What's with the Slug Speed fetish lately?

Another reason is BC is affected by velocity. So in your example, a given slug going 900fps at the muzzle will have more wind drift at all distances than if it starts at 1050fps. And that is then multiplied by the TOF difference between the two speeds. Admittedly in some cases the difference is very very small, but why leave performance on the table? If you are just punching paper at 25/50 yards it wont matter. But many of us are using our rigs at extended ranges where the extra 100-150fps really makes an obvious difference.
Simply not true. I think you skipped over what Bob Sterne and @Ballisticboy have been saying repeatedly on AGN for years now. But hey, feel free to believe what makes you happy. Kinda like believing the economy is better now than two years ago. It makes some people happy to think that. 😉
 
All of it. Faster doesn’t mean less wind drift for subsonic projectiles. TOF has no bearing on wind drift or BC. Go ahead and plug your 900 and 1050 in a left to right 10mph cross wind. You’ll be surprised.
Ok I guess we just fundamentally disagree. I have a lot of experience (anecdotal perhaps) shooting the same projectile through the same rifle at different muzzle velocities and have clearly observed differences in wind deflection. TOF doesnt affect BC, but then again thats not what I said anyway. Using a ballistic calc is misleading since you cannot calculate the difference in starting BC changes due to different speeds. No offense meant to Bob or @Ballisticboy, but BC does change with velocity and has been well documented. You have to remember what BC actually is and represents.

Maybe you can explain to me how TOF "has no bearing on wind drift.." because that seems crazy to me lol.
 
Yup. Science is science. And science doesn’t care whether you believe in it or not. You can disagree all you want, but the Earth isn’t flat…
Maybe the science @Ballisticboy can step in here, but he’s probably tired of explaining the same thing over and over and over…
Just repeating that you are right and I am wrong doesnt prove anything or further the discussion. Lets try this, can you explain what BC represents without using google?

Wanted to ad: Im going to take the explanation given by organizations like Berger over "You can disagree all you want, but the Earth isn't flat...". You made the claim TOF has no bearing on wind drift but wont explain it.
 
Here I have a better idea you can argue with Berger or Applied Ballistics instead. I have made a counter argument and will even provide a source for your reading pleasure.

"It’s a relatively well known fact that the BC of a bullet is different at different velocities. Not many shooters know why it changes, or what the consequences are. To understand why a BC changes at different speeds, we have to go back to the definition of BC, which is: The ability of the bullet to maintain velocity, in comparison to a ‘standard projectile’. It’s the ‘standard projectile’ part of the definition that we need to key in on. What is the ‘standard projectile’? What does it look like?"

 
There is a lot of misunderstanding regarding BC's that is true, the most common one being that BC varies with speed. BC will have small changes with speed, since any reference drag curve cannot match the drag curve for every design of projectile. However, the fact is that in the vast majority of cases, large changes in BC with speed are entirely due to the use of an inappropriate reference drag law. When the correct reference drag law is used, a single value of BC will be correct at all speeds, this is the entire basis of the BC system as it was originally envisaged. Many of the so-called experts who claim BC always varies with speed basically do not know what they are talking about., as they are using the wrong reference drag law.

The biggest example of the wrong drag law and the one which clearly shows up the problems is the use of G1 for large meplat slugs as represented by the majority of available slug designs. Below is a calculated drag law for a 50% meplat .22 30grain slug compared to the G1 reference drag law. Yes, the slug drag law is calculated but data being collected suggests it is a good initial representation of slug drag, showing substantially smaller changes in BC with speed.

Slug G1.jpg


The reference drag law is supposed to be the same shape as the actual drag law, and clearly it is not, leading to multiple BC values being needed to try to approximate to the real shape. This means that G1 based BC values at around 1000 ft/sec are hugely optimistic for any other speeds, but it enables manufacturers to make claims for measured BC values.

There is another point which many do not seem to grasp. The increased BC value at high speeds does not mean the drag is miraculously reducing at higher speed. You can see from the actual drag curve it is still increasing, just not as much as the G1 drag law and hence the increased BC value.

In terms of down wind drift, BC is also somewhat misleading. If a perfect reference drag law is used and a single value of BC can be used, that does not mean the drag coefficient is not increasing. You cannot see the drag increase in terms of the BC value because it is hidden in the reference drag law. So your drag coefficient is increasing with speed and giving increased cross wind effect and more down wind drift.

