GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: GadgetX on June 24, 2020, 01:50:11 PM
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Helping a friend out with his Daystate .25 cal Safari.
He is shooting JSB 25gr pellets. He said it was TERRIBLE on high power, but grouped at low power, get this, at 3/4" at a 108yard outdoors. His FPS 940 on low power. I shoot MKIIs at high power which I get dime size groups at 60 yards. My FPS is ~950fps.
I think this open up my eyes on FPS being extremely important for accuracy. And the reason MKIIs work best in all my Daystate airguns is because I like to shoot on high power... I may go down to low power with JSB 25gr and smile when I get 200+ shots on a fill.
Thoughts??
M
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900 to 975 sure seems to be the optimal FPS for pellets, regardless of caliber. Be it .177, .22 or .25, I generally shoot for between 925 and 950 FPS and get very satisfying results! :D
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Staying outside of the transonic region of velocity is quite important when shooting. You either want your projectile to stay super sonic during its entire range of flight (and be designed around super sonic flight) or you want your projectile to remain sub-sonic for its duration of flight. Hitting just the edge of the region isn't detrimental, but the deeper into it you go, the less stable your projectile will become. HTH
-Matt
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Why some rifles shoot well faster than others (with the same pellets) pretty much eludes me....they just do.
Generally, when velocity starts reaching 925-970fps, will more often look for the next heaviest pellet and give that a try....moving up in weight if adjusting/tuning gets me back to that speed.
Some times I get trapped....nothing else heavier, and there is still more speed to be had...so I'll just have to keep tuning for faster if I'm looking for power(or stop adjusting and live with what I got).
I now have no dobuts about the wind at close range screwing up long range when speed gets to 4 digits. Can shoot great when calm,does really stupid stuff when the wind hits the pellet early in it's flight.
So I'd much prefer something like 30gr. at 875fps than 20gr. at 1075fps.
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In addition to the stability of the pellet possibly changing at different velocities.... the barrel harmonics can also affect the group size.... As you change the velocity, you change at what point of the barrel vibration the pellet arrives at the muzzle.... Have it arrive near the end of a swing, when the barrel is pausing, and the group size can shrink dramatically....
Bob
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Bob beat me to it.
Barrel harmonics can change at HV vs. LV, altering your POI. This is due at least in part to our airguns barrels not being as stiff as firearm barrels since they're usually made of a somewhat milder steel. A loose fitting shroud can also cause harmonics issues.
As a counter, if the shroud fits and works as designed and its indeed a barrel harmonics problem, some folks are float the barrel with some success. Tensioning the barrel is another way some go. If those are not an options one is willing to try, and if the muzzle is threaded, then adding some weight to the muzzle (air stripper, a muzzle brake, s heavy moderator, I've even seen a guy use metal collars once) can help as well. Adding some weight helps counter the inclination of the muzzle to flip upward during the shot as the projectile the barrel, by either directing and dispersing the blast in the case of an air stripper, or with weight alone if using a heavy brake or moderator.
Hope this helps.
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I challenge everybody to find wadcutter pellets that group at a much-closer 50 yards when muzzle velocity exceeds 900 FPS. I'm in the same camp as Mister Dean (Ribbonstone)
I've found the most accurate velocity for most domes to be right ~ 880. Mind you, if you find 920 is even more accurate than 880 then good on you, but this has not been my limited experience. OTOH, Travis has mentioned similar results and he's had pretty much everything under the sun.
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I challenge everybody to find wadcutter pellets that group at a much-closer 50 yards when muzzle velocity exceeds 900 FPS. I'm in the same camp as Mister Dean (Ribbonstone)
I've found the most accurate velocity for most domes to be right ~ 880. Mind you, if you find 920 is even more accurate than 880 then good on you, but this has not been my limited experience. OTOH, Travis has mentioned similar results and he's had pretty much everything under the sun.
Quite a few variables go into this...form factor (18.1's and redesigned 25.4's wont obey that same fps rule to the T...) and your barrels twist rate, all have compounding effects on ultimately what fps is best...one pellet may do best at 750, where as another does best at 850, and another at 950...really can't generalize all domed pellets being best at 880 IMO...although if one were required to give one number, and one only, then 880 is probably not a bad one to give...
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Thanks for all the input.
After reading replies and shooting airguns for 30 + years, IMHO I think a 34ish gr pellet at 920 fps is my best shot at hunting. This has opened my eyes up shooting 25gr at 900ish at low power for target shooting is the "Cats Meow". 200+ shots per fill (nearly a tin).
Thanks for all the replies.
M
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Anti squirrel:
Do think there is more going on with WC's than just weight/diameter...somthing hooked up with base drag vs.head drag with increased speeds.
Even at 25-30 yards and match rifles/low speeds, very often find RN pellets doing better than WC's.
GAgetX:
No complaint....could have picked anything from 860-920fps and I'd just nod.
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I try set up my guns to shoot in the -/+ 900 fps regardless of pellet weight, power, caliber.
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Anti squirrel:
Do think there is more going on with WC's than just weight/diameter...somthing hooked up with base drag vs.head drag with increased speeds.
Even at 25-30 yards and match rifles/low speeds, very often find RN pellets doing better than WC's.
GAgetX:
No complaint....could have picked anything from 860-920fps and I'd just nod.
:)
I'm just a huge fan of wadcutters, and they Do Not Like going fast. I wish we could obtain .25 and .30 wadcutters easily. I'd have jumped to .30 the millisecond they were available. Even at 450 FPS I bet it would be awesome for pesting. I may be lucky in that the gun I shoot the most, my 2400KT, has a decided preference for RWS Meisterkugeln.
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Wow quite pest you have there. .30 required...
M
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Anti squirrel:
Do think there is more going on with WC's than just weight/diameter...somthing hooked up with base drag vs.head drag with increased speeds.
Even at 25-30 yards and match rifles/low speeds, very often find RN pellets doing better than WC's.
GAgetX:
No complaint....could have picked anything from 860-920fps and I'd just nod.
:)
I'm just a huge fan of wadcutters, and they Do Not Like going fast. I wish we could obtain .25 and .30 wadcutters easily. I'd have jumped to .30 the millisecond they were available. Even at 450 FPS I bet it would be awesome for pesting. I may be lucky in that the gun I shoot the most, my 2400KT, has a decided preference for RWS Meisterkugeln.
well how about .410.. ;) https://www.ebay.com/itm/410GA-wad-cutter-pellet-bullet-mold-AS-Lyman-style-/292198322361 (https://www.ebay.com/itm/410GA-wad-cutter-pellet-bullet-mold-AS-Lyman-style-/292198322361)
https://www.gunpartscorp.com/products/595510A (https://www.gunpartscorp.com/products/595510A)
https://www.gunpartscorp.com/search#query=.410%20barrel (https://www.gunpartscorp.com/search#query=.410%20barrel)
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a related thread...
https://www.gatewaytoairguns.org/GTA/index.php?topic=174899.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=174899.0)
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From 850, to 920 is like 8 persentage faster. Not much.
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From 850, to 920 is like 8 persentage faster. Not much.
The reason I said that is that some refer to shooting at the 800 range as low power, while shooting higher than 900 as high power, while the persentage difference is not that much. So if a gun does not shoot good at 950, but do at 880, the it probably does not make much practical difference, except the one shooting at 880 probably will have more shots on a fill.
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From 850, to 920 is like 8 persentage faster. Not much.
The reason I said that is that some refer to shooting at the 800 range as low power, while shooting higher than 900 as high power, while the persentage difference is not that much. So if a gun does not shoot good at 950, but do at 880, it probably does not make much practical difference, except the one shooting at 880 probably will have more shots on a fill.
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It may be only 8% faster, but energy is is a function of the speed squared. So moving from 850 to 920 FPS increase the FPE by a little over 17%, not just 8%.
Of course accuracy is most important - 17% more FPE in a missed shot does no good. But speed and energy are not the same.
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Good point Alan. I also don't think 8% of anything is 'minor' or negligible...that is quite a large margin in any change...
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It may be only 8% faster, but energy is is a function of the speed squared. So moving from 850 to 920 FPS increase the FPE by a little over 17%, not just 8%.
Of course accuracy is most important - 17% more FPE in a missed shot does no good. But speed and energy are not the same.
Well you are right, did not thought about that:-)
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A case against maxi-maxi speeds.
If accuracy isn't any different,even with the up-powered rifles,sill end up with a choice of shot count vs. energy....and how much of one is worth how much of the other. The last 5-10% or so of velocity can be quite costly.
BUT...if adjusting for the most you can get out of a system...then the most is what you want, not "a bit less". Understand that urge for the MAXand how it leads to the little changes in PCP modding to getanother 5-10%.
Buteven if the "max of the max" is the goal, it's got to stop somewhere...or you'll be modding/adjusting and not out shooting/huntinglooking fgor that loast 5%...then 3%...then 1% "better".
