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nailgun + 6mm breech

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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nailgun + 6mm breech

Unread postAuthor: jackssmirkingrevenge » Thu Oct 04, 2007 9:46 am

Following on from this project and my newly discovered love for air nailers, I decided to combine the two. This was the prototype before firing:

Image

I basically replaced the nailgun's hammer piston with a 6mm port that fed into the blow forward breech I had made. I was expecting a considerable increase in power, it turned out to be a little too much however - on the first shot the bolt piston as well as the front end of the breech were shattered. as you can see from the attached photos, the bolt is jammed forward instead of having been returned by the spring. I blame this mostly on the air vent I had but at the bottom of the outer tube, had it not been there I'm sure the air being compressed would have cushioned the impact of the bolt.

I ran a few shots through the chrono, they were erratic ranging from 450-550 feet per second for a 0.25 gram BB due to the misaligned bolt allowing air to leak out of the vent, but still enough power to drive the BB clean through the bottom of a soup tin.

The current setup is beyond repair, I could make a smaller, stronger bolt but I'm thinking 6mm is a little two small a calibre for this sort of power, perhaps a semi-auto marble gun is a better idea....
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Unread postAuthor: goose_man » Thu Oct 04, 2007 10:04 am

That is really cool. A marble version would be awesome, or a steel ball bearing version :twisted: Anyway, I always love your innovations.

-goose_man
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Unread postAuthor: mega_swordman » Thu Oct 04, 2007 11:15 am

Jack, I have to say that you never cease to amaze me.
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Unread postAuthor: iknowmy3tables » Thu Oct 04, 2007 2:06 pm

wow thats really good I think I might start having a liking for pneumatic nail guns
hmm maybe i ought to buy a used nail gun

should you build a larger area piston in the bolt to absorb more air and move slower or a smaller one to reduce the area that pressure can be applied

however I think you should try a blow back bolt like on paint ball guns, it should have less pressure on it to avoid breaking since barrel is always open to vent to the barrel
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Unread postAuthor: Novacastrian » Thu Oct 04, 2007 9:42 pm

At least someone else breaks thier pneumatic gear, and is still able to smile about it :D

Instead of .25gram bb's i think 6-8mm bb's or lead sinkers would be kinder to your gun due to the heavier weight, of course it would drop your fps lots but you would still have plenty of lbs.
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Unread postAuthor: noname » Thu Oct 04, 2007 9:50 pm

If I did that I would end up destroying the nail gun as well, out of my frustration for breaking the blow forward part.
Either that or I'd load up some nails and shoot up everything in my workshop.
I can barely run now because I kicked a post really frickin' hard after the spark strip on a combustion didn't work, after working on it for 2 1/2 hours.
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 04, 2007 10:51 pm

Thanks all for the comments, I love this place - you get complimented for failure :D

I can barely run now because I kicked a post really frickin' hard after the spark strip on a combustion didn't work, after working on it for 2 1/2 hours.


You're a spudder, your SOP for dealing with frustration should be to shoot something :) I once got back home from work to find some epoxy I had left to set had leaked horribly, in despair I kicked with wardrobe - forgetting I was still wearing my safety boots. I still have a 6" hole in the door, covered by an oddly placed poster :D

At least someone else breaks their pneumatic gear, and is still able to smile about it


when working with epoxy, you have to laugh :) The intended ammo for this project is 0.22 lead pellets, I just use BBs for now 'cause they're cheaper and reusable.

should you build a larger area piston in the bolt to absorb more air and move slower or a smaller one to reduce the area that pressure can be applied


I'm thinking a smaller piston here to reduce the shock on the system, currently looking at clide's GB cannon breech for inspirtation.

wow thats really good I think I might start having a liking for pneumatic nail guns
hmm maybe i ought to buy a used nail gun


I really don't know why more people don't adapt them for spudguns - they are very cheap even when brand new, and what you get for less than the cost of a good QEV is a ready made semi-automatic coaxial piston valve.
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Unread postAuthor: clide » Thu Oct 04, 2007 11:26 pm

jackssmirkingrevenge wrote:I'm thinking a smaller piston here to reduce the shock on the system, currently looking at clide's GB cannon breech for inspirtation.


Hah, I never really figured out how to reduce the shock on the system and still get the speed and solid opening I needed. My inelegant solution was just building it stronger. I broke two casings at the front and I've just about broken 2 bolts (but one was defective).

I guess this doesn't really apply to yours since your is different than mine, but I found that if I made the big disk a solid fit so that it would have an air spring, I would just end up bouncing the bolt and getting leakage out the magazine. So thats why my bolt is all hacked up to just let air bypass the large disk thing that now just serves as a stopping mechanism for the bolt. I tried keeping the large disk solid and venting it like you did on yours, but that weakened it and caused the second casing to break (the first was just built too weak in the first place).

Man, just thinking about that freaking bolt I am still amazed how you are able to build stuff that works so well without being able to disassemble it. I spend more time disassembling, tweaking, and reassembling my stuff than I spend actually building it in the first place.
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Unread postAuthor: hyldgaard » Fri Oct 05, 2007 2:08 am

Any idea of how much air it uses? Im thinking if its possible to add a chamber instead of hooking it up to the compressor, and still get a few good shots?
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Unread postAuthor: jackssmirkingrevenge » Fri Oct 05, 2007 4:05 am

guess this doesn't really apply to yours since your is different than mine, but I found that if I made the big disk a solid fit so that it would have an air spring, I would just end up bouncing the bolt and getting leakage out the magazine.


This is how the setup was originally, as you can see from the first video - I subsequently cut a hole in the vent to get the bolt to move faster - which boosted velocity by 50 feet per second in the original setup - I believe that had I patched that hole up before attaching it to the nailgun it would still be in one piece. I think I can make a minature version of your design massively reinforced with epoxy that could withstand the repeated hammering.

I was planning on a larger calibre "autocannon" setup, with a motor driven cam to give automatic fire, I think I'll keep the latter idea but smaller calibre high velocity seems a better idea, especially given the limited air capacity of the small nailer, so I think I'll stick to 6mm calibre.

Man, just thinking about that freaking bolt I am still amazed how you are able to build stuff that works so well without being able to disassemble it. I spend more time disassembling, tweaking, and reassembling my stuff than I spend actually building it in the first place.


Epoxy teaches you to get it right the first time, something I learnt the hard way. I spend far more time planning and scribbling (and usually running ideas by the forum :) ) before actually building something. The downside is that when something goes wrong as in this case, you need to have fortitude to declare "f*** it" and start from scratch.

Any idea of how much air it uses? Im thinking if its possible to add a chamber instead of hooking it up to the compressor, and still get a few good shots?


If I shut off the air from the compressor, there's still enough inside it for one good shot. Off hand I'd say a 3 litre pop bottle as a chamber at 100 psi would give you at least 5 good shots.
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Unread postAuthor: wannabie » Sat Oct 06, 2007 5:59 pm

Very nice jack *claps*
I wish I could afford a nailgun but i have no money :(
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Unread postAuthor: THUNDERLORD » Sun Jun 28, 2009 7:06 pm

I am dying to know how These air-hammers work???
Seems like the large spring is overpowered by the air, then exhuasts it or??? (it's pulsing pressure somehow ?)

Also, They are so cheap and seem more sturdy than other blow-nozzles (despite rating).
Makes me wonder if the rating is on internal parts (which would be removed for blow-nozzle operation anyway).
They have a bunch of similar stuff with even better shaped handles too.

I was thinking, if a rifled barrel with tighter fit had been used (OP),
it would've slowed down the bolt some.
Other thought on it, maybe the exhaust (from tool or different pilot) could shoot in front of bolt creating a temporary air-shock cushion??? 8)
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Unread postAuthor: jackssmirkingrevenge » Mon Jun 29, 2009 3:11 am

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Unread postAuthor: THUNDERLORD » Mon Jun 29, 2009 7:22 pm

jackssmirkingrevenge wrote:Take a look...


Thanks JSR!!!
I had no idea there were so many parts inside. :shock:
Reminds me of a miniature jack-hammer(???)
On page 6 there was interesting info about preventing damage from slamming of piston.
Reminds me of a ready made BFB almost(?)

I got a pneumatic tool "bug" when I got a tire changed (for a bargain) and they loaned me the 125psi air wrench for lug nuts...VVVVVRRRRPPP!!!! sure had torque and speed compared to hand removal...Almost made an "ITWOST" about it. (But I still had the last reply there).

BTW, next time I got $10 (bucks) to blow on "other than Beers" thing, I will definately buy one similar!!! 8)
Thanks.
Oh, And do you think a nail-gun could pilot a .375 bore (w/1" Piston) BFB design for semi action???( just your opinion???) .
(This seems like a great, but overlooked post IMO). 8)
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Unread postAuthor: farmerboy32 » Sun Aug 02, 2009 11:20 am

pit like a one way valve behind the retacting part so the backpressure hrlps it
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