2nd Bat
Master sergeant
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Post by 2nd Bat on Dec 17, 2012 0:58:08 GMT -5
In trying to comprehend why (in some circumstances) a heavier BB achieves greater velocity than a lighter one when fired from the same gas gun, here is the explanation: The heavier bb initially starts slower than the lighter bb once launched INSIDE the barrel. Because it remains inside the barrel longer, MORE accumulated pressure is generated behind the BB prior to its departure from the muzzle. As you know a .36 gram bb travelling at 350 FPS has far more inertia and far more destructive power than a .20 gram bb travelling at the same speed. Thats why chronoing a gas gun with a bb weight different than what is actually going to be used is actually quite meaningless. There are tables that will provide comparative jouelles for assorted weight bbs at varied velocities.
For a truly consistent chrono station you need to establish what Jouel rate is acceptable for the assorted weapon types (semi auto, bolt actions and full auto) and then have folks chrono using the bbs they actually use. For 90% of the players using 20 grams for chrono will tell you what you need to know. For gas guns using 20 gram it can be completely misleading and in fact dangerous.
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Post by Rekkon on Dec 18, 2012 14:07:03 GMT -5
I had a local player report seeing inconsistent energy levels for differing BB weights in his AEG, so I do not think this issue is unique to gas guns. The difference may just be quantitative rather than qualitative since a piston is still pushing a volume of gas. I have meant to sit down and see what data I could collect from an actual test, I have just been too lazy. It would be interesting to see if this bit of conventional airsoft wisdom actually holds up.
I do not think a heavier BB can actually achieve an equal or greater velocity than a lighter BB in the same weapon, but I could potentially see it accumulating more energy. Even assuming there is an energy increase for heavier BBs, I was dubious the difference could make the difference between "safe" and "dangerous," so I looked up the Z87.1 impact standards, which involve an impact of about 3.05 Joules. A .20g BB travelling at 400 FPS is a little under 1.5 J. To get to 3 J, a .20g BB has to be travelling approximately 571 FPS. The sniper limit at many fields is 550 FPS, so not much variation would be needed to generate a greater than 3 J impact. Obviously our eyewear is unlikely to fail catastrophically at 3.06 Joules of impact, but exceeding the rated impact standard is at best a gray area we do not want to enter. Of course the above assumes that the operator is ignoring minimum engagement limits and shoots someone point blank. That seems rather unlikely, and ignoring field rules is unsafe in any number of ways.
A number of chronos will calculate muzzle energy for you, as long as you tell it what weight BB is being used (mine has this option). The problem, as always, is FPS cheating. An unscrupulous player can always say they are using lighter BB than they actually are, and it is impractical to actually weigh everyone's ammo. This means the chrono station either has to stock a bunch of different BB weights or use a single weight with fixed velocity limits and assume energy does not fluctuate appreciably. An alternate idea might be to switch the standard chrono BB weight from .20g to something heavier and calculate new acceptable FPS standards (the Lion Claws serious uses .25s). If muzzle energy really does increase with BB weight, anything that chronos fine with a heavy BB should be fine when switched to a lower one. The only downside is that heavier BBs are more expensive. Ultimately this is probably unnecessary. A whole lot of airsoft has been played with gas guns for a long time without something causing a dramatic reexamination of the safety standards.
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2nd Bat
Master sergeant
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Post by 2nd Bat on Dec 19, 2012 0:31:46 GMT -5
It was way back at an earlier Lion Claws that this gas gun, heavier BB issue came up. along with what back then was chronic efforts to skirt the chrono regs. Anything folks might try they did. tape in the barrels. Heavily oiled barrels. Crazy stuff. Since then Lion Claws Chrono staff use their BBs and runs a rod down the barrel, tests with no hop up etc.
The phenomenon with heavier BBs is absolute fact though not universal in all guns under all circumstances. The deviation in jouelles is pronounced. One of the guns the chrono marshall tested showed the equivalent of 720 FPS with 20 grams when 36s were used. It however passed chrono with 20 grams coming in at 530 or so. He was by rule allowed to play but not someone you wanted to get shot by. In California terrain the engagement ranges are often quite far apart so not really an issue. I know back when i had a marushin gbb garand the heavier bbs shot at a higher fps than the lighter ones by quite a bit.
