šŸ”“ Your Gun's Ideal Power Level ā€“ What Pellet/Slug WEIGHT Have To Do With It

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JungleShooter

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Choose the Power of Your Gun Wisely ā€“ As It Restricts Your Pellet/Slug Options



For a long time I have been agonizing over the choice of a new gun. One important factor I kept coming back to was the question how much power I should get.

The same "agony" with current guns -- When modding a PCP (or moving the power selector) -- What power level should I choose?



The answer of course depends on a host of factors:



ā€“Caliber: the bigger caliber the more power I need

ā€“Range I want to shoot at: the farther I want to shoot the more power I need, in order to keep the trajectory reasonably flat

ā€“Punching targets or killing game/pests: paper requires very little power, tough racoons a lot of it

ā€“Pellets or Slugs: pellets are usually less heavy and require less power, slugs are and require more

ā€“...



ā—ļø Another important factor are the pellets/slugs I want to use.





So, I started calculating (ChairGun WIN) which velocity a certain muzzle energy would produce with each of the pellets/slugs Iā€™m interested in. And my table finally ended up in the diagram at the end of this post.







Considerations

Here are some important consideration for choosing the power level of a gun ā€“ as far as pellets/slugs are concerned:

Letā€™s assume midrange shooting (30+ yards) and beyond, since 10-yard target shooting with wadcutters is a whole different animal.



(1) To avoid extreme levels of drag and instability at transsonic speeds ā€“ pellets/slugs should have a max. velocity of c. 950fps.*



(2) To avoid unreasonably steep trajectories and instability ā€“ pellets should have a min. velocity of c. 650fps ā€“ and slugs preferably higher like 800fps.**



(3) In order to find just the right pellet that the gun likes (best precision, smallest groups) ā€“ it is better to have more pellets to choose from rather than less.



(4) To have a flatter trajectory for mid range and especially long range shooting ā€“ it is better for pellets/slugs to have a higher velocity. Also, hollow points generally have a better expansion at higher velocities.







Some Examples of How to Use the Diagram to Choose the Power Level of a Gun ā€“ or to See Pellet/ Slug Options

[Diagram at the end of this post, and also for download with a higher resolution.]



Example #1:

Say I wanted to have the most amount of pellets to choose from to increase the chances of finding the pellet that my gun likes. āž” For that I go to the red numbers (muzzle energy in FPE) and find the number that is abeam of the highest amount of gray boxes and pellets to its right. In this case, 24FPE is abeam of almost all the pellet boxes (P1 through P8 = 22 pellets not counting tinĀ­Ā­/zinc alloy pellets). Even at 17FPE, I still have 19 pellets to choose from.



Example #2:

Say I wanted to have the most amount of slugs to choose from to increase the chances of finding the slug that my gun likes. Note that the slug boxes have a gray portion that shows the muzzle energy for 800fps through 950fps. Separated with a red line is the white portion of the box that goes all the way down to 650fps, and which many find is too low for slugs. Here we only consider the gray part 80https://www.gatewaytoairguns.org/GTA/index.php?topic=25008.0

https://www.gatewaytoairguns.org/GTA/index.php?topic=70230.0

**Nielsen Specialty Ammo (NSA)

https://nielsenspecialtyammo.com

***BC table at https://www.gatewaytoairguns.org/GTA/index.php?topic=149053



1555269388_10037512625cb3870c3c2de4.21687198_How Muzzle Energy Restricts Pellet Options. 16. H...jpg








Download link for the diagram ā€“ with much better quality!


download.png
View attachment 1555269354_19936867925cb386eaf0c8f2.99593739_How Muzzle Energy Restricts Pellet Options. 16. H...pdf





Happy shooting! šŸ˜Š

Matthias
 
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Thatā€™s a lot to attempt to plow through. I missed what you are shooting at.

Slugs are changing the game entirely. I am shooting 15.5 grn .177 slugs at 29 FtLb with lots of joy
1f44d-1f3fb.svg
BC is between .069 and .071. Still amazed at the capability of the set-up.

Joe
Click to expand...

Iā€™m very interested in the 15-29 grain.177 slugs. Please let me know your platform & any suggestion for real life expectancies from such.

OP Matthias, lots of work you put into post. Great job. I have to disagree on ONE thing. I owned an AZ Rapid that preferred .22 CPHP out of the tin out to 100 yards. Many a 10 shot group covered by a dime with them. Past 100 though JSBā€™s always did better with much less drop.
 