Neither is down wind drift a function of time of flight. It is a function of the "lag time" (not usually called lost time) which is the difference between the actual time of flight to the target and the time of flight if there was zero drag. This means that if your actual time of flight is the same as the time of flight with no drag there is zero down wind drift. This has been shown on many occasions with projectiles with a form of propulsion. It has also been shown that accelerating projectiles which have a negative lag time drift up wind, not down.

On the question of speed and the effect of muzzle velocity on wind drift, as said, Bob Sterne has shown diagrams on many occasions demonstrating the effects of increased speed on wind drift. I knocked out the diagram below for the slug described above using the actual drag law, not BC or G1. The model is similar to ones I used when working which use purpose drag laws, not BC.

Slug wind drift.jpg



In every case at all ranges the minimum down wind drift is around just below 1000 ft/sec. The longer the range, the more the drift increases at higher speeds. The reason they are all have the same optimum speeds no matter what the range is probably because the optimum speed is a function of the drag curve shape rather than the range which you may expect.
 
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There is a lot of misunderstanding regarding BC's that is true, the most common one being that BC varies with speed. BC will have small changes with speed, since any reference drag curve cannot match the drag curve for every design of projectile. However, the fact is that in the vast majority of cases, large changes in BC with speed are entirely due to the use of an inappropriate reference drag law. When the correct reference drag law is used, a single value of BC will be correct at all speeds, this is the entire basis of the BC system as it was originally envisaged. Many of the so-called experts who claim BC always varies with speed basically do not know what they are talking about., as they are using the wrong reference drag law.

The biggest example of the wrong drag law and the one which clearly shows up the problems is the use of G1 for large meplat slugs as represented by the majority of available slug designs. Below is a calculated drag law for a 5% meplat .22 30grain slug compared to the G1 reference drag law. Yes the slug drag law is calculated but data being collected suggests it is a good initial representation of slug drag, showing substantially smaller changes in BC with speed.

View attachment 369222

The reference drag law is supposed to be the same shape as the actual drag law, and clearly it is not, leading to multiple BC values being needed to try to approximate to the real shape. This means that G1 based BC values at around 1000 ft/sec are hugely optimistic for any other speeds, but it enables manufacturers to make claims for measured BC values.

There is another point which many do not seem to grasp. The increased BC value at high speeds does not mean the drag is miraculously reducing at higher speed. You can see from the actual drag curve it is still increasing, just not as much as the G1 drag law and hence the increased BC value.

In terms of down wind drift, BC is also somewhat misleading. If a perfect reference drag law is used and a single value of BC can be used, that does not mean the drag coefficient is not increasing. You cannot see the drag increase in terms of the BC value because it is hidden in the reference drag law. So your drag coefficient is increasing with speed and giving increased cross wind effect and more down wind drift.

Neither is down wind drift a function of time of flight. It is a function of the "lag time" (not usually called lost time) which is the difference between the actual time of flight to the target and the time of flight if there was zero drag. This means that if your actual time of flight is the same as the time of flight with no drag there is zero down wind drift. This has been shown on many occasions with projectiles with a form of propulsion. It has also been shown that accelerating projectiles which have a negative lag time drift up wind, not down.

On the question of speed and the effect of muzzle velocity on wind drift, as said, Bob Sterne has shown diagrams on many occasions demonstrating the effects of increased speed on wind drift. I knocked out the diagram below for the slug described above using the actual drag law, not BC or G1. The model is similar to ones I used when working which use purpose drag laws, not BC.

View attachment 369228


In every case at all ranges the minimum down wind drift is around just below 1000 ft/sec. The longer the range, the more the drift increases at higher speeds. The reason they are all have the same optimum speeds no matter what the range is probably because the optimum speed is a function of the drag curve shape rather than the range which you may expect.


Spectacular. Again. ⭐

Thank you, Miles. You enrich our hobby with science-based useful knowledge. 😊

Matthias
 
I got into pellet guns to shoot pellets… slugs? No thanks! My rim fire with CB Caps is just right, many pigeons would attest if they could. Don’t see the need to reinvent the wheel…


Yeah, Luis, for many that might be that way! 👍🏼

However.... 😉

🔘 There are places where a firearm is just not the best option:
• Noise (firearm silencers are very complicated to get)
• Legality
• Size (firearm bullpups are not very common — thanks to EDgun's Ed we get to have lots of bullpup options in airgunning)

🔘 Many of us are in airgunning in part for the challenge: The challenge to shoot small groups consistently, the challenge to get a high score on the paper target, the challenge to find and hunt down a prey:

Some even switch from PCPs to springers — for the challenge of mastering the springers' hold-sensitivity.

