Tuning BAR per shot

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Sell682

Sell682

Member
Nov 30, 2017
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NJ, United States
Hello All,

I seen a lot of discussion on efficiency and tuning to get the best harmonic sound and pellet velocity. 


Has anyone determined how many Bar per shot is considered efficient? I would assume it would be relative to Reg/ hammer and valve but taking into consideration there has to be a point of let’s say 1 bar per shot is more effective than 2 bar per shot getting the same velocity for a pellet. Maybe I am wrong and just thinking out loud and wonder if anyone else went down that rabbit hole. 
 
It's great to see an airgunner asking an important question related to the actual science and mechanics of the sport. These use to be the most common topics of discussion in years past on various forums. If you really want some 'nerdy' knowledge, check out Bob Stearns and Lloyd Sikes page over at the GTA forum. There is a lot of info over there but you do have to look for it.
 
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Following Gregor's video on the Prophet I have mine set at 130 bar, turned up the hammer spring until the FPS maxed out, then turned the hammer spring back until the FPS dropped about 30 fps. Per him that's peak efficiency. Shooting 18 grain pellets I got 126 shots and the bottle went from 290 to 140 bar. So 1.19 bar per shot. Useless for anyone else though.

FYI I'm averaging 1028 fps at that setting and very accurate. 
 
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off the cuff , most guns fall into the 1 bar per shot to 2 bar per shot. now the whammy is power . A good number of guns suck down the air but yield good power. you can also tune some guns down to lower power and increase shot count by 50%. A direct inverse ratio. some guns suck down the air regardless of power setting. Currently ,as far as I know , 1.5 bar per high power shot is about as good as it gets. you can't bitch about that. Now in a year or two? who knows.
 
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Remember if you use this calculator for bottle guns, the air volume is easy, it’s the size of your air bottle. 480cc being the most common. If you have a regulated tube gun, you need to use the volume on the high pressure side of the regulator, NOT the overall tube volume. This allows apples to apples efficiency comparisons with bottle guns.

Actual pressure (bar) drop per shot tells you absolutely nothing unless you are comparing the exact same guns shooting at the exact same power with the exact same pellet/slug…
 
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This came watching Steve’s AEAC video about wasted air around the pellets. I would assume there has to be a point where shot bar per FT you hit that happy point. I can see a person shooting x-pellet at x-speed and then another person who has the same gun and setup and has less shots so one is not configured properly… people say tune by sound … my hearing isn’t what it used to be with powder burners lol
 
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Seems IF...pressure accuracy is your question, and accuracy is the goal, measuring in "BAR" is mostly useless. It's much too gross a value.

1 BAR = 14.5 PSI

That's a big difference if you are looking for pressure accuracy. Plus, even using BAR as the value desired measurement, the tiny gauges that we all use are...useless at measuring BAR in "fine" terms ! I see one note above saying "1.5 BAR". Just how do you know that it isn't "really 1.4 or 1.6 BAR ? Again, the little gauges are NOT fine enough to tell you. I also doubt that they are very accurate when "scaled down" to show .5 or EVEN 1 BAR..!

If you REALLY, TRULY want pressure accuracy, you need to plumb in a quality, 2" dia., gauge reading PSI, into the system. THEN...you can talk "true" pressure values.

OR..."best guess", using the little toy gauges that all of our guns use.



Mike
 
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Following Gregor's video on the Prophet I have mine set at 130 bar, turned up the hammer spring until the FPS maxed out, then turned the hammer spring back until the FPS dropped about 30 fps. Per him that's peak efficiency.
Click to expand...

Just to clarify, this state of tune does not yield peak efficiency, but decent efficiency with optimal consistency (low extreme spread).

Higher efficiency can be obtained with less hammer strike but the ES will suffer.
 
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Hi All,

I started investigating the sikes calculator a few weeks ago. I'd have to say that I've still got work to do.

Nervoustrig's mention of the low hst giving less stable velocity but better efficiency has been evident looking at my data. The best stability is not even close to the best efficiency configuration. (Target vs. taking friends out plinking set-ups)

I've examined two Lelya 2.0 in 22 and a R5M Long in 177. The best efficiency has been with a "stock" configuration Lelya 2.0/22 with the hst dialed back. It shoots roughly 1.24 fpe/cuin per shot (13.2 bar-cc/fpe per shot). The R5M Long/177 (which I thought would be pretty good) is only 1.1 fpe/cuin per shot (15.3 bar-cc/fpe per shot).

Per my reading the transfer ports on the R5M Long are oversize for lower power shooting. In the near future I plan to make some parts to reduce the diameter of the transfer port path to something closer to or less than pellet diameter. It will be interesting to see if that increases the efficiency substantially.

I've not been able to hit the higher efficiency numbers mentioned on the calculator link. The next gun for testing is an HW100/177 with a 600mm barrel. It should be intersting.

Great hobby,

Nugria
 
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