Golf ball mortar discussion

[Double D]

OPPs!  Tried to split the Golf ball discussion out of the pop can mortar discussion and only got Dan's post.  No merge function.  Here is a quote from him  that opened Discussion...sorry Dan, i am elderly.

if you are planning for an extreme precission mortar for serious target shooting , would it then be possible to minimize the windage ??
of course it will need an extremely careful cleaning between each shot .

lets say an gb size mortar made for 30 yard shooting with very small charges, would it be possible to go down in bore diameter to such a small bore as somewhere in between 1,697 and 1,7 inch ??

For a 30 yard Golf ball mortar or a 100 yard pop can mortar  or any mortar the 1/40 windage is probably just fine.  If you want to increase accuracy go to a more accurate uniform projectile-change the diameter.
 

[dan610324]

yeah its the accurazy Im looking for
but I dont understand what you mean now , it cant be much more uniform than the fox balls

[Double D]

yeah its the accurazy Im looking for
but I dont understand what you mean now , it cant be much more uniform than the fox balls

But what kind of accuracy are you looking for in a mortar?  The Mortar is an area weapon. 

This past week when Ernie and I were shooting my GB mortar we were aiming by eye ball.  These mortars are only 7" to 8" long  We stood back and by eyeball aimed the mortar by looking down the center line of the base and barrel and aligned it with the aim stake at 30 yards.  When we fired we noticed while tracking the ball we could see the flight line was in alignment with the stake. When the balls impacted they impacted in line with the stake.  The only exception was the full chamber loads and longer range.  They had a higher altitude and always struck down wind of the line of sight.

We were loading with a volumetric measure and the balls of the volume charge always struck in the same general area, usually for with a foot or two of each other.  Dispersion was varied more by up the range, down the range than windage right to left.

I reported these results from our shooting.

30 grains Fg sent the golf ball 10 yards.
40 grains FG- GB's went 20 to 35 yards.
45 grains FG-GB went 40 to 50 yards.
85 grains Fg-GB went 390 feet and few inches
85 grains FFFFG went 156 feet.

40 Grains FG steel ball went 10 yards
50 grains Fg steel balls went 20-25 yards
60 grains Fg  steel balls went 40 yards.
85 grains Fg steel ball went 126 feet
85 grains FFFFG steel ball went 114 feet.