So, for some it's the challenge to achieve firearm performance with "pellet-guns" — performance as in range and precision, for for some, killing power in hunting big game.


🔘 Lastly, some of us are not as fortunate to live in a country with a 2A.
I have attempted to get my firearms license for a measly .22 carbine THREE TIMES. 😖
➔ And even though I fulfill the local requirements easily.... — I still don't have the license in my posession. (Nor the gun I paid for.)
I spent way more money on the license paperwork than what the gun cost.... 😵



So, yeah, I get it, for many slugs appear to be just an unnecessary accessory that creates a lot of fuss.
⁍ For others, however, slugs are an exciting option that widens the horizon of our hobby. ⁌


😊 I'm thankful to Nick from NSA slugs who's slug offerings and prices put pressure on other manufacturers to increase their offerings and lower their prices! 👍🏼

Matthias
 
@JungleShooter, Points well made and taken…. And in your situation, I see where slugs might appeal. And though we in the USA have easier access to firearms. I have no desire to pursue that venue. For fun I will lob my pellets as far as I feel like. For shooting at a living thing like a pest or small game? 100 yards max, but more like the 25-60 yard range in practice. So for me slugs aren’t a game changer.
 
Accuracy, accuracy, accuracy! Speed is not necessarily THE defining factor in accuracy. However, when I got my new Huben tuned to 38.5 NSA. Kelly had her tuned 920 and it had a great group @ 75yds. Just for giggles I give the dial a twist and dang if I didn't see something happen. Gave it another, now they're all touching in tight little circle. 950-960 fps. So the right speed had a lot to do with my accuracy. But just slinging it out @ light speed is NOT the answer.
I really try to tune as low as possible for accuracy. Mark 2's @ 870. A lot of air usage @ light speed.
 
Until very recently, I’ve been whole-heartedly uninterested in slugs. I’m not really into the faster and more powerful stuff. I mostly just shoot paper and steel. Then I read weevil’s 1701p thread. Which led me to some YouTube videos on sub 12 and slug shooting. Since most of my airguns are sub 12 and .177, I’m going to give it a go. I bought some ZAN 10 and 13 grainers to start. We’ll see how it goes.
 
Until very recently, I’ve been whole-heartedly uninterested in slugs. I’m not really into the faster and more powerful stuff. I mostly just shoot paper and steel. Then I read weevil’s 1701p thread. Which led me to some YouTube videos on sub 12 and slug shooting. Since most of my airguns are sub 12 and .177, I’m going to give it a go. I bought some ZAN 10 and 13 grainers to start. We’ll see how it goes.
I read that too and bought some Zan 13s. Out of my 1720 they were not acceptable @600ish if I remember correctly. I should have bought a box of 10gr too, but didn’t.
That was with the stock tp. I will try them again when I bump it back up to 11-12 fpe.

I see no need in my low power world other than experimentation.
 
I read that too and bought some Zan 13s. Out of my 1720 they were not acceptable @600ish if I remember correctly. I should have bought a box of 10gr too, but didn’t.
That was with the stock tp. I will try them again when I bump it back up to 11-12 fpe.

I see no need in my low power world other than experimentation.


It’s fun to experiment! A while back I tried sub12 slug challenges in my FX DreamTact compact with 300mm barrel, results in hind sights are damn good!
 
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That’s what is so entertaining about forums and the internet. Right now I could go grab a random gun out of my safe, grab a random slug, shoot a good group then post it on a forum. Instantly 200 guys with that gun are placing orders for that slug. Little do they know that the next day my gun was shooting like sh#t. So funny.
 
That’s what is so entertaining about forums and the internet. Right now I could go grab a random gun out of my safe, grab a random slug, shoot a good group then post it on a forum. Instantly 200 guys with that gun are placing orders for that slug. Little do they know that the next day my gun was shooting like sh#t. So funny.


Yeah, I remember you mentioned something like this elsewhere.

➠ Was the first group just an "accident" — a lucky group? And the groups the next day representative of the average precision the gun/slug combination is capable of?

Or what would cause such a curious discrepancy?


I need to understand this before I slide deeper down the slug rabbit hole. Thanks! 👍🏼

Matthias
 
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