Hey so I have replaced the standard 16mm rubbers on my gun with newer shorter ones as the older ones were old and worn. They are already about 1 inch shorter than the stock ones and I can load quite easily loading it using my chest (i used hip when started out and that was hard).

So I guess the question is can you over stretch them too much that it will reduce accuracy or even break the rubber (no I dont think I could break the rubbers using my arms)?

http://www.legendary.com.au/sizing-powerbands.php

hey mate we use this formula with all our Torelli and Picasso guns, hope this helps.
oZ

ps. you can OVER power spear guns! decreasing their accuracy.

Thanks for that. I will measure it when I get home. The new spear on my gun (Omer Dragon) is 150cm 7mm compared to the original 130cm 6.5mm one. Hoping the extra 20cm overhang which in total will be around 35cm wont make it much slower.

Is adding a second rubber going to make it innacurate due to overpowering. I am just concerened the extra length and thickness will make it slower. I already have bulk rubber in 16mm size so would prefer to keep that thickness.

hahah, i have tried this with my HF. the gun never shot as well as a 6.5mm (1m gun@ 140cm shaft) . a 7mm made the gun too heavy. as well as the extra over hang.... you may have the same problem.... if you take the muzzle out there may/may not be a LED weight. take it out and throw it away! this may help your buoyancy with the gun. my bet is the 7mm shaft is too heavy for the gun.2x16mm rubbers may help trajectory but its all trial......
good luck.

Thanks Ozdog. I will see how I go I guess. Worst case I have to buy an original 6.5mm spear for it which will be dearer but no point having it if its always trying to sink on me while im holding it. I will see if there is a weight inside the muzle although the gun floats once the spear is shot so thinking no weight. Will check it out anyway.

Geez, Kurt I thought the same thing when I saw the heading

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Learner Spearfisherman.