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Old 05-26-2018, 08:44 PM   #1
Straits
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Straits Cray Gun Build

Hi all,

Building my first gun and hoping the collective wisdom here can help guide me through it. Thanks in advance.

Workshop is coming together. Tools/equipment include: thicknesser, drill press, router, router table, table saw, chisels, hand saws.

I've got 4 x lumps of merbau (kwila) wood that are 90mmx90mmx600mm. The blocks float in fresh with approx 20% above water, without any parts attached. From another thread on this topic I understand this short gun won't float, but as it's a cray gun this isn't an issue.

I'm hoping I can ask questions in this thread and continue to add to those questions as I go through the build.

Gun plan:
Shaft: 600mm length, 7mm diameter, short flopper 25mm from point, aiming for shortest overhang possible. Square cut Riffe style with 2 x shark fin tabs.
Band: single 14mm small ID.
Components:Neptonics reef trigger mechanism, handle undecided at this stage.
Barrel: open track, 550mm from butt to tip, see question below about volume/dimensions.

Questions:
1) How much space do I need behind this trigger mech to the butt of the gun? I'll keep this minimal, and loading will be off the chest, with wooden butt square and clean.
2) How wide should the gun be but still fit the trigger mech with enough wood on both sides? Neptonics lists width as 12.5mm (0.5 inch). I'd like the gun to be bulky and solid so was thinking 40mm width.
3) How deep should the gun be? Neptonics lists height as 25mm (1inch), and I expect it to sit flush with the top of the gun so only the shark fins are above the top surface. How much wood is required beneath this to allow handle attached and trigger protrusion? I was thinking of 50mm, but just guessing here.

Thanks again.
Straits.
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Old 05-27-2018, 07:40 AM   #2
Mendicant
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Re: Straits Cray Gun Build

I am afraid I am not familiar with the term "cray gun."
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Old 05-27-2018, 03:48 PM   #3
Straits
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Re: Straits Cray Gun Build

Cray=Crayfish=lobster. Sorry, should have explained.
Close range short gun for manoeuvring in tight ledges and caves.
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Old 05-27-2018, 10:41 PM   #4
doyenofcastle
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Re: Straits Cray Gun Build

1) How much space do I need behind this trigger mech to the butt of the gun? I'll keep this minimal, and loading will be off the chest, with wooden butt square and clean. (2 to 3 in for me)
2) How wide should the gun be but still fit the trigger mech with enough wood on both sides? Neptonics lists width as 12.5mm (0.5 inch). I'd like the gun to be bulky and solid so was thinking 40mm width (depend on line release mine is 2 inch).
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Old 05-28-2018, 04:58 AM   #5
Straits
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Re: Straits Cray Gun Build

Thanks Doyenofcastle,
I'll plan 50mm behind the mechanism to the butt, and go with 50mm width.
No line release for this gun. Line will be anchored near the snout of the gun with short bungie to mono. These guns don't need much range, and will have approximately 100cm from muzzle to spear point when shot. Basically you get right in front of the crayfish and shoot through it at point blank range.

I suppose going 50mm deep will make it a nice square prior to any further shaping. Would a gun this deep allow for enough trigger to protrude?
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Old 05-28-2018, 01:40 PM   #6
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Re: Straits Cray Gun Build

Some of those questions can answer themselves once you buy your parts. I would mock-up the trigger mech first, then hold whatever handle you choose underneath it to make sure it all lines up correctly. One way to get the right trigger protrusion is install the trigger mech, then start shaving material away until it looks and feels right. Your handle frame will determine how far back you can mount the handle/mech, so I would make that decision when you have parts in hand. Keep ballasting in mind when you mock this stuff up, you'll have to hide some lead in there once the gun is shaped and built.
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Old 05-28-2018, 04:09 PM   #7
Charles dT
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Re: Straits Cray Gun Build

Hi Straits,

the design you describe looks a lot like the hole gun I built.
I'm attaching a picture here as well as a competitor Riffe 00 that shoots the same shaft so you can compare.

my gun has minimal overhang, actually I even carved out the end of the muzzle so that the flopper can be resting on the gun and still have the shaft lay flat. If I would start over I would have it rest even more or not at all.

