Crosman MK I HPA Project

[sholo]

Hi guys,

This is my first review of...well...anything, so I will apologize in advance for any/all short-comings, or info that I may have missed. If you are expecting an "Rsterne" type of detailed thread, you are probably going to be quite disappointed!

Let me start by saying that all the credit for machine work done on this project goes to Leonardj/Suprmatic. My only part in this was to supply base gun, new barrel, a multitude of questions, and clean/paint, re-seal, and re-assemble once I got gun back.

I had originally purchased this MK to use as a parts gun. It had been modified by the previous owner, with extra holes drilled/tapped for wire stock, scope/red dot(?), plus a few more that to this day I have no idea what they were for. Rear sights were missing, the "wings" that locate the windage screws was ground off, a bolt of sorts was threaded into the cocking knob, and a hokey looking 2-barrels-made-into-1 setup. IMO, it was FUGLY as hell! (ask Eric - he seen it the same day I picked it up)
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I thought about it for awhile, and decided that rather than use it for parts, it would be a good candidate for an LD "clone" project I had been pondering. Much better to have her shooting again, rather than stripping it for parts!
After gun was dis-assembled, the extra, un-needed holes were filled with aluminum threaded rod (with a bit of epoxy resin added to threads to keep them tight), then carefully peened to fill the voids aroung threads, and finally filed flush with frame.
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[sholo]

The barrel used was a Crosman 14" (ScopesAndAmmo) cut down to 12", and threaded accordingly. I would have liked to have had a LW barrel, but my wallet said "No can do". ($15 vs $100+). Shroud is 7/8" in diameter x 9" long.
TD-03.jpg

I wanted to be able to shoot this gun all year long, and Co2 just wasn't going to cut it. So...I decided to go the HPA route. Now, having said that, I didn't go HPA for max power/fps (I have other guns better suited for that, plus I don't have an R-PAL), but more for reliably consistant fps (as close to 499.999 as I can get) in all temps. I will be using a 13 ci bottle regulated @ 750 - 800 psi attached to gun via a remote coil hose.

Note: MK I/II frames are made from a zinc alloy. Maximum safe pressure to be used is 800 - 850 psi. Failure to stay at or below this point may result in serious damage to your gun, as well as a prosthetic hand being fitted where your real hand used to reside! Make sure you have a low pressure burst disc on the downstream side of your reg in case of reulator failure.

In order to attach coil hose, I needed a custom end cap. This was made from an old push button cap, fitted with a mini Foster fitting. Knurling was damaged, so it was turned down and milled to what you see here. I think it looks sweet!
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The valve is stock, except for this TP o-ring mod. It effectively eliminates any air leakage that the MK's are known to have between valve and frame. It does make installing the valve a little more tricky, but with a bit of care, and some lube, not too bad at all....
TD-09.jpg

Now I just have to clean/paint, install new seals, re-assemble, and get this puppy shooting again! Better get busy...
Hopefully next post I will have some #'s to show, along with more pics.

Thanks for looking, hope you enjoy.
Todd

[Fastair]

Nice Idea. good to see an old gun brought back to life.

[SeanMP]

Looks outstanding Sholo. You and Len have done amazing job on that so far.

I admit I have a huge soft spot for MK1's. I toted one for miles as a kid thru my teens as my trusty sidearm.

[sholo]

Thanks for the comments, guys.

Fastair: My thoughts, too. It just didn't seem right to take a MK out of commission, and relegate it to a parts source!

Sean: Thanks. Although, up to this point, I've done pretty much nothing, except offer a few ideas/suggestions on what I was wanting.
On a side note, you'll be pleased to know that I got through my bout of "Airgun Neglect" fairly un-scathed! Future looks promising now...LOL!

I have all the casting lines removed now. Just a bit more cleaning/washing off, and I should start painting pieces this afternoon/evening.

Todd

[Fastair]

I still have the MK1 I bought 40 years ago and it is still shooting after some new seals a year ago.

[sholo]

Well...after some quality time with the dremel, and a bunch of sanding/buffing, I finally got all the casting marks and imperfections in the frame smoothed out. I then went to see a buddy who has a bead blaster, only to find out that he's in Florida 'till the end of Feb!.... So much for bead blasting...

I took it back home and went over the whole gun with 800 grit wet/dry sandpaper, then washed everything off with Varsol. Each piece was blow dried and painted immediately, before oxidation could start. I ended up putting on 4 coats of Krylon Camo Flat Black. Looks good, just not sure how durable it is. Guess I'll find out soon enough!
The cocking knob, bolt knob, and safety were all given the wire wheel treatment, polished, and clear coated for a bit of contrast.

Ready to assemble (and...NO... the barrel isn't bent! Wonky camera angle, or something)
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I know I should have let the paint cure for 5 - 7 days rather than 36 hrs, but..well...you know how things go! Gingerly got everything back together without marring the paint, and except for the scope (which I haven't purchased yet), she's pretty much done - for the moment, anyways. I'm using the factory grips for now, but plan on getting a custom set later on.
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Comparison of my new MK vs stock. Don't mind the condition of bottom gun, it's my next 'refurbish' project!
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I haven't scraped up enough cash yet for my next order (pump, scope, light kit for chrony, among other things), so for now I'm limited to Co2 (12 gr). Good enough for a baseline, plus, I did say that I would show you some #'s.
So with daylight fading, I took a Co2 end cap from one of my other MK's, set the chrony up on its stand (roof of car), and grabbed some CPHP. I'm not sure how accurate the numbers are, as it was only +2* C outside. I would take 2 -3 shots, go inside for 10 min or so, back out for 2 - 3 more, and so on - so take it for what it is. I really need to set up some chrony lights in the basement!

Anyways, here is some #'s from her maiden voyage:
1 - 497.2
2 - 510.4
3 - 519.7
4 - 531.4
5 - 530.1
6 - 538.1
7 - 537.8
8 - 539.6
9 - 539.1
10-536.7



I am quite happy with the results so far, to say the least. Obviously I'm going to have to "de-tune" it to keep it legal - either by lowering reg pressure, or hammer spring, or both - but not before I try it on HPA in its current configuration (stock hammer/valve springs, reg pressure, etc...) and see what it is capable of...

HPA is less dense than Co2 (therefore flows more easily), so if these numbers are even half-arsed accurate, then......!

Once I get my pump and can actually do HPA, I will do a proper set of shot strings on both Co2 and HPA, as well as shot count and some accuracy tests.

'Till then, cheers!

Todd

[SeanMP]

Dude I'm drooling that thing is so wicked.

You have done a great job restoring(refurbishing) that MK.

Your numbers look great. Nice and stable after the first few shots to loosen things up. Looks like your gonna have a great target pistol there.

[rsterne]

The "bent barrel" look is called, interestingly enough "barrel distortion" and occurs to some degree in all wide angle lenses.... While items in the center of the frame are straight, straight lines along the edges end up curved at the focal plane of the lense.... If you take a photo of a rectangle, it ends up looking like a barrel.... hence the name.... The extreme case is with a "fish-eye" (180 degree) lense where the edges of the image are bent so much they become a circle....

Bob

[AirGunEric]

And just for the purpose of stating it- obviously Sholo has the proper licensing for this. Kids, don't do this at home without the correct paperwork.