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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 05-18-2017, 11:08 AM   #16
Behslayer
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

easy. skip all that other stuff and increase shaft to 7.5mm or 5/16" as long as it doesn't sink the gun you'll be good. 14.5mm small Id bands at 380%.
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Old 05-18-2017, 11:14 AM   #17
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

7mm shaft and double 14 should work great.....
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Old 05-18-2017, 02:29 PM   #18
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

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Originally Posted by Behslayer View Post
easy. skip all that other stuff and increase shaft to 7.5mm or 5/16" as long as it doesn't sink the gun you'll be good. 14.5mm small Id bands at 380%.
Jon, you cut those bands to 380% these days? I thought the general rule of thumb was to stretch to 350% based on the Primeline guidelines.
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Old 05-18-2017, 03:22 PM   #19
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

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Originally Posted by Alexrom1207 View Post
I've got a 7mm shaft on it now. The bands, I believe, are 18mm.

The power isn't bad and accuracy is good. However, I'd like to be able to use the gun for striped bass (30+ pounds), and it has limited penetration for that purpose. I'm not looking to power the thing to the extreme, because it's going to kill the accuracy. That was why I was leaning towards converting to a roller setup that would provide a longer pull = more power without risking shaft whip.

I was under the impression that multiple bands on the C4 trigger mechanism could be a problem, so I avoided that. If I can use 2x14mm bands, and get good power with minimal shaft whip, I would like that set up too. The single band is kind of a pain to load, especially since the butt of the gun is slick and slides around easily when chest loading.
Does your Mr. Iron have the bolt/insert style muzzle or the screw in band muzzle? Multiple bands absolutely will not be a problem with that mech. If it's penetration and accuracy you're after, first change that 18mm band to a Sigalsub 14.5mm extreme (small internal diameter) band cut at 360-380% stretch. Stretch this band as high as you can comfortably load.

Next, make sure your shaft is sharp and add a cone to it. The cone alone will make a significant difference in penetration. Those two things alone may well get you the penetration that you're after while keeping accuracy the same or better. If they don't, a second set of 14.5mm bands, running each pair at 350% or cheaper Primeline 14mm small ID at 380% will certainly do the trick and be fine for a 7mm shaft. Let us know what you find.
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Old 05-18-2017, 03:55 PM   #20
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

Grizzle, originally I thought this was a gun which was getting amped up for Canyons, ie Big Mahi, Wahoo, even Tuna. But it's for Bass in Clearwater I'm presuming now. I love the C4's. They're extremely well built. But the standard set ups on those guns are a bit strange. single 18-20mm 6.5mm-7mm shafts.

Gun could shoot much better with small ID 14-14.5mm bands.

If I was shooting 7mm (9/32") I'd go with 2 x 14.5mm @ 340% and see how that went. Maybe go up a little to 350%.

If I wanted more range I'd go with a 7.5mm (19/64") shaft with 2 x 14.5mm and tie them a little hotter ie 360%.

If I wanted more range and the gun wasn't sinking with the extra bit of weight I'd go with 8mm (5/16") with 2 x 14.5mm and tie them hotter ie 380%. (But that might kick a bit) I'm not sure.

Probably the sweet spot is more like 7.5mm with 360%.

But yes. with a 5/16", 21/64", or 11/32" can go up to 380%. Not terrible to load. Bands wear out faster. But one very real consideration for our purposes with the bluewater stuff is that 3 bands at 380% vs. 4 bands at 330% is 87" vs 139".. that's a whole heck of a lot of mass of bands difference and that has implications to the recoil, platform stability, gun design. especially on a Rear Handle.
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Old 05-18-2017, 06:39 PM   #21
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

Makes sense. Those general guidelines are helpful. I use 5/16 or greater shafts on all my guns and love the idea of increasing stretch to 380%. Fewer bands equals slimmer profile, and a cleaner sight profile before and after the shot.
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Old 05-19-2017, 01:53 AM   #22
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Re: C4 roller conversion (Mr. Carbon/Mr. Iron)

Band stretch is totally relative to how soft the rubber is. I had some Sigalsub Extreme 14.5mm bands that were impossible to pull back even at 370% while I have several batches of Primeline small ID 16mm bands that can easily be pulled back to 380% even though they are 1.5mm thicker. For longer guns ... say 110cm stretch and higher, the stretchy bands give better performance than the harder bands. At shorter stretches maybe the harder bands perform better. At the moment the only bands I will use are the Primeline small ID bands ... they just perform better in the pool are much easier to load.

For a 7mm @140cm shaft you need 2 x 14mm small ID bands @ about 110cm to 115cm stretch to get the shaft to TV. This assumes a high handle and a generally sound gun design. For 8mm @ 160cm shaft you need 2 x 14.5mm small ID bands @ about 135cm to 140cm band stretch to get the shaft close to TV.

As for % stretch with the Primeline, I would go with 360% at the lighter shafts and up to 380% on the heavier shafts.
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