If you really want a compact gun, go with a reverse mech, look at my gun and you will see that the mech is all the way back and yet the trigger is in front. Compare that to trigger/mech placement on the Riffe 00. That's part of the reason the shaft protrudes so much on the Riffe vs mine. With the reverse mech you reduce the length between the butt and the tip of the shaft so you have a more compact design. My speargun is shorter and yet the length from band to tab is longer so in theory packs more punch (not that it is required at that distance)

My gun is very bulky because it was built from 3 pieces of wood bolted together basically ( I didn't have any tools at the time and still don't have many) so you can disregard that aspect however from butt to tip etc it should give you an idea of what you are looking for.
Can take a few pics and measurements if you want. I remember that the width on mine is 40mm and that is way more than a Riffe, it already feels plenty bulky. 50mm sounds like a lot, but just personal opinion.
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Old 05-28-2018, 10:14 PM   #8
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Re: Straits Cray Gun Build

Quote:
Originally Posted by doyenofcastle View Post
1) How much space do I need behind this trigger mech to the butt of the gun? I'll keep this minimal, and loading will be off the chest, with wooden butt square and clean. (2 to 3 in for me)
2) How wide should the gun be but still fit the trigger mech with enough wood on both sides? Neptonics lists width as 12.5mm (0.5 inch). I'd like the gun to be bulky and solid so was thinking 40mm width (depend on line release mine is 2 inch).
a gun this short does not need to be fat or bulky at all- also - it should be muzzle heavy - since you will be shooting down all the time

what you want - is a finished dimension of 1.5"x 1.5""
the track should be open deep - right?
if you do that - use a neptonices reverse mech - and use either a mortise in style - or flat plate style ar handle frame system
neptonics has two types - the flat plate allows for a smaller gun behind and below mech - by 1/4"
but the mortise in type allow for round gun profiles and sleeker look in general - but if your gun is wide enough at the back to allow the flat plate style - then you can make the gun a bit narrower in back.

I would recommend - making 42"gun - anything shorter - is just lacking in power
go 1 7/8" x 1 7/8" x 44"for the rough lam - then mill down to 1.5"x 1.5
flat straight square and true (hardest part of the whole build)
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Old 05-28-2018, 10:32 PM   #9
doyenofcastle
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Re: Straits Cray Gun Build

Quote:
Originally Posted by Hpwatson View Post
Some of those questions can answer themselves once you buy your parts. I would mock-up the trigger mech first, then hold whatever handle you choose underneath it to make sure it all lines up correctly. One way to get the right trigger protrusion is install the trigger mech, then start shaving material away until it looks and feels right. Your handle frame will determine how far back you can mount the handle/mech, so I would make that decision when you have parts in hand. Keep ballasting in mind when you mock this stuff up, you'll have to hide some lead in there once the gun is shaped and built.
100% accurate
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Old 05-29-2018, 05:33 AM   #10
Straits
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Re: Straits Cray Gun Build

Thanks all.
Makes a lot of sense.
Mechs haven't arrived yet, so I'll do the mock up when they arrive.
CharlesDT, that's a great looking little gun.
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Old 05-29-2018, 10:38 AM   #11
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Re: Straits Cray Gun Build

https://r.tapatalk.com/shareLink?url...9&share_type=t


I just finished a 42" mid that might be something to work off of. Minimal volume with maximum band stretch was the goal of the build. The only change I would make is I did not set my mech deep enough and their is about a 1/8" shaft drop from mech to track, I also already had the reef mech or I would have used the neptonics reverse mech. Gun has power for its size, I took a 30 pound fish this weekend from 7-8 feet out.

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Old 08-11-2018, 10:05 PM   #12
Straits
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Re: Straits Cray Gun Build

Finally getting somewhere.
Blanks have been squared up and planed/thicknessed down to 40mm square.
All componentry except shafts have arrived (7mm diameter 575mm long).
Neptonics reef trigger mechs.
Handle is https://neptonics.com/product/ar-15-...n-handle-rear/ and I'm having some trouble finding information on the dimensions of the insertable part. With a couple spanners it measures between 15mm and 15.8mm. Does anyone know the definitive width? I'll get a router bit specifically for this insert, and keen to get it right first time. I don't particularly trust any of my spanners to tell me the truth.

All your earlier advice was spot on. Once the bits arrived, it was easy to see how it would fit together. I'll try get a photo uploaded.

Thanks.
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Old 08-11-2018, 10:23 PM   #13
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Re: Straits Cray Gun Build

Attempting to upload pictures.
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Old 08-12-2018, 12:40 AM   #14
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Re: Straits Cray Gun Build

I use a 5/8" bit for that handle insert.

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Old 08-13-2018, 04:32 AM   #15
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Re: Straits Cray Gun Build

I think you need some more wood behind the mech. Otherwise the lower lip of the handle will contact your body before the butt pad (non existent in the picture) does, and loading will be awkward.
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