Airgun trajectory, how flat is flat?

Jump to latest Follow Reply
Centercut

Centercut

Member
Jun 9, 2017
7,652
1
4,468
People's Republic of California (PRC)
open.spotify.com
I must be on a roll this week, or perhaps its that time of the month... ;) But there's another thing I've been pondering, and that's all this talk of just how "flat" some trajectories are compared to others. I've heard just in the past week:

- I shoot the .22 JSB RD Monsters at 950 FPS because its got a "flatter" trajectory than say a .30 JSB exact 44.75 grain at 880 FPS, or a .25 JSB Mk2 34 grain at 890 FPS. 

- I shoot slugs vice pellets because they shoot so much "flatter" than pellets.

So what really is "flat"? How "flat is flat", and does it really make that much of a difference? Let me try and give some real world specific example, and perhaps you can decide how flat is flat... Lets look at three specific examples, two pellets and one slug, all three sighted in at 50 yards (a common sight in distance for airguns), and holdover at distances of 75, 100, 125, and 150 yards. All data from Chairgun and Strelok Pro. 

- First the .30 grain JSB Exact 44.75 grain at 880 FPS, BC of .040 (confirmed from my .30 FX Bobcat with LabRadar)

Drop at 75 yards 4.3", drop at 100 yards 13.0", drop at 125 yards 27", drop at 150 yards 51.3" - with a speed of 950 FPS, these numbers go to:

Drop at 75 yards 3.6", drop at 100 yards 11.2", drop at 125 yards 23.4", drop at 150 yards 41.0"

- Second, the .22 RD Monster 25.4 grain at 950 FPS, BC of .048 (confirmed from .22 EDgun R3 Long with LabRadar)

Drop at 75 yards 3.4", drop at 100 yards 10.5", drop at 125 yards 21.8", drop at 150 yards 37.8"

- Third, the .22 VK slug, 22.5 grain at 950 FPS, BC of .074 (from VK web page on eBay)

Drop at 75 yards 3.0", drop at 100 yards 9.3", drop at 125 yards 19.2", drop at 150 yards 33"

So as you can see, with a 50 yard zero scope height about 2.6 inches, speed is much more significant a factor than BC up to around 125 yards. the slug drop becomes less compared to the typical pellets past 125 and especially at 150 yards and beyond. But at 75, 100, and 125 yards, flatness of trajectory is pretty much not that different. When calculating holdover on your scope, does 2 or 3 inches really matter when comparing 22 inches to 19 inches? Even at 150 yards the .22 RD Monster is only dropping 5 inches more than the VK slug (38" to 33")...

Thoughts?


 
CC! is your week! jajaja

For me flatter trajectory is how long the ammo stay in the "flat line" I might be wrong, but is how I understand flat is ... do not have exact number to share (btw add graphs if you can... they are much more understandable ;) )

Meaning for example, if a shoot a slug 28gn @ 1000 fps will give me a flat liner from 20 to 80 yards (donno really just an example, I might be wrong) but if I shoot it at 800 fps that flat line will be from 20 up to 50 yards. The flat liner is cool because I know that in that distance I do not to hold shi... ;) Do I make any sense? LoL :D
 
Upvote 0
I have spent a fair bit of time (and $ for that matter) trying to get a solid long range, small bore regulated PCP to add permanently to my arsenal. That said, I have also been running the numbers too a lot lately, but with the other dimension of wind drift. 

With small bore PCPs, a low BC flying at 900 seems to have a significant increase in drop rates in 25y increments from 100-175y or so (just using an 18gr JSB at 900fps as an example). The same type of curve with something like the 47gr NSAs (same speed) have a slightly similar curve, but it's drop curve rate doesn't grow until it passes the 200y mark.

The one rule that has also stuck with me as I have tested different subsonic PCP ammo and calibers, is that you can shoot two guns of different calibers and speeds side by side at the same horizontal angle, and both of the projectiles will fly for about 2 seconds. Staying in the subsonic range decreases drag, which increases as supersonic speeds are approached from 900fps > Mach 1.

