What?!? 😟 Slugs Give Me LESS Muzzle Energy than Pellets?

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JungleShooter

JungleShooter

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Sep 5, 2018
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🔶 What?!? Slugs give me LESS muzzle energy than pellets?! 😡 🔶

Please help me to understand what's going wrong on my first-ever venture into slug territory. 😟




I find that slugs have significantly less ME than pellets of comparable or lighter weight.
(Also, they are hitting all over 4 inches at my 100 yard target.)




🔶SET UP:
—Diana Skyhawk, with drop-in LW choked barrel, 17.7 twist rate, Huma, 22cal
—Mean muzzle energy (ME) was determined over a 10 shot string
—Pellets unsorted from the can
—Extreme muzzle velocity spread is usually less than 20fps
—Range to target 100 yards
—10-shot groups
—Very little wind



🔶 PELLETS:
The heavier = the more ME, just like expected ✔️

29.3FPE —> 15.89gr at 912fps = JSB Domed, 5.53mm head | 😊 3.0" group
30.1FPE —> 16.76gr @ 910fps = H&N Terminator
30.6FPE —> 18.13gr at 872fps = JSB Heavy
31.3FPE —> 21.14gr at 817fps = Baracuda Match, 5.52mm head
33.3FPE —> 25.39gr at 769fps = Monster Redesigned
30.8FPE —> 29.17gr at 690fps = Piledriver



🔶 SLUGS:
Heavier than pellets —> but less ME than pellets!?! 😟

27.6FPE —> 15.0gr at 910fps = Slug with .217 head | 9.1" group (only 6 shots)
27.5FPE —> 17.5gr at 841fps = Slug with .2175 head | 9.0" group
27.2FPE —> 20.2gr at 779fps = Slug with .217 head | 4.5" group
28.1FPE —> 20.2gr at 791fps = Slug with .218 head | 4.1" group
28.7FPE —> 23.0gr at 749fps = Slug with .217 head | 7.5" "group" while 3 missed the target!)



🔶QUESTIONS:
(1) The slugs are heavier than the pellets, but they still don't produce more power in the rifle?!? — I need it to be the other way around!
❓❌ What's going on here?


(2) The JSB Domed (15.89gr) made a 3" group with 10 shots, at 100y. At 50y I usually get 1".
Of five types of slugs two made a 4" group, three 8-9".
❓❌ What do I need to do to hit smaller groups with both pellets and slugs?




Lots to learn for me!
Thanks for your help! 😊

Matthias
 
With the same tune, slugs will lose more energy to barrel friction than pellets. 

For the most part pellets will all have about the same amount of rifle engraving, around the skirt and on the sides of the head. So a 16gr pellets will lose about the same amount of energy as 21gr.



Slugs on the hand will continue to lose more energy as the weight increases since the whole body of the slug is engraved. 
 
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I checked the math on some of your numbers and it looks correct. Your slugs are shooting slower at their given weight therefore have less energy. They shoot slower most likely due to the increased surface contact and friction between the slug and barrel whereas pellets have less surface contact and friction with the barrel so their velocity and energy is higher at their given weight. 
 
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At the muzzle which ever projectile is traveling faster will give highest fpe. Down range if the BC is higher you retain much more of that energy. So if you are shooting your target at point blank range a pellet might be a better choice. If you are shooting at further range where BC comes into play then a slug might be a better choice. 

Slugs are going to leave the barrel slower so the fpe near the muzzle might be less if you compare to a pellet. There will be a point downrange where the fpe of the slug is higher because it retains it's fpe over a longer distance where a pellet slows down quickly. After that point the fpe of the slug will get higher and higher compared to the pellet at the same range.

The biggest advantage to a slug that is over looked is the compensation in wind. Were you might be holding 3-4 mildots on a pellet, with a slug with a better BC it may only be 1 mildot. That makes for significant more hits when hunting.

For you accuracy, it would look like either that barrel is not liking slugs, or at least not liking those slugs.
 
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The biggest advantage to a slug that is over looked is the compensation in wind. Were you might be holding 3-4 mildots on a pellet, with a slug with a better BC it may only be 1 mildot. That makes for significant more hits when hunting.

Click to expand...

This right here became a disadvantage (because of my ignorance and lack of experience) I kept missing shots on iguanas because I kept holding over instinctively and the slugs just kept flying over their heads 😂 
 
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This is why FX calls their new slugs as "Hybrid" because they are hollow with less mass, therefore they can reach a faster speed and make up for the loss friction. They are a slug that can work with lower powered guns. You don't need to buy a power house to use them.
Click to expand...

They are hollow with less mass but more friction surface than a similar weight slug. You want to shoot a lightweight slug? Try the 17.5gr NSA or the 20.2gr. which are actually lighter and still hollow pointed. 

Also FX didn't call them that. Rat Sniper did before FX came into the picture.
 
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Dairyboy,

well, I already bought the smallest head size available, .217....

And no, I wasn't really planning on buying ready made ammo just to run each slug through a sizer....



Light weight slugs? Yupp, I tried those exact ones.... 😟





Nick,

you're preaching the gospel of slugs to the already fervent believers...! 😄

The advantages of slugs are so overwhelmingly clear that I'm willing to spend, sacrifice, tune, tinker, WHATEVER, to find just one slug that gives me 2" groups at 100y (I'm good with 7 out of 10 shots for that group size).





Before starting my slug journey I just assumed that with the amount of slug options available nowadays, I'll somehow get one of them to work....



Well, tomorrow I'll hit the range and try out the rest of the slugs, still have some 16, 17, 18, and some heavy weights to try.





