Leyla in .25 caliber..too much weight to do well?
Gather ’round children and let’s talk about velocity and such.
My first thought about a .25 Leyla was “Wow…the worlds smallest quality bullpup in the largest caliber offered by the maker! Hmmm…new, untried, untested, big pellet, small air supply, unknown valve/regulator configuration…hmmmm.”
To my knowledge, there are but three prime variables in pellet speed and foot pounds of energy.
First, the function of the valve/regulator is to give adequate feet per second and foot pounds of energy, but it does so at the cost of air usage/shot count. (Ed says 20 shots, ok for such a tiny gun.)
Second, barrel length is a variable that will increase velocity by roughly 50 fps per inch of barrel added. (Leyla = 12″ barrel, same as the Talon SS)
The last variable is pellet weight. Ed is designing the Leyla .25 around the JSB 25.4 gr. pellet, and therein lies our ability to initially affect the velocity we get from the Leyla .25 and not adjust or modify anything on or in the gun.
Here are some viable .25 caliber options:
Beeman Silver Ace…a 21 gr. domed pellet, standard skirt, and has what appears to be “gas rings” cut around the head of the pellet. (180 ct) It’s a 4.4 grain weight drop from the JSB.
H & N Field Target Trophy…a domed 19 grain pellet. ((200 ct)) Looks good in the box, with a 6.4 grain weight loss .
Pylarm (BSA) a semi-dome head, standard skirt, coming in at 18.6 grains. (200 ct) I have no experience with these, and don’t know availability in the U.S. but the lads in the Motherland should be able to give us some input. It gives us 6.8 gr weight reduction. I have one full tin in hand for testing.
Lastly, Beeman Laser pellets, 18 gr. (180 ct) a full 7.4 grain weight loss, and a respectable weight. Like the Pylarm, they have a semi-dome head, and regular skirt.
Now…when I get my .25 Leyla, I paid in full, so I should get a few days head start on the rest of the herd in the U.S. I will grab my chrony and do some fps/fpe testing and post the results. Accuracy may/may not reflect reality…remember I’m 71 with not so good eyes, but I can use a bench rest, so I hope I can give some reasonable idea of whether any of these will tend to “fly” on us.
I’m assuming that a 3 mm increase in .25 head diameter over a .22 (6.35 -5.5mm) will make any appreciable difference in pellet speed.
In closing, these are top quality pellets at a reasonable price. They will absolutely increase the velocity. By how much? I don’t know. But Sir Issac Newton says it will increase, and I believe him.
Perhaps Ed might share some information on the valve/regulator to be used in the new Leyla…same? new? modified? different per caliber?
Now, if anyone knows how to calculate velocity increase, per each one grain weight reduction, that would be most interesting. I don’t have those skills.
Thoughts….someone out there is bound to be smarter than me on this subject!!!
Hoot:
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just an idea.
Lars,
That’s actually a very good idea. While different calibers, valves, regulator settings, etc. will have different impact on the airflow, the result should be close enough to get a good feeling of the change (specially if you compare guns with similar regulator pressure). I don’t have a 25 cal, but have 22s. If I set my cricket HST to shoot JSB monster 25.4 grain at 720 fps, I get then the JSB 18.1 shooting at around 850 fps. The result may be different for Lelya but should not be very far.
Awny
Duke! I bow to your knowledge uncle hooter. I finished the tenth grade and went to work. That is very close to brain surgeon in my holler. I’m piled much deeper than than your hootness.
I did make some trips to local colleges, but only for non educational matters.
I’m must now return to my jizz mopping duties at the lusty lady, and bid you all good night .
I am but a lowly Master’s degree from Duke…thus I bow to superior subject matter knowledge by those holding the esteemed “Piled Higher & Deeper” degree in a more applicable major course of study!
One must know their place in the pecker order on this forum.
That being said…21 gr @ 785 fps, and 18 gr @ 856 fps, is more than adequate to achieve superior results from such a tiny pcp! I’m sure your calculations are close, as the fpe in 25 gr, 21 gr, and 18 gr, at the velocities in mention, all come very close to 30 fpe, which is what Ed stated it would produce, give or take a pound here or there.
Those velocities, and fpe’s, have never failed to kill any critter I managed to hit over the years, and I never shoot over 50 yards. Once I get my scope’s POC (point of chicken) dialed in, at the 100 to 150 foot distances I must deal with, (My deck to my Bitch neighbor’s chicken hangout) I’m good to go!
The only way I’ll come out behind on this endeavor is after I die, the first sound I hear from the Almighty’s domain is “Cluck….Cluuuuck!!!” 
Yours in sin and general mayhem….
Kindly ‘Ol Uncle Hoot:
I doubt we will have to shoot lighter weight pellets through our .25 lelyas. I got a .22 cal s200 that is setup to run around the same velocity with 15.89 jsb’s.
The trajectory is arched but manageable. Fifty yards maybe a little more is my limit. I have taken crow around seventy yards with it, so I’m not really concerned about the .25 lelya if the advertised velocity is what we get.
Can you take a handful of diff weight .25 or .22s and chrony them from your std length matador? then you can show real world measurements that may give you a rough idea of velocity changes due to weight.
just an idea.
I believe the 18gr pellet will get the Leyla up into the 900 fps range.
If we divide the 721 fps indicated for a .25.4 gr pellet, that equals almost 29 fps per grain. Shaving 7.4 gr off the weight, theoretically should get us close to an increase of 213 fps gain in velocity. 721 + 213 = 934 fps, or thereabouts. That’s over 40 fpe !!!
Hmmm….21.4 grains is a 4 gr increase. 4 X 28 = 112 fps gain, or 721 + 112 = 833 fps. That’s not bad if the math holds up to actual practice.
Now, agreed that’s pure math and other factors will affect this, but it’s as close to the truth as we can come to at this moment.
Hoot:
Hi Hoot,
The math (or more precisely the physics) above is not correct. An actual formulation of the relationship between the pellet muzzle velocity and the pellet mass is actually very complex and hard (hard for me at least and I have a PhD in physics, though admittedly did not practice it in many years). There are many reasons why the exact problem is complex that I dont want to bore you with. However we can do some simplifications to get approximate formulas that can hold within a certain region of the curve. The simplest approximation is that of basic equations of motions assuming a constant force. This is a rough assumption but a good start. The total work exerted by the air on the pellet is equal to
Work = F x D
where F is the average force applied on the pellet (overage over distance not over time), and D is the barrel length. Now if we assume that F is independent of the pellet mass (which is an assumption we will challenge later), and if we ignore both pellet rotational energy and heat energy from friction then we can conclude that the linear kinetic energy of the pellet is constant and that 1/2*M*V*V is constant and as a result
V2 / V1 = sqrt(M1 / M2)
or
V2 = V1 * sqrt(M1 / M2)
This means that for your example above, the 18 grain pellet will have 856 fps not 934 fps; and the 21.4 grain will get 785 fps not 833 fps. While the equation shown here is based on rough assumptions it should hold well as a computation for the maximum speed you could get by lowering the pellet mass.
The main problem with this simple formula though is that it assumes that the force applied is independent of the pellet mass and as a result the pellet final energy is also independent of the pellet mass, which we know is not true. The formula holds well when the pellets velocities are low but it should start diverging as pellets speeds get closer to the speed of sound. The problem is that heavier pellets will move slower than lighter pellets and hence gives the air behind more time to build higher pressure and pushing them with higher force. That is the heavier mass resulted of higher pressure buildup and higher force. That’s exactly why heavier pellets end up getting more energy than lighter pellets. Now since lighter pellets have less energy (1/2*M*V*V) this means that in reality they will get even lower velocity than what’s predicted by the simple formula above which can now be used as upper limit (assuming M1 is the heavier pellet. Lower limit otherwise).
I think the formula should also hold well as an approximation (not just upper limit) for velocities well below speed of sound, say 800 fps and less.
Hope this helps.
Awny
Clean hole isn’t it?
The fact is I shot off three bagworm limbs that afternoon. I did, in fact, have to adjust my scope for that distance, and that hole was likely one created when I was fine tuning the crosshairs before I got really serious. Normally I shoot at about 50 to 75 feet, the depth of my back yard, but this tree added a 100 feet to my usual scope POI.
Once I got it dialed in, I could’t miss. That was my first Edgun and accuracy was downright eerie, even with a cheap scope I could get down to “minute of bagworm”.
Hoot:
What was that little guy? a sighter? 
What happened to all the grey stock R2.5 Matadors.. even with all the new R3s and R3M’s out there never seems to be any pop up for sale..
2010, bagworms at the top of a 100 foot hardwood tree, Edgun Standard, 18 gr JSB’s, .22 caliber @ a measured 150 feet. Shot the 1/4″ limb off a tree in my backyard. UTG 3 X 12 Compact Swat scope.
My wife laughed at me when I told her what I was going to do. I told her three shots. The first one hit center mass, the second cut the top of the limb, the third clipped off the bottom, and down it came. She didn’t laugh after that.
Hoot:
I forget what my 22 is tuned to, need to chrony it again. It is 50 or 100 fps slower than the big boys but it shoots through the same hole at 25 yards all the time, I shoot a hole in a leaf for a target in the summer and will bet you I can put another shot through it and only slightly enlarge it and will more times than not !!
Ed indicated his aim is 220 meters per second in .25 caliber, roughly 721.7 feet per second. That’s not shabby at all!
Hoot:
PS: No thanks on the crab bait. I’ve had crabs and didn’t care for them. :suprisedn:
Has Ed indicated what speed he’s after? Most of his guns shoot pretty hot, out of the box.
Aside from weight and speed of the pellet, there’s the rate of spin/ barrel twist to consider.
:hoot: you’re looking at closer range “minute of chicken head” accuracy, so you need some chicken heads to practice with. Those should be free, if you visit the right farm.
Then, you can hang them from a limb (out of reach by your uber-dog). Bet your neighbor would enjoy watching your progress 😯
If she has a fit, tell her you’re just trying to get the feathers off so you can use them for crab bait.
A lengthy post to be sure.
I believe the 18gr pellet will get the Leyla up into the 900 fps range.
If we divide the 721 fps indicated for a .25.4 gr pellet, that equals almost 29 fps per grain. Shaving 7.4 gr off the weight, theoretically should get us close to an increase of 213 fps gain in velocity. 721 + 213 = 934 fps, or thereabouts. That’s over 40 fpe !!!
Hmmm….21.4 grains is a 4 gr increase. 4 X 28 = 112 fps gain, or 721 + 112 = 833 fps. That’s not bad if the math holds up to actual practice.
Now, agreed that’s pure math and other factors will affect this, but it’s as close to the truth as we can come to at this moment.
Hoot:
Not to get too boring, on the pellets listed you will get anywhere from 80 to 100 fps increase. I really think that we have to remember what this gun is for. Shooting relatively close range. This won’t (at least I don’t think it will be) be a 100 yard plus gun. For that range I’ll reach for a 25 Matador. So looking at this little bullpup, it the 50 yard kill zone the 25 will put a smack down on critters. I have been thinking about range but I don’t think it’s a factor for this gun.
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Hoot,
Agree. I think 30 ft.lb is plenty of energy and I cant think of a small game that one cant kill cleanly with this much energy. With 30 ft.lb airgun I can easily drop a large texas jackrabbit 100 yards away. Often I feel we are very energy hungry in our demands. One only need enough energy for clean kill. If the gun has the enough energy then my personal priorities are accuracy, quietness, and weight. Those are far more important to me than an extra power that I don’t need.
Not saying that I wont go to a 50 ft.lb 25 cal one day if I developed interest in bigger object such as coyotes. But for now the 30 ft.lb is plenty for me.
Awny