.357 Gen 1 Mrod based pistol

[mackeral5]

My LDC adapter arrived from Poland yesterday.  I made slight modifications to it to accommodate the .357 caliber then cleaned the ID of it and the OD of the CF barrel sleeve with acetone.  I coated both with a light coat of Loctite 680, then slid the adapter onto the barrel.  after curing overnight the 2 are joined as one. 

I now understand why some Crosman pistol owners affectionately refer to their guns as Lego guns.  The possibilities are endless. 

Here I've configured this as a 8lb 3oz, 45" , truly BACKYARD QUIET 115fpe little monster.  This is very close to what I have planned as the final configuration....I think. 



I had the valve apart earlier to convert from PH back to SBV configuration.  Here is a pic showing the poppet with delrin valve seal and slightly enlarged stem vent.

[Wayne52]

That gun is way cool Mike !!! That's what I should do with my Gen2 Mrod, at the moment it's been in limbo for quite some time now, I never did like the barrel that came with the gun to begin with (Green Mountain).

[YEMX]

Which LDC did you go with?

[mackeral5]

Which LDC did you go with?

I have an emperor and a ronin with extensions.  The picture shows the Ronin/extension combo.  Both of my large Neil C units are reflex, slip on type so they won't fit this gun.  The Emperor does well, but not quite as good as the Ronin/etension combo.  I haven't run the Emperor w/extension, one can only assume it gets even quieter...

I made some valve adjustments that have quieted it down even further.  The adjustments are basically doing my best to mimic Bob's Simple Balance Valve that he described developing for his Hyabusa build----key elements are .056ish vent, .125 stem protrusion from valve, balance chamber adjusted to just barely deeper than full valve lift.  Had to go to an OEM (a little over 70 grams, IIRC) due to closing forces becoming so great.   The valve is much more adjustable with HST prior to these changes it "wanted to run where it wanted to run", so to speak, with very little room for HST adjustment....more to come...

I'll post some data after I have a chance to organize it, perhaps over the holidays.

[mackeral5]

That gun is way cool Mike !!! That's what I should do with my Gen2 Mrod, at the moment it's been in limbo for quite some time now, I never did like the barrel that came with the gun to begin with (Green Mountain).

Thank you Wayne.  So far I am liking my first Marauder.  Currently in the 220cc brod carbine configuration it is doing roughly 10 shots  765-800-760 with 88gr slugs.

[FuzzyGrub]

I now understand why some Crosman pistol owners affectionately refer to their guns as Lego guns.  The possibilities are endless. 

That is a blessing along with a curse.     

The curse being, you will always find another config you want to try. 

[YEMX]

That is a blessing along with a curse.     

The curse being, you will always find another config you want to try. 

It's more of a curse...      But a fun curse!

[mackeral5]

My Chrosman Lego kit has been put through many configurations since starting this thread.  I spent some time testing a regulated .357 Brod with the 21" barrel.  I did a caliber change with a Green Mountain .25 barrel, this yielded some interesting results.   The GM was cut down to 18.25", removing the choke.  850fps 34gr JSB pellets running efficiency numbers over 1.6, reg'd at 2000psi.  Dialed up to 3000psi they ran 1065fps.  Anyway, that's a thread in itself. 

Another I learned a cool thing about the Gen 1 platform is caliber changes are simple--- remove the barrel, remove the cocking lug from the bolt, swap bolts, and install another barrel.  SSG's are simple to set up and tune as they can be removed without disassembly.  I really wish I would have started my PCP journey with the Gen 1 Mrod platform vs. QB.....

Back to the pistol.  The 21" barrel configuration put this kit in a niche that is better filled by my regulated Bulldog.  The Bulldog does everything the .357 regulated Brod did, but better and it can be turned up to over 300fpe in unregulated form.  So, I decided to take the 21" Mrod barrel and turn it into 2 pistol barrels.  a 12.5" and an 8."  I don't have the muzzle adapter to finish the 8.5", so it is still a work in process.  The 12.5" is complete.  When all is said and done I will have a 16" carbine, 12.5" big pistol, and 8.5" pistol barrel for this particular Lego set. 

Here's a picture of the 12.5" barrel configuration.



I also added an SSG, which is still under development--it is functional but not in its final form.  With the 12.5" barrel it gives 4 shots of JSB 81gr pellets 695, 710, 715, 690fps.  With the 8" barrel it gives 4 shots 632, 655, 645, 630fps.  There's still room for fine tuning but this is close to where it will stay. 

I'm not the best shot with a pistol, but here is an obligatory 3 shot group at 20 yards, from a rest.



Once I have the short barrel finished I'll update the thread. 

[FuzzyGrub]

Looking good, Mike.         

A nice powerful pistol. 

Are you using the JSB or maybe those red ringed slugs that worked in the BD?

[mackeral5]

Looking good, Mike.         

A nice powerful pistol. 

Are you using the JSB or maybe those red ringed slugs that worked in the BD?

Thanks John.  Testing so far has been with JSB's.  The 88gr HP's from GT bullets would likely run 25fps or so slower.  i am running low on them and have an order in but GT Bullets has a crazy 90 day backlog right now---I likely won't see that next order until late Jan/early Feb.  Based on previous testing the 88gr should do fine with the shorter barrel/lower velocities.  Penetration is a different story.....  at 915fps, the 88gr slug expands to almost nickel-sized, and gets trapped in the second gallon jug of water.  At 700fps, they pass through 2 jugs of water.... 

