What is more important? Speed V Pellet V Barrel

[cavedweller]

Need some stink tank advice - translation = like a think tank with airheads as contributing members.

What is most important in accuracy

for the sake of "this" discussion assume all other variables which affect accuracy like the shooter and the wind are set aside

BC of a pellet
Speed of a pellet
Barrel choice

Or?

Guessing and emotional attachments do not matter to this topic... real world experience, or science do.

 

[Vetmx]

They all are of equal importance. One or two of the three choices will never get you there.

 

[JungleShooter]

Airhead #2 to Rudy in the Cave,

the BC of the projectile only matters for two things:
➊ amount of wind drift
➋ amount of projectile drop over distance


➊ If wind is not a factor (as per OP)
➧ then BC is not important for accuracy (as far as wind is concerned).

➋ If ranging correctly (or range error) is not a factor (as I would assume since Wind and Shooter are no factors)
➧ then again BC is not important for accuracy.


Cheers,

Matthias

 

[cavedweller]

Airhead #2 to Rudy in the Cave,

the BC of the projectile only matters for two things:
➊ amount of wind drift
➋ amount of projectile drop over distance


➊ If wind is not a factor (as per OP)
➧ then BC is not important for accuracy (as far as wind is concerned).

➋ If ranging correctly (or range error) is not a factor (as I would assume since Wind and Shooter are no factors)
➧ then again BC is not important for accuracy.


Cheers,

Matthias

now we're stinking... i meant thinking.
People often discuss a barrel being pellet fussy without discussing the speed a pellet is being pushed at? So...?
kinda goes back to my original thought train of finding a "correct" barrel as the most important thing?

 

[JungleShooter]

One of the principal stinkers.... I meant, Princes of Thinkers in airgunning, Bob Sterne —
has blessed airgunning with lots of deep thinking and analysis and science.
He is usually active under rsterne on

Airgun Forum | GTA International Airgun Forum | 17,332+ Members

The Gateway to Airguns forum is the oldest, largest, and most active airgun forum & knowledge archive. Used internationally by airgun enthusiast and industry professionals to discuss and share all things related to airguns. From vintage airguns to the most modern PCP airguns.

www.gatewaytoairguns.org

He published an eye-opening, what do I say, an eye-popping graph he had assembled — where he compares the influence of several factors on accuracy:
● Range error [here: 2%]
● Muzzle velocity variation ["extreme spread" = ES] [here: 4% of MV]
● Wind estimation error [here: 2mph]


In the graph below you can see how the influence on accuracy of these 3 different factors changes as range increases.

The further out you shoot.... — Wind wins every time — meaning, getting a correct wind call is more important than most other things.
And that is why the importance of BC increases with range.

Matthias

 

[Vetmx]

now we're stinking... i meant thinking.
People often discuss a barrel being pellet fussy without discussing the speed a pellet is being pushed at? So...?
kinda goes back to my original thought train of finding a "correct" barrel as the most important thing?

It goes back to what I originally said. You have the greatest barrel. A tin of MRD’s all sized and weight sorted. But your gun won’t push them to let’s say 945fps without being a blubbering air cannon. I will flat out admit that I’m a barrel guy. I absolutely believe it’s the foundation of everything accuracy related. But it still is only one component of the whole chase.

 

[Vetmx]

Oh and with airguns, pellets or slugs, I don’t care about BC. Why? I want the smallest most consistent groups at distance. When I find that, the BC will be what it is and I will deal with it because it’s consistent and accurate. Great BC and bigger groups will never win me over.