This is is where the wind drift research that I heave done led me to a really good post on the NOE forum that coincided with the flat trajectory research that I had been doing. Some of the drift principles have overlap with this, the takeaway there is slower projectile speeds do not necessarily mean worse drift. If drift is a concern, use higher BC ammo. I'm also no longer pursuing >1000fps velocities with small bore slugs that have relatively low BCs due to the nature of wind drift effects and the additional drag introduced as transonic speeds are approached. It just destroys accuracy 3/4 or more of the time.

https://noebulletmolds.com/smf/index.php/topic,1729.0.html
 
Upvote 0
@edosan - yeah, to your point - finding a good, maximum velocity for a flat trajectory to a given distance seems doable with small bore PCPs shooting high BC ammo. I think your 20-80y range is perfect for shooting with almost the same POI. I have found that the real challenge becomes shooting at distances where the drop curve kicks in, where you really need to know what those rates are with either a lot of practice or a ballistic calculator to map with the scope.

I'm still working on finding the right combination of rifle and ammo to be able to shoot and hunt long range with consistent predictability. A question that I have presented to myself is what a good, realistic maximum POI drop height should be for hunting and target shooting. Like it was said once before, at a certain distance, you're more like handling an artillery mortar and lobbing the projectile vs. shooting flat 😆 
 
Upvote 0
PS., I don't want members to think I'm anti slug. In fact, after I use my .22 EDgun R3 Long at RMAC, I'm going to jack it up a bit to shoot the 24 grain VK slugs, or the equivalent Nielsen slugs at 950 to 960 FPS. Shouldn't be that hard since it already shoots the VK 22.5 grain slugs at about 925 FPS thanks to Derrick's @zx10wall power tune. Huma with the power plenum and heavier hammer should easily get me to that point, maybe even shooting heavier than 24 grain slugs at mid 950's speed. My point was that from 50 up to around 125, there really isn't that much difference in performance between the 22.5 VT slugs and the 25.5 grain .22 RD Monsters. Except of course the pellets are much less expensive...

@mtnghost, I totally agree. Once you get much past 150 yards, even with slugs, you're more or less shooting a mortar at your target... Nothing wrong with that, since last summer I had two shots at exactly 200 yards on ground squirrels with my .30 FX Bobcat that resulted in a solid hit. Both were the first shot, and then after each (on different days), I took about 5 more shots at other squirrels at the same range and didn't even come close enough to scare them! The drop on those pellets (44.75 grain) was around 109 inches if I remember correctly. Definitely in artillery territory. ;)
 
Upvote 0
The gun's inherent accuracy, the BC of the projectile and the velocity at which it's being pushed all have an influence on the overall performance of your set up. When talking about really pushing the velocity for any particular projectile, there always seems to be those asking... why do you need to push the pellets or slugs so fast? This is exactly why, the shorter the amount of time the projectile is in the air, the less time it has to be effected by external forces. A fast flight time to target is exactly what I think of when I'm thinking of a "flat" shooter. If you can find a projectile that can be pushed really fast and still be accurate at those velocities, BINGO. If on top of that it has a super high BC, even better! One of the reasons why slugs offer an advantage over pellets at intermediate ranges when most would reach for pellets is that they can generally be pushed a lot faster without becoming unstable.

When you take into account that slugs can be pushed faster, have BC's that are sometimes triple that of a pellet, carry energy much more efficiently, can be made "to order" and will shortly be coming down in price, you can see why there is a lot of hype about slugs. Yes, they are more expensive but after spending a large sum of money on a particular air gun, I'm willing to pay more to maximize the accuracy of my gun at medium, long and super long ranges... when extreme accuracy is needed anyway. Don't get me wrong, I still shoot pellets and lots of them. If I'm shooting for fun and can shoot groups at 40yds that are between 3/8-1/2", pellets will be loaded in my magazine 95% of the time...unless I need more energy for pests or have to contend with the wind. 

My point wasn't to be pro slug or push slugs down your throat some more. An example of what I am talking about is being able to push a .25 caliber, 28gr slug with a BC of .079 at 1000fps. Just an example...the faster a projectile can get to the target, accurately, the better!

Stoti
 
  • Like
Reactions: Ezana4CE
Upvote 0
Of course 'flat-shooting' is a relative term, certainly subject to individual interpretation(s) and applications. Not being into airgun shooting beyond 100 yards, largely because I use diabolo pellets to maximize the advantage(s) of airguns in the first place, my primary goal in airgun related 'flat-shooting' is minimizing trajectory guesswork when hunting; often from offhand positions when any distractions from concentrating on simply making good the shot can be the difference between success and failure.

Consequently my two examples of flat-shooting hunting airguns below might seem light-years different from most of the posts in this thread. But considering I seldom attempt airgun hunting shots beyond 50 yards, notice the notes toward the bottoms of each rifles information and it might make better sense.

.177 Beeman Falcon Rs bolt-action PCP repeater

1557356360_15161622485cd35f484b62a5.90184952_Bee Fal Rs.JPG


10.3gr JSB, 3000 PSI fill, 24 shot powerband- Lo= 971, Hi= 995, ES= 24, SD=7, Avg= 986/22.2

6/14/12- Four consecutive 5 shot groups at 50 yards with 10.3gr. Exacts averaged .60” c-t-c.

Very flat-shooting; sighted in to hit within 1/2” of aim point from 12 to 50 yards.



.177 Shin Sung Career III lever-action PCP repeater

16gr EunJin, 2600 PSI, 36 shot power-band- Lo= 912, Hi= 944, ES= 33, SD= 6, Avg= 931/30.7

4/2/2013- Got a .25” c-t-c five-shot group at 50 yards, then a .58” eight-shot group.

Zero’ed at 40 yards, a 16 grain EunJin at 930 FPS is within 1/4” of aim point from 15-44 yards.






 
  • Like
Reactions: Ezana4CE
Upvote 0
AirNGas-

Nice try but completely wrong...missed the mark with that one!

LOL, just joking!

I always love when you're involved with the discussion, whatever the discussion might be. We often have differing opinions or different ways of looking at something but always get each others point. It's nice to have people on the AGN that are always nice, civil and willing to share their insight. (not just A&GM, everyone!)

The point being, I wouldn't have thought of a flat shooting being interpreted as a gun that a zero that covers ranges from 14yds-44yds although that's exactly what it is in my book too. This is probably why CC started another discussion like this one, just to get the dialogue going so people can share, learn and enjoy. Isn't that why we're all here in the first place. 

Thanks CC and A&GM(everyone). Have a great evening!

Stoti
 
Upvote 0
CC! is your week! jajaja

For me flatter trajectory is how long the ammo stay in the "flat line" I might be wrong, but is how I understand flat is ... do not have exact number to share (btw add graphs if you can... they are much more understandable ;) )

Meaning for example, if a shoot a slug 28gn @ 1000 fps will give me a flat liner from 20 to 80 yards (donno really just an example, I might be wrong) but if I shoot it at 800 fps that flat line will be from 20 up to 50 yards. The flat liner is cool because I know that in that distance I do not to hold shi... ;) Do I make any sense? LoL :D
Click to expand...

1557360951_4878038625cd3713708d3f3.39494253_026D40E6-9DF6-47B7-930A-1C6EFE5EBCCF.jpeg


In this example .5 mil holdover covers 20-55 yards. I too look at flat as that portion of the trajectory curve where range estimation error is minimized.

Interesting topic.




 
Upvote 0
I'M TAKING A CHANCE with this little dissertation of annoying you guys. Thought I'd give it a try. Draw a straight horizontal line. That is the representation of the ideal flat shooting rifle. Now draw a semi circle beginning at one end of the flat line, rising upward and terminating at the other end of the horizontal line. That is the representation of the worst trajectory of an air rifle. The most desired trajectory is the flat line. It takes projectile speed and aerodynamics (BC). for us pellet shooters 900fps is about the best you'll get because you are approaching the shock wave of the speed of sound which is detrimental to accuracy. The better the ballistic coefficient the less velocity is lost in transit to the target. Therefore less time for gravity to work on bending the "flat line" of ideal trajectory. The more dense and higher BC your projectal the more resistant it is to slowing down due to air friction. The more dense your projectal the more difficult to reach launch speed of 900fps. Now people are switching over to slugs to improve the BC of the projectile. now the speed of sound shock wave has much less effect on the projectile. But now your slug could well pass through the intended target. In one of the forums someone said air guns fill a niche for low power hunting and target shooting/plinking. We are now entering the realm of the powder burner. The air gun is becoming as deadly and destructive as the powder burner. with slugs the .30, .357,.45, are becoming the equal of the .38 special. And the .45 is in range with the old .44-40 black power winchester rifle and pistol cartridge use to fight gun battles and hunt deer and even larger game in the west prior to the coming of the .30-30. We are no longer the BB gun and low velocity pellet rifle. Given the anti gunners and the states with varying laws regarding air guns, catapults (slingshot), and snowball and pebble throwing. I wait to see if I pass before ....
 
Upvote 0
I'M TAKING A CHANCE with this little dissertation of annoying you guys. Thought I'd give it a try. Draw a straight horizontal line. That is the representation of the ideal flat shooting rifle. Now draw a semi circle beginning at one end of the flat line, rising upward and terminating at the other end of the horizontal line. That is the representation of the worst trajectory of an air rifle. The most desired trajectory is the flat line. It takes projectile speed and aerodynamics (BC). for us pellet shooters 900fps is about the best you'll get because you are approaching the shock wave of the speed of sound which is detrimental to accuracy. The better the ballistic coefficient the less velocity is lost in transit to the target. Therefore less time for gravity to work on bending the "flat line" of ideal trajectory. The more dense and higher BC your projectal the more resistant it is to slowing down due to air friction. The more dense your projectal the more difficult to reach launch speed of 900fps. Now people are switching over to slugs to improve the BC of the projectile. now the speed of sound shock wave has much less effect on the projectile. But now your slug could well pass through the intended target. In one of the forums someone said air guns fill a niche for low power hunting and target shooting/plinking. We are now entering the realm of the powder burner. The air gun is becoming as deadly and destructive as the powder burner. with slugs the .30, .357,.45, are becoming the equal of the .38 special. And the .45 is in range with the old .44-40 black power winchester rifle and pistol cartridge use to fight gun battles and hunt deer and even larger game in the west prior to the coming of the .30-30. We are no longer the BB gun and low velocity pellet rifle. Given the anti gunners and the states with varying laws regarding air guns, catapults (slingshot), and snowball and pebble throwing. I wait to see if I pass before ....
Click to expand...

1557372949_11801475965cd3a015e71995.26585161_64AE531C-8A36-432F-B982-13925DC3471E.jpeg

 
Upvote 0
😂

Simple exercise

0.22 36gn slug @ 1.000 fps vs best jsb pellets for long range

(Note: I took the 36gn slug from nielsen, since they remove any other slug 0.22 from their page https://nielsenspecialtyammo.com/collections/22-caliber ...is all I have to check it fast)

1557401784_21371003565cd410b86fd6f4.67318734_slug.png


1557402670_3334540435cd4142eacc569.80234006_pellet.png


1557402471_18676133815cd413670a42f7.23076719_pellet2.png


1557402481_13813265095cd41371cc2ee8.50243830_pellet3.png


1557402494_18684418395cd4137e40b458.25599959_pellet4.png


https://www.hornady.com/team-hornady/ballistic-calculators

pellets bc: https://hardairmagazine.com/ballistic-coefficients/ 

which is flat? pretty clear NONE! jaja but check the fps fpe and trajectory, one of the reasons slugs are more accurate at long distances, due the BC they travel faster and that is a big plus (like stoti says, less external influence), and just a few of those pellets will be accurate @ 1000fps
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu