples include a variety of foreign SMG’s,

some Italian rifles and light MG’s, H&K roller-cam rifles and pistols

(remember 1960’S era literature that leads one

to believe H&K tried this on a .50 BMG rifle and gave up),

original Thompson SMG (its NOT the “Blish effect” its RETARDED BLOWBACK fellas!)

SIG-AMT modified roller-cam, FAMAS lever amplification, various Benelli broken toggle

(all require fluted chambers) and the .276 Pederson broken toggle

(smooth chamber so VERY THIN GREASE required on cartridge cases!)


cartridge case-chamber friction retarded blowback” –

examples include MAB Model R 9mm pistols that have spring loaded barrels

(small coil spring), various 5.7x28FN FiveseveN firearms and the Ruger-57 pistol –

with spring loaded barrels. (FiveseveN pistol spring loads barrel with a torsion spring).


5.7x28FN firearms designer had the freedom to spec / optimize a brand new cartridge.

Common cartridges cannot necessarily withstand the axial stretching force

without the cartridge case head blowing off. 5.7x28 FN obviously handles well.

Believe Ruger just copied it but never got one to eyeball….


When 5.7x28FN caliber pistol goes BANG, coefficient of STATIC friction is important first,

then once cartridge starts slipping out of the chamber,

switch to coefficient of DYNAMIC friction.

(Brave souls out there can try shooting longer cartridge case CCI Stingers

in some of the small .22 RF long rifle pocket pistols.

Have gloves and safety glasses on when the cartridge case head blows off!

Even braver souls could try to make some lathe turned 5.7x28FN cartridge cases

from high strength steel that won’t expand to “grab the chamber”,

shoot handloads and “see what happens”.

>>> NO - DO NOT DO THIS ! <<<

Wouldn’t be a HUGE deal with conventional short recoil pistols,

but could easily blowup the FiveseveN, probably Ruger-51 too!!!)


Bottom line - any math model of these FiveseveN type actions

sure needs exceptionally detailed knowledge of the friction coefficients!

Usually isn’t the BIGGEST deal in firearms math models,

but here its just as important as “inertial” and “spring loaded” terms

in the dynamic equations!

Weird – but have to admit my FiveseveN “shoots Just Fine”!


Have fun in any event, and DON’T blow yer head off!
 
I picked up a Ruger 57 yesterday, but from the sounds of this thread, suppressing it wont be feasible as I plan to reload too ... I guess I'll just have to be content shooting my suppressed AR57 and non-suppressed Ruger 57.

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