• GBBR. AKA (Gas Blow Back Rifles)
    125 replies, posted
[QUOTE=The Slick;24629867]Venom, you're right. Kinda. Basically, it is like throwing a sheet of paper as opposed to a sheet of steel- the paper (like a .12) will go nowhere. A sheet of steel (which could be anything from .2 to .4, depending on the gun, snipers really only covering that top part) will go farther, in a straighter line. That's obviously your best bet. But if you get too heavy, say... a sheet of lead, you're not throwing it anywhere usable anymore, that's when you have too heavy bb's. Depends on the gun set up, more than anything.[/QUOTE] Yeah, that's exactly what I was thinking.
There's some concerns in the blowback community that using heavier bbs can cheat the chrono in a number of ways on GBBRs. One concern was that it's a gas that's expanding inside the barrel, not just air being pushed through the barrel like an AEG or springer. With a heavier bb, it moves slower through the barrel, allowing the gas to expand further and thus increase the finally velocity even more. Some worry that it would have more kinetic energy as well due to this gas expansion. I'll be putting this theory to the test when I get some heavier bbs. I'll use the chrono to get the results of 10 shots of .20g, .25g and something heavier. After taking the average I'll calculate the theoretical force the bb should have exiting the barrel, and see if they match up. If they don't match up, then this gas expansion effect has some merit to it.
:science: Science!!
[QUOTE=xXEnder007Xx;24633115]There's some concerns in the blowback community that using heavier bbs can cheat the chrono in a number of ways on GBBRs. One concern was that it's a gas that's expanding inside the barrel, not just air being pushed through the barrel like an AEG or springer. With a heavier bb, it moves slower through the barrel, allowing the gas to expand further and thus increase the finally velocity even more. Some worry that it would have more kinetic energy as well due to this gas expansion.[/QUOTE] Not sure if I fully understand, do chrono's have an issue with GBBR's? Or is it [I]because[/I] of the fact that gases expanding use a more gradual force? Couldn't this be easily remedied by just using the Chrono's with the two metal hoops for GBBR's?
The problem is this. Most fields make you chrono with .20g bbs. Then you can use any heavier bbs you want and the kinetic energy should be more or less the same. With a GBBR, they believe using heavier bbs will cause an increase in kinetic energy due to the gas expansion. It will still chrono lower, but the bbs are hitting with more force, causing potential safety issues, especially the WE M14 which is shooting right around the 390-400fps mark.
I thought kinetic energy was directly related to the mass and velocity of the projectile? If I remember from my Grade 10 basic physics, it was something like: Ek = ½mv² Where Kinetic Energy is equal to half of the object's mass multiplied by velocity squared. Correct me if I'm wrong, but unless the BB's actually have a higher velocity than what's being chrono'd, the Ek should remain the same. [editline]04:19PM[/editline] Sorry if I completely butchered that formula, it's been a while since I've done any sort of physics equations.
ITT: We act like scientists.
[QUOTE=FPKawaii;24655434]ITT: We act like scientists.[/QUOTE] ITT: I sit here dumbfounded.
[QUOTE=FPKawaii;24655434]ITT: We act like scientists.[/QUOTE] :science: Haha, I'm just trying to find an answer since I'm curious. Plus, because I don't have a Chrono to actually test, I thought I'd actually try to apply what I've learned in school, since just about nothing else I've learned applies to anything.
[QUOTE=facepuke;24655558]ITT: I sit here dumbfounded.[/QUOTE]
Well let me just make a quick example of what should happen. Lets say when using .25g bbs, the velocity increased an extra 5FPS compared to that of an AEG. Lets assume this is due to the heavier bb taking a longer time to exit the barrel, thus building up the expanding gas pressure behind it. [IMG]http://a.imageshack.us/img265/2030/fpschronotest.jpg[/IMG] Keep in mind the FPS readings are made up numbers. Though I did calculate on the AEG what the FPS should be for a .25g bb if it hits with the same KE as a .20g bb, and it looks more or less correct. When I get around to chronoing it the results will be entered in a similar format. Fuck making me do physics again and I'm not even back in school yet lol.
-snip- I get it now. Rate me books for not reading correctly. So, relative in BB weight, AEG's with light BB's = Higher muzzle velocity because of less weight, more of an arc because of low inertia (less range) AEG's with heavy BB's = Lower muzzle velocity because of more weight, less of an arc because of higher inertia (more range) and GBBR's with light BB's (relative to below) = Lower muzzle velocity because of less weight, more of an arc because of low inertia (less range) GBBR's with heavy BB's = Higher muzzle velocity because of more weight, less of an arc because of higher inertia (more range) Is that right?
Arc can't really be factored in, as we have hop-up. It's more like AEG w/ .20g = Higher FPS, same impact force as .25g AEG w/ .25g = Lower FPS, same impact force as .20g, less affected by wind due to more inertia GBBR w/ .20g = Highers FPS, less impact force than .25g GBBR w/ .25g = Lower FPS, Higher impact force due to gas expansion, less affected by wind due to more inerita
Well, I mean best possible arc. Wait what, heavier BB's in a GBBR have slower muzzle velocity? How does it have higher Ek then? HNNGGG :psyduck:
My mind is full of confuse. :psyduck:
My head might explode. I'm so glad I'm taking biology and chemistry instead of physics.
I'm in AP Bio, my book weighs about as much as an M4.
Ap physics is busting my balls right now. It's getting easier but it's still hard.
That's what you get for taking Ap Physics.
I'm terrible at math so I would fucking die in physics.
Taking Physics 1A in college in a couple of weeks. Going to be a bitch relearning it using Calculus this time around. Being an Engineering Major can be a royal pain in the ass when it comes to classes.
What kind of engineer? My Dads a Civil Engineer.
Going for Mechanical, but nowadays it's best if you know electronics and programming along with it. If it doesn't work out for me I always got machining to fall back on.
That's pretty cool, but I don't know how you'll manage to fit in any programming in there. At most colleges I've seen, they share very few, if any, courses. Electronics I can understand. I'm going for Computer Science and Video Game Design, assuming I get accepted to the places that have both. But I think I have pretty good chances.
[QUOTE=Newbienice99;24676875]That's pretty cool, but I don't know how you'll manage to fit in any programming in there. At most colleges I've seen, they share very few, if any, courses. Electronics I can understand. I'm going for Computer Science and Video Game Design, assuming I get accepted to the places that have both. But I think I have pretty good chances.[/QUOTE] I was interested in going into the vidya game design industry but it is really difficult to get into.
That's why I'm making sure I get a degree in Computer Science as well. It's a very reliable backup plan, plus a crap ton of vidya game programming classes count as Computer science credits.
I actually enjoy doing Physics, I kinda wish my school offered some sort of Physics AP. But Chem is still my favorite science.
I can't wait until we do particle physics, I am really into that.
[QUOTE=xXEnder007Xx;24676715]Going for Mechanical, but nowadays it's best if you know electronics and programming along with it. If it doesn't work out for me I always got machining to fall back on.[/QUOTE] Cool, I was planning to do Mechanical Engineering when I get to college too.
Well, I've probably already said it, but I'm going into medicine.
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