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I have to disagree on ONE thing. I owned an AZ Rapid that preferred .22 CPHP out of the tin out to 100 yards. Many a 10 shot group covered by a dime with them. Past 100 though JSBā€™s always did better with much less drop.
Click to expand...



Yupp, James, thatā€™s the tension we have to balance out, I think, precision vs. BC:

(a) There is the precision of the pellet/slug, how small it groups at the attempted distance (no wind).

(b) There is the BC of the pellet/slug, how good it bucks the wind.





I always have wanted to see how this plays out, so here it goes (using ChairGun Mobile):

Sorry, dixieduo, your head might hurt a little more before it gets better...! šŸ˜



Finding the Balance Between High Precision (Small Groups) and High BC (Small Wind Drift)





Pellets P1 and P2

A shooter has a .22cal rifle, developing 20 FPE of muzzle energy with both Pellet P1 and Pellet P2.

Pellet P1 consistently produces 1" groups at 70 yards (no wind). It has a BC of 0.023 (14.30gr).

Pellet P2 consistently produces 1.5" groups at 70 yards (no wind). It has a BC of 0.036 (17.90gr).





Shooting Scenarios 1 and 2 ā€“ at 70 yards

In shooting scenario 1, at 70 yards, with no wind, P1 clearly is the best choice, it groups better than P2 by 0.5".



However, in scenario 2 there is a light to medium wind, 2 to 8 mph.



Pellet 1 drifts between 2" to 6" (2mph=2" | 3.9mph=4" | 5mph=4.9" | 6mph=5.9" | 8mph=7.9")

Pellet 2 drifts between 1.3" to 3.9" (2mph=1.3" | 4mph=2.6" | 5mph=3.3" | 6mph=3.9" | 8mph=5.2")



Of course, the shooter will try to compensate for the wind, but wind is often variable, and a 2-mph estimation error (or larger!) is very hard to avoid.



Committing a hard-to-avoid 2-mph wind estimation error ā€“ the wind was 6 mph instead of estimated (and corrected for) 8 mph ā€“ will drift Pellet P1 off target by 2". Pellet P2 gets drifted off by 1.3".

That is a difference of 0.7" between P1 and P2. This difference is slightly larger than the difference in group sizes (0.5").

Therefore, P2 would be preferable in scenario 2.



If the shooter is less than stellar in estimating wind, a probable 3-mph estimation error with P1 will send it 3" off the anticipated POI. P2 will only go off by 1.9" ā€“ a difference of 1.1".

Again, the precision that can be gained by P1ā€™s smaller groups (0.5") is lost to the larger wind drift due to estimating the wind speed incorrectly (1.1").





Shooting Scenarios 3 and 4 ā€“ at 100 yards

Letā€™s shoot out to 100 yards, where Pellet 1 consistently groups with 1.5" and Pellet 2 groups with 2.2".



In shooting scenario 3, at 100 yards, with no wind, P1 groups by 0.7" better than P2.



However, in scenario 4 there is a light to medium wind, 2 to 8 mph.

P1 drifts between 4.2" to 16.8".

P2 drifts between 2.7" to 10.9".



Committing a common 2-mph estimation error ā€“ wind was 6 mph instead of estimated (and corrected for) 8 mph ā€“ will drift P1 off target by 4.2". P2 gets drifted off by 2.7".

That is a difference of 1.5" between P1 and P2. This difference is three times larger than the difference in group sizes (0.5").

Therefore, P2 would be preferable in scenario 3.



A 3-mph estimation error ā€“ sends P1 off by 6.3" further than estimated, and P2 by 4.1".

That is a 2.2" difference, over four times the precision difference between the two pellets!





Summary

So it seems that the advantage that an excellently grouping pellet has over a mediocre grouping pellet can be lost IF the mediocre grouping pellet has a higher BC. In that scenario, the performance of the mediocre pellet gets better (a) the longer the range of the shot is, and (b) the larger the wind estimation error is.


 
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I found out yesterday that pellet FPS can make or break the accuracy of some pellets. I tuned my .22 Gauntlet to shoot 18.13 gr. JSB's at 860 FPS and they scattered all over the target at 27 yards. Re-tuned to 830 FPS and they stabilized back to almost hole in one 10 shot strings.

As for other weight pellets, they may or may not be more forgiving.
 
