Counter intuitive or obvious: why lower pressure is faster?
So here’s the deal, I adjusted my regulator (from jdsairman) down to 1776 psi from 1960 which was down from the original 2100 that I specified when I bought it.
I selected this new air pressure after shooting down the bottle until my trajectory started to drop, which occurred around 1600 psi. 1776 was the closest without going below that number.
Now for the part that has me amazed: At 1960 psi the trajectory began dropping when the power wheel was below about 4 plus or minus a couple of minor points. With the psi now at 1776 the trajectory is still at it’s flattest with the power wheel at 1.0 or even the little below that setting that you can drop down on the wheel. So less spring force applied to the hammer gets better results.
The only thing that I can figure out is that the pressure holding the valve shut is now much lower and therefore less force is required to open it.
Just to fill in the blanks, it is a spinloc Condor with a .22 12″ barrel.
I’m going to remove the Condor hammer weight to see if I can get enough adjustment to have some room to work with.
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Nothing the matter with that!
Mrnewbie, thanks for the laugh:
I didn’t catch that the first read through and just about wet myself laughing when I caught it the second time through.
The close one…U picked 35 yards…then goes 1/2″ or so high from 40-50 then comes back down at whatever..lets guess at 55 or so.
ALWAYS use the far..outer intersection point, then adjust for perfection.
If you want 35..then site in at the 55..and adust from there
I don’t think that technique will work for me. My longest shot will never be more than 50 yards due to the dense forest that I live in. And that makes the point “Kill Zone” just two small points at either intersection on the trajectory. If I use the 35 yard “Zero Range” then my 1.00″ “Kill Zone” is from 18 yards to 40 yards which is more practical I think for my hunting purposes.
The curve intersects at 2 points..
The close one…U picked 35 yards…then goes 1/2″ or so high from 40-50 then comes back down at whatever..lets guess at 55 or so.
ALWAYS use the far..outer intersection point, then adjust for perfection.
If you want 35..then site in at the 55..and adust from there
I set my LONGER one at 41 yards…thats the size of my yard.. the shorter one intersects at about 20 yards
so…10 to 15 I aim high, 15-30..dead on, 30 to 35..1/2″ low, 35-45..dead on, farther than 45..aim high…
But you should not listen to me…I can’t hit shit! 😆 😆
Doug, thanks for the link to the post on the reg plenum combo. That is some slick work. I’ll have to think on that for a long time. I would guess that my use of the CO2 adapter to connect my reg to the valve does much the same thing just not as big or as cool. But that’s just a guess.
Mrnewbie, in chairgun, in the box labeled “Zero Range”, what value are you using? When I plug in 35 yards, no matter what “Muzzle Velocity” I plug in it is 0,00 at 35 yards; and the point where it crosses through 0.00 on the rifle side of the curve is always about 15 to 18 yards. The only way to get the numbers in your post is if the “Zero Range” is either 60 yards for the 800 fps figures or 55 yards for the 700 fps figures.
I don’t think I said that but rather, with the pw at 2 and the reg at 1776 psi was the same trajectory as the pw at 7 and the reg at 1960 psi, or something like that adjusted for your statement above. At least that is what I had wanted to say though I’ve been unable to make a point or two clear to others in the past. My communication skills need more work than my shooting skills. Just ask my x-wives.
Of coarse a drop in speed from 700fps to lower will result in a lower POI. But from your description, I don’t think that is whats going on.
You are opening the REG all the way..pw..(high 5-13) and your hitting low. Because it has MORE power..see 800fps below
When pw is low..(less than 5 or whatever u mentioned) pellet hitting high..or what you call on target.Higher than pw=5+. Because it has less power..see 700fps below
You can set your ZERO you range for whatever you want..
Hitting the target at 35 yards means…
700 fps
10 yards ..3 in low
20 yards ..2 in low
35 yards ..dead on
45 yards ..1/2″ high
55 yards ..dead on
60 yards ..pellet drop
70 yards ..more drop
800fps
10 yards ..3.5 in low
20 yards ..2.5 in low
35 yards ..1.5 in low
45 yards .. dead on
55 yards .. 1/2″ high
60 yards .. dead on
70 yards ..pellet drop
80 yards .. more drop
The higher fps takes LONGER to PEAK out..thus getting you more range.
More fps= longer trajectory as does lighter pellet (just less power to target)
Study the curve..the above are not accurate..just the principle is the idea
45 yards ..dead on
So the fact that your pellets at pw is set at 7 hits lower at 35 yards than pw2 ..does not mean..they are slower or have less power..in fact they have more.
The pellet will not reach its peak till further down the shot curve..at 40-50 yards. Your poi drop means nothing.
You need a Chrony for such testing. Your title says lower pressure is faster…Bunk, lower pressure means dead on at 35 at 700fps…while 800 fps will hit lower..and it is suppost to! Thats just how it works.
You need a chrony to get accurate results. You can not guess at more/less power.
Advise..
Get chairgun pro..a great free prgm. Googgle it..its even in the D/l section of this board. GET IT!
Figure out what speed FPS you want..and what REG pressure is needed to get it 1776 or 2100…You can get an idea from the poi drop info in chairgun.
