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Old 11-17-2017, 11:10 AM   #1 (permalink)
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Mod 85 questions

So I jumped on a Mod 85 that came up on ebay last night and I'm wondering about the ammo. I know it shoots .357/9mm paintballs out of a nylon primer powered cartridge and that OEM ammo is rarer than hen's teeth. As far as I know .357 paintballs aren't made anymore, the closest would be .43/11mm. What I'm hoping is that there's some way to convert one to .43 cal and bring the thing back to life. I'm pretty sure I could pull off a new barrel/breach but the sticking point is going to be cramming .43 cal into a case sized and designed for .357. Are there drawings of the cases out there somewhere? Anybody out there willing to take some dims from one of their spent shells?
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Old 11-17-2017, 02:22 PM   #2 (permalink)
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I believe the paintballs are .375 caliber, not .357.

I looked into this conversion many years ago, and decided that the amount of work would be tremendous. The easy stuff would be boring the plastic barrel to 11mm (.43 cal) The hard part would be designing the new shells, and making it so they do not self destruct upon firing. I looked into using 45 ACP casings, but you run into an issue with the firing pin on the Mod85. It is HUGE, and would not strike the primer in such a way as it would cause ignition. In order for the recoil system to work, the 45 ACP shell casing would need to "rearragned" internally. The original nylon cases had the parts stacked up "backwards"

O | > c ]

O is the paintball

| is part of the casing with a set of restriction holes to divide the gas between the ball and the recoil mechanism

> is the firing pin, which is steel, and semi fixed in the case

c is the primer, which is "backwards" compared to a real firearm, with the open end facing the rear of the cartridge.

] is the recoil cap, which goes around the primer.

The firing sequence outside the cartridge is pretty much normal for a firearm. The action sequence inside the cartridge looks like this...

The firing pin from the marker strikes the recoil cup, driving it and the primer forward. The primer strikes the firing pin, and ignites. The expanding gases drive the recoil cup toward the back of the cartridge, which imparts enough energy on the marker's firing mechanism to blow the action open and recock the marker. In the mean time, the recoil cup and the primer have come apart and the gas flows around the primer and through the firing pin to act on the paintball and drive it down the barrel.

I hope that makes sense, as I am not going back to proof read it.

PM me if you want more information... If you can contact Weltman or any of the Damage, Inc guys, they have a LOAD more experience with these markers than I do.

Ty
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Old 11-17-2017, 08:27 PM   #3 (permalink)
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Fun bit of Mod 85 history... When they first came out our supply company was touting them as the next best thing in paintball. I had an inside track and test fired one at the NRC's lab and found they were still running over 450fps thanks to the massive Oheler chronograph. Need a 30 round mag of 9mm through a submachine gun checked? This baby could do it back in the day... NRC is the National Research Council, essentially a civilian scientific *cough spy cough* agency predating CSIS that looked after our country. Went to a field owner's open house in southern Quebec with a number of other field owners. They demo'd the Mod 85 in a classroom, pausing only when the instructor inserted a full magazine into the demo marker!!! One crappy box chicken lunch, a bunch of cartridges, and three empty magazines later and we were off to play! Couldn't hit anything with it. 20 feet away and rounds were going everywhere. Mine had the surprise capability of "burst fire" as the seer was screwed up. (The full auto versions were for law enforcement only) The tech guy fixed it and after an afternoon of romping around in the woods hitting exactly nobody we were all herded back to the demo room. "I'm not buying it, but if you buy it I will" said other field owners. "Screw you guys", I said. .19 cents a round, uncertain supply of reloading ammo and equipment, and players who used my gear 99% of the time as walk-ons were next to non-existent, meant the investment wasn't worth the potential income. Side note, the first press of them being used in Canada was when an ex-cop named Robin Erfle (yep, the guy that got shot in the head during a bank robbery, and who's partner died on the same botched response) used one to hose down a water-skier who kept coming too close to his houseboat... Not exactly the best press in the early days of the sport...Loved wearing my Mod 85 t-shirt though...
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Old 11-17-2017, 09:32 PM   #4 (permalink)
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Quote:
Originally Posted by tymcneer View Post
I hope that makes sense, as I am not going back to proof read it.

PM me if you want more information... If you can contact Weltman or any of the Damage, Inc guys, they have a LOAD more experience with these markers than I do.

Ty
Actually, it does. The patent drawing for the case makes a lot more sense now too. The backwards primer threw me a little along with the prolapse on the back of the case.
I figured I wouldn't be the first person to think of resurrecting these things and that it wouldn't be easy but, what the hell, maybe I'll be the guy that pulls the sword from the stone. Maybe.
Once I get a chance to look the thing over I'll reach out and pester some folks via PM.


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Fun bit of Mod 85 history...
That IS a fun bit of history. I'm kind of surprised there wasn't more bad behavior with these things back in the day. Non-lethal full-auto UZI... words to stir the soul of every stone-washed jeans wearing 80's mullet sporter.
I'd been thinking that they were all full-autos, little disappointed, semi just doesn't seem as fun. Oh well, maybe I'll luck out and get one that was found in a cop's attic.
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Old 11-20-2017, 05:52 PM   #5 (permalink)
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Originally Posted by Rusty Brass View Post
I know it shoots .357/9mm paintballs out of a nylon primer powered cartridge and that OEM ammo is rarer than hen's teeth.
-Actually, the cases were a variant of Lexan, which is part of the problem, The plastic degrades over time, especially given the chemical residues of firing. Basically factory cases can be reloaded and fired a few times, but will inevitably start to crack.

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As far as I know .357 paintballs aren't made anymore, the closest would be .43/11mm.
-Technically, the barrels weren't .375, they were closer to .400, but with heavy rifling. I never had a live round, but I'd bet the ball was supposed to just touch the tops of the rifling, so I bet the ball itself would have been closer to .375.

Quote:
I'm pretty sure I could pull off a new barrel/breach[...]
-The factory barrel is plastic, a .400 or .410 reamer would be all you'd need. (Check the actual size of the paint, first- nobody makes .43 cal Freak inserts. )

Quote:
[B]ut the sticking point is going to be cramming .43 cal into a case sized and designed for .357.
-Not really, the cases could be lightly reamed out. But the problem there is making already-antiquated and brittle cases even weaker.

Yes, a bigger case could be made, and the 'chamber' reamed out to fit. The problem here is simply the cost per round. You'd need to machine, or have molded, hundreds of plastic cases, or possibly aluminum ones- and IF you reused factory cups and anvils, I could see that costing around $2 a shell in small bulk.

You could drop that further with a good shop and buying 10K or more shells, but I'd be really surprised if you could get it much below a buck a shell.

If you also have to make cups and anvils, double that- and again, only in bulk, like ordering 10,000 parts. If you only order 200-300 of each, you're probably looking at $5-$8 a shell. Plus paint, plus primers.

Injection molding would be the way to go- but again, the cost of the molds is fabulously high, and you'd have to make a quarter of a million shells or more to justify the cost- and while there's a lot of Model 85s out there, there aren't that many, and most of the ones that are still around, the owners are only going to buy a box or two just to finally try it out. Nobody's going to order three cases of ammo and play a game with it.

(Okay, a couple of you will, but still, not enough to justify the cost. )

If you're willing to throw some stupid money at the project, no sweat. I'd bet you could, with the help of a competent machine shop, put together a couple magazines full of fresh aluminum-shelled ammo stuffed with .40 cal blowgun paintballs. Should only cost anywhere from $8 to $12 a round.

Doc.
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Old 11-20-2017, 06:07 PM   #6 (permalink)
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Originally Posted by tymcneer View Post
I looked into using 45 ACP casings, but you run into an issue with the firing pin on the Mod85. It is HUGE, and would not strike the primer in such a way as it would cause ignition. In order for the recoil system to work, the 45 ACP shell casing would need to "rearranged" internally. The original nylon cases had the parts stacked up "backwards"[.]
-The thing to keep in mind here is that the primer does NOT act directly on the paintball. Primers are actually fairly powerful bits of explosives, and the speed of the pressure wave they produce WILL burst the ball rather than propel it.

In the Model 85, the primer is enclosed in a "cup and anvil" arrangement, that forms what is in effect a small piston. When the assembly is crushed together by the "firing pin", the primer detonates and the expanding gas tries to push the two halves of the cup back apart.

Inertia of the bolt/hammer of the gun, however, prevents the parts from popping apart, at least for a few milliseconds, and in that time, imparts some of the gases' energy back into the bolt in order to propel it back to the rear.

That has taken some of the energy out of the primer's gas blast, and the rest is channeled through small ports in the shell, before it can contact the ball. The reduced energy of the gas wave brings it down to the point where it can fire the ball without blowing it up at the same time.

Any new or replacement shell would pretty much absolutely have to follow this same design, or something very close to it.

Back when I had mine (I had two, with six magazine, the factory reloading kit, the factory instruction manuals, and about 200 rounds of spent ammo) I looked into it hard. I probably still have some drawings around here somewhere (that is, cocktail-napkin type sketches, not, like, CAD models ) of a couple of ideas I had (but of course never tried or tested) for alternate options, but really, the stock design was the most workable.

What I really wanted was a two-piece shell, that "captured" the cup and anvil parts- which tended to get "blown free" of the shell when fired, and were commonly lost.

But asking around to some of the CNC shops I was dealing with at the time, I was told basically what I said above- unless I was willing to buy 10,000 of each part, or more, I was looking at $5 to $8 per shell, another buck or so each for the cup and anvils, then the cost of paint, then the cost of primers.

I might have still tried a short run back then, if I'd had any spare money for the project, but I didn't have $2,000 to throw at just 200-250 shells.

Doc.
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Old 11-20-2017, 06:40 PM   #7 (permalink)
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-The thing to keep in mind here is that the primer does NOT act directly on the paintball. Primers are actually fairly powerful bits of explosives, and the speed of the pressure wave they produce WILL burst the ball rather than propel it.
Dueling-3.jpg

Counterargument - in my shells the primer was acting "directly" on the paintballs, with about an 1" of space for expanding gasses and a tight mesh to trap any shrapnel (usually the primer anvil) from impacting the paintball. No wadding (yes, singed paintballs). I only had several barrel breaks with Valken Grafitti in the mid 200's the couple dozen times I fired them, was working to improve that when I got tired of the primers shattering my 3d-printed shell parts. New stronger plastic is on hand, but haven't ever gotten around to v2. It's also a futile experiment because it would never be field legal, but I think there's another reason the Mod85 components are stacked backward -

I'm not saying the anvil-cup arrangement in the mod85 doesn't lighten the blow and indirectly propel the paintball. The cup definitely restricts and redirects the expansion of the charge, but (and this is my 2nd reason for letting my pistols sit) I believe it's also partly to prevent real ammunition from being loaded into it. The striker in the Mod85 is comparatively huge and wouldn't ignite a normal centerfire round. The actual "firing pin" is the anvil inside each Mod85 shell as a safety/legality mechanism.
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Old 11-21-2017, 02:20 PM   #8 (permalink)
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It showed up last night and I did a tear-down immediately. Interesting little gun. I'm pretty sure it's a full-auto, there doesn't seem to be a disconnect for the sear. No particular signs of wear, I'd be surprised if it's had more than one mag run through it.
Anyway - Pics:









With the way it's designed I'm thinking the breach and barrel would be pretty easy to convert to brass or steel. All it would take is cutting a block into the breach plate shape and either threading in or pressing a barrel section. The feed ramp could be taken care of with a big rat-tail file.

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If you're willing to throw some stupid money at the project, no sweat. I'd bet you could, with the help of a competent machine shop, put together a couple magazines full of fresh aluminum-shelled ammo stuffed with .40 cal blowgun paintballs. Should only cost anywhere from $8 to $12 a round.
Doc.
There's the sticking point. Going into production on the shells would be a large investment with little hope of payout. I'd be happy to just have two mags worth of shells to burn off at the chrono station every once in a while. My brain has been whirling trying to come up with a design for a two-piece brass case that would have a captive anvil whacker thing - think I'm onto something but it'll take some more CAD work. Making 50 rounds worth seems do-able at some point in the coming decades. Hope springs eternal in the heart of a fool...
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Old 11-21-2017, 08:20 PM   #9 (permalink)
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Who was 3d printing shells on here? I recall seeing the pictures, but I don't recall them having much success due to durability.
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Old 11-21-2017, 09:20 PM   #10 (permalink)
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Brass casings though... with the forward piece having the anvil built in/retained... Never going to see field use but man it was fun to rip off the rounds.
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