The .25 testing I referenced---I learned a lot there, will share whenever you're ready to do more Cothran testing......

[FuzzyGrub]

That's some backlog, but doesn't sound like there is much benefit to them given the velocity.

Yea, I know.       I do have to get back at it.   Certainly, will share notes.    

[mackeral5]

That's some backlog, but doesn't sound like there is much benefit to them given the velocity.

Yea, I know.       I do have to get back at it.   Certainly, will share notes.   

IMO, benefits of the 88gr GT bullet are 2 fold.

Price

Call it $81 shipped for 500 JSB's


Call it $59 shipped for 500 88gr GT Bullets.  Even though they say .356, they measure at .3575-.358 when  ordered unsized/unlubed/as cast. 




Accuracy.

 The top left is a 4 shot group of as-cast, unsized/unsorted GT Bullets 88gr.  The other 4 groups were shot with 81gr pellets.  I see the difference in accuracy across all 4 of my .357 barrels,  with the 88gr getting the better of the 81gr in each instance. All are TJ's 1:26 barrels.  This could have something to do with my barrel prep?  I don't know .  Barrel port is .280 wide so I do not think it should be affecting pellets, but maybe that is it.   Either way I feel more confident in the GT Bullets 88gr HP over the JSB 81gr pellets. 

Note targets were shot in the following order, with scope adjustments in between groups of 4. Center (3 shots), top right, bottom right, bottom left, top left being the last group. Refilled from 1800psi to 3000psi between groups.

[FuzzyGrub]

That is impresive.

If I recall correctly, they shot well out of your BD barrels, as well.  I think that is how I ended up with a sample pack.   

[YEMX]

Ah, beauty!!  You got a link for those 88 gr. slugs?  All I'm seeing is 115 gr on up.  Also, what alloy are they using?  Or is it pure lead?

[mackeral5]

Ah, beauty!!  You got a link for those 88 gr. slugs?  All I'm seeing is 115 gr on up.  Also, what alloy are they using?  Or is it pure lead?

https://www.gtbullets.com/index.php?main_page=product_info&cPath=10&products_id=31

Supposedly 2-2-96.  I have no knowledge to interpret those numbers.  What I can tell you is they FULLY expand and get stuck in the second gallon jug of water at 60 yards, with a muzzle velocity of 915fps.  They must not be too hard....

[mackeral5]

In post 27 I failed to include any data around the hammer system.  For that testing I was using an OEM hammer weighing in a little over 75 grams and a fairly stout spring in the SSG.  Previously I was shooting slugs with the longer barrels so the extra dwell was needed.  The spring is from McMaster Carr and is .055 wire stainless.  I don't have the specs, but it is much heavier than an OEM QB78 spring, for example.  Cocking effort not uncomfortable, but fairly significant.

While digging through my excess junk I found a spring I ordered back a couple of years ago when NVreloader/Don was posting about the merits of flat wire springs.  It is a 20lb spring for a 5 " full sized .45ACP running +P loads, part number 614620.  I checked compressed height and it will indeed fit my SSG. 

I put the light 47 gram hammer back in and put the flat wire spring in the SSG.  After a bit of testing I found this string and repeated it a few times.

JSP 81gr, 3000psi to 1500psi

 653, 657, 664, 661, 678, 685, 672, 649fps. 

8 shots averaging 664fps (79fpe) out of ~60cc of air and a 12.5" barrel. 

Also, all of the things Don previously said about flat wire springs were finally proven true to me.  it is a lot easier and buttery-smooth to cock this thing now....

[YEMX]

I'm probably wrong, but 2-2-96 could be 2% tin, 2% antimony 96% lead...  If this is the case, it should be fine for airgun use. 

[mackeral5]

I've spent some time now practicing my pistol shooting.  I am "cheating"---shooting from a well-rested position.  However shooting accurately without a shoulder stock is something new for me.  it also helps that a Ronin is installed (to be more respectful of our neighbors) but it also helps keep things stable.

I stretched a target out to 50 yards to demonstrate the valve's functionality.  Remember this is a Cothran Powerhouse valve, with a modified poppet.  Touched off by a 47gram hammer and reasonable cocking effort.  8 shots of JSB 81gr running right at 80fpe.  Not tethered, shot from a full fill.  3000psi fill shot down to 1200-1500psi on a ~60cc reservoir.  Remember there is a gauge block in there consuming valuable space....

A pic with the Ronin.



A pic of the shooting position.



The target---again 8 shots at 50 yards.  Same point of aim for all 8 shots.  This group was not cherry picked, it is the first and only 50 yard group I have shot with this gun and I'm a relatively new pistol shooter.



I didn't quite position my target properly so an oak tree suffered a little damage.  I shifted the target over a bit to prevent further damage.  I couldn't help but marvel at the damage inflicted by a "pellet pistol" at 50 yards.

[FuzzyGrub]

Excellent group for for 50yd, especially on first attempt!  WOW!   

Eight 80fpe shots!   You have me rethinking 357 in a pistol.  Didn't think that was possible.   I think CARM needs a 25/35 mag!   

[YEMX]

Most Impressive!!