🔶 Say, so far no-one has suggested that I up the power.

So I take it that the precision I see at 100y will not improve with more power? 🤔



Matthias
 
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Say, so far no-one has suggested that I up the power.
Click to expand...

Actually therealld did in a sense, as did I in the AGW thread. The slugs will spend more time in the barrel than their lighter weight pellet counterparts so there may not be adequate valve dwell to accelerate them fully or consistently. Or we can say it like this, if the rifle is adjusted properly to shoot pellets, it’s not at an optimal state of tune to shoot the slugs. A big clue would be that the groups were predominantly stringing vertically...well, assuming you weren’t shooting in especially windy conditions.
 
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Jungle shooter , I have tried numerous times to get both choked and non choked LW barrel to shoot bullets in just about every size and weight , cast and swagged. Got some acceptable groups but not what I would call stellar. I think you will find just like most of the bullet shooters out there , (even though Matt Duber says bullets need a choked barrel ) that choked barrels and bullets don’t mix. The LW barrels with the 12 land and grove displace too much lead and the groves are too deep IMO. Have you tried the factory barrel.? And as you yourself mention speed is good with bullets. I’d tune to 1000fps and work your way down from there. I usually tune a gun to one specific bullet at a certain speed and try to stick with it. Last this is sizing, very little makes a big difference is group size .0001 “ can make a good group stellar . 



Good luck on your adventure, hope you find a magic bullet for your gun .
 
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Thanks, guys, I'm just re-reading Bob Sterne's instructions on how to tune a regulated PCP, "below the knee" and all that.

On the Skyhawk stock I just finished routing the wood away that covered the hammer spring tension screw, so now I'll try to do some adjustments before I head out to the range tomorrow.



I appreciate the suggestions of a slug-dedicated gun, buying a non-choked barrel, and all that. However, THAT'$ not really an option.... 😊



I'll get the chrono out now.

Matthias
 
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Muzzle energy is produced by the velocity and weight of the slug exiting the barrel. 

If you are losing energy then adjust your hammer spring and/or regulator to provide the extra fps you need to retain accuracy and fpe on impact. I believe any slug needs to be in the mid 800's to 900's to correct for the other variables involved between pellets and slugs.



Hoot
 
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This is why FX calls their new slugs as "Hybrid" because they are hollow with less mass, therefore they can reach a faster speed and make up for the loss friction. They are a slug that can work with lower powered guns. You don't need to buy a power house to use them.
Click to expand...

They are hollow with less mass but more friction surface than a similar weight slug. You want to shoot a lightweight slug? Try the 17.5gr NSA or the 20.2gr. which are actually lighter and still hollow pointed. 

Also FX didn't call them that. Rat Sniper did before FX came into the picture.
Click to expand...

Thanks Dairyboy,

I never said I wanted to shoot the lighter slug the OP was questioning why slugs shoot slower. I was just reiterating what how they are marketed and the reasons why they are marketed that way. I am aware these were originally Rat Snipers Slugs, but FX is calling them that. They are different than NSA, or any other Hollow point. I got a bunch of them in September and played with them. Believe me they shoot different and expand different that the 19 grain NSA's. They are much more hollow and the centrifugal force cause them to be stable with slower spins and speeds then other slugs with just a small indentation for a hollow point.

I'm not a big FX fan either, but when they are able to buy-out the "little guy" like this and bring something cool to the masses as if it was their own invention, you gotta give them credit where credit is due. Rat Sniper were really hard to get, believe me I tried for a long time.
 
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Thank you all for your comments and help!! 😊




🔶 I have done it and jumped down the modding rabbit hole.
Today is a first for me. Never opened up a gun before. Not really a mechanic/ technician, either. But hey, here we go!
Hopefully I won't mess anything up too bad — in the country where I live there seems to be no capable gunsmith for airguns....
shocked.gif





I adjusted the trigger pull, and routered the access to the HST screw of the Skyhawk.





Then I chronied the Baracudas:
810fps = 30.8FPE




Then I turned the HST screw all the way in till coil bind (3 and 5/8 turns from the position I received the gun at).
And chronied again:
853fps = 34.2FPE





Now, that is plain disappointing.
That's all that the HST gives me, lousy 3.5FPE (43fps)? 😟
I expected a whole lot more power increase — looking at Bob's very helpful article in HAM.
The graphic there gave me hope that I'd be able to up the power much more with only the HST....
https://hardairmagazine.com/wp-content/uploads/2019/03/HAM-2-Pellet-Weight.jpg






Well..., it didn't work for this gun, I guess.
Now if I understand this power tuning business correctly, I'd need to increase the setpoint(?) of the regulator from (I think) 140bar to 150bar, or more, and mess again with the HST.




That means, degassing (I handpump), and disassembling the gun even more, to get to the regulator.... (Not being a pro-tinkerer like many here on the forum I wanted to avoid that....)






O well, tomorrow at the cow farm range I'll see what the other slugs will do that I haven't tested yet.
🔶 And maybe I find the silver bullet after all, without messing with the reg (or worse, getting an extended plenum, for an extended sticker price....). 😄

Matthias

 
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Correct, if you want to increase the energy, your best bet will be to increase the regulator's setpoint. The alternative to that would be to enlarge the porting but since you indicated you are new to this sort of thing, I presume you prefer to start with changes that are reversible.

If and when you decide you want to really crank it up, do both.

Note that as you increase the setpoint, you will need ever more hammer spring tension to properly knock the valve open. If you find you cannot reach the maximum velocity at something shy of coil bind, you will need a stronger spring.
 
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