Arnie Posted February 28, 2005 Report Share Posted February 28, 2005 Please post your comments here about the article entitled "FPS, Distance and Time .20 vs .25" Written by Zinger 084 here. Thanks folks Quote Link to post Share on other sites
Marlowe Posted March 18, 2005 Report Share Posted March 18, 2005 I have to say, good work Zinger. I found the article quite informative, not being particularly adept in the fields of mathematics or physics myself, and I have been wondering what realistic changes I would see in using .25s.... Quote Link to post Share on other sites
RedDog Posted March 18, 2005 Report Share Posted March 18, 2005 Zinger, well done on a very informative and well thought out article. I have one point that I thought might be worth raising. You say that only cross-sectional area has an affect on drag and hop-up does not. I seem to remember (from aerodynamics lectures many years ago) that drag is made up of (at least) two components - form drag (= cross sectional area) and "lift" drag (depending on how much aerodynamic lift a body is producing). The hop-up, by back-spinning the bb, causes the bb to generate its own lift - the amount of lift depending on the speed of rotation (amount of hop). The more lift, the more extra drag. For a straight flightpath, you would guess a .25 bb would need more lift (= drag) since it it heavier. This might slant the results for .25 more towards those for .20 if hop is used - but it would be difficult to say by how much. Let's hope someone can do some practical trials on this one day - or even theoretical work (since it is possible to calculate the lift produced by a rotating spherical body). One thing is for sure, your article has opened an interesting debate! RedDog Quote Link to post Share on other sites
Arnie Posted April 2, 2005 Author Report Share Posted April 2, 2005 It'd be great if someone did some practical tests that compared range and accuracy to known barrel lengths too. Quote Link to post Share on other sites
g-force Posted May 21, 2005 Report Share Posted May 21, 2005 Nice article !! Quote Link to post Share on other sites
Connery Posted May 25, 2005 Report Share Posted May 25, 2005 You did NOT just post that, g-force... Quote Link to post Share on other sites
ctitanic Posted June 21, 2005 Report Share Posted June 21, 2005 (edited) It'd be great if someone did some practical tests that compared range and accuracy to known barrel lengths too. <{POST_SNAPBACK}> I wonder if somebody has done that already. Edited June 21, 2005 by ctitanic Quote Link to post Share on other sites
Joefahey Posted July 7, 2005 Report Share Posted July 7, 2005 I found it suprising, very helpful however! Quote Link to post Share on other sites
The Bushman Posted July 8, 2005 Report Share Posted July 8, 2005 well interesting, but it is all on paper, isn't it? I am going to sort this out once and for all this summer! I have a high quality CHRONO and access to a sheltered shooting range with unlimited distance. Once I get some 0.25g (need some for pending VSR) then I will fire my different guns (got plenty) at the chrono from all different ranges (in a prone braced position and record the amount of hits (shots logged) and the velocity. Then I will be able to corelate the data on a similar table, to that in the article. Will not be able to record time taken though, although the data from the chrono will help establish this (fps). Personally, I have always favoured the 0.20g over the heavy 0.25g just because the trajectory is flatter for longer. (personally I often set my HOP high and like the pellet to lift up before it drops off, as we often fire at extreme range here.) I find the 0.25g are great at penetrating cover, while 0.20g can be deflected easily. This high hop setting can slow the pellets down and they float at the end of their flight. But hey, I maybe proven wrong........ Will report back when the testing is complete........ will also look at APS ammo (I have 0.30g MARUZEN and 0.36g STRAIGHT) and the new TM AEP GLOCK18C with 0.20g will prove interesting due to it's low power (I think this will suprise many of you.) This particular gun will prove very interesting next to a high end sniper rifle and full size AEG's. Also comparing a short barrel with a long barrelled AEG (Spetznaz vs SUPERMAS) (just remembered) We have a stockpile of EXCEL 0.23g ammo and will be testing these alongside the TM 0.20g and 0.25g. These mid weights are not widely used but have proven popular with some ultra short AEG barrel users (MP5K and PDW). I'll try to get together as many different Airsoft guns as possible and make a massive table to be able to compare the results. Have access to these toys so