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Need some ideas/plans for a semi-auto portable bb-rifle

Posted: Sun Dec 16, 2007 5:00 am
by SleekZ
I'm heaps keen to make a fairly accurate bb gun/rifle (won't bother actually rifling the barrel tho) and need a bit of help with the design, basically;
-I want it to have pretty decent range/power and accuracy
-it needs to be portable i.e. have it's own air source (I realise each shot will get progressively weaker)
-I'd like to get like at least ten shots out of each refill of the reservoir/tank
-the simpler the better
-fairly cheap
-semi-auto or not....(doesn't need to be a machine gun is what I'm trying to say!)

any ideas on this would be much appreciated as I'm keen to get this project underway.
Sorry if there are similiar posts that I didn't see...
thanks everyone :wink:

Posted: Sun Dec 16, 2007 5:22 am
by Novacastrian
PM MrCrowely, he will be more than pleased to provide you with COMPLETE plans :D

any ideas on this would be much appreciated as I'm keen to get this project underway.
Sorry if there are similiar posts that I didn't see... I failed to search also...

Posted: Sun Dec 16, 2007 5:26 am
by jackssmirkingrevenge
What you're proposing is fairly ambitious, but not impossible, it depends on your budget and facilities.
-I want it to have pretty decent range/power and accuracy


This means using a long and tight fitting barrel, at least 2 feet long.
-it needs to be portable i.e. have it's own air source (I realise each shot will get progressively weaker)
-I'd like to get like at least ten shots out of each refill of the reservoir/tank
-fairly cheap
You have several options here, but the "fairly cheap" clause is limiting. Ideally, you could fork out $89 and get something like this, but that might be beyond your budget. The cheaper alternative is to have a large chamber at 150 psi or so, or a smaller chamber taken to high pressure with a shock pump.
-the simpler the better
The simplest valve option is using a blowgun directly as a valve, like so:

Image

At pressures of 100 psi+, this will give good enough flow for decent power through a long enough barrel - provided you squeeze it quickly enough. It will only open for brief instant, giving you much more than one shot per fill.

As to reloading there are several easy options, simplest of which is probably to cut a slot at the breech end of the barrel big enough to fit a projectile, then sleeve it with an appropriately sized piece of tubing that either rotates or slides back and forth.

Posted: Sun Dec 16, 2007 5:28 am
by us sniper
Do you have any other bb guns like a pump one, because I am also building a semi automatiic/ bolt action gun using the boss valve that I got from my old pump gun. If not do you know how to weld or have avalible steel or aluminum pipe? Also are you trying to make a spud gun type bb gun or a professional type pcp bb gun?

Posted: Sun Dec 16, 2007 6:37 am
by Hubb
Novacastrian wrote:PM MrCrowely, he will be more than pleased to provide you with COMPLETE plans :D

any ideas on this would be much appreciated as I'm keen to get this project underway.
Sorry if there are similiar posts that I didn't see... I failed to search also...
Sarcasm in its finest. Normally, I wouldn't congratulate something like this but I must give credit where credit is due. :lol:

Posted: Sun Dec 16, 2007 7:33 am
by SleekZ
hey yeah I'll probably pump it up using a compressor plugged into the cigarette thing in my car- it's taken a marble cannon to 240psi before, so no worries!
nah no bb guns I'm afraid...that's what I get for living in Australia.
So I've heard brakeline would make a good barrel- where would I get this and are there fittings available to connect it to the blowgun, or will I have to do something dodgy?
thanks for the replies!

Posted: Sun Dec 16, 2007 9:11 am
by VH_man
What are you going to use for BB's first of all?

if you can get a hold of 10mm bb's 3/8 (or 10mm) aluminum tubing is a perfect fit......

i know that its not hard to get 10mm bb's..........

Posted: Sun Dec 16, 2007 9:19 am
by jackssmirkingrevenge
coincidentally, I think ant is your man :D

Posted: Sun Dec 16, 2007 7:25 pm
by schmanman

Posted: Sun Dec 16, 2007 8:28 pm
by Novacastrian
hubb017 wrote:
Novacastrian wrote:PM MrCrowely, he will be more than pleased to provide you with COMPLETE plans :D

any ideas on this would be much appreciated as I'm keen to get this project underway.
Sorry if there are similiar posts that I didn't see... I failed to search also...
Sarcasm in its finest. Normally, I wouldn't congratulate something like this but I must give credit where credit is due. :lol:
To explain i was PUI, i didn't mean to offend and am glad people took it the right way, as i have told MrC i will refrain from making comments like this one (not that he minded :D )
I also ask your forgiveness SleekZ. I would never intentionally upset a fellow Aussie :P

Posted: Mon Dec 17, 2007 7:13 am
by SleekZ
thanks for the replies again guys;
yeah i realised it probably doesn't need to be semi-auto, just as long as i don't have to pump it up after each shot! cocking or whatever would be fine tho

schmanman- yours is heaps good man- it's a piston design tho right? i really can't be bothered with that for this one- a blow gun should be alright for mine tho won't it? I'll prob just use a piece of 1" wide galv pipe as the reservoir and give it over 200 psi, or 300 if i end up getting one of those shock pumps

so is brakeline the way to go- is it easy to get hold of?
i'm just using normal bb's i think- I've got a couple of hundred of them, but I don't know where to get hold of any more in Australia

good onya fellas, thanks

Posted: Mon Dec 17, 2007 10:26 am
by schmanman
thanks!

piston valves are not as hard to build as you would think....

for brakeline, go to an auto parts store....

Posted: Mon Dec 17, 2007 10:40 am
by Carlman
im sorry if this counts as hijacking but it may help SleekZ, does anyone know where bbs are available in australia, or should i say who.

Posted: Mon Dec 17, 2007 6:28 pm
by VH_man
for brakline, what size do i buy.... lol. im sorry this isnt my thread but i went to the auto parts store and.......

it was flared at both ends, not smooth on the inside AT ALL and kinda ugly. not like the brakeline ive seen on other projects. the guy got P-oed at me because i got my airsoft BB stuck inside of the part he gave me and i had to buy it..........

Posted: Mon Dec 17, 2007 6:43 pm
by schmanman
the stuff by me is not like that at all.....

I dunno.