Author Topic: Done Did The Right Thing? (RAMI Recoil Spring Assembly)  (Read 2232 times)

Offline PappaWheelie

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Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« on: March 31, 2018, 11:17:35 AM »

Just having read lewmed's post about recoil spring failure at ~450 rounds (!!!)
http://www.czfirearms.us/index.php?topic=95795.msg736672#msg736672
and having repeatedly tried to find, after reading the CGW recommendation to replace at 1000 rounds
https://cajungunworks.com/product/60001-rami-recoil-spring-assembly/
and having been on CZ-USA's Notify Me list for months without response, I decided that I'd pop the USD 100 for DPM Systems Technologies RAMI kit
https://dpmsystems.com/cz-2075-rami-b-db-30-barrel-9mm-40sw
so as to be able to carry with fresh springs. I'll swap out back to the stock spring assembly for firing range practice (where a failure would be of little consequence), until a failure occurs, by which time (hopefully) the factory USD 15 kits will have become available. Believe me, I'll order two or three when they're finally available!
Imho this is CZUB irresponsibility to allow such a defensive carry-critical subsystem to remain unavailable for so long. I'm copying them on this post.
Opinions welcomed...
http://www.czforum.com/forum/index.php?topic=5398.msg23061#msg23061
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CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
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-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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Re: Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« Reply #1 on: April 19, 2018, 09:57:47 PM »

The DPM springs finally arrived from Greece. Substantially stiffer to rack. The DPM RAMI springpack is a two-spring solution (like comes stock), not triple springs as described on the webpage https://dpmsystems.com/cz-2075-rami-b-db-30-barrel-9mm-40sw :

"MECHANICAL RECOIL REDUCTION SYSTEM
This system works due to the multi spring intricate rod (three springs) and controls the functionality of the gun. The third spring which is contained within the rod controls the movement of the slide so it never rams on the frame. Also three separate external springs accompany this system. The springs are different in length with the longest being heaviest when the slide is on the battery, so the shooter can fine-tune the weapon for his/her personal standards."

April 21, 2018 Update:
Digging in a bit with measurements, the stock RAMI outer spring is #18 AWG spring wire (1.024mm; 0.0403"), 11mm OD, 33mm Free Length, 6.5 coils with closed and ground ends. The DPM Systems Technologies outer springs are exactly the same diameters, but 51mm, 58mm, and 62mm free lengths, and appear to be music wire (better stuff, hey, they ought to be for the price!).

I was going to calculate the rates of the three DPM Systems Technologies for comparison with the factory stock spring using something like https://www.thespringstore.com/spring-calculator.html when it dawned on me to simply use my Rapala digital fish scale and measure them directly.  Doing so, with the slide gripped in the 3X5" card padded jaws (high spot dusted, but unnecessary) of my massive YORK 150* vise, I came up with the following data:

SPRING     PRELOAD, lbs       MAX LOAD, lbs       AVG. LOAD, lbs      % INCREASE
RAMI 33        2.0                      17.8                        9.9                         0     
DPM 51         4.0                       23.0                       13.5                       36.4
DPM 58         7.5                       23.5                       15.5                       56.6
DPM 62         7.6                       24.0                       15.8                       59.6

So it appears that the series-coupled little inner spring compensates for the bulk of the differences between the three outer spring options in the DPM kit.

Hopefully the higher racking energy will suffice to properly absorb the increased kick of my "short barrel" duty ammo https://underwoodammo.com/product/handgun-ammo/9mm-luger-p-90-grain-xtreme-defender/ per the reality of physics that higher-power ammo needs to be paired with stiffer recoil springs http://www.czforum.com/forum/index.php?topic=5424.msg22926#msg22926 in order to not abuse the hardware.

For now I'm carrying with the 51mm spring until I have opportunity to verify that the higher preload DPM options aren't too beefy for the (short barrel limited) kick of the Underwood ammo, i.e., won't prevent full slide travel and thus rechambering. 

I've advised DPM that I'm grateful that they have provided the springs I need to carry safely in absence of factory support (in terms of recoil spring inventories). For the record I'm also grateful for (industry-highest quality, imho) Underwood Ammo for offering product that enables my 2.93" barrel length invisible Subcompact carry pistol to punch above its weight!

Stay tuned...

*(http://www.york.cz/en/workshop-bench-vices-york-text) as scored in my youth (for $35.00; now retailing for $462.64!) while working at a Jawa-CZ motorcycle dealership...
« Last Edit: May 04, 2018, 02:22:47 PM by PappaWheelie »
Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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Re: Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« Reply #2 on: April 23, 2018, 08:21:58 PM »
As of moments ago, CZ-USA has RAMI recoil spring assemblies back in stock. I ordered three, for target practice. I'll continue to carry concealed with the stiffer DPM Systems Technologies springpack in light of the "short barrel" duty ammo I've adopted.


