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2" sleeved GB barrel vs SDR 21 1.5

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2" sleeved GB barrel vs SDR 21 1.5

Unread postAuthor: jmeyer1022 » Tue Nov 18, 2008 12:06 am

So I finally made a pneumatic cannon today and just wow... Shot alot of stuff and loved the fact that it had actually kick to it. Pneumatic won me over combustion.

I'm looking to make a golf ball barrel and SDR 21 is not easy to grab around here but a decent drive and I can get some. So I'm wondering is there a huge performance difference between Sleeved 2" vs SDR 21 1.5 pipe.
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Unread postAuthor: starman » Tue Nov 18, 2008 12:58 am

A sleeved barrel will be MUCH straighter and stiffer than an SDR 21 pipe by itself. It will also allow somewhat higher psi shots than SDR 21 alone.

Pneumatic won me over combustion.

You just haven't done combustion to its height yet my friend... :wink:
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Unread postAuthor: Ragnarok » Tue Nov 18, 2008 11:57 am

starman wrote:A sleeved barrel will be MUCH straighter and stiffer than an SDR 21 pipe by itself. It will also allow somewhat higher psi shots than SDR 21 alone.

I don't think that's what he means, you may confuse him.
I think he's talking about another technique, not often seen, the self sleeved 2" SCH 40, described here.

A golfball fit is not quite as tight as 1.5" SDR 21, but it's a solution if you're not able to get SDR 21 easily. It takes a while and a bit of patience to make up properly, but you get a decent enough barrel.
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Unread postAuthor: starman » Tue Nov 18, 2008 12:09 pm

OK maybe he meant that, it isn't completely clear. I've built one of those slit 2" crammed into a 2" and there's no way it is as good a performer as an SDR 21 barrel. For one, making one any longer than 4 feet or so is virtually impossible. Then once you have it, you have a slit you have to deal with down the length of the barrel.

Jmeyer, make the effort to find some SDR 21. Yeah, it's rare but it is available. Check your local Tractor Supply Center.
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Unread postAuthor: Ragnarok » Tue Nov 18, 2008 12:51 pm

starman wrote:Then once you have it, you have a slit you have to deal with down the length of the barrel.

Depending on how well you cut the slit to the right dimensions, this can be next to nothing.

I've done similar before (although with UK sizes) for other things, and getting very fine, or even non-existent gaps with a little force fit is entirely achievable.
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Unread postAuthor: Cannibal Corpse » Tue Nov 18, 2008 3:30 pm

I've built one of those slit 2" crammed into a 2" and there's no way it is as good a performer as an SDR 21 barrel. For one, making one any longer than 4 feet or so is virtually impossible


I built a 5FT one and it was acually very easy to sleeve.
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Unread postAuthor: starman » Tue Nov 18, 2008 3:56 pm

Cannibal Corpse wrote:
I've built one of those slit 2" crammed into a 2" and there's no way it is as good a performer as an SDR 21 barrel. For one, making one any longer than 4 feet or so is virtually impossible


I built a 5FT one and it was acually very easy to sleeve.


Without knowing any more details, I find it dubious that your 5', slit 2" into 2" barrel was very easy to sleeve, because it isn't. Nothing in your previous posts on Spudfiles indicates you achieved this.

Ragnarok wrote:Depending on how well you cut the slit to the right dimensions, this can be next to nothing.

I've done similar before (although with UK sizes) for other things, and getting very fine, or even non-existent gaps with a little force fit is entirely achievable.


Yes I'm fully aware of the slit being the right dimension and proper cut angles. This is best done with a table saw or a router table, of which I have both. A non-existent gap is impossible as you do have to squeeze smaller than the hole to get it in. A 1/32" to 1/16" gap is for all practical purposes what you will end up with. And this with a multi-person, almost herculean effort.
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Unread postAuthor: FLONE » Tue Nov 25, 2008 12:49 pm

starman wrote:Jmeyer, make the effort to find some SDR 21. Yeah, it's rare but it is available. Check your local Tractor Supply Center.


Found mine at Menards, special order 1-20' stick, don't recall the price but it was less than $1 per foot last fall.

Good luck.
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Unread postAuthor: jitup » Tue Nov 25, 2008 1:47 pm

TSC does have SCH 21, it costs $8.29 for a 10 foot stick of 1.5 inch pipe (1.5 is what is used for golf balls isn't it?) I do not remember what the guy said 2 inch cost. I live in the Boonies so it is a 30-45 min drive to the area were walmart home depot and other stores are located, so you are pretty much able to find any thing you need there. (I live in a farm community and we use a lot of PVC for irrigation, so parts are easy to find near me.)
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Unread postAuthor: starman » Tue Nov 25, 2008 2:00 pm

jitup wrote:(1.5 is what is used for golf balls isn't it?)


Yep, perfect golfball fit, plus very nicely sleevable into sched 80 2". I don't think any other SDR size has any significant usage for a mainstream ammo.
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