far: electrics.... TM CAR 15 TM MP5 PDW TM BETA SPETZ TM SUPERMAS TM FAMAS (non Hop, bought in '91) pistols.... TM 1911A1 spring hop pistol TM AEP GLOCK 18C TM Hard Kick DE GBB TM M92f BERRETTA GBB shotties.... TM SPAS 12 shotgun Maruzen cutdown shotgun (cannot remember name) ITHACA M37 shotgun sniper rifles.... Maruzen APS2 MK2 SPORTER TM VSR 10 Gspec So 4 different categories. Will probably fire 5 rounds with each gun at each range. Repeating for each pellet weight. Noting amount of hits on a target just behind the chrono (Target size will be approx chest size, will measure it for test.) Ranges fired from 5m, 10m, 15m, 20m, 25m, 30m, 35m, 40m, 45m, 50m, 55m, 60m. Weather conditions will be noted too. Looking forward to a whole weekend at the range now........ will be in AUGUST '05 when I do this. I'll try and make some videos while I'm there to show the test area (with windsock) to provide evidence for my findings. Interesting for us all to finally see the answer to the riddle? Quote Link to post Share on other sites
Phreakish Posted March 28, 2006 Report Share Posted March 28, 2006 coming from someone in aerospace: hop DOES and WILL make drag - lift makes drag - this is due to many things, but mostly just the direction in which the lift is applied, its not straight up, but canted back and this rearward component increases the drag slightly. Skin friction, reynolds number, velocity, cross sectional area, fineness ratio, all affect the drag produced - and a round BB is NOT the greatest projectile, very hard to consistently produce the same results and flight path - I've always been amazed at how well these guns actually work... Quote Link to post Share on other sites
rallymad_nad Posted May 1, 2006 Report Share Posted May 1, 2006 After shooting on a sheltered range with .2's and .25's in a modified VSR, the .25's did travel the last leg flatter and you could hear that when they hit the target they had a lot more force behind them still. I would have liked to try this in the AEG's but didnt have enough ammo. L8rs Nad Quote Link to post Share on other sites
MRab2 Posted May 13, 2006 Report Share Posted May 13, 2006 (edited) coming from someone in aerospace: hop DOES and WILL make drag - lift makes drag - this is due to many things, but mostly just the direction in which the lift is applied, its not straight up, but canted back and this rearward component increases the drag slightly. Skin friction, reynolds number, velocity, cross sectional area, fineness ratio, all affect the drag produced - and a round BB is NOT the greatest projectile, very hard to consistently produce the same results and flight path - I've always been amazed at how well these guns actually work... <{POST_SNAPBACK}> Not in the aerospace industry myself but did study engineering and thermodynamics/fluid mechanics and concur with the above statement. Drag isn't merely the result of cross-sectional area but also a result of a partial vacuum that forms behind the object as it travels. Hop, or backspin will change the characterstics of the vacuum behind the BB and thus the drag. The obvious example is golf balls, which also exhibit backspin in flight and are dimpled to help the ball "pump" (for lack of a better word) the air around itself and reduce the vacuum. At one point in golf's history a golf ball with outward dimples was produced and almost immediately banned as they went like rocket-ships The company that 1st produces economical dimpled BBs is going to make a fortune Edited May 13, 2006 by MRab2 Quote Link to post Share on other sites
littlejerry Posted March 23, 2007 Report Share Posted March 23, 2007 Not in the aerospace industry myself but did study engineering and thermodynamics/fluid mechanics and concur with the above statement. Drag isn't merely the result of cross-sectional area but also a result of a partial vacuum that forms behind the object as it travels. Hop, or backspin will change the characterstics of the vacuum behind the BB and thus the drag. The obvious example is golf balls, which also exhibit backspin in flight and are dimpled to help the ball "pump" (for lack of a better word) the air around itself and reduce the vacuum. At one point in golf's history a golf ball with outward dimples was produced and almost immediately banned as they went like rocket-ships The company that 1st produces economical dimpled BBs is going to make a fortune <{POST_SNAPBACK}> Hmm.. I work in an R&D firm and have access to a 3D printer. Might have to model up a dimpled sphere and print out a few as a test. Gotta wait until the boss man is out of town though. Quote Link to post Share on other sites
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