 

[JimD]

I think of accuracy as different from influences of ambient conditions. I agree wind is a big influencer of where the pellet hits but I don't think it influences the smallest group I can shoot when it isn't windy or the highest score I can shoot on a 30 yard challenge target. I want to know what setup will give me the best accuracy under good conditions but it is important to know how to shoot when wind is around too,

I think finding the most accurate setup for your gun starts with finding a projectile or projectiles your gun likes. In my experience that is not strongly a function of velocity. As an example, one of my 5 pcps is a 25 caliber P35. It was my first P35. I shot a bunch of pellets out of it and noticed it shot JSB 33.95 grain pellets well but only at about 700 fps. I did not want to standardize on a pellet at this velocity and it shot H&N FTTs pretty well too and they were going nearly 900 fps. So I turned the regulator down a little and they were going about 875 and I shot this tune for a couple years, Recently I got a Extreme Airguns plenum and put it on this P35 raising the plenum space from about 10cc to about 35cc. I again tested a range of pellets. The FTTs are not accurate now but they are going well over 900 fps which I think is too fast for them. 25.39s that didn't shoot great at the old tune still didn't shoot great. But the 33.95s that shot well initially now shoot really well. The best 30 yard challenge score I shot with the old tune was a 155. Part of that is scope, it's normal scope is a 4-14 and I like more magnification for this target. But now it's best is a 192. I think it will do better, But the big point for this discussion is the pellet that shot well at 700 fps also shoots well at 800 fps.

After you find a pellet the gun or barrel likes then I think it is appropriate to try modest changes to the tune to try and improve things a bit. Mainly change hammer spring force. Possibly a little different regulator setting. I have had zero instances where making these changes caused a good shooting projectile to start shooting badly. But the 33.95 pellets that shot pretty well at 700 shoot better at 800. I don't think it is so much the velocity as it is the gun likes the current tune better.

I would put bc into the "ambient conditions" camp for accuracy. I think it affects drop and especially wind drift but I don't think the barrel knows the bc or likes projectiles that have a particular bc, Making POI errors from misjudging range or wind is a good thing but only if the projectile is accurate in your gun.

When my 25 caliber P35 was shooting a 155 I decided it needed a new barrel and I ordered one from Krale. Snowpeak doesn't fill parts orders very promptly so it's taken a few months for my new barrel to make it on a boat but it is supposed to be on it's way to Krale now. When I get it, I am interested to see how it shoots. Will it like the same pellets the current barrel likes? Will it want a little different tune? If it wants a major retune it probably won't get it. I am pretty happy with the current barrel now. My guess is it will like the same pellets pretty well but we'll see.

 

[dens228]

Shooting too slow or too fast out of a good barrel won't be the best but you could adjust.
Shooting perfect speed out of a crap barrel will suck and changing speed won't make a bad barrel good.

I choose to shoot the best speed for my needs that are accurate out of a good barrel. LOL

 

[Vetmx]

I think of accuracy as different from influences of ambient conditions. I agree wind is a big influencer of where the pellet hits but I don't think it influences the smallest group I can shoot when it isn't windy or the highest score I can shoot on a 30 yard challenge target. I want to know what setup will give me the best accuracy under good conditions but it is important to know how to shoot when wind is around too,

I think finding the most accurate setup for your gun starts with finding a projectile or projectiles your gun likes. In my experience that is not strongly a function of velocity. As an example, one of my 5 pcps is a 25 caliber P35. It was my first P35. I shot a bunch of pellets out of it and noticed it shot JSB 33.95 grain pellets well but only at about 700 fps. I did not want to standardize on a pellet at this velocity and it shot H&N FTTs pretty well too and they were going nearly 900 fps. So I turned the regulator down a little and they were going about 875 and I shot this tune for a couple years, Recently I got a Extreme Airguns plenum and put it on this P35 raising the plenum space from about 10cc to about 35cc. I again tested a range of pellets. The FTTs are not accurate now but they are going well over 900 fps which I think is too fast for them. 25.39s that didn't shoot great at the old tune still didn't shoot great. But the 33.95s that shot well initially now shoot really well. The best 30 yard challenge score I shot with the old tune was a 155. Part of that is scope, it's normal scope is a 4-14 and I like more magnification for this target. But now it's best is a 192. I think it will do better, But the big point for this discussion is the pellet that shot well at 700 fps also shoots well at 800 fps.