Take Dayotat100 (Doug) up on his offer to set your reg exact…he knows his stuff..hell, he builds and sells his own super high power regulators
I don’t see any problems with 2100psi..its a pretty good place to be.
You will however hit LOW at 35 yards..and be dead nuts on at 40-45 yards. Get Chairgun…play with it, study the shot curve and how it works
After getting chairgun and playing with it for a bit I see what you are saying and it appears to me that we are talking about slightly different scenarios. If I enter in all of my values your statements would only apply if the gun were sighted in for 50 yards or at least something longer than 35. Since mine is zeroed at 35 a drop in speed will yield a drop in poi not the other way around; or am I still missing something?
But thank you for suggesting chairgun because now I have yet another tool to attack the problems of making the perfect shot group. Well, at least dreaming of making the perfect group.
Here is the thread. http://www.talonairgun.com/forum/viewtopic.php?f=11&t=20036
This is the medium size one I made. Now I make them as big as possible.
Thanks Mrnewbie, and Dyotat100,
This kind of help / discussion is why I love this site so much. I’m fairly new to air gunning and just trying to get up to speed ( no pun intended ). Learning from you guys continues to improve my knowledge base and hopefully others as well. I’ll check out that program and report back.
And just to report the results of my experiment with removing the extra Condor hammer weight. it seems to work just fine. At about 6 on the power wheel I’m back to the original poa/poi, so the trajectory is back to being as flat as the 12″ barrel will shoot at 35 yards with JSB 18.13 Jumbo Exact Heavy pellets. Dropping the power wheel setting down to 5 drops poi about 3/4″ and going to 7 only makes the impact on the steel plate louder not higher. So I’m good with it the way it is and maybe tomorrow I can get some accuracy testing done.
You do of coarse realize..that if you are only shooting at 35 yards…With more power you would expect a LOWER pellet impact..Right?
The pellet will not reach its peak till further down the shot curve..at 40-50 yards. Your poi drop means nothing.
You need a Chrony for such testing. Your title says lower pressure is faster…Bunk, lower pressure means dead on at 35 at 700fps…while 800 fps will hit lower..and it is suppost to! Thats just how it works.
You need a chrony to get accurate results. You can not guess at more/less power.
Advise..
Get chairgun pro..a great free prgm. Googgle it..its even in the D/l section of this board. GET IT!
Figure out what speed FPS you want..and what REG pressure is needed to get it 1776 or 2100…You can get an idea from the poi drop info in chairgun.
Take Dayotat100 (Doug) up on his offer to set your reg exact…he knows his stuff..hell, he builds and sells his own super high power regulators
I don’t see any problems with 2100psi..its a pretty good place to be.
You will however hit LOW at 35 yards..and be dead nuts on at 40-45 yards. Get Chairgun…play with it, study the shot curve and how it works
It is a ported condor valve in a Etac-reg i modify. That is a chamber for more air. On a regular Etac-reg there isn’t enough volume so you have to run higher pressure to make up for lack of volume.
I think it takes close to a 2500 psi reg to get the same fps I get with 1800 psi.
It starts as a piece of 2″ bar. I bore it so it slides over the Etac-reg. Then I take a special tool a ground and hollow it out like a tire. Then I take the Etac-reg and bore thru the top and bottom but leave the sides.
Then the collar slides on and I weld both sides.
I’m on location for work and I don’t have the pic’s of the pieces as they are made on me in my phone.
Works real good.
WOW Dyotat100, that is some rig you’ve got there!!! If you don’t mind me asking, what kind of valve is that and what are the advantages? I’ve only seen specialized valves for the “HIGH POWER” slug shooting rigs, never for someone shooting standard pellets and normal speeds.
The only problem with the small gauges is accuracy. I have one that is 300+ psi off. No to many of those gauges are right on.
I know on my .25 with reg setup PW does nothing.
I have it set at 1800 psi and it shoots 25.4 JSB’s at 950 fps for around 90 shots. Set at 1500 psi it got 134 shots around 904 fps.
You can set 2 regs the same and they will read different. The washers are not consistent at all.
Only way is with a setup that reads the output pressure.
If you are replying to me I appreciate your gracious offer. I had a new style valve with a gauge for a time there and was able to confirm the first two settings, and the math was close enough to be ballpark, at least with the small gauge on the valve. But I do thank you for the offer and will keep it in mind in the future.
And just to report the results of my experiment with removing the extra Condor hammer weight. it seems to work just fine. At about 6 on the power wheel I’m back to the original poa/poi, so the trajectory is back to being as flat as the 12″ barrel will shoot at 35 yards with JSB 18.13 Jumbo Exact Heavy pellets. Dropping the power wheel setting down to 5 drops poi about 3/4″ and going to 7 only makes the impact on the steel plate louder not higher. So I’m good with it the way it is and maybe tomorrow I can get some accuracy testing done.
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Run into the same problem with CO2 during the Texas summer. Summer heat causes the CO2 pressure to increase, the increase pressure put back pressure in the valve. The hammer has a harder time opening the valve, so velocity either is significantly reduced – or quite often the valve locks up completely.