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Crossbow Barrel Length?


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#1 OfAllTheNerf

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Posted 12 April 2008 - 06:40 PM

Since I've posted a ton of write-ups in the past two weeks I don't feel so bad about making a ? topic.

Anyways, to the point. I'm going to make a 17/32" brass breech for my Crossbow, but would like to know an ideal barrel length. I'm mainly pointing this at the Vets who have used they're crossbows since the beginning of time. My darts will be slightly tight in the barrel, but not hard to push in and out of the barrel. There will be no nested piece. There also cannot be any PVC after-barrel.

If you would suggest using a completely different barrel setup, please post that too.

Thanks,

-OfAll'
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#2 sam

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Posted 12 April 2008 - 07:26 PM

I use 12" of PETG, and it has a perfect fit with my darts.
I would try 10", but I would really do since your making a breech, is temporarily hot glue a coupler on the x-bow and test different lengths.
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#3 ompa

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Posted 12 April 2008 - 07:31 PM

What kind of breech are you planning on that only uses one piece of brass? Do you have a pvc sheath that slides around to close the breech? Or is the whole piece of brass going to move to enclose the dart in pvc? I'm just kind of curious, no offense intended.

To be quite honest, without having your gun and dart in front of me, I'd start somewhere around 10-12", test it, then cut off an inch or two after each batch of test firings. When you feel that the range has maxed, then stop. You could probably graph your results and when the range increases start leveling off you know to stop at the next cut, but I'm not sure about the exact relation between barrel length and darts, considering how dependent the results are on various factors.

I also ask about the breech because depending on how efficient it is, you could probably start at a shorter barrel length.

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#4 xNFx 37

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Posted 12 April 2008 - 08:07 PM

For 17/32 brass, depending on the fit, I'd say 9-11 inches.
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#5 OfAllTheNerf

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Posted 12 April 2008 - 08:14 PM

What kind of breech are you planning on that only uses one piece of brass? Do you have a pvc sheath that slides around to close the breech? Or is the whole piece of brass going to move to enclose the dart in pvc? I'm just kind of curious, no offense intended.

To be quite honest, without having your gun and dart in front of me, I'd start somewhere around 10-12", test it, then cut off an inch or two after each batch of test firings. When you feel that the range has maxed, then stop. You could probably graph your results and when the range increases start leveling off you know to stop at the next cut, but I'm not sure about the exact relation between barrel length and darts, considering how dependent the results are on various factors.

I also ask about the breech because depending on how efficient it is, you could probably start at a shorter barrel length.

~ompa


I'll be using a cut down verison (or not as the case may be) of my breech. The only reason I don't really want to do experimental testing is because brass is expensive, and the breeches take a bit of time to make. Thank you for your input, though. I'll probably start at a full 12", and then cut off inch by inch.

Sam, I'm going to glue a coupler on anyways (to make sure it's straight), but I'll probably keep the final lenght under 12" (I'm leaning towards 8-9). Possibly 10... I'll probably star the PVC part of the breech off shorter to allow for a barrel as short as 8".

Thank you everyone for your input, and everyone else feel free to post.

-OfAll'
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#6 sam

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Posted 12 April 2008 - 09:44 PM

12" may seem long, but it actually feels perfect on an X-Bow, so don't shy away from using a longer barrel if it gets you more range.
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#7 OfAllTheNerf

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Posted 13 April 2008 - 11:17 AM

12" may seem long, but it actually feels perfect on an X-Bow, so don't shy away from using a longer barrel if it gets you more range.


I'm going to range test with my already-made 12" breech, and see how it does. I just need to figure some way of improving the seal on the plunger head. I can't get e-tape to stay on for the life of me.

Suggestions?
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#8 nerfboi

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Posted 13 April 2008 - 11:21 AM

Did you make sure there wasn't any lube left on the plunger head? Then try to hot glue it on, but not directaly on the plunger head, wrap the E- Tape on the plunger head and then glue it together from the top or the very bottum of the plunger head.
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#9 ompa

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Posted 13 April 2008 - 11:22 AM

Did you dry off the plunger head first? Sometimes there is still some lube left on it that doesn't let the tape stick. Otherwise, you could try a wider tape and wrap it around the plunger head, instead of just around the part that comes in contact with the plunger tube.

Whoa, that's a first, someone beat me to posting! But yeah, nerfboi beat me to it.

Sam's post below reminded me of something else; you *could* try putting a washer approximately the size of the plunger tube at its most constricted point at the head of the plunger, to help keep the plunger head in its expanded state. It should in theory work, but I don't have much practical testing behind it, so take my advice for what it's worth.

My Crossbow just has a bunch of masking tape (yuck) on the plunger head.

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#10 sam

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Posted 13 April 2008 - 11:32 AM

Don't hot glue it. That would most likely fuck the plunger head real bad.

Here is the best way to fix the plunger head, take the rubber plunger head and bend it backward then put it back in the plunger tube with the seal backwards and let it sit for a while, then pull the plunger head out and put it back in normal. It should have a much better seal. Hopefully that was clear.
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#11 OfAllTheNerf

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Posted 13 April 2008 - 12:14 PM

Thank you everyone.

ompa, I was actually thinking about doing something like that, but with an o-ring. But I might just try sams method and see if it works.

Don't hot glue it. That would most likely fuck the plunger head real bad.

Here is the best way to fix the plunger head, take the rubber plunger head and bend it backward then put it back in the plunger tube with the seal backwards and let it sit for a while, then pull the plunger head out and put it back in normal. It should have a much better seal. Hopefully that was clear.


I'll try that, it worked on my SSII.

-OfAll'

Edit: Does anyone know a good lube? Ive been using silicone spray, but it dries up really fast.

Edited by OfAllTheNerf, 13 April 2008 - 12:17 PM.

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#12 CaptainSlug

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Posted 13 April 2008 - 12:24 PM

Does anyone know a good lube? Ive been using silicone spray, but it dries up really fast.

?
The silicone spray I use leaves a really long-lasting film. If you want stuff with more grip get the paste.
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#13 OfAllTheNerf

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Posted 13 April 2008 - 02:10 PM

Does anyone know a good lube? Ive been using silicone spray, but it dries up really fast.

?
The silicone spray I use leaves a really long-lasting film. If you want stuff with more grip get the paste.

Mine might just be shitty, because it doesn't even make a film on the inside of the plunger tube. If I spray some in ad then hold it upsidedown it will all drip out. I I push ad pull the plunger head a few times the stuff is all gone. Is there a certain brand you would recommend?

Edited by OfAllTheNerf, 13 April 2008 - 02:11 PM.

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