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Post by jimmiroquai on Dec 19, 2012 18:17:31 GMT -5
Gas guns use gases that expand. Heavier bbs have more inertia, giving the gas more time to expand, thus making the shot more powerful. AEGs and springers on the other hand, use compressed air and thus no additional expansion occurs. AEGs are inconsistent because of the varying positions of the piston and the multiple potential leak areas.
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Post by Rekkon on Dec 20, 2012 11:39:21 GMT -5
You are listing reasons AEGs can be inconsistent, not claiming they are inconsistent, quiaff? How can piston position affect anything other than trigger response? It can only be released from the fully compressed position. 2nd Bat, I have no reason to doubt the claim, especially given your experience, but being a scientifically minded individual, I prefer to see data over anecdotes. I suppose I will have to run some more trials, though it may have to wait. I have an event next weekend, and there is a holiday or something this weekend. I also need to retract my previous statement regarding CO2. I checked the phase diagram, and it can be liquid at room temperature. For some reason I thought the triple point was higher. Whether this comes into play with the G&G mags would depend on the size of their expansion chambers and the pressure in the 8-grams. And finally, here is a nice chart for those that do not like to look at a bunch of numbers. I am hesitant to draw general conclusions regarding CO2 vs green gas given the limited nature of this trial (only one gun and one pass through four magazines) and the drastic performance difference. I know there are CO2 pistols with muzzle velocities much closer to their green gas counterparts, but I do not own any. There was also quite a bit of variation between magazines of the same type. For the green gas mags, I could assume they did not get filled to the same level, but the CO2 range makes me wonder if it was a magazine difference or consistency issues with the 8-grams themselves. There must be some reason all the high end GBB manufacturers tend toward green gas.
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2nd Bat
Master sergeant
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Post by 2nd Bat on Dec 20, 2012 17:55:57 GMT -5
I witnessed the tests with chrono on a multitude of assorted rifles using varied weight BBs. The pattern was quite pronounced in most (but not all) of the rifles tested. On my own Marushin Garands I tested assorted weight BBs in both rifles and the heavier .43 gram shot harder than the .34s that came with the guns. I have the data somewhere but it has been many many years. Both rifles being Marushin gas blow backs have long been relegated to non functional wall hangers and are long gone.
The fellow who conducted the Lions Claws testing and no doubt still has all the data is BBMAGNET who was quite well known on the Classic Airsoft site for many many years. I assume he is still kicking around somewhere?
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Ersatzjack
Corporal
"That silly Franz... he thinks we are winning."
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Post by Ersatzjack on Dec 20, 2012 20:11:45 GMT -5
I have an event next weekend, and there is a holiday or something this weekend. With this comment is it safe to say it's likely you'd not be a good candidate to include as part of a Christmas truce scenario? Interesting science experiment. You offer up some useful data.
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Ersatzjack
Corporal
"That silly Franz... he thinks we are winning."
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Post by Ersatzjack on Dec 20, 2012 20:12:41 GMT -5
The fellow who conducted the Lions Claws testing and no doubt still has all the data is BBMAGNET who was quite well known on the Classic Airsoft site for many many years. I assume he is still kicking around somewhere? Maybe not, with a name like BBMAGNET.
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Post by jimmiroquai on Dec 20, 2012 20:27:23 GMT -5
Rekkon, you are not alone in testing these things. And since we're being very specific with our constructive criticism, for your tests to be valid enough to form a conclusion, you would need a large, statistically significant sample size, otherwise, your test results will be limited to the the rifles you have on hand only and cannot be used as generalization. This is where all these "anecdotes" and all these reports from all around the world come in. There is such a thing called a cochrane review, or a meta analysis. If you care to, you can actually critically appraise all the data available and combine them statistically with yours to make a more meaningful study. In fact, over at the WW2 UK site, there is a thread in which a test was done on the GnG kar98 GG and CO2 mags, also with data. About the inconsistencies of the AEG, yes the piston releases once the sector gear clears the teeth but the varying positions of the piston will have an effect on potential energy, inertia, vibration, etc. Or you can just take any AEG (without an active breaking mosfet) and chrono it on semi. I come from a scientific background too. plus 20+ years of airsoft experience... But anyway...we're veering off topic. The GnG's stock was too rectangular and thick compared to my Tanaka which feels great in the hands...so i reprofiled the GnG stock. Feels less like i'm carrying a garand now.
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2nd Bat
Master sergeant
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Post by 2nd Bat on Dec 20, 2012 23:56:02 GMT -5
Interesting. Always great hear from someone who owns several brands of the same rifle.
