Diabolos speed vs stability vs caliber?

[GA_LeadHead]

I've seen multiple posts where it mentions that the 'ideal' speed for accuracy and pellet stability with diabolos is in the mid to upper 800's. Few posts saying low to mid 900's. My question is, does that apply to all calibers? For example, I shoot .22, .25, and .30 hades. Should I tune all three to shoot for that 'magical' speed, or is it different for each caliber? And then what about weight? I would think that king heavies, for example, would stabilize better at a faster speed than say a regular. Thanks.

 

[Franklink]

My two cents......

It's not caliber specific so much as situation specific. Certain pellets (25.4gr/.22 Monster RDs) actually do better at 950+, which goes against the traditional views on pellet speeds. 

Then there's also the type of rifling. It seems that poly barrels can generally take more speed than traditional rifled barrels and still be really accurate at those high speeds.

I personally feel like the truly diabolo shaped pellets (I call them wasp waisted pellets) don't like to go very fast. The newish stuff that is heavy for caliber (NOT wasp-wasted), like the aforementioned 25.4gr/.22s, and the 16.2/.177s can handle more speed. (this is where the generalization is going to get me though, cuz somebody's going to pipe up and say they shoot the .22/18.1s at 1010fps and they're phenomenal)

I also really like the JSB 10.34 in .177, (a straight-walled pellet), around 920fps from a polygonal barrel.

So, yeah, very situation specific.

 

[Franklink]

One more thought......The Heavy .20s from JSB taught me an interesting concept. I was measuring their ballistic coefficients and found them to have a significantly higher (better) BC at around 910fps than they have at 860ish. 

The best part of all that though, is that you get to do the testing to figure out what your gun and barrel and chosen pellet like best. And that means getting to shoot. 

 

[Raider03]

The 25.4gr .22 Monster RDs have a shallow skirt that generates less drag stablization. So it can fly stablely at higher speeds. Deeper skirted pellets will have more drag stabilization and become over-stabilized and unstable at a lower speed. The combination of spin stablization from barrel twist rate and drag stablization determines the maximum stable muzzle velocity for gun/pellet combination.

Polygonal barrels deform pellets less then regular rifling. Less deformation produces less drag and a higher maximum stable velocity. As wind increases pellet velocity will have to decrease to maintain stability. Many details, but, that makes for an interesting problem.

IMHO

 

[dizzums]

well as you approach mach 1100 or so it has a destabilizing affect, and the harder your mechanics are wrking to make speed the more 'artifacts' that are likley to be imparted to your projectile .. everythings a compromise .. you want enough energy to be effective .. and ideally you want a trajectory youre familiar with since everthing falls at the same rate .. about 900 is a good compromise and you can tweak it from there depending on what your up to and the tradeoff thats gonna work ... 600fps and ultra accurate is fine 30ft indoors targeting .. alittle faster on 177 is prolly better at longer range as it wont get pushed around as much. and so on ...

 

[Franklink]

The 25.4gr .22 Monster RDs have a shallow skirt that generates less drag stablization. So it can fly stablely at higher speeds. Deeper skirted pellets will have more drag stabilization and become over-stabilized and unstable at a lower speed. The combination of spin stablization from barrel twist rate and drag stablization determines the maximum stable muzzle velocity for gun/pellet combination.

Polygonal barrels deform pellets less then regular rifling. Less deformation produces less drag and a higher maximum stable velocity. As wind increases pellet velocity will have to decrease to maintain stability. Many details, but, that makes for an interesting problem.

IMHO

Very interesting thoughts on the shallow versus deep skirts, as it does seem like the shallow skirt commercial pellets (heavy ones) do sometimes seem to be the ones with the best long range accuracy potential. Although, casting NSA .22 pellets that have pins to change the depth of the skirt, the pellets produced with the most hollow skirt shoot better than the ones with shallower skirts.

That drag stabilization concept of pellets was covered by Miles Morris in this link. "debunked" as he puts it.

https://www.gatewaytoairguns.org/GTA/index.php?topic=169459.0

He prefers to call is flare stabilization, which might just be a puhtayto, puhtahto situation. Anyway, very interesting read as I understand he is a ballistician out of the UK, quite literally, that is his profession. 

Anyway, good read over there. Most of it over my head, even if I read it a couple times. I'm more of a, let's-shoot-and see-what-the-results-are type of guy than one that gets into the theoretical stuff much, although I do enjoy the theory and discussion (just would rather shoot and compare results). 

 

[Jayson]

Great feedback on all accounts! But like they said, go shoot them? For years I stayed away from the no no over 900’s? I really don’t know anymore?
I just went shooting with a friend, that was shooting 25 cal 25 grn kings @ 960 fps unbelievably well? Moa @ 100 yds all day??

I really would have lost money on that one? 

 

[BackStop]

Unfortunately, the only real way to know how ANY projectile will perform is to shoot it, and shoot it a lot.

The unfortunately part comes in when you find out that the projectile you thought would or wanted to work well in your gun/barrel simply doesn't have acceptable accuracy/precision at the power level(s) you need.

So... so far, I have found no way to establish that criteria more effectively or efficiently than shooting a lot of projectiles, while measuring fps with a chrony, and taking notes on the effects of fps at every range you intend to shoot with that specific projectile.

Ballistics apps/software really does help, but so far, I have found that nothing takes the place of actually shooting and taking meticulous notes on what works and doesn't work with any projectile in any barrel in any gun.

Yep, it can get expensive... (sigh...)

 

[Raider03]

The 25.4gr .22 Monster RDs have a shallow skirt that generates less drag stablization. So it can fly stablely at higher speeds. Deeper skirted pellets will have more drag stabilization and become over-stabilized and unstable at a lower speed. The combination of spin stablization from barrel twist rate and drag stablization determines the maximum stable muzzle velocity for gun/pellet combination.

Polygonal barrels deform pellets less then regular rifling. Less deformation produces less drag and a higher maximum stable velocity. As wind increases pellet velocity will have to decrease to maintain stability. Many details, but, that makes for an interesting problem.

IMHO

Very interesting thoughts on the shallow versus deep skirts, as it does seem like the shallow skirt commercial pellets (heavy ones) do sometimes seem to be the ones with the best long range accuracy potential. Although, casting NSA .22 pellets that have pins to change the depth of the skirt, the pellets produced with the most hollow skirt shoot better than the ones with shallower skirts.

That drag stabilization concept of pellets was covered by Miles Morris in this link. "debunked" as he puts it.

https://www.gatewaytoairguns.org/GTA/index.php?topic=169459.0

He prefers to call is flare stabilization, which might just be a puhtayto, puhtahto situation. Anyway, very interesting read as I understand he is a ballistician out of the UK, quite literally, that is his profession. 

Anyway, good read over there. Most of it over my head, even if I read it a couple times. I'm more of a, let's-shoot-and see-what-the-results-are type of guy than one that gets into the theoretical stuff much, although I do enjoy the theory and discussion (just would rather shoot and compare results). 

The best example of drag or skirt stabilization of a projectile is a bandminton Shuttlecock. No spin, but, it will flip around so the front matches the direction of flight. In order for drag stabilization to work the pellets center of mass must be ahead of the center of pressure. The hollow shirt produces more drag at the back of the pellet and since it is hollow the center of mass is further towards the front. The shallows skirt pellets have more mass towards the rear, moving the center of mass backwards which reduces the distance between the center of pressure and mass. The drag force doesn't change but the torque it can produce decreases. If the center of mass is actual behind the center of mass then only spin will stabilize the pellet, effectively you now have a poorly designed slug. 

If your interested, this video explains why pellets spiral, https://www.youtube.com/watch?v=pR5j4aZwNH0

I use the background as a guideline so I don't try something the won't have any hope of working. Too cold to get to the range and test out some pellets. Ultimately, the proof is in the shooting of the pellet, but, I won't be shooting wadcutters at 50yards.

Thanks for the discussion topic. 

 

[Raider03]

Jayson, was it a calm day, no wind?

 

[Jayson]

Jayson, was it a calm day, no wind?

Fairly calm, 3-5 mph. He was using a 700mm sup hvy liner? Still no fliers, no spirals?

 

[GA_LeadHead]

A lot of interesting and appreciated responses to my question. The science behind all of this is what makes this hobby so much fun. Thanks!!!

 

[tor47]

It seems like thouse which compete, like in extreme benchrest, usually shoot in the mid 800 range, as they often shoot in windy condition. The thing is that most tune theire guns for accuracy when there is dead calm wind. In dead calm wind the gun can probably be accurate with relative high speeds, but the same pellet will get destabilised in windy condition. So for practical use, if you can get the gun to shoot acurately in the mid 800 range, it will probably be more acurate in windy condition also.

 

[muzzlebrake]

I recently bought a few tins of Air Arms Diablo Field 25.39gr 25cal and they shoot as good or better than JSB or FX. I understand they are the same thing made by JSB. They are a little cheaper too. I got mine from https://www.airgun-us.com/ and shipping was fast and reasonable. My FX Impact is shooting them just below 900 fps with the Ken Hicks factory tune.

