rollerguns

hello

i would like to make a roller gun and need some advise

Do you need to use rollers? I have seen some guns that look like they only use a stainless steel pin, and the rubbers are pulled along this. How about just drilling the holes for the rubber through the barrel and the rubbers will then be pulled over the timber ( something like the muzzle on the persiko's gun)
How are the rubbers attached underneath the barre? I have seen either a hook attachment and the rubbers are hooked behind this. It does make me think that with a bit of pull the screws or the whole hook might come undone?
Drill a small hole through the barrel, insert a stainless or brass small dimaeter hollow tube and thread a dyneema through it, tie the rubbers to this. I 've seen that persiko ( again) uses a articulated bridle and hooks the rubbers onto a hook.
are there any advantages/disadvantages for a enclosed track / open muzzle.

I prefer to make a 100cm roller gun, suing a picasso basic mechanism with a 18 or 20 mm rubber and use a 7 mm or 8mm x 140cm spear. I am not sure whether to use a ( partial) enclosed track or an open muzzle?

any help, advise appreciated

If I have understood it correctly , a rollergun has the same power and range as a longer "non" roller gun but the added advantage is that is has a shorter barrel. This should allow for faster movement of the barrel through the water.
For a quick calculation, a 120 cm gun has normally about 1/3 of its length slack rubbers. So the actual effective stretched rubbers is 120cm - 1/3 *120cm = 80 cm stretched rubber. So if you were to make a roller gun with a barrel length of 80 cm length, and add 40cm rubbers underneath, you have the same kind of gun as a 120cm standard rubber gun. I hope I explained this correctly?! I guess what you always are looking for is a gun that is easier to move around under water yet maintaining your hitting power or your range. By reducing the drag ( by reducing the length of the barrel) you increase the maneuvrability of the gun.