First speargun

[flandersander]

So I'm starting my first speargun build. I'm building my own trigger too. here's what I have so far.

The little blue line is where a spring will go.
That's my design. I'm currently in the process of cutting it from 1/4 inch 6160 aluminum I had lying around. For the cassette I'm using 3/4 inch square aluminum tubing. 1/16th wall. I wanted 1/2 by 1, but I think i'll be able to make it work. The shaft notch piece is going to be 1/2 inch thick, because of the size of the cassette. The piece you pull will be 1/4 but will be centered on the pin using a spacer of pvc. Going good so far.


The stock I think is going to be maple, or oak. Probably do a pine one to work the bugs out.

I'm going for a 70cm trigger to band distance. I'm thinking of doing a very open track, or no track at all. Supported only at the muzzle and trigger. It's for short, low viz shots.

Probably go with one 9/16 or 5/8 band. I can always add another if I think I need it, but after talking with foxfish, I dont think I will.

 

[Tin Man]

I love tinkering with trigger mechanisms, so I would be quite the hypocrite if I said "don't do this", but . . .

Please take a better look at the commonly available mechs. There are some very good reasons why they are all built from 304 or 316 stainless (at a minimum). Many incorporate heat treated 17-4, or higher alloys like Inconel. So far as I know, NONE are built from aluminum. Galvanic corrosion and galling being just two reasons why. You will also want to study spring placement on the sear, and the geometry of the little "bump" that the spear tail pushes against to re-latch the mechanism. Popgun Pete has some great information out there.

Goodness knows I never listen when someone tells me I shouldn't do something, and if they tell me I "can't" then I get complete tunnel vision. So I won't tell you not to build your own trigger mech. But I will strongly suggest that you not start there on your first gun.

 

[flandersander]

I understand and appreciate your concern. I absolutely will not dive in the company of anybody (that I like ) while trying this mech.

Why do you suggest I look at spring placement?

And honestly, I dont mind if this trigger doesn't work perfectly, just as long as it's safe. I am currently using a jbl mini carbine. Have you seen the trigger in those? It's one piece, where if there is a load placed on the sear, it allows the release of the shaft.

My mech's gotta better than that!

 

[Tin Man]

. . . Why do you suggest I look at spring placement?

On most of the mechs that I have seen, the spring is placed a bit lower (counter clockwise around the pivot pin in your photo). So if the gun is unloaded (no band load), and you want to pull the trigger to remove the shaft, the spring will help pull the sear around to release the shaft.

The mech on the left is the Neptonics Reef, and the one on the right is a Bill Kitto mechanism.

 

[foxfish]

I will go along with Tin Man but, just add, please be very careful as virtually all the top gun builders just buy there units for good reason, the tolerance & hardness of metal is difficult to work with & achieve.

 

[flandersander]

On most of the mechs that I have seen, the spring is placed a bit lower (counter clockwise around the pivot pin in your photo). So if the gun is unloaded (no band load), and you want to pull the trigger to remove the shaft, the spring will help pull the sear around to release the shaft.

The mech on the left is the Neptonics Reef, and the one on the right is a Bill Kitto mechanism.

Oh yeah, that's a good point. I'll do some playing around with it after work today.


And thanks foxy, I appreciate your concern aswell.

 

[flandersander]

Well I got the mech done. Well, almost done. It's functioning well. I just gotta build a gun around it now. I've got a nice chunk of oak. For a 70 cm gun, do I need to laminate it? My test stock will be ceder. Easy to work, and I had it lying around...

 

[Tin Man]

Before going any further with the build, I think it would be best to mount your new mechanism in a 2x4 and load test it somehow by suspending a load of stones, water, iron weights, etc just off the floor and testing the trigger pull. Your mechanism isn't the same size as the typical "off the shelf" mechs, so it will be a little tougher to replace if your design is unsatisfactory for any reason.

Others may disagree, but I probably wouldn't laminate a 70cm stock unless it was particularly slender.

 

[flandersander]

That's my plan. How much pressure will this mech see with one 5/8 band? Probably should have had that in mind when I was building it.

I'm going to build a mock stock from ceder to get everything just right.

How would thompson's water seal do as a finish? That's what the guy at home depot recommended, but I have a hard time trusting their judgement.

 

[flandersander]

Well, I load tested the mech with 4 cinder blocks. Worked pretty well. It should be good to go. Anyways, here's some pictures.

By the way, I dont have access to a router. I did the track the old fashioned way. By hand. Cut a little starting grove down the center, then wrapped a pen in sandpaper. Took a couple hours, but it did the job. I dont really want an open muzzle, so what are my options there? I've seen a loop right on the end, thinking maybe i'll go that route.

After doing this, I think i'll save my oak for a neptonics mech. Haha.

 

[flandersander]

Mounted the handle.

 

[growingupninja]

My first gun was a JBL woody magnum and when I finally lost it for good I was almost grateful to the ocean. They say it always tastes better when you shoot it yourself. If you also built the gun you used to shoot it.. Well, the fish you kill with that particular gun may be the finest you will ever taste.

 

[flandersander]

That's a better start than I have. I'm using a jbl mini carbine!

So I've got a question.

I'm almost ready to finish it off. A little final sanding, add a butt pad, and I'm ready to seal it up. My question is this, should I go with a paint on varnish, spray on varnish, or will thompson's water seal do the trick?

Going good so far, now I really can't wait for season to open. May 5th!

 

[growingupninja]

Wood guns are all the rage in California and have been for decades. Most builders to my knowledge use teak or mahagony which are both extremely durable and water resistant, or sometimes custom guns are made from other 'boat woods'. Most teak/mahagony guns are oiled at the factory and can be maintained by sanding and reoiling (although some guys have had their teak guns for decades and don't do anything but rinse them in fresh water), and some guys who build guns coat them with epoxy resin. Sorry I don't have more specific info. But for real be careful with your trigger mech--aluminum is never used in any guns I have heard of. Nonexpert though.

If I were you I wouldn't use Thompsons. Maybe epoxy since your wood isn't typically used for marine applications. Teak and mahogany are favored because they're tough and don't warp or crack in water. Epoxy coatings are very tough and water tight.

 

[flandersander]

I could do an epoxy I guess. I was kinda hoping to use a varnish though.

 

[growingupninja]

If you are wanting to use varnish for the color then just apply varnish and then topcoat it with epoxy, which is usually transparent but slightly yellowish when dry. If you want to use varnish for any kind of sealing property I think you would get further with epoxy in that department. Try a google search to see what comes up...

 

[flandersander]

Well I did a little research, and i'm now thinking i'm going to use pure tung oil. I just gotta remember to re oil every dozen dives or so. Right?

 

[foxfish]

Mate that trigger looks terrifying!!
Epoxy would probably cost more than a trigger unit anyway but, most folk coat with epoxy & cover the epoxy with polyurethane varnish.
Oak is one wood that was traditionally use to split rock, a large dry, oak wedge would be placed into a crack in a rock face & then soaked with water, such is the power of expansion the rock face would crack further to cause a piece to fracture off!!
So I would treat you gun wood with numerous coats of whatever you use, the truth is it probably wont be under water long enough to absorb that much water but it still might swell or crack?

 

[flandersander]

Granted, it's a little crude.

That's interesting, didnt know they used oak for that.

I'll coat the heck out it then. Thanks

 

[sjurba]

One trick Ive learnt from a friend which is a bit of woodenboat nerd.Is to put whatever you want treated in a plastic bag with the oil,then leave it for a couple of weeks to be completely soaked.I didnt know that you could split rocks with oak though,but I presume that if the wood is already full of oil,there wont be much room for water?