Benjamin Introducing the M-Rod Cobra

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3Crows

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Mar 14, 2022
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Wichita, KS, USA
I worked on the stock all of yesterday. It turned out to be a PITA despite my having done dips before, this was my first rifle stock and it required a double dip. What a fuss, I am exhausted. Veil camo hydrodip over metallic graphite base (One Hit Wonder paint). I shot over with SprayMax 2K clear matte. Looks pro to me.



Cobra tech valve, Huma reg with XXL plenum, Tim Hill gage block, cut down shroud, JSAR aluminum reservoir, AGR FFG/SSG hammer system, AGR cocking thumb rest, .196 porting and "special" built transfer port (thanks ;) ). It is in the mid-50s fpe +/- depending on the exact gap I give the hammer and for 16+ to 24 shots. The Cobra valve cycles really fast so this rifle does not like the JSB 34 pellet. The valve is closing before the pellet leaves the barrel. But with the 25.4 JSB or even the H&N Barracuda 28 grain pellet (which it really likes) it really zings them out there and match the valve cycle well. Rifle is 6 pounds and 7 ounces with scope and is 39.75 inches long.
 
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3Crows said:
I worked on the stock all of yesterday. It turned out to be a PITA despite my having done dips before, this was my first rifle stock and it required a double dip. What a fuss, I am exhausted. Veil camo hydrodip over metallic graphite base (One Hit Wonder paint). I shot over with SprayMax 2K clear matte. Looks pro to me.



Cobra tech valve, Huma reg with XXL plenum, Tim Hill gage block, cut down shroud, JSAR aluminum reservoir, AGR FFG/SSG hammer system, AGR cocking thumb rest, .196 porting and "special" built transfer port (thanks ;) ). It is in the mid-50s fpe +/- depending on the exact gap I give the hammer and for 16+ to 24 shots. The Cobra valve cycles really fast so this rifle does not like the JSB 34 pellet. The valve is closing before the pellet leaves the barrel. But with the 25.4 JSB or even the H&N Barracuda 28 grain pellet (which it really likes) it really zings them out there and match the valve cycle well. Rifle is 6 pounds and 7 ounces with scope and is 39.75 inches long.
Click to expand...
Who makes the cobra valve?
 
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3Crows said:
I worked on the stock all of yesterday. It turned out to be a PITA despite my having done dips before, this was my first rifle stock and it required a double dip. What a fuss, I am exhausted. Veil camo hydrodip over metallic graphite base (One Hit Wonder paint). I shot over with SprayMax 2K clear matte. Looks pro to me.



Cobra tech valve, Huma reg with XXL plenum, Tim Hill gage block, cut down shroud, JSAR aluminum reservoir, AGR FFG/SSG hammer system, AGR cocking thumb rest, .196 porting and "special" built transfer port (thanks ;) ). It is in the mid-50s fpe +/- depending on the exact gap I give the hammer and for 16+ to 24 shots. The Cobra valve cycles really fast so this rifle does not like the JSB 34 pellet. The valve is closing before the pellet leaves the barrel. But with the 25.4 JSB or even the H&N Barracuda 28 grain pellet (which it really likes) it really zings them out there and match the valve cycle well. Rifle is 6 pounds and 7 ounces with scope and is 39.75 inches long.
Click to expand...
There’s a word I haven’t heard in a while. Lol.
Fun fact, the name Cobra was being thrown around when the now Gunnar was under development. I call my personal Gunnar Cobra to this day because of that.

Nice Marauder.
 
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Nice looking marauder. Cobra valves are interesting but in reality only require more hammer strike much like running a heavier valve spring. I should make a animated GIF explaining exactly how they work/their function. They certainly have a home in many peoples hearts though but no real added benefit, in reality its a hindrance, and frankly for that very reason you'd never see them in production ran rifles. Its why the gun struggles with 34's, the cobra valve simply cuts dwell / requires more hammer strike.

But for very niche cases, with very small plenums and low power (but high power relative to plenum volume), I can see their benefit, primarily for cool factor in controlling the resistance of the poppets opening with air more than spring.

-Matt
 
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I am using a light weight nylon hammer (for the aluminum tube) and light(er) spring. Rifle cocks with ease. I was trying for 1900 psi on the regulator. If I was not regged then it would probably need more hammer and/or more spring rate but as it is, it just shoots and shoots producing very nice flat strings, good power and no low first shot like my JSAR balanced valve rifle will do if it has sat for a while.

I was given the valve :) and it was a working valve when I got it but it was suggested I clean it up and so I did. Maybe I made a few changes, maybe I did not, ;). It has some pretty large passages. I am sure I could increase the dwell but it is working so well with the mid-weight pellets like the Hades 26 and the Barracuda 28 that I just decided leave well enough alone.

I gave away a couple of decent spring guns on GTA. I guess Karma rewarded me but this rifle has a gifted stock, a new barrel I was given, the trigger guard was free if I recall as the stock I was given did not have one and the valve and the Huma XXL Plenum and I just have no idea where the nice TP came from! Sincerely thanks to the air gunners who helped me get this last M-Rod together.

I was mostly wanting to show off the hydro dip stock :cool:. I have done a few things, mostly a few motorcycle and car parts and some custom scuba regulators but this was a lot more challenge due to having to dip one side and then the other. For some years I was a wroking A&P and the company always gave me the female mechanics. That is because I never curse and say things like gee whiz or good grief instead. Well, I may have said a few bad words yesterday :eek:.
 
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Dr. Kralenstein said:
@3Crows

Any plans to make this one a side lever?

I can't believe crosman hasn't made a gen 3 Mrod and just go side lever already. They'd increase sells for sure.
Click to expand...

No sir, not at this time. The side lever breech from JSAR is not currently available and it is expensive (and worth it too). Going forward it might be time to start researching an FX or BRK, not to replace but to supplement my M-Rod fleet.

This rifle is very easy to cock especially with the light spring and the AGR thumb rest. Thumb on rest, forefinger on the inner portion of the bolt and squeeze my hand, very positive and easy. I suppose the rifles with the heavy springs and preloaded valves might be easier with a side lever but this rifle is very easy and smooth. The AGR lightweight Nylon hammer is probably part of why it cocks so easy.

A Gen 3 M-Rod is going to need:

1. Side lever
2. Larger and better TP design
3. Light weight not over 6 pounds
4. Aluminum or titanium air tube with a 3,600 psi fill minimum
5. A .30 caliber version
6. Factory (drop) bottle kit option
7. And maybe two more O-rings, one either side of the barrel port
8. A regulated version using a Huma reg

Oh, and a Veil Camo stock option!
 
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Did a little re-tuning, minimal. My latest string with the H&N Barracuda Hunter 28.3 grain pellets:

Mag 1 (3000)
850
842
849
845
840
859
846
845
Mag 2
852
853
851
838*
845
851
847
850
Mag 3
844
846
844
851
842
847
849
852
(still on reg which is set approx. 1900 psi)

* Quick shot, did not allow reg to refill plenum possible, this lower velocity in middle of string?

Reading about the EdGun .25, gets 22 shots at 850 fps (standard reservoir) with the 23.4 grain pellets, pretty good, but the Cobra does the same with a heavier pellet, 24+ shots at 840ish with the 28 grain pellet. Oddly, I get the same velocity with the lighter JSB Hades 26 grain pellet. Makes me think the valve is still open when the pellet leaves whereas with the H&N pellet being heavier reaches max efficiency for this tune.

The rifle is shooting sub-MOA, at 20 yards all go through the same hole, at 30 yards about a dime or less, at 40 yards, still very tight groups. Beyond 40 yards it is time to reach for the 1022 or the ol'39A or maybe the 9422M XTR.

Someday I will buy one of those EdGuns, BRK or FX, but not today :cry:. Part of the fun is dreaming about such a gun while shooting my M-Rods ;). Reality check.
 
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