More on vintage spread-shot pellets

[evert]

A very inspiring post!

So we can conclude that confining the spread shot in either a chalk matrix or in a casing helps to give a more uniform distribution of the shot compared to muzzle loading with wads. This is an effect that John Atkins and Arthur Pickford also noted and discussed several years ago. So why does the wadding process always produce such a pronounced ring-shaped spread pattern? Anyone any ideas?

I'm curious if rifling plays a role here. Do you have any smooth bore airguns to test the chalk cartridges in?

[Jerry Cornelius]

Very interesting. I feel a Giffard experiment coming on.

[DrGunn]

I also suspect the rifling will have some affect on the patterns you are getting. I have read elsewhere (for example see here: https://www.theboxotruth.com/threads...un-barrel.377/) that shot fired through a rifled barrel results in a large spread and a “doughnut pattern”.
In this case I would hypothesise that the chalk sticks don’t engage the rifling that well and so don’t spin that much. The tight fitting wad is more likely to engage the rifling and impart spin to the mass of shot, throwing it outwards. I think it would be very interesting to repeat these tests with a smooth bore barrel and compare the results.

[keith66]

^^^ This is true, Gough Thomas experimented with this many years ago & there is an article in one of his books on the subject, He was talking spreader cartridges for shotguns of mainly 12 bore & the same effect was noted. Rifled chokes opened the shot cloud markedly. Obviously such items would need an fac today.
As Jerry cornelius points out a Giffard shotgun may work quite well with these. But from experience with a 9mm rimfire shotgun you are never going to get good patterns from shot clouds this small. The 9mm rimfire is good for about 8 yards max, 10 yards is stretching it. The driving wad disturbs the pattern centre so much that by that distance the pattern is like a donut.

[ccdjg]

A very inspiring post!



I'm curious if rifling plays a role here. Do you have any smooth bore airguns to test the chalk cartridges in?

It seems that you are right, and rifling is the culprit here. Unfortunately I do not have a smoothbore rifle in .177 or .22 calibre with sufficient power to give meaningful results, although I do have a powerful heavy .25 Gem. I will have go at making some chalk shot in that calibre.

[ccdjg]

Well I did eventually get round to using my smoothbore .25 heavy Gem to test the theory out. The doughnut type of spread pattern is only a problem with the wadded shot technique, as when the shot is contained in a ‘cartridge’ casing or embedded in chalk, you do not seem to see it.

So I used the wadding method with my Gem and packed about 16-17 of the small shot into the barrel, sandwiched between a loose fitting wad of tissue at the front and a tight fitting wad at the rear. I then recorded the spread pattern at a distance of 16 feet from the target. Here is a typical result, alongside a typical result, also at a range of 16 feet, obtained with my rifled .22 Webley Mk.3, charged with shot in exactly the same way.




So it is clear that rifling definitely causes a doughnut type of spread pattern, whereas with a smoothbore the shot spread is more uniform and concentrated over the point of aim. Interestingly the maximum spread of both patterns is about the same.