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This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 20, 2008 7:54 pm

You mean the thumbhole stock? Very ergonomic :)
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Unread postAuthor: potatoflinger » Sun Jan 20, 2008 9:07 pm

SPG wrote:
potatoflinger wrote:Alright, to end this efficiency battle, take another look at the slingshot/car analogy. If each car is given the same amount of fuel, the more efficient car will be able to pull the slingshot back farther than the less efficient car.


Maybe but it depends on the power output of the car

But, if the less efficient car has an unlimited amount of fuel, then it will be able to pull the slingshot back farther because it has more power.


Wrong, fuel doesn't equal power, power equals power, in your analogy eventually one of two things will happen, either the force needed to stretch the slingshot will be greater than the power of the car and the car will wheelspin, bog down, stall, or the power of the car will overcome the elastic of the slingshot and break it.


The amount of fuel that each car is given is the same as the air chamber size on a potato cannon, with the same size tank and barrel, the more efficient gun will have more power, but if you give the less efficient gun a way oversized chamber, it will have more power.


We shouldn't compare efficiency in two different sizes of gun, efficiency is all about getting the most out of the gun you have, which is about optimising design. There are two ways to do this, one is to decide for the power you want and build the gun to meet your specs, the other is to build you gun as efficiently as possible knowing that you've got the max power out of it.

An efficient gun will always be as powerful as it can be, it may however be a lot less powerful than another gun of different specifications.

Think .22 rimfire and .50 calibre.


I was referring to the original post where I said that newer cars are more efficient, but have less power than most older cars.
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Unread postAuthor: Ragnarok » Sun Jan 20, 2008 11:41 pm

Carlman wrote:quoted from henry ford

Actually, that's a myth. One of the things that they cover on QI - black was one of the colours it wasn't available in.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 21, 2008 1:43 am

Ragnarok wrote:
Carlman wrote:quoted from henry ford

Actually, that's a myth. One of the things that they cover on QI - black was one of the colours it wasn't available in.


Initially, this was true, but apparently to speed up production (as black dried the quickest) in later years, and he did indeed mention this quote in his autobiography.

By 1918, half of all cars in America were Model T's. As Ford wrote in his autobiography, "Any customer can have a car painted any colour that he wants so long as it is black"
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Unread postAuthor: SPG » Mon Jan 21, 2008 6:54 am

potatoflinger wrote:I was referring to the original post where I said that newer cars are more efficient, but have less power than most older cars.


Oh, OK, well Ok maybe for US built cars, but not of course Ok for anything European, where the quest is to get the greatest efficiency and more power ot of a given engine capacity.

But that's cos our fuel's much more expensive, so we need to burn it wisely.

Interestingly, and to bring this slightly back on topic, that mindset seems to show up in spudgunning. If you look at a lot of euro-spudguns, it's all about max power out of small size, and using the energy source as efficiently as possible - whether compressed air or combustion gases. JSR's quest for an auto-BB being a fine example, he's not happy with a cloud or vortex because of their inherant wastefulness; he wants something which uses the air sparingly.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 21, 2008 7:50 am

If you look at a lot of euro-spudguns, it's all about max power out of small size, and using the energy source as efficiently as possible - whether compressed air or combustion gases. JSR's quest for an auto-BB being a fine example, he's not happy with a cloud or vortex because of their inherant wastefulness; he wants something which uses the air sparingly.


So true, this cultural rift is something I noticed very early on in Spudtech and the same applies here.
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Unread postAuthor: Hotwired » Mon Jan 21, 2008 7:52 am

I can't help feeling economics and legality have major parts to play in it.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 21, 2008 8:01 am

Hotwired wrote:I can't help feeling economics and legality have major parts to play in it.