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Your barrel may also determine what pellet does well at which speed.Ā 

My .30 Flexes with TJ barrels shoot .30 Polymags well up to 875fps or so. Faster than that they start to tumble. My .308 Texan SS shoots Polymags well at any speed, even up to1000fps or faster.Ā Each barrel as a different twist rate so there is another variable at play between theĀ barrels.Ā 
 
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This is a really good post - thank you for sharing. This topic is something I think about all the time when I am looking into a purchase. I've never put it on paper because, as we see, it's gets a bit confusing when trying to put it into words and pictures.

To try and paraphrase what I believe this post is trying to get you to think about:

Title: Ideal pellet/slug choice based on fpe.Ā 

Body: For any given fpe output there will be slugs and pellets which are in their 'ideal' speed range and ones which would be traveling too fast or too slow to be useful and/or accurate. This chart gives you a starting point for what pellets are 'ideal' to test in gun A with specific fpe output X.
 
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ctsshooter,


thanks! šŸ˜ŠĀ 

Yes, actually the chart goes both ways ā€” thank you for your input:


(1) What power should I get ā€” i.e., either purchase, or tune)?

(2) What projectiles can I shoot at my current power level?



As far as "ideal" power level for a given projectile ā€” actually I should make a diagram for that one...! šŸ˜„
Because....

šŸ”¶(1) the faster the projectile the less drop, and thus:

ā–Ŗthe longer your point blank range (PBR) where you don't need to make any elevation corrections, and also,

ā–Ŗthe less ranging errors will affect your POI.

ā–ŖBut there are limitations:


šŸ”¶(2) Generally, velocity for slugs should always stay under 950fps (1000 for heavy). Velocity for heavy pellets under 950, and for lighter pellets less, say under 850 (as they will have a better BC, at least the JSBs that Bob Sterne researched in .22), and for wadcutters even less. If velocities are higher they will increase drag and thus the BC will suffer, which will increase wind drift and decrease power delivered at the target.



šŸ”¶(3) Hollow point pellets should have a target velocity of at least 600fps (.22cal) in order to expand ā€” that's why we shoot them in the first place....
And of course, that is not the muzzle velocity (MV) but the target velocity (TV) = way out there where your HP tears into the flesh of the not-worth-to-live pest animal.... šŸ’€

However, 600fps might not be sufficient to assure expansion, so 700fps TV is a more realistic value.

And the minimum TV for HP slugs to expand ā€” well, I posted a question on that but haven't gotten much response yet....



ā–ŖHollow points "are more open" to expansion if they have wide open cups.

Some HP with wide open cups are: Destroyer, Daisy HP, Hornet (with tip), Crow Magnum, Skenco NewBoy HP.

ā–ŖHPs are also less resistant to expansion if they are "softies" ā€” i.e., if they are made from softer lead. Harder pellets have more antimony in the lead mix and thus are:Ā 

(a) more resitant to deformation when your friendly postal service throws your valuable box of pellets into his truck.

(b) more resistant to deformation when your carefully aimed shot passes smoothly right through your quarry's flesh (not so good because we want HP expansion).

Some soft lead HP are: Hades, Polymag, Metalmag, Daisy HP, Red Fire.



šŸ”¶ (4) Limitation: The faster the projectile, the more air you use, the louder your gun gets, and the less shots you get.Ā  And the more modding you might need to do in order to get to that velocity.Ā 

None of these things are desirable, so you need to find your personal balance between the advantages and disadvantages of a high velocity.... Everybody has their own ranking of criteria what's more important to them. šŸ‘šŸ¼


!!! All these are general guidelines, in the end the gun will decide what pellets/slugs it likes, but when it likes several there are some choices the shooter can make.... šŸ˜„

Matthias
 
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Yupp, I learned that from the author of the graph in your post...! šŸ˜„

Bob Sterne, aka rsterne, mainly active on GTA.Ā 

Untiring experimenter and modder, deep technical analyst, and such a clear writer! šŸ‘šŸ¼



His very own sub-forum:

https://www.gatewaytoairguns.org/GTA/index.php?board=224.0





šŸ”¶ Bob has since updated that chart, improving on the more extreme values, and using a drag function more suitable for pellets (GA instead of G1).



I use his chart frequently (and long for similar charts for other pellets...!) šŸ˜Š.

Also,Ā in my ballistic app Strelok Pro I use Bob's variable BCs.



Here is his updated chart attached. šŸ˜Š

Matthias



BCs of JSB .22 Pellets ā€” Variable with Velocity (Bob Sterne)



1592257835_11970848975ee7ed2b6a8ff9.70995475.jpg

 
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