After you find a pellet the gun or barrel likes then I think it is appropriate to try modest changes to the tune to try and improve things a bit. Mainly change hammer spring force. Possibly a little different regulator setting. I have had zero instances where making these changes caused a good shooting projectile to start shooting badly. But the 33.95 pellets that shot pretty well at 700 shoot better at 800. I don't think it is so much the velocity as it is the gun likes the current tune better.

I would put bc into the "ambient conditions" camp for accuracy. I think it affects drop and especially wind drift but I don't think the barrel knows the bc or likes projectiles that have a particular bc, Making POI errors from misjudging range or wind is a good thing but only if the projectile is accurate in your gun.

When my 25 caliber P35 was shooting a 155 I decided it needed a new barrel and I ordered one from Krale. Snowpeak doesn't fill parts orders very promptly so it's taken a few months for my new barrel to make it on a boat but it is supposed to be on it's way to Krale now. When I get it, I am interested to see how it shoots. Will it like the same pellets the current barrel likes? Will it want a little different tune? If it wants a major retune it probably won't get it. I am pretty happy with the current barrel now. My guess is it will like the same pellets pretty well but we'll see.

So while your post seems to indicate that you are leaning on the pellet is the most important, your search for the right projectile was dictated by your barrel. Or bad barrel. Your leade is cut too deep and that’s why your gun always favors the 33.95, fast or slow. So your foundation is bad but you were able to find a work around with a longer projectile.

 

[bigHUN]

In my eyes .... The good barrel / twist rate is the most important.
Slug it and find a pellet/slug for it.
Better luck also better performance you can get if you resize to the barrel.
And from here chasing for correct speed/RPM begins.

 

[Spartan]

One of the principal stinkers.... I meant, Princes of Thinkers in airgunning, Bob Sterne —
has blessed airgunning with lots of deep thinking and analysis and science.
He is usually active under rsterne on

Airgun Forum | GTA International Airgun Forum | 17,332+ Members

The Gateway to Airguns forum is the oldest, largest, and most active airgun forum & knowledge archive. Used internationally by airgun enthusiast and industry professionals to discuss and share all things related to airguns. From vintage airguns to the most modern PCP airguns.

www.gatewaytoairguns.org

He published an eye-opening, what do I say, an eye-popping graph he had assembled — where he compares the influence of several factors on accuracy:
● Range error [here: 2%]
● Muzzle velocity variation ["extreme spread" = ES] [here: 4% of MV]
● Wind estimation error [here: 2mph]


In the graph below you can see how the influence on accuracy of these 3 different factors changes as range increases.

The further out you shoot.... — Wind wins every time — meaning, getting a correct wind call is more important than most other things.
And that is why the importance of BC increases with range.

Matthias

View attachment 420334

That graph is one of the most useful and meaningful "info-graphics" I have ever seen. I've seen it before—presumably you posting it elsewhere—but I was just reminded of that. Well done. Thanks

 

[cavedweller]

Oh and with airguns, pellets or slugs, I don’t care about BC. Why? I want the smallest most consistent groups at distance. When I find that, the BC will be what it is and I will deal with it because it’s consistent and accurate. Great BC and bigger groups will never win me over.

That makes absolute sense

 

[beerthief]

It goes back to what I originally said. You have the greatest barrel. A tin of MRD’s all sized and weight sorted. But your gun won’t push them to let’s say 945fps without being a blubbering air cannon. I will flat out admit that I’m a barrel guy. I absolutely believe it’s the foundation of everything accuracy related. But it still is only one component of the whole chase.

and if you have a sucky barrel to start with your shots are going to be sucky so that is the first step .

