What are the largest diameter .177 pellets

[Lol Moore]

You could be right Lawrence .

I've just re-read my thread on the other site .

You're also correct in that i cant possibly tell that the pictured pellet has not been fired .
If it has then hats off to the contributor for capturing the pellet in such condition .

Phillip....my name is Lol....confusing in this day of text speak I know

I think we are interpreting the picture differently, its two of the same type pellet, to my eye the skirt of the "fired" pellet has indeed expanded (it looks more rounded) as you say a very good job of capturing has been done. If you cover the bottom quarter of the skirt and just look at the top portion of the skirt it does look different.

This was not intended to join into the debate about whether pellets sealed completely in the grooves of rifling, it just shows that the pellet skirt deforms (as stated by a few on here) and as such the deformation will effect the pellet flight, which is ultimately what counts.

Before all your testing I believed that sealing was probably the case - not so sure now.

I agree there appears to be no evidence on this picture of "sealing".

Anyway, the article is by Hector Medina in the states, he writes some really interesting stuff (as do you ), here is the article:

https://www.ctcustomairguns.com/hect...to-the-rifling

The bit that caught my eye and set me off messing with breeches was this:

Careful experiments have shown that pellets DO DEFORM upon firing. And one of my preferred methods of choosing the best possible pellet for a barrel involves soft-capturing fired pellets and measuring how much they expand at the waist or the column. The more they expand, the less are we in control of the final shape of the pellet once we have pulled the trigger.
Once the pellet starts to move, depending on how the chamber was machined (or not), the head engages the rifling before the skirt and this also exerts a TORSIONAL stress on the waist or the column. At times, this stress may be enough to deform the pellet substantially, in most cases it is not, but it is still mentioned here to point out to problematic barrels that, in reality, need only to have their chambers fitted to the pellet the shooter wants to use.

Great believer in the importance of the skirt - how good do these Qiang Yuan bad boys look

https://photos.app.goo.gl/QXwKC4TaERJgQKxA6

One or two tiny nicks in there but easily fixable on the pellet tin lid with a rub

[RobF]

Phillip....my name is Lol....confusing in this day of text speak I know

I think we are interpreting the picture differently, its two of the same type pellet, to my eye the skirt of the "fired" pellet has indeed expanded (it looks more rounded) as you say a very good job of capturing has been done. If you cover the bottom quarter of the skirt and just look at the top portion of the skirt it does look different.

This was not intended to join into the debate about whether pellets sealed completely in the grooves of rifling, it just shows that the pellet skirt deforms (as stated by a few on here) and as such the deformation will effect the pellet flight, which is ultimately what counts.

Before all your testing I believed that sealing was probably the case - not so sure now.

I agree there appears to be no evidence on this picture of "sealing".

Anyway, the article is by Hector Medina in the states, he writes some really interesting stuff (as do you ), here is the article:

https://www.ctcustomairguns.com/hect...to-the-rifling

The bit that caught my eye and set me off messing with breeches was this:

Careful experiments have shown that pellets DO DEFORM upon firing. And one of my preferred methods of choosing the best possible pellet for a barrel involves soft-capturing fired pellets and measuring how much they expand at the waist or the column. The more they expand, the less are we in control of the final shape of the pellet once we have pulled the trigger.
Once the pellet starts to move, depending on how the chamber was machined (or not), the head engages the rifling before the skirt and this also exerts a TORSIONAL stress on the waist or the column. At times, this stress may be enough to deform the pellet substantially, in most cases it is not, but it is still mentioned here to point out to problematic barrels that, in reality, need only to have their chambers fitted to the pellet the shooter wants to use.

Great believer in the importance of the skirt - how good do these Qiang Yuan bad boys look

https://photos.app.goo.gl/QXwKC4TaERJgQKxA6

One or two tiny nicks in there but easily fixable on the pellet tin lid with a rub

This bell shaping has been shown before. Unfortunately I believe it's caused by the rapid decelleration of the pellet. I don't know that though but capturing pellets at short range which went from 800fps to zero in a few feet caused showed enough force was still present about 2 feet in to imprint the texture of one of the baffle materials significantly in the head of the pellet in the lead. (it was a unique material at that depth so it was obvious where it came from).

Kevin Lewis did some experiments on this and found the bell shape was not so visible in pellets in flight.

One day I hope to be able to capture pellets at around 300 yards when they have considerably less energy to deform. If there's an obvious difference in shape between them and those captured by whatever method at short range then we could deduce it's the distance vs the method of capture which causes the shape and not the air pressure. If there isn't then it may hold true. Certainly at 50m there's a lot of energy left to do this but pellets we've captured don't always show bell shaping.

I might add that often people look for experiments in airgunning and draw a single conclusion that suits their theory after the experiment rather than listing other possibilities which don't.

Anyway Phil asked me to stick these up... he knows what they're from... I don't. To me there doesn't seem to be an equal expansion of the skirt. Dunno if it was indented deliberately, on or before impact, either.

[bucketboy]

If deceleration of the pellet from 800pfs to zero in two feet shows deformation of the head of the pellet then accelerating it from zero to 800fps in 16” must deform the skirt more.

Bb

[TenMetrePeter]

If deceleration of the pellet from 800pfs to zero in two feet shows deformation of the head of the pellet then accelerating it from zero to 800fps in 16” must deform the skirt more.

Bb

not to mention zero to 48,000 rpm in the same distance.
(Assuming 800 fps and 1 in 12 rifling)

[Rich]

If deceleration of the pellet from 800pfs to zero in two feet shows deformation of the head of the pellet then accelerating it from zero to 800fps in 16” must deform the skirt more.

Bb

Yup.

Force = mass x acceleration.

[Lol Moore]

....."Kevin Lewis did some experiments on this and found the bell shape was not so visible in pellets in flight."

https://photos.app.goo.gl/zvz5gW6sVvQyGapw8

Looks bell like to me.

As the original statements were not qualified i.e. the pellets bell from a low power pcp, then this picture surely proves that deformation of the skirt can occur in the barrel, wether it does for us low power pcp shooters is another matter.

Springer, PCP, low power, high power, breech shape, regulator/hammer balance, rifling or lack of, choke or lack of, pellet hardness, pellets sized.....lots of varibles that should all be included in any experiments if you want a definative answer.

From what I have READ I think belling can occur, as you have observed though not in every scenario.

The Cardews did a shed load of work on this (chapter 18 of Trigger to Target) as have several other American chaps I am yet to see one come to the conclusion that skirt deformation/expansion/belling of some kind does not occur, that aside from rifling marks.

I dont know how Hector caught his pellets but the Cardews used jelly - Lemon flavour I believe

[TenMetrePeter]

just shoot straight up, wait, then catch it in your hat

[Lol Moore]

just shoot straight up, wait, then catch it in your hat

Just looking at that, way too complicated for me to calculate but Googling bullets seems they would come down at around 300ft/s, so about 1.5fpe for a run of the mill pellet.....like firing it 300 yards and catching maybe Rob

Would need an awfully big hat though

[RobF]

Just looking at that, way too complicated for me to calculate but Googling bullets seems they would come down at around 300ft/s, so about 1.5fpe for a run of the mill pellet.....like firing it 300 yards and catching maybe Rob

Would need an awfully big hat though

Yeh I’m not about to try and catch a pellet at 300 yds even at 1.5 ft-lb because something that has the weight of 1.5 lb being dropped a foot but the frontal area of a blunt 6” nail is still going to smart a bit.

I’ll see if we can get it into something soft and deep.

[ballisticboy]

Just looking at that, way too complicated for me to calculate but Googling bullets seems they would come down at around 300ft/s, so about 1.5fpe for a run of the mill pellet.....like firing it 300 yards and catching maybe Rob

Would need an awfully big hat though

Vertical fire is a standard method for testing large calibre (105 to 155mm) shells when you don't want to damage the front of the shell since when it comes back down it comes back down backwards. The shells land in soft ground which decelerates the shell slower than the shell accelerates in the barrel Thus any deformation at the front of the shell or internally has been caused by the barrel acceleration, not the shell being stopped. The landing point is calculated before firing based on measured wind so that the shell lands in the range when the gun is pointed slightly upwind. The calculation does not always work though and shells have been known to land on the other side of the main road. The tops of the buildings on the range have a very thick roof.
If you measure the wind you could fire your airgun slightly upwind and then catch the pellet in a bath of water or something as it come back down backwards but I wouldn't like to be the one to try it as it may take more than a few goes to get it right.
The Cardews photographed pellets in flight with distorted flares about 30 years ago.

[RobF]

If deceleration of the pellet from 800pfs to zero in two feet shows deformation of the head of the pellet then accelerating it from zero to 800fps in 16” must deform the skirt more.

Bb

Not necessarily. Think of a car. If you do 0-60 in 5 secs and 60-0 in 5 nothing happens. But drive it into a load of soft air bags that do the same deceleration and you will see compression on the front.

In addition stretch isn’t the same as compression and certain shapes are better one way than another. Think like a submarine. Very good at withstanding huge pressure from outside, from inside not so much.

[bucketboy]

Not necessarily. Think of a car. If you do 0-60 in 5 secs and 60-0 in 5 nothing happens. But drive it into a load of soft air bags that do the same deceleration and you will see compression on the front.

.

Wrong, push the car from 0-60 in 5 seconds and the rear bumper will show sings of compression.

Bb

[RobF]

Wrong, push the car from 0-60 in 5 seconds and the rear bumper will show sings of compression.

Bb

True, but we're not pushing the just the bumper when we accelerate a pellet. The tail is the wider part of a pellet, not a head, the tail offers the resistance not the head. If anything you could argue by the same theory the skirt should stretch as it's fired as the head pulls the pellet away from the skirt.

Have a look at this :

https://www.youtube.com/watch?v=K4FK_GiFBCg

At 1.40 you can see a pellet deforming as it hits something. Despite the poor quality you can see how there isn't an obvious bell shaping compared to when it hits. Then skip to 2.50 when the pellet is split by a razor and you can see straight edges of the tail. It's not belled pretty clearly. Yet when it hits something solid at 3:00 it bells again.

[RobF]

Kev had to drop the speed down to capture pellets well...

https://photosbykev.deviantart.com/a...ning-135418637

https://orig00.deviantart.net/f11a/f...y_kevlewis.jpg

No belling, but then it's only 85 fps so inconclusive.

https://www.telegraph.co.uk/news/pic....html?image=15

Not sure what speed that is. But you can see belling on other pellets when they have hit more solid targets.

[Lol Moore]

True, but we're not pushing the just the bumper when we accelerate a pellet. The tail is the wider part of a pellet, not a head, the tail offers the resistance not the head. If anything you could argue by the same theory the skirt should stretch as it's fired as the head pulls the pellet away from the skirt.

Have a look at this :

https://www.youtube.com/watch?v=K4FK_GiFBCg

At 1.40 you can see a pellet deforming as it hits something. Despite the poor quality you can see how there isn't an obvious bell shaping compared to when it hits. Then skip to 2.50 when the pellet is split by a razor and you can see straight edges of the tail. It's not belled pretty clearly. Yet when it hits something solid at 3:00 it bells again.

Nice find, some very cool images.

But back to the photos I linked, the pellet that is claimed to have been shot and to my eye shows some skirt belling has no visible head damage so if it belled at impact it must have been stopped in some way that was gentle enough to reduce head deformation, unlike the ones which are shown stopped and the skirt bells in that moment, but at he same time the head is destroyed!

Also doesn't explain the pellet shown in flight that has clearly been belled in the barrel ...albeit probably at high energy levels.

Its all so interesting but academic, as target precision/accuacy is what counts, it would be nice to know which factors effect that in rifle/pellet combo's....this may be part of that jigsaw but other than machining the breech and lead in to suit the pellet I am not sure how we could use the knowledge?