.700 Desert Storm

[Pookydarts]

Hi Guys! (And girls?)
Okay, I've been holding out on you, I've been working on this new project for a few weeks now and really wanted to wait 'til it was complete with a stock and a paintjob and everything before I posted it but I got it running yesterday and broke the stock in half today and well... you know how it is...
So, its a copper/brass/stainless piston valve pneumatic running on good old-fashioned squished air. The chamber is about 3 feet of 1" class 'm' copper and holds 650mls of water, the barrel is 1m of 3/4" stainless (with an ID of near enough to .700 of an inch, hence the name...)
The piston is delrin, turned on a wood lathe (as were many of the brass parts... don't try this at home...) with a tap washer that i threaded and screwed in as the sealing face, the whole piston weighs 25 grams. It had an o-ring but it sealed too well so I pulled it out and it functions perfectly without it.
The projectile is (was) a 310 grain pure lead .430 (44 mag) slug stuck in a silicone nozzle and half-filled with 5min epoxy. May have to re-think the projectiles as I suspect some of the 'skirts' may be blowing apart in the barrel.
The shot in the photo (@200psi) went over the chronograph, through a plank of marine grade 9-ply and stopped up against the steel plate back-stop.
Projectile weight 25 grams (385 grains) @ 343 fps = 100.55 ft/lbs!


Edit: I have added a new 'progress' photo of the stock now nearing completion, but had to remove a few photos of the piston etc to fit it in...
Enjoy!

[inonickname]

Nice, is part of that piston one of the tap washer things? Cool build..I'd just do a stock and polish up the copper nicely...then you have one mother of a gun.

Good works

[jonnyboy]

Nice gun.

Although your chamber is HUGE. I bet this thing is loud. If you play around with ggdt you can find the best chamber to barrel size it looks like it should be about 1/3 of the current set up .

[Ragnarok]

If you play around with ggdt you can find the best chamber to barrel size it looks like it should be about 1/3 of the current set up .

Define "best". All GGDT's optimiser tells you is the smallest size chamber you should be using for the barrel.

[jackssmirkingrevenge]

Nicely done you might want to check if 12 gauge shotgun sabots fit in the bore, proper slugs would make much mroe relaible ammunition

[SpudsMcGee]

The projectile is (was) a 310 grain pure lead .430 (44 mag) slug stuck in a silicone nozzle and half-filled with 5min epoxy.

Can you explain that better, how are they lead and epoxy?

Edit: Oh yeah, nice job... it looks very good. And powerful...

[Gippeto]

Indeed, nicely done.

Good job using a wood lathe to turn your piston. Looks like you put some thought into it.

If you wanted to try the o-ring again, all you need to do is drill a shallow hole into the side of the piston.

Drill the hole so that it is "half" in the o-ring groove, and "half" on the chamber side of the o-ring groove.

It's time to try increasing the chamber pressure.

[daniel323]

great cannon love the design

[Pookydarts]

Good job using a wood lathe to turn your piston. Looks like you put some thought into it.

Gippeto,

I must give credit where it it due, the piston was modelled off your 'protruding' past the bearing surface piston from your copper gun, the only thing I could do to make it different was 'skeletonise' it for weight saving.

Nicely done you might want to check if 12 gauge shotgun sabots fit in the bore, proper slugs would make much mroe relaible ammunition

Jack,

I'm hoping that to be the case! I picked up a wad a few months ago that fitted that barrel tube perfectly but now that I go looking again all the wads seem to be of a different type with a slightly over-bore diameter! Will have to change brands!

Johnnyboy and Ragnaroc,

Yes, the chamber is oversize, (by how much I don't know because after downloading ggdt three times and spending two hours trying to make it go I still can't get it to even open! ) (Computers are not my specialty... )

The idea was that this would be my final gun and I didn't want to make it too small and have leftover performance questions, so I havn't been to town yet to buy a 3m barrel to put on it!
(Having said that, the chamber will probably be shortened to make it look more in proportion and save filling time!)

Now I have to learn more about annealing as I would have annealed the copper as I was silver-soldering! Ooops!

And build a high-pressure hand pump!

[D_Hall]

May have to re-think the projectiles as I suspect some of the 'skirts' may be blowing apart in the barrel.

Just as a point of information, there is a proper name for your "skirts". It's called a "sabot."

Now, before somebody pipes up and says that sabots are not part of the projectile, I'll point out that there are two types of sabot.

Discarding.

Non-discarding.

Most people are familiar with discarding sabots. Your's is of the non-discarding type.

[jonnyboy]

If you play around with ggdt you can find the best chamber to barrel size it looks like it should be about 1/3 of the current set up .

Define "best". All GGDT's optimiser tells you is the smallest size chamber you should be using for the barrel.

When your feet per second gain is very low for say 6 extra inches of chamber. But if you already bought it you might as well use it!

[sputnick]

Looks fantastic, I like your ammo, looks very stable and powerful, and I don't believe I've ever seen that method of having an over under cannon before,

Overall just awesome looking!

hope to see some more elaborate damage pictures in the future.

[starman]

I like the side by side, lane change design, really just for the different look and uniqueness of it. It might not hurt to tie them together to keep them from clanking against each other.

Great work on your piston, and the cannon overall!!

[jonnyboy]

Yes, the chamber is oversize, (by how much I don't know because after downloading ggdt three times and spending two hours trying to make it go I still can't get it to even open! ) (Computers are not my specialty... Sad )

I believe you have to have all the files in one folder becuase they use each other to make the program work if that's not the case I would contact D_hall

[Pookydarts]

Dear God!

IT WORKS!!!!!


I'm going to be playing with GGDT for the next few weeks!

Many thanks to D_Hall and Johnnyboy! Also for telling me about the sabots, you were right, I DID mostly think of them as discarding!

Cheers sputnick! I tested the assymetric 'sideways' O/U idea on my PVC sprinkler valve gun: "First Submission"
http://www.spudfiles.com/forums/first-s ... 16896.html
...This gun (with a 1.5m sleeved barrel upgrade) at 150psi shot a 225grain projectile at 434fps for 94ft/lbs... I was slightly miffed that I "only" got 100ft/lbs out of this new copper creation... What would you like to see shot?

Starman, the barrel will get fastened during the future upgrades... And I hope it will deserve sights too!

Cheers!