GONRA's FiveseveN pistol ACTION / MECHANISM thoughts....

[GONRA]

GONRA’s FiveseveN pistol ACTION / MECHANISM thoughts.

Would really appreciate YOUR thoughts on this.
Many times, discussions of firearms mechanisms are a Real Mess.
Trying to doit right this time….

Listed below are some (not all) modified blowback actions
categorized with my nomenclature – makes sense to me 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 only common example 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 they 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) and various 5.7x28FN FiveseveN firearms 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.

When pistol goes BANG, coefficient of STATIC friction is important first,
then once it 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 !!!)

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 it “shoots Just Fine”!

Have fun in any event, and DON’T blow yer head off!

[blueorison]

I like muffins.


Especially the blueberry kind. Chocolate chip is nice, too.

[PainKillaX]

This thread is way over my head. Except the part about muffins. I'm partial to poppy seed.

[Llagoud]

I remember doing some reading a while back on John Blish and static friction....I'm not sure what took me down that path but it might have been when I got curious about welding dissimilar metals with explosive forces.


+1 to Blueberry muffins if they are real blueberries....not those dyed/flavored gritty apple chunks.

[ninthinning]

"5.7x28FN FiveseveN firearms 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."

This sounds interesting. Could you explain a little more?
9th

[Hebs]

I can't stop hearing gonorrhea my head for some reason...

[tdevince]

Blueberry muffins give me heartburn. I prefer raisin bread with honey drizzled on it instead.

[GONRA]

ninthinning brought up a good point.
GONRA thanks you for your interest.

My .22RF Long Rifle Iver Johnson TP 22 double action pocket pistol is fun to shoot with select Hi Speed ammo. First (and last) .22 RF CCI Stinger shot blew the head off the case.

Every shot, regardless of ammo, cartridge case body momentarily elastically swells
and sticks to the chamber – an essential “gas seal”.
Force inside cartridge head (from internal pressure and crossectional cartridge case area)
tries to push the case out of the chamber.
Longer the cartridge case (Stingers are much longer than normal long rifle cartridges)
greater the cartridge case body area “stuck” to the chamber.
Means a greater force is needed pull (push internally here) / slide case out of the chamber.
With CCI Stingers, head blows off the cartridge case since .22 RF cartridge case
material is too thin to stretch to accommodate the additional force without fracturing.

If there was a ”crimp” little above the rim, maybe this would just “stretch out”
instead of fracturing. (Pretty sure the patent literature has stuff like this,
decades ago, with center fire cartridges., at least.)

If the .22 Stinger case was made out of some magic material,
so head DIDN’T blow off, this would serve as a retarding effect.

Our 5.7x28 FN pistols exploit such a retarding effect thru the combination of a
a spring loaded barrel and axially strong cartridge case,
not to mention the plastic cartridge case coating that
governs static and dynamic friction coefficients.

One assumes FN fired ZILLONS of rounds and
uses an extremely detailed computer simulation to
“get this all correct” for the normal purchaser
whilst allowing plenty of “wiggle room” for the
tender mercies of the American Handloader. (Scary!)

[blueorison]

Gonra, a certain member who was contending that Jay and other members was wrong in their assumption to leave the lacquer coating on reloaded brass might want to ascertain his true fallacy by reviewing your anecdotal observations.

tdevince: man, raisin bread sounds amazing. My mom makes an awesome banana raisin walnut bread; making those into muffins with clover honey drizzled on top... :drool:

[panzermk2]

Besides stripping the coating off FN brass with acid we tried our prototype NON-coated brass. We had issues with both due to a lack of coating.

[maverick23jhp]

Dang It! Now I want a muffin! Thanks alot Blue.

[MikeS]

Well, thanks for the info. I understood most of it. Thank Costco I have both cornbread and blueberry muffins in the house.

[murphies_finest]

Well, thanks for the info. I understood most of it. Thank Costco I have both cornbread and blueberry muffins in the house.

Whay you know bout "coan bread"?

[Kerberos]

Muffins have been ruined for me...anytime someone says muffin, the only thing that comes to mind is muffin-tops...and I just laugh :laugh: