Energy or Speed for penetration?

[39M]

The soap is outside the OP's question also, since he asked which would penetrate deeper in wood...

I guess we'd have to know what kind of wood, and how far away(or how fast at impact).

[anti-squirrel]

~~~~
since he asked which would penetrate deeper in wood...

I guess we'd have to know what kind of wood, and how far away(or how fast at impact).

Yup... exactly.  Shoot a piece of balsa, apple, some cedar, and osage orange.  Even a piece of pine can have variance- not just one piece to another, but one end of a board to another, especially if there are knots or heartwood involved.  Even getting into the spacing of annular rings can impact penetration in wood.

It's why I ignore wood tests completely.  If I'm looking for a good "test" of a pellet, I apply the pellet at the intended speed to the pest's skull.  Just because I shot the squirrel in the nugget doesn't mean I can do some extra tests  

If I want penetration, an arrow or high-speed bullet is far better than an airgun.  It's why I have always considered airguns more adept at dumping energy, especially since wadcutters and HPs work great at the distance I'm pesting. 

[rsterne]

Yep, you're right.... and which part of the grain the pellet hit, as well.... Exactly why I use soap, it's consistent, and more similar to something you might care about the penetration of.... 

Also correct, it's the IMPACT velocity that matters, not what it started out at....

Ramin, to answer your precise question, and assuming you are using the impact velocity (ie point blank range if that is the MV).... and further assuming that the wood is completely uniform in density, hardness, and grain structure, so that the impacts meet identical resistance.... the caliber is the same, so not a factor.... all that remains is the weight times the velocity....

25 gr. @ 910 fps = 22750
34 gr. @ 810 fps = 27540

so the 34 gr. @ 810 fps should penetrate about 21% further.... in theory.... even though it only has 7.7% more energy....

Bob

[DarkRattle]

Guys I shot a coke bottle at 130 yards today with my .25 wildcat, the impact was 18 fpe, and guess what... it didn't break it. it just hit it over.... I'm guessing the pellet wasn't hard enough? Never experienced anything that weird :/ Was using 25 grain JSB exacts.

[39M]

So should we also come to the conclusion that the same rifle that shoots the 25 grain .25 pellet @ 910fps, could not, in the same state of tune, push that 34 grain .25 pellet to the stated 810 fps?

I really don't know. But it would seem you'd need a different setup to only lose around 12% velocity when raising the weight by near 40%.

[39M]

Guys I shot a coke bottle at 130 yards today with my .25 wildcat, the impact was 18 fpe, and guess what... it didn't break it. it just hit it over.... I'm guessing the pellet wasn't hard enough? Never experienced anything that weird :/ Was using 25 grain JSB exacts.

Where do you get a glass coke bottle?
Was it a Mexican coke?

Anyway, I was shooting at a beer bottle with my 1377 a few weeks ago. And from about 18 yards, the first shot didn't break it. I think it was an off center hit, a glancing blow, because I heard the pellet go whizzing off to the left. On the second shot I took a little more care to make an on center shot and it broke.
Kinda felt bad after, as I don't like to break glass.

[rsterne]

39M, the specified velocities for the two pellets work out to 46 FPE for the 25 gr. and 49.5 FPE for the 34 gr.... PCPs generally gain a bit of energy without retuning when going to a heavier pellet, so it is likely you wouldn't have to change anything, or maybe just tweak the hammer spring preload a bit.... 46 FPE with the 34 gr. actually works out to 780 fps (instead of 810), and you almost never get less energy with a heavier pellet.... I would expect 790-800 fps with the 34 gr., but 810 is possible, it just depends on the actual tune involved....

If we assume the worst case, and use the 46 FPE (780 fps) for the 34 gr., doing the same math we get....

34 gr. x 780 fps = 26520.... compared to the 25 gr. @ 910 = 22750.... That still works out to about 17% more penetration predicted for the 34 gr. compared to the 25 gr.... My tests confirm that when the FPE is held constant, in the same caliber, heavier pellets tend to penetrate further.... because they have greater momentum.... ie reality matches theory....

Bob

[DarkRattle]

Guys I shot a coke bottle at 130 yards today with my .25 wildcat, the impact was 18 fpe, and guess what... it didn't break it. it just hit it over.... I'm guessing the pellet wasn't hard enough? Never experienced anything that weird :/ Was using 25 grain JSB exacts.

Where do you get a glass coke bottle?
Was it a Mexican coke?

Anyway, I was shooting at a beer bottle with my 1377 a few weeks ago. And from about 18 yards, the first shot didn't break it. I think it was an off center hit, a glancing blow, because I heard the pellet go whizzing off to the left. On the second shot I took a little more care to make an on center shot and it broke.
Kinda felt bad after, as I don't like to break glass.

it was a mexican coke, do you even realize how surprised I was when 18 fpe didn't shatter it lol?

[DarkRattle]

39M, the specified velocities for the two pellets work out to 46 FPE for the 25 gr. and 49.5 FPE for the 34 gr.... PCPs generally gain a bit of energy without retuning when going to a heavier pellet, so it is likely you wouldn't have to change anything, or maybe just tweak the hammer spring preload a bit.... 46 FPE with the 34 gr. actually works out to 780 fps (instead of 810), and you almost never get less energy with a heavier pellet.... I would expect 790-800 fps with the 34 gr., but 810 is possible, it just depends on the actual tune involved....

If we assume the worst case, and use the 46 FPE (780 fps) for the 34 gr., doing the same math we get....

34 gr. x 780 fps = 26520.... compared to the 25 gr. @ 910 = 22750.... That still works out to about 17% more penetration predicted for the 34 gr. compared to the 25 gr.... My tests confirm that when the FPE is held constant, in the same caliber, heavier pellets tend to penetrate further.... because they have greater momentum.... ie reality matches theory....

Bob

super interesting...

[39M]

Excellent! I knew that pneumatics in general respond well to higher weights. But had no idea that a powerful PCP air rifle could keep that kind of pace with heavier pellets.
Mr. Sterne, you truly are a wealth of knowledge and I appreciate the chance to absorb some of it.

[rsterne]

Here is some hard data for you.... JSB Exact series pellets, in .22 cal, fired from a PCP tuned for 20 FPE.... Penetration distance in soap, point blank range....

13.4 gr.... 79 mm
14.3 gr.... 87 mm
15.9 gr.... 93 mm
18.1 gr.... 98 mm
25.4 gr.... 106 mm

The 34 gr. Beasts were not available when I did those tests.... but the trend is obvious.... The heavier pellets, even though travelling slower, had greater penetration.... in accordance with their greater momentum....

Bob

[DarkRattle]

Here is some hard data for you.... JSB Exact series pellets, in .22 cal, fired from a PCP tuned for 20 FPE.... Penetration distance in soap, point blank range....

13.4 gr.... 79 mm
14.3 gr.... 87 mm
15.9 gr.... 93 mm
18.1 gr.... 98 mm
25.4 gr.... 106 mm

The 34 gr. Beasts were not available when I did those tests.... but the trend is obvious.... The heavier pellets, even though travelling slower, had greater penetration.... in accordance with their greater momentum....

Bob

See I was at the range today, I had my rifle chambered in .308 and my friend had his ar 15 in .223, now his rifle out penetrated mine and his argument was his bullet was going faster and my counter-argument was no it's because his bullet diameter was much less than mine. Good to know I was right

[39M]

Or maybe he was shooting FMJ ammo?
Or long for caliber bullets...high weight?

[DarkRattle]

Or maybe he was shooting FMJ ammo?
Or long for caliber bullets...high weight?

We were both using FMJ so I don't think it was that, his was shooting 77 grains at 2800 fps and I was shooting 185 grains at 2500 fps, so I had nearly double his energy.

[rsterne]

77 gr. in .223 cal has an SD of 0.221 x 2800 fps = 619

185 gr. in .308 cal has an SD of 0.278 x 2500 fps = 696

With equal projectile shape, construction, and hitting the same medium, the .308 should have had more about 12% more penetration.... That can easily be reversed by the other factors.... but it gives you an idea how to work stuff like this out.... Any expansion or yawing of the projectile after impact, changes things in a hurry....

Bob

[DarkRattle]

77 gr. in .223 cal has an SD of 0.221 x 2800 fps = 619

185 gr. in .308 cal has an SD of 0.278 x 2500 fps = 696

With equal projectile shape, construction, and hitting the same medium, the .308 should have had more about 12% more penetration.... That can easily be reversed by the other factors.... but it gives you an idea how to work stuff like this out.... Any expansion or yawing of the projectile after impact, changes things in a hurry....

Bob

Ya that's interesting aint it? It could have been so many aspects, my guess is my bullets might have went in an angle while his went straight, crazy how many aspects are in bullets and penetration.

[DarkRattle]

77 gr. in .223 cal has an SD of 0.221 x 2800 fps = 619

185 gr. in .308 cal has an SD of 0.278 x 2500 fps = 696

With equal projectile shape, construction, and hitting the same medium, the .308 should have had more about 12% more penetration.... That can easily be reversed by the other factors.... but it gives you an idea how to work stuff like this out.... Any expansion or yawing of the projectile after impact, changes things in a hurry....

Bob

Ok can you explain to me how 18 fpe didnt crack nor go through a mexican coke? I didn't even see a mark on it.

[K.O.]

77 gr. in .223 cal has an SD of 0.221 x 2800 fps = 619

185 gr. in .308 cal has an SD of 0.278 x 2500 fps = 696

With equal projectile shape, construction, and hitting the same medium, the .308 should have had more about 12% more penetration.... That can easily be reversed by the other factors.... but it gives you an idea how to work stuff like this out.... Any expansion or yawing of the projectile after impact, changes things in a hurry....

Bob

Ok can you explain to me how 18 fpe didnt crack nor go through a mexican coke? I didn't even see a mark on it.

I think ya missed an it went a wizzin of a rock..

[DarkRattle]

77 gr. in .223 cal has an SD of 0.221 x 2800 fps = 619

185 gr. in .308 cal has an SD of 0.278 x 2500 fps = 696

With equal projectile shape, construction, and hitting the same medium, the .308 should have had more about 12% more penetration.... That can easily be reversed by the other factors.... but it gives you an idea how to work stuff like this out.... Any expansion or yawing of the projectile after impact, changes things in a hurry....

Bob

Ok can you explain to me how 18 fpe didnt crack nor go through a mexican coke? I didn't even see a mark on it.

I think ya missed an it went a wizzin of a rock..

haha xD Nah man hit it dead on @ 130 through that thing but I swear didn't even leave a mark on it lol... JSB 25 grains too soft I guess :/

[rsterne]

Hit a thick part of the bottle, no different than a rock hitting your windshield.... The angle and relative strength is everything....

Bob