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Old .30 co2 rifle

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Old .30 co2 rifle

Unread postAuthor: Gippeto » Mon Apr 03, 2017 10:37 pm

Was loaned this to see if it could be made usable. Yep. 8) Cool old rifle IMHO.

Barrel is 28" from transfer ports to muzzle and cut rifled. Slugged the bore and got readings of .3000" and .3005"...a perfect fit for modern .30 jsb pellets. :D With 1000psi N2 it launches 46.3gr JSB's @ 775fps. Should find out tomorrow what it does with co2.

Bolt probe retracts away from the projectile when you cam the bolt lever closed...cool feature. Have seen retract probes on a couple home builds and some Philippine big bores before but not done this way.

Image

Pics of the tear down, tools, parts and fittings made;

http://s245.photobucket.com/user/gippet ... l%20airgun
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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Mon Apr 03, 2017 11:22 pm

Saw this referred to elsewhere, very nice! Any details of its history?

Bolt probe retracts away from the projectile when you cam the bolt lever closed...cool feature.


Interesting, I thought about doing this, seems like a no-brainer that would have already been tried. Did you try to quantify the difference it makes in velocity though, as in is there a way to fire it with this feature disabled for comparison purposes?
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Re: Old .30 co2 rifle

Unread postAuthor: Gippeto » Mon Apr 03, 2017 11:38 pm

No markings or signatures/initials to be found. The story that was passed down with the rifle is that it was a prototype for the military, but I cannot bring myself to believe it. Highly skilled home gamer is where I'd be placing my bet. Scribe marks on the bolt, mix of metric and sae threads AND dimensions, odd ball threads too...3/16-32NS for the stock retention screw. Pin wrench holes in reservoir fittings are close to but not AT 90 degrees apart...no dividing head/rotary table. ie...limited tooling, not a "pro" shop.

Bob (rsterne) did some testing on the retract probe benefits. He uses a "J" shaped slot for the bolt handle. Likely CAF or GTA will yield search results. The pin that causes the probe to retract rides in an angular slot in the bolt body. Could put a spacer behind the probe and make a shorter pin, but suspect it would be blocking off the transfer ports. Will have a look tomorrow.
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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Tue Apr 04, 2017 6:42 am

a prototype for the military


The foot poundage you're getting is conveniently close to the the 58 foot pound minimum criterion for lethality generally agreed upon but I agree that this is very unlikely, even if it was professionally made. A suppressed .22LR rifle is much quieter and more compact than an airgun equivalent producing the same energy, and doesn't require a pump or air tanks. The only benefit would be a survival situation where you would not need to source firearm ammunition.

mix of metric and sae threads AND dimensions


guilty :oops:

A really fascinating piece, nice that it's in good hands! I hope that future generations of tinkerers will pore over my prototypes with the same rigor and sense of wonder :)
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Re: Old .30 co2 rifle

Unread postAuthor: Gippeto » Tue Apr 04, 2017 3:01 pm

jackssmirkingrevenge wrote:
a prototype for the military
I hope that future generations of tinkerers will pore over my prototypes with the same rigor and sense of wonder :)


Some of them will be trying to figure out why the thing won't write.. :lol:
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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Tue Apr 04, 2017 5:39 pm

Future forum post:

Was loaned this old pen to see if it could be made usable. So far have only managed to blow holes in paper, desk


:D
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Re: Old .30 co2 rifle

Unread postAuthor: Gippeto » Wed Apr 05, 2017 2:54 pm

Filled it up with co2 yesterday and let it sit overnight to warm up. Thermometer in the shop says 22C.

With the 46.3 JSB's, 698, 694,684 and stopped there. Reservoir was cooling so pressure was dropping. Not too bad. 8)
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Re: Old .30 co2 rifle

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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Thu Apr 06, 2017 7:11 am

That's pretty healthy! Any indications what the design pressure/gas was?
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Re: Old .30 co2 rifle

Unread postAuthor: Gippeto » Thu Apr 06, 2017 7:00 pm

Pcp being a less common thing until recent years, figure it was built for co2. Bulk fill co2 has been common since the end of WW2.

Poppet diameter and porting is...large. Valve throat is .500", poppet sealing diameter a tich larger..say .520".
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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Mon Apr 10, 2017 9:44 am

That's pretty big... Perhaps it was intended for a bigger bore?
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Re: Old .30 co2 rifle

Unread postAuthor: Gippeto » Mon Apr 10, 2017 11:04 pm

Very big. It's possible the fellow wanted a larger bore, but considering the time and effort that went into making/profiling/fitting the .300" barrel, I have trouble believing it was intended to be anything other than what it is.

Choice of bore size is still bugging me. Honestly can't think of a pb cartridge that uses a .300" bullet. Was originally thinking .30 Luger or 7.62 Tokarev but didn't take long to rule them out...bullet diameters are .309" and .311" respectively.

#1 buckshot is about right, but why go to so much trouble to make a barrel and then not size it for a common cast round? Twist rate is way faster than needed with roundball as well. 1:15.75
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Re: Old .30 co2 rifle

Unread postAuthor: mark.f » Mon Apr 10, 2017 11:43 pm

Nice work as per usual. :D
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Re: Old .30 co2 rifle

Unread postAuthor: jackssmirkingrevenge » Mon Apr 17, 2017 9:22 pm

Gippeto wrote:#1 buckshot is about right, but why go to so much trouble to make a barrel and then not size it for a common cast round? Twist rate is way faster than needed with roundball as well. 1:15.75


Surely an eccentric builder with no care for standards and conventions would have been casting his own projectiles too, or swaging down existing ones? Failing that, perhaps he didn't full appreciate the right twist rate needed for buckshot.
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