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Post by Nactan on Dec 31, 2009 1:43:06 GMT -5
I have a question regarding the location of the oval like cylinder hole. From what I have gathered on this forum the hole is used "...to provide consistency in the compression of the air inside..." the cylinder. (Slapjack, SRC G36 low FPS) Also, "The volume of the cylinder and the volume of the barrel need to be matched..." which is somehow related to the location of the hole. (Knief, accuracy issues with CA mp5sd) So...what does this all mean? Exactly how does the cylinder hole work? Does this cause a decrease in pressure and FPS? Sorry if these are stupid questions.
Thanks
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Post by Knief on Dec 31, 2009 7:43:15 GMT -5
The hole in the cylinder essentially reduces the volume of the cylinder. As the piston begins to move through the cylinder, the holes allow air to escape before it can exert pressure on the bb through the nozzle. However, once the piston passes the holes, the air can only be driven out through the nozzle, and thus, be directed behind the bb. So, the hole in the cylinder is a way to "shorten" the cylinder to match the barrel length of a short barreled gun without actually shortening the body of the cylinder (so as to keep as many parts interchangeable between gearboxes as possible).
If they didn't do this, MP5s would require drastically different gearboxes than G3s, for example. But that would be pretty ridiculous from a production standpoint, since both guns have pretty much the same lower receiver, aside from the magwells and stock attachment. So instead, the manufacturer can just produce one part with a minor variation for each gun instead of designing a whole new gearbox with different length pistons and cylinders, and probably different gear set ups and springs to boot.
The function of the cylinder hole is to maintain minimum pressure on the bb until the piston is at top speed, and can exert the most pressure possible. Without the cylinder hole in a short barreled gun, the bb would be pushed out of the barrel before the piston was more than halfway through its forward cycle. According to the dynamics of springs, the piston is at its top speed at the end of its forward cycle (since the spring has pushed it, and is still pushing it the whole way). When the piston is moving faster, it can "hit" the air harder, which in turn, can "hit" the bb harder. This, of course, translates to a higher bb velocity in a short barreled gun, compared to another short barreled gun with a non-ported cylinder. The short answer is, it does cause a decrease in pressure, but only initially, and only when it doesn't matter. That decrease in pressure results in an increase in pressure later.
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Post by BoredKender on Dec 31, 2009 10:14:39 GMT -5
Lemme see if I can phrase it a little more simply than Knief...
With a full cylinder (non-hole) on a short barreled AEG the air built up inside the cylinder would push out the BB too early, before it can reach maximum compression. Longer-barreled AEG's, however, need the extra air volume from the cylinder to push the BB completely out of the barrel with out dragging. This is why MP5K's have a hole half-way through the cylinder and M16's have full cylinders.
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Post by Nactan on Dec 31, 2009 15:50:32 GMT -5
OK thank you very much. I appreciate your time and willingness to explain this to me...I hope this wasn't a common n00b question. So...I guess you can close this thread...?
Thank you.
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Post by BoredKender on Dec 31, 2009 15:52:19 GMT -5
No point in closing informational threads. Someone else in the future may have another question regarding the topic.
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Post by Knief on Dec 31, 2009 18:28:30 GMT -5
And it definitely wasn't a noob question. A lot of people don't think about this question for a while, and some vets wouldn't know the answer.
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Post by BoredKender on Dec 31, 2009 23:14:08 GMT -5
Knief- Worthy of a "Pro Tip" move?
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