I think it's more of an attitude issue - compare American muscle cars to their European equivalents, the former generally tend to get their oomph from massively overpowered engines, while the latter use more modest powerplants but are lighter to make better use of available horsepower.
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Unread postAuthor: SPG » Mon Jan 21, 2008 12:14 pm

Although of course I'd actually say a lot of American cars use massively underpowered engines, for their cubic capacity. You only have to look at the bhp/cubic inch figures of American and European cars to see the difference.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 21, 2008 2:02 pm

Back to the subject of this thread, I ran three mags through my CB-625 from a 200 bar fill, data in feet per second for 16 grain JSB exact pellets:

907, 906, 906, 905, 900, 904, 900, 902, 899, 896, 894, 889

896, 892, 891, 886, 887, 881, 878, 876, 875, 866, 863, 863

862, 860, 852, 847, 846, 841, 833, 826, 820, 815, 809, 805

Not bad at all, the first magazine has an extremely low shot-to-shot variation, can't wait to test out the accuracy potential once I get bored of dumping mags in a couple of seconds :D
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Unread postAuthor: Antonio » Fri Jan 25, 2008 5:48 pm

Brian the brain wrote:Nope.

When the reservoir has the volume to keep the barrel behind the projectile at maximum pressure, the projectile will travel faster, but as the projectile leaves the barrel, a lot of gas will be wasted.

In that sence, it is much less efficient.

I choose power ( hence the sawed-off at 23 bar) over air efficiency


I dont think it has to do with pure pressure. I have noticed that the speed the valve opens is more important> acceleration of the valve. An efficient gun to my build experience has a fast opening acceleration and short dwell time. A waste of gas can be caused by a long dwell time (too long) or bc of slow opening accel of the valve. Hey Jack I think u could fix up this gun if its not too expensive. I am not sure how this gun works, but a lighter hammer would make it more efficient. Maybe a stronger valve spring for a shorter dwell time. Of course change one at a time :) Nice airgun btw

jackssmirkingrevenge wrote:Back to the subject of this thread, I ran three mags through my CB-625 from a 200 bar fill, data in feet per second for 16 grain JSB exact pellets:

907, 906, 906, 905, 900, 904, 900, 902, 899, 896, 894, 889

896, 892, 891, 886, 887, 881, 878, 876, 875, 866, 863, 863

862, 860, 852, 847, 846, 841, 833, 826, 820, 815, 809, 805

Not bad at all, the first magazine has an extremely low shot-to-shot variation, can't wait to test out the accuracy potential once I get bored of dumping mags in a couple of seconds :D

Hey jack if you have some time could you please test how close my chronmethod is to ur chronograph measurements? If you send me the raw data if would be fine as well. I would like to add a correction factor to the formula used. thnx
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 26, 2008 6:37 am

ant wrote:Hey jack if you have some time could you please test how close my chronmethod is to ur chronograph measurements?


I could do that, just need some empty house time as projectiles flying in the vicinity of the PC don't go down too kindly around here :roll:
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Unread postAuthor: Antonio » Sat Jan 26, 2008 7:44 am

jackssmirkingrevenge wrote:
ant wrote:Hey jack if you have some time could you please test how close my chronmethod is to ur chronograph measurements?


I could do that, just need some empty house time as projectiles flying in the vicinity of the PC don't go down too kindly around here :roll:


Btw its better to do it outdoors> if you have the option. I used about 4-5 meters of my garden. If you do it inside its a bit harder as u get more echo but thats also depended on the type of airgun. Btw if you shoot in a box most airgun going around 400m/s (0.12-0.2g balls) will get stuck in the second wall this way the balls dont fly all over the place.
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Unread postAuthor: Sticky_Tape » Fri Feb 01, 2008 2:23 pm

That`s why you don`t need to make a sniper rifle...
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 29, 2008 3:21 pm

Just though I'd show off some upgrades, I fitted my Harris bipod an a massive 8.5-35x52 Simalux scope :D

Image


Image


Image


Image


And here's a 4 shot group shot at 120 yards, a little to the right because of a crosswind but 2 inches at that distance is pretty good for an airgun :D

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Last edited by jackssmirkingrevenge on Fri Feb 29, 2008 3:24 pm, edited 1 time in total.
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