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What do you think is a tolerable oversize for a GB barrel?

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What do you think is a tolerable oversize for a GB barrel?

Unread postAuthor: dongfang » Wed May 30, 2007 7:30 pm

Hi

I am looking for a suitable golf ball barrel. Before you say sch-xx PVC, I have to tell you we're metric here. There is no "schedule-..." pipe here.

A golf ball is minimum 42.67 mm (says wikipedia). The specimen I have found is made very, very exactly to spec - 42.7 almost.

I can get a nice nice aluminum pipe. ID is 43.4 mm. 0.7 too large. Or a not so nice steel pipe. 0.7 too small.

I wonder if:

- Any of you has seen golf balls that are slightly larger than 42.67 mm. Does size vary between brands and models? The one I picked up is a Crane Sports / soft distance.

- Any of you has some feedback abt whether 0.7 mm oversize is tolerable? I have calculated the area of the leak to be about 50 square mm's.

- A golf balls gets flattened a little with xx bar of pressure on one side but not on the other, and hundreds / thousands of g's of acceleration. Did anyone with a GB cannon make any observations on that? Like excessive wear in a tightly fitting barrel -- or, maybe, having a working gun with an oversize barrel, try to paint crayon circles inside the barrel and see if the GB touched them at the full circumference?
I'm pretty sure that some math genius on usenet can compute the deformation given the problem (and some material constants), but practical experience is almost better.

- And finally, can anyone with a "really good" GB cannon and a caliper tell me how much oversize / slack diameter he has between golf ball OD and barrel ID?

Thanks in advance.
Soren
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Re: What do you think is a tolerable oversize for a GB barre

Unread postAuthor: hi » Wed May 30, 2007 7:39 pm

dongfang wrote:Hi



thats a good way to start, just kidding.

.7 mm is very tolerable, most of my ammo is about 2 mm to small. you may loose about 20 or 30 fps, but thats ok.
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Unread postAuthor: Bubba05 » Thu May 31, 2007 12:38 am

I got a 45mm pipe for my golf ball barrel and they fit pritty snug with a shaving of polystireen around them. you could use tape to bulk em up if you had the larger barrel?

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Unread postAuthor: pyrogeek » Thu May 31, 2007 12:57 am

Just put a stud in the breach end of your barrel to stop the ball from going into the chamber when you load it. On mine, I drilled, tapped and screwed in a piece of a bolt like 1/16inch (like 1/2cm) in.
Then, make a patch from an old shirt, sock, underwear, etc. That will make a better seal than if you had a barrel the correct size. You could use tape or something, but it's not biodegradable and you can't always find it.
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Unread postAuthor: jackssmirkingrevenge » Thu May 31, 2007 1:17 am

pyrogeek wrote:Then, make a patch from an old shirt, sock, underwear, etc. That will make a better seal than if you had a barrel the correct size. You could use tape or something, but it's not biodegradable and you can't always find it.


lol, spudgunning with an environmental conscience, what times are these?

What's wrong with using tissue paper? much cheaper, readily available and still environmentally friendly if you use the recycled kind ,)
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Unread postAuthor: boilingleadbath » Thu May 31, 2007 7:35 pm

The pipe we recommend for this usage in the states is .02" ( .5 mm) oversize.

.7mm oversize isn't much worse, and should work fine.

Anyway, your standards for what constitutes a "good enough" fit are probably different than mine - model the situation using the GGDT and decide if you can put up with .7mm of over-size-ness.
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Unread postAuthor: joannaardway » Fri Jun 01, 2007 5:33 am

.7mm gap is no problem whatsoever on a barrel that diameter IMO.

And as others have said, a little wadding could be used if you still have problems with the gap.

I'd be very happy with a gap of .7mm for a golf ball.
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Unread postAuthor: Bubba05 » Fri Jun 01, 2007 8:52 am

Yeah i've had no problems with my small gap!
goes pritty good! I can put dints in car doors at about 20 feet!

PS Car doors are on dumped burnt out wreaks at my range.

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Unread postAuthor: rna_duelers » Fri Jun 01, 2007 7:34 pm

So you use a metric system?Do you want to use steel or PVC because in PVC PN12-40mm pipe is a PERFECT fit,much like a SDR-21(Correct me).

If steel is wanted to be used just get a golfball and go to a piping place and test different tube sizes,most effective way to find the right size.
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Unread postAuthor: Cool » Sat Jun 02, 2007 5:16 pm

I bought an aluminum pipe that is 50 mm outer diameter with 3,5 mm walls, 43mm inner diameter. Golfballs fits perfect, when the ball is on place, i can hold it in any angle, without the golfball falling out.
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Unread postAuthor: Pete Zaria » Sat Jun 02, 2007 5:19 pm

Cool wrote:I bought an aluminum pipe that is 50 mm outer diameter with 3,5 mm walls, 43mm inner diameter. Golfballs fits perfect, when the ball is on place, i can hold it in any angle, without the golfball falling out.


Your pipe might actually be a teeny bit TOO tight, and the friction might be diminishing your performance. With a regular (1.5" sdr21) GB barrel, the ball will slide down, but slowly due to air resistance.

None the less, can you tell us what kind of pipe this is, what markings it has (if any) and where you got it? Some of us would be interested in a metal GB barrel.

Peace,
Pete Zaria.
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Unread postAuthor: Cool » Sat Jun 02, 2007 5:24 pm

Some golf balls have to be pushed down, but most slide very slowly down (have to blow them down), so their size vary, but not much.
I ordered the pipe on a factory where they build oil rigs (in Norway),i had to buy 5 meter for about 90$.

The pipe is named: 50x3,5mm EN AW 6082-T6 Aluminum Pipe, the name is the same as in USA, so you should find it easy, the ISO name is Al-Si1MgMn.

If you can read Norwegian you can find the pipe and info here: http://www.norskstaal.no/varekatalog/va ... egr=755_1#
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Unread postAuthor: dongfang » Sun Jun 03, 2007 5:26 am

Hi all,

Thanks for all the response.

It seems GGDT doesn't compute a very large performance degradation for 0.7 mm.

OK I will look at the 40mm PN12 (40mm?? That's smaller than the GB. Did you mean 50mm?). The ultimate thing seems to be the 50mm OD 3.5 wall aluminum pipe. 43 mm ID, so there is still a little room for the ball flattening and the oversize is only 0.33 mm max...

The pipe I had a look at must have been with about 3.3 mm walls.

As for bringing a golf ball to try out the pipes, guess whether I lost the ball inside a pipe on 1st try ...

Thanks again
Soren (yes I do read Norwegian -- WOW this is the first time I ever saw a wholesaler have product prices on his web site)..
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