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All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

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Old 03-07-2021, 08:07 PM   #1
Ron S
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17.5mm rubber?

The gun I find the most useful here in NorCal is my little Rob Allen 70. On a gun that small Iím a fan of just a single band. With a 7mm shaft, a 19mm band cut to 23 inches gives the most accuracy. I really tried to use a single 16mm band cut to 17Ē or less, but for some reason, it always shoots high. Iím just wondering if a single 17.5mm band cut somewhere in between the above two would be effective. Anybody use this oddball sized rubber for single band applications on short guns?
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Old 03-09-2021, 04:01 AM   #2
Mikel_24
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Re: 17.5mm rubber?

Oddball? Not at all... That's what I use for my single band guns. Granted I use thinner shafts (due to my kind of fishing). Usually 6,25 or 6,5mm

Currently I use PrimeLine 17,5mm... and I have a sealed blister with 3m coil of Cressi Sub Khaki Pure (17,5mm) waiting to replace that Primeline once it dies...

The problem is that the 17,5mm Primeline DOES NOT WANT TO DIE!! What a resilent rubber!

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Old 04-05-2021, 01:10 PM   #3
Ron S
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Re: 17.5mm rubber?

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Originally Posted by Mikel_24 View Post
Oddball? Not at all... That's what I use for my single band guns. Granted I use thinner shafts (due to my kind of fishing). Usually 6,25 or 6,5mm

Currently I use PrimeLine 17,5mm... and I have a sealed blister with 3m coil of Cressi Sub Khaki Pure (17,5mm) waiting to replace that Primeline once it dies...

The problem is that the 17,5mm Primeline DOES NOT WANT TO DIE!! What a resilent rubber!

Mikel
It is indeed good stuff! So, silly question, but as to cutting 17.5 to length. Iím thinking I would just go halfway between what I would cut 16mm to and what I would cut 19mm to? As an example, on my little RA 70, I either use a 16mm band cut to 18Ē, or a 19mm band cut to 23Ē, so maybe cut the 17.5 mm band to 20.5Ē?
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Old 04-05-2021, 03:19 PM   #4
musubi
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Re: 17.5mm rubber?

I think it would be a good length to start at and go from there. That's providing the bands you're using are of the same brand since the band force per length can vary a lot.
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Old 04-05-2021, 07:34 PM   #5
Ron S
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Re: 17.5mm rubber?

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I think it would be a good length to start at and go from there. That's providing the bands you're using are of the same brand since the band force per length can vary a lot.
Thatís a very good point! Right now everything I have is Primeline rubber, but Iíve had a few batches in the past that varied a lot. I think Iíll just start at 22Ē and trim it down from there. Never used this diameter rubber before, so this is pretty much an experiment.
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Old 04-13-2021, 02:05 AM   #6
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Re: 17.5mm rubber?

When I cut rubber I try to be conservative. You can always cut a bit more if you find them too soft... but if you are too short from the start... you just wasted a fair piece of rubber. You can always reuse it a shorter gun or cut a piece for a tender-shot setup in another gun, but that's not the point.

What I do is the following (initial cuts):
- 14mm rubber (Cressi Brown), cut to 330%
- 16mm rubber (Primeline), cut to 300%.
- 17,5mm rubber (Primeline or Cressi Khaki Pure), cut to 280%.

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Old 04-18-2021, 02:35 PM   #7
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Re: 17.5mm rubber?

Got back from the coast last night. Got a chance to do a quick shore dive and chase a few fish with the RA70. I tried out the 17.5 primeline rubber. Itís cut to 230% loaded to the first notch, and 260% at the second notch. I found this to be noticeably harder to load than the 24Ē 19mm band Iíve been using, but that band, while Primeline as well, is pretty old.
This seems to have plenty of power to the end of a single wrap. (I know this because I missed two hail Mary shots at fish that were just out of range). Also plenty accurate since I didnít miss the few fish I managed to get within range of. Think Iíll stick with this setup on the hole gun for awhile.
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