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Post by Rekkon on Dec 21, 2012 12:16:44 GMT -5
Yes, I know. I minored in statistics. I just did not feel like running 31 additional tests for each magazine. It still would only have been a single rifle anyway. It would be nice if we could get a couple G980 owners together to set up a factorial experiment.
In any event, I found and plotted the UK green gas data. It is interesting that his lasted so much longer than mine. Perhaps it is the rifle or I was not filling mine to capacity or just my higher initial velocity consuming more gas. The consistent FPS spike on his first round of the second clip is also interesting. Too bad we do not know how he was handling the magazine while switching clips. My data had something similar, though less noticable. It could simply be the delay to change clips gave the gas more time to warm. I also made an effort not to jostle the mags more than necessary or invert them.
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volk
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Post by volk on Aug 29, 2013 2:26:44 GMT -5
Sorry fo reviving an old post, but i have a question regarding G&G K98. WIth mine i also have problems with low fps. On high power mag i get 270fps and on low power mag only 100fps. The gun has steel sear instaled. Did anyone have the same problem and how did you solve it?
Regards
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stuka
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Post by stuka on Aug 29, 2013 8:01:24 GMT -5
that seems strange, does it actually feel like its shooting that low?If so i'd try a different chrono.
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Post by brownien on Aug 29, 2013 9:28:45 GMT -5
It may not be the crono, the valve mech may have become stuck, causing it to operate slower than normal, or there is a broken lemon part in the hammer/valve assembly. But before you go ripping it apart and ordering new parts, try to check over all the o-rings and rubbers to make sure none are torn or missing. Use some silicone oil to relive everything liberally, as long as everything's intact. I don't have one of these guns, but from my time with my gbb m1911a1, I'm guessing its either a bad seal, or a sticking/ broken valve.
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Post by <2>nd Rangers M/Sgt. Tom on Dec 19, 2013 16:10:42 GMT -5
I found a method to for getting a jammed c02 cartridge out of a G&G k98 clip.I noticed at the bottom of the clip there is a hex screw, at first i thought it was a bleeder hole to prevent suction in the tube. However upon loosening the screw it allowed me to slide off the bottom plate. This revealed a hole which i was able to fit a small screwdriver into which helped me to loosen the co2 cartridge. Once it was loose i then dropped the clip onto a dounble layered carpet twice from about a foot and a half off the ground; BAM it slide out!
P.S. I will be adding pics and more gun and gear repairs to the repair section.
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2nd Bat
Master sergeant
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Post by 2nd Bat on Sept 16, 2015 0:03:06 GMT -5
So with these now out for a couple years and hopefully with the initial teething problems solved. What are peoples long term experiences with these GnG bolties?
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Post by hennepin15 on Aug 31, 2016 15:15:10 GMT -5
Does anybody have experience with a G&G G980 that was manufactured recently? I am thinking about purchasing one since I cannot find a Bar98k. From research I've heard newer production models have increased magazine reliability and more steel parts in the gun itself. Hopefully the research is true because the gun looks great. I'm just 4 years late in buying one.
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2nd Bat
Master sergeant
Posts: 11,813
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Post by 2nd Bat on Aug 31, 2016 16:41:20 GMT -5
The reality is that waiting a while before purchasing a newly introduced offering is probably not a bad idea. Manufacturers often make adaptations and improvements based on customers experiences. It would be great to know on not just the G980 but other WW2 releases.
I usually rush out and buy every newly released WW2 weapons and have often paid the price of being "bleeding edge" instead of "cutting edge".
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G&G Kar98k
Sept 14, 2016 13:09:39 GMT -5
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Post by hennepin15 on Sept 14, 2016 13:09:39 GMT -5
Earlier in the thread an external air source was mentioned. Maybe that is the key to reliability that you were looking for 2nd bat. The good part is you only have to use one magazine, but speed loading every 9 rounds sounds like a pain. As long as the gun itself doesn't have problems, mag inconsistency would be fixed. I pmed the guy to see how his performed after 1000 shots.
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2nd Bat
Master sergeant
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Post by 2nd Bat on Sept 14, 2016 19:13:00 GMT -5
I know external gas solves many of the chronic issues associated with gas guns but the notion of a tube routed from a gun to a tank stored somewhere to lug around has no appeal to me whatsoever. I might consider it for a crew served weapons but not a personal weapon.
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