SpudFiles

Hi guys,

(for tl;dr skip these first 2 paragraphs)
I made a few topics (1, 2) almost a year ago with some questions on pipe sizing and advice on how to solder copper.

Unfortunately I've been incredibly busy since that time, quit my job and ended up going back to TAFE (which is a tertiary education thing, kind of like university if you don't live in Australia). Things have finally settled down a bit so I decided to finish off the airgun I started building back then.

It's nothing special, but I'm kind of proud of it as it's the first one I've made. It's a single shot QEV style launcher with a scope mounted and a custom stock. It's filled through a schrader valve I've epoxied into the side and designed to fire 6mm ball bearings through an arrow shaft sleeved in a piece of 1/2" copper that JSR kindly recommended I use all that time ago.

I've become a bit more confident with my soldering abilities so I think I'd be able to take this one up to 400psi without any issues, however so far I've only taken it up to 250psi to fire some wadded screws out of as a test.
The stock was kind of a rush job and I'm not completely happy with it as I messed up the butt a bit and made a few rough cuts, but I think looks okay and does it's job.
The scope is a 4-16x illuminated adjustable objective, which is kind of overkill for an airgun but I had it lying around so why not.

Anyway, here are some pictures, unfortunately I am still waiting on my ball bearings to arrive, so I haven't even sighted it in yet. As soon as they get here I'll upload a damage video to Youtube.

Wow this is very nice for a first :thumbright:
the barrel bore maybe too small, it will detract the air flow from that qev, you should make a bigger bore(+6 mm) or use a smaller qev

Thanks wyz2285.

It is a 1/2" QEV, when I bought it I was planning on using 1/2" copper as the bore without anything sleeved in it, but since then I decided to go for more of a plinker that I could fit generic BBs in as they're cheap and easy to get.

I might get a smaller one down the road but this was more of an experiment than anything and I already have plans for another one with a hammer valve so I'll more than likely end up just leaving this one as it is.

nice that stock looks thick as though.

what do course do you do at tafe? I'm in the first year of my mechanical engineering(makes me sound smart its just fitting and turning lol) and its more like trade school than uni.

First of all, props for sticking with the project, I usually lose interest within a few weeks and move to something else

Secondly, very nicely done! As a first effort it's better than most people's third or fourth launchers

The one thing I don't like is the moving barrel. In order for reasonable consistency to be achieved (on spudgun levels at least), the barrel and sight should be fixed as a permanent unit irrespective of any other moving part. Any play in the system will translate into sloppy accuracy at anything above point blank range.

Personally I'm an advocate of cutting a hole in the barrel then sleeving it, and mounting the bolt on the sleeve.

Have you made any provision to retain the projectile, such as an o-ring or magnet?

Crna Legija wrote:stock looks thick

Yeah unfortunately due to the size of the fittings for the chamber I couldn't really narrow it down any more than it already is.

Next time I might epoxy the ends in to try and keep it down a bit, but it was a learning experience.

Crna Legija wrote:what do course do you do at tafe?

I'd love to do mechanical engineering, it'd probably help me out a lot with this hobby, I'm doing boring web development though.

jackssmirkingrevenge wrote:First of all, props for sticking with the project, I usually lose interest within a few weeks and move to something else

Secondly, very nicely done! As a first effort it's better than most people's third or fourth launchers

Thanks! I'm normally like that with all my other projects, spudding seems to be different though, it's very satisfying to finish one of these.

jackssmirkingrevenge wrote:moving barrel

Yeah I completely agree, I was going to sleeve it in some 3/8" copper and drill a hole through the 1/2", not sure why I didn't end up doing that, I guess I was worried about losing a bit of air through it when it fired. There's still time I guess.

jackssmirkingrevenge wrote:Have you made any provision to retain the projectile, such as an o-ring or magnet?

Not yet, I was planning on throwing a magnetised washer on the back of the barrel or putting a tiny mark just inside it to hold it still so the shot won't roll away.

To be honest I'm kind of hoping that the bearings I ordered will be a tight enough fit that they will hug the barrel close enough and I won't have to worry about it, it's wishful thinking though.

r00kie wrote:Yeah I completely agree, I was going to sleeve it in some 3/8" copper and drill a hole through the 1/2", not sure why I didn't end up doing that, I guess I was worried about losing a bit of air through it when it fired. There's still time I guess.

Even without o-rings, a tight fitting sleeve will have minimal air loss and the benefits in accuracy should be worth it.

Not yet, I was planning on throwing a magnetised washer on the back of the barrel or putting a tiny mark just inside it to hold it still so the shot won't roll away.

A few shallow holes drilled in the breech face in the barrel and filled with cheap powerful neodymium magnets should do the trick.

To be honest I'm kind of hoping that the bearings I ordered will be a tight enough fit that they will hug the barrel close enough and I won't have to worry about it, it's wishful thinking though.

Mindless optimism I fear, such a tight fit means there will be far too much friction and significant performance loss. Remember, what you want is maximum friction at the breech (because the longer it takes the projectile to start to move, the more time the valve has to fully open) and minimum friction along the rest of the barrel, so none of the accelerating forces will be wasted overcoming friction.

Some further reading that might be of interest

At least you build right to the end i only build to the point where its shoots but good job very nice for a first.
Loving the scope by the way

Much better than my first gun. Well done on finishing it.

Nice

instead of cutting holes in the barrel you can use a T and load ammo from the rear port then push it into the barrel with a bolt

Looks very decent for a first! Did you make the stock out of a 2 x 4? Seems very heavy looking. Good job though and its nice to see you stuck with it to the end. You definatly need to paint or stain it though! Is the scope accurate??

Another TAFE "customer" here, cert III lab skills. Anyway, no one noticed that you're left handed.

Good job, only thing I can pick you up on is stock dimensions, but if it works for you.

Otherwise, have more faith in you're soldering, and have more fun.

That looks great. Nice job man.

Great first effort! Have you thought about trimming your blowgun some? Also, you could even try a normal 1/2" copper barrel instead of the 6mm one, I'm sure you won't be disappointed with it at 400psi

Thanks guys.

neodymium magnets

I have a hard drive graveyard in my garage that's ripe for the picking, they each contain a few rare earth magnets.

too much friction

Yeah you're right, I'll wait for the ammo to get here and then decide what to do there.

load ammo from the rear port

Only problem there is I'd have to reposition the QEV, ergo the stock wouldn't fit properly. I'll keep that in mind for my next one though if I use a QEV as it's a good idea, thanks.

stock

It was a piece of wood I bought from my hardware store, I just cut it in half, used a circular saw to get the basic shape, a router to bore out the middle and screwed them together. An electric plane and sander was used to round the edges.

I will probably end up staining it when I sort out what I'm going to do with the breech.

Is the scope accurate??

It was when it was used on a rifle, I am waiting on some ball bearings to get here so only time will tell.

left handed

Indeed I am.
I'm sure it's going to annoy my friends when they try it out.

trimming your blowgun

Yes I plan on hacking that useless bottom part off, I got a bit lazy.

1/2" copper barrel instead of the 6mm one

I thought about it, but I'd rather keep the ammo a bit smaller, I've fired homemade airguns with that bore before so I want to see how 6mm bore performs in comparison first hand.