I intend to do another YouTube comparing 9mm Lehigh HERO, 9mm Underwood +P+ 90 gr Xtreme Defender, and Underwood 45 Super 120 Grain Xtreme Defender using 1 gallon water jugs' explosion intensity: I expect penetration to better that of (6"-12") HERO while maintaining comparable explosion intensity based on currently-published Xtreme Defender YouTubes. Not that water jug explosion intensity is THE measure of impact damage, but it sure can show significant energy differences that ballistic jell doesn't seem to capture quite as vividly. It seems ballistic jell penetration is ~20% less than water, so the Max Expansion's 12" (exactly, based on 6" jug dimension) water penetration would be less than 10" in jel.


https://youtu.be/JULgWoLJGmQ Apologies for the too-fast scroll rate, it was my first post...


April 25, 2018 Update:
Punching Above Weight http://www.czfirearms.us/index.php?topic=96929.msg746657#msg746657
« Last Edit: April 25, 2018, 10:30:51 AM by PappaWheelie »
Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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Re: Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« Reply #3 on: May 01, 2018, 02:35:43 PM »
Got back to the shooting range this morning, with twofold objective: sight alignment confirmation and recoil spring testing.
Re. the former, good success: http://www.czforum.com/forum/index.php?topic=5063.msg23283#msg23283


Re. the latter:
The tested average force of all three DPM outer spring options had me concerned that perhaps they all might be too stiff for reliable cycling, even though they are, after all, designed for normal SAAMI-spec pressures.

It turns out my concern was unfounded; the longest DPM outer spring resulted in Underwood Xtreme Defender +P+ spent casing discharge average (of five) distance = 10.78 ft., roughly comparable to that of the stock RAMI springpack with 115 gr Speer Lawman, 9.84 ft., while the lighter two springs gave increased average discharge distances with Xtreme Defender, up to 11.98 ft.

The long outer DPM spring with the Lawman ammo averaged 6.63 ft.      For obvious reasons I didnít test the Xtreme Defender +P+ with the stock RAMI springÖ

As a carry duty-only combination, hopefully never to be needed, Iím OK with the less than one foot discharge distance increase that Underwood Xtreme Defender 90 gr +P+ ammo and the DPM long outer spring comprise.

It seems a potential market for specialty shops like DPM to pursue would be to develop deliberately heavier-yet carry-only springpacks for Subcompacts like the (2.93Ē barrel) CZ RAMI to be able to better control NATO (+P+) rounds that particularly well combine with such short barrels for the maintenance of muzzle energy without incurring undue frame damage.

Are you in, Panagiotis?  Still above target: https://cajungunworks.com/how-to-select-the-proper-recoil-spring/
« Last Edit: March 28, 2019, 03:12:55 PM by PappaWheelie »
Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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Re: Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« Reply #4 on: June 14, 2018, 02:00:16 PM »
I intend to do another YouTube comparing 9mm Lehigh HERO, 9mm Underwood +P+ 90 gr Xtreme Defender, and Underwood 45 Super 120 Grain Xtreme Defender using 1 gallon water jugs' explosion intensity: I expect penetration to better that of (6"-12") HERO while maintaining comparable explosion intensity based on currently-published Xtreme Defender YouTubes. Not that water jug explosion intensity is THE measure of impact damage, but it sure can show significant energy differences that ballistic jell doesn't seem to capture quite as vividly. It seems ballistic jell penetration is ~20% less than water, so the Max Expansion's 12" (exactly, based on 6" jug dimension) water penetration would be less than 10" in jel.


Finally got to it, results in line with expectations: Underwood Ammo Xtreme Defender rules!
https://youtu.be/CtvfiJgTQic
Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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  • "This is war, and in war, time is of the essence"
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Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth

Offline PappaWheelie

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Re: Done Did The Right Thing? (RAMI Recoil Spring Assembly)
« Reply #6 on: April 06, 2019, 02:52:46 PM »
Not so happy update:

CZ 9mm pistols don't reliably feed Xtreme Defender ammo (4/19/2019 UPDATE: when limp-wristed)!
https://czfirearms.us/index.php?topic=102671.msg803459#msg803459
Virtually every other shot results in FTF b/c the flat cruciform nose of the bullet tends to snag one of its legs on the bottom of the feed ramp in both 2075 RAMI and 75 SP-01. Seemingly a conical face whereby the cruciform legs "cam past" the bottom of the feed ramp could solve the issue. I'll try several different truncated cone angles and flat diameters to see if a 100% reliable configuration is possible. I've contacted both Underwood Ammo and Lehigh Defense (bullet source) with the above URL link. Stay tuned: meanwhile I'm carrying with Xtreme Defender in the chamber only, followed by (alternately) Lehigh Max Expansion 105 gr and Max Expansion 70 gr HERO.



4/19/2019 UPDATE: see https://czfirearms.us/index.php?topic=102671.msg803459#msg803459
« Last Edit: April 19, 2019, 05:56:30 PM by PappaWheelie »
Member, Gun Owners of America
CC: CZ 2075 RAMI BD in PappaWheelie Invisible 15 Round RAMI Holster
Homeboy: CZ 97 BD, Underwood 45 Super 120 Grain Xtreme Defender ammo
UBG: CZ 75 SP-01 Tactical Urban Grey Suppressor-ready
-all w/ CGW Short Reset Kit/1485-T2 Disco, 5 "Thick" Trigger, polished SA tooth