At some point, will either call it "done"or accept that it'salways going to be a work in progress...at least until you do something that screws up what you already did.
Lets test-post that: If you have a "maxed out"PCP...is there really NOTHING you could do to make it even faster?....or did you just blow a whistle and call it "good
nuff"?
Even on my "fast ones", tend to back off bit....usally not much. Choice between 64 foot pounds/6 shots (call that 34gr. @922fps) vs 58 foot pounds/ 11 shots (call that 34gr.@ 877fps) seems pretty easy for me.
Bigger air volumes/longer shot counts/but the proportion remains the same...I just tend to hunt with the thin/lighter PCP's.
Don't keep many 22's or 25's jacked up in power....just not over run with larger critters that need shooting.... so even the hot-rods are not at absoulte max power.
FREELY ADMIT...the paper balistics are worse for the 877fpsvs. 922fps version.
BUT (good assumtion that I ran the two (877 vs 922fps) through calculators) what is the real world difference?
1. You have to either adjust the scope up or hold off at 100 yards. If you know it's 100 yards from your sight in,how much real world difference in clciking up/holding off 15 1/2 inches than 17 1/2 inches?
2.Energy at 100 yards? No dobut 29 1/2 foot pounds is more than 26 1/2footpounds. Doubt by use that it's a serious amount of difference.
3. Windage (using a mild 5MPH wind from 90degrees to flight line)...the difference in like 1/4th inch.
(this is the one that decided me....can get a ranage finder...can't really get a 100yard average speed wind finder.)
4. Shot count?(in the little air tube example). Nearly 2X the shooting before stopping to refill.
NOPE...not going to change the minds of power-heads. A small dfiffernce looms large in their minds....doesn't loom large in my mind.
Once you start getting to holding or scope adjusting off, it's a matter of how well you can judge the range in order to figure out the right hold-off.
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I like your incisive thinking and your carefully weighing the pro's and con's, Ribbonstone! 👍🏼
🔶 Often I play these what-if games, pro's and con's, like:
➔ What if I increased the power of my PP700 from 12FPE to 16FPE....:—How much less wind drift would I get, at 20y and at 40y?—How much longer would my point blank range be?
Ribbonstone, I'd like make a case in favor of maxi speeds — but only for one particular application... — otherwise I very much agree with you, the performance difference for upping the power are often much less than I imagine — until I run the numbers.... 🙄
🔶So, lately, I have been looking at the expansion of hollow points — pellets and slugs.
And here the chasing of max. power is quite relevant —
because hollow points have a need for speed — otherwise they don't expand in the quarry (and using them makes no sense the first place).
Look at one of the expansion tests Rick Eutsler ran (pic below): This particular pellet needs somewhere around 800fps for a healthy (and deadly) expansion.
Because a hollow point pellet has a low (or abysmally low) BC it needs to leave the muzzle pretty fast, as it sheds its velocity rather quickly.
For example, if you wanted to reach quarry at 30y with the pellet in the pic — it needs to leave the muzzle with 955fps MV to still have 800fps target velocity (TV) in order to expand....
Just some thoughts going through my covid-ized brain.
Matthias
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What if 920 fps shoots .25 MOA better at 100 yards than 877 fps due to harmonics? What about the application for br shooter versus hunter versus casual versus someone who won't shoot the gun for more than a year before moving onto other things...
What if 920 fps isn't considered 'hot' for your gun being it has plenty of barrel and plenty of pressure and your ammo weight is within reason, and you want every bit of the flattest possible trajectory, even for shots within 30-70 yards...
26 vs 29 fpe at the target is a difference of 10%, what if that is the difference between breaking the bone and hitting the off switch, and not...well that depends on application and game size, which varies for all, so no need me bringing in my personal needs which yours may be different, so I'll leave it simply at just that...be responsible and ensure enough terminal energy to effectively down game without any shadow of a doubt...
Its not one size fits all here, and what suits one person, may not suit another, and for very good reason...there really are two sides to every story, or to every argument, and when you bring in two sides (880 fps vs 920 fps) then you can absolutely argue for or against either without being wrong in any technical sense...
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What if 877fps shoots 1/4moa better?...would you give up the 10% difference for "extra" accuracy?
Takes a whole lot of shooting paper to get a valid analysis of 1/4MOA long term difference....but it could happen either way.
Here is where I do differ from most posters.
Don't usually shoot long range.....more of a get up close kind of hunter...a "grunt"rather than a "sniper".....so the higher powered airguns don't really get used farther away. They get used on larger critters no farther away than what the lesser powered airguns are used on little critters.