 

[muzzlebrake]

Interesting video. Maybe helps explain why I am getting more spiral and flyers shooting slugs and JSB heavies and not being able to get MOA at 100yds with the heavy projectile pellet or slug. I use an old Chrony that is a pain to set up but I guess if I am going to turn down the speed for the slugs and heavies then that's what I will have to do to get closer to MOA at 100yd. 75 to 100 is mostly the distance where I am shooting coons and hogs and I want to be able to use heavier slugs and be able to ear hole them for quick kills. Wind is always a factor out where I hunt so this video helps give me a direction to work toward.

 

[btsteelman]

I’ve tried running JSB knockouts real slow and some pellets rather fast and had some surprisingly accurate results. Always pays to test stuff out and see what your gun likes.

 

[broekzwans]

The 25.4gr .22 Monster RDs have a shallow skirt that generates less drag stablization. So it can fly stablely at higher speeds. Deeper skirted pellets will have more drag stabilization and become over-stabilized and unstable at a lower speed. The combination of spin stablization from barrel twist rate and drag stablization determines the maximum stable muzzle velocity for gun/pellet combination.

Polygonal barrels deform pellets less then regular rifling. Less deformation produces less drag and a higher maximum stable velocity. As wind increases pellet velocity will have to decrease to maintain stability. Many details, but, that makes for an interesting problem.

IMHO

Very interesting thoughts on the shallow versus deep skirts, as it does seem like the shallow skirt commercial pellets (heavy ones) do sometimes seem to be the ones with the best long range accuracy potential. Although, casting NSA .22 pellets that have pins to change the depth of the skirt, the pellets produced with the most hollow skirt shoot better than the ones with shallower skirts.

That drag stabilization concept of pellets was covered by Miles Morris in this link. "debunked" as he puts it.

https://www.gatewaytoairguns.org/GTA/index.php?topic=169459.0

He prefers to call is flare stabilization, which might just be a puhtayto, puhtahto situation. Anyway, very interesting read as I understand he is a ballistician out of the UK, quite literally, that is his profession. 

Anyway, good read over there. Most of it over my head, even if I read it a couple times. I'm more of a, let's-shoot-and see-what-the-results-are type of guy than one that gets into the theoretical stuff much, although I do enjoy the theory and discussion (just would rather shoot and compare results).

Flare and drag stabilization is not really the same I also wouldn't call a pellet drag stabilized, there isn't much of a surface for drag stabilization on a pellet.

I've posted a theory a while ago on here about pellet stability and distance estimation: link to topic. If you can follow the explanation a bit it might also help to clarify some stability issues

 

[HogKiller]

I was watching a video on different pellets, most from the same company, guy shot like 8, indoors, same PCP, I'm going to guess about 20 meters, the first mag was nice and tight, after than went to hell fast, all over the place. Much like what I'm getting out of my cheap Remington Nitro BB. I thought it was my gun and it was a bit but I bought a sampler of pellets and oh the differences. I'm going to flip the switch on a Zbroia Sapsan 550S today. The Zbroia gal demonstrating various rifles out to 100 meters is scary good, I think she's a competitive shooter. Being cute doesn't hurt the viewing at all.

 

[cavedweller]

Unfortunately, the only real way to know how ANY projectile will perform is to shoot it, and shoot it a lot.

The unfortunately part comes in when you find out that the projectile you thought would or wanted to work well in your gun/barrel simply doesn't have acceptable accuracy/precision at the power level(s) you need.

So... so far, I have found no way to establish that criteria more effectively or efficiently than shooting a lot of projectiles, while measuring fps with a chrony, and taking notes on the effects of fps at every range you intend to shoot with that specific projectile.

Ballistics apps/software really does help, but so far, I have found that nothing takes the place of actually shooting and taking meticulous notes on what works and doesn't work with any projectile in any barrel in any gun.

Yep, it can get expensive... (sigh...)

Feel like sharing your notes and observations?

 

[BackStop]

Feel like sharing your notes and observations?

I truly wish I had taken notes (written them down or recorded them in some way), but I have not. Yes, I did say that taking meticulous notes is necessary, but I never wrote down anything.

So, I guess I am busted! (sheepish grin)

As much as I like using Chairgun for trajectory estimates, and they are usually pretty accurate if I can put in the correct data, there is no better way to KNOW what any projectile will do than shooting it a LOT. And nobody can say what any projectile will do in YOUR gun with YOUR tune better than YOU shooting it with that projectile a LOT! (smile)

(chuckle)