 

[JimD]

Vetmx, the leade might be generously sized, all three of my P35s like a heavy for caliber pellet. I shoot a 10.6 grain in 177, 21 grain in 22 and the 34s now in 25. But I used 20 grain 25s in the previous tune. They were not as accurate in the current tune but shot about as well as the 34s did at the low power tune I was using at the time. I've killed 18 squirrels with the 20s. I don't know what it means about leade but some slugs shoot decently in the 25 at it's current tune. Not as good as 34 grain pellets but at least as well as anything shot at the previous tune. 34 grain H&N and 26.8 grain Nielsens (shooting what I had on hand, lighter H&N did not shoot well).

I was really surprised at how differently and well my 25 caliber shot after retuning. I was totally convinced I had a bad barrel. The best it could do was an occasional 3 shot 1/4 inch group at 25 yards. 5 shot groups were over 1/2 inch. But now it will put 5 into about 1/4 inch at 30 yards. Makes me wonder how many "bad barrels" are at least as much bad tunes as bad barrels.

I think we really need a barrel, pellet, and tune that work well together. If any are not good, the gun is not going to shoot as well as it can. I don't think we can make a gun like a pellet by changing the tune/speed (I've tried). But if the pellet shoots reasonably well at whatever tune we are using we can make it shoot better in many cases by improving the tune. The velocity may go up or down in the search for best accuracy but I don't think the velocity is the key, I think it is finding a tune/velocity that is harmonically good for the gun/barrel/pellet.

 

[Ballisticboy]

There are a lot more factors deciding group size than the ones in Bob's graph, some of which affect accuracy rather than group size. In order to be able to hit a target with the first shot, you need a combination of small group size and accuracy, in that the shot lands on or near to your point of aim. Just being able to put ten shots in a dime sized hole at a known range under ideal conditions, does not mean you will hit the intended point on your first shot. Many will claim that is just down to the skill of the shooter once you have a small group, but there are also other factors to consider, such as atmospheric changes, bullet or pellet performance changes with conditions, range errors etc. etc.

As for group size, other factors to be considered are pellet initial yaw rate, centre of gravity consistency, pellet shape consistency, barrel twist rate, barrel pellet fit, to name but a few. Normal trajectory apps are not capable of modelling any of those, or the errors they produce. You need much more data and complex programs.

Pellet, barrel, gun and shooter need to work as a system, just considering one or the other does not give you the results you want.

 

[lbc_PSI]

What about OAL of the pellet and the depth of the skirt?

Are airguns like PBs where you try to seat the bullet in the case to the depth that results in the bullet just touching or shy of the lands when chambered?

With all the different lengths of pellets due to weight and varying depth of skirts and the probe (pellet pusher) being the only constant, maybe the “favorite” pellet is just determined by how far into the barrel the probe pushes the pellet.

It would be interesting if there were an adjustable length probe.

 

[JungleShooter]

What about OAL of the pellet and the depth of the skirt?

Are airguns like PBs where you try to seat the bullet in the case to the depth that results in the bullet just touching or shy of the lands when chambered?

With all the different lengths of pellets due to weight and varying depth of skirts and the probe (pellet pusher) being the only constant, maybe the “favorite” pellet is just determined by how far into the barrel the probe pushes the pellet.

Someone else of the XLR shooters here mentioned something like that...!

 

[lbc_PSI]

Someone else of the XLR shooters here mentioned something like that...!

Thx missed that

 

[JimD]

I don't think the pellet seating depth is a large factor but it wouldn't be too hard to make a simple tool to push the pellet further into the barrel if you wanted to test the effect. On a PB the distance from the point of the bullet that will contact the rifling and the rifling changes the pressure build up. The peak pressure is lower if you let the bullet jump a little to the rifling. Chambering the bullet hard into the rifling will increase pressure. But in an airgun we are not burning anything (hopefully) so we cannot affect powder combustion. I guess you could theorize that pushing the pellet firmly into the rifling would allow pressure to build a little more in the "chamber" possibly increasing velocity a little. Anything like this could affect the harmonics and thus accuracy but my guess is the sliding of the pellet down the barrel is a much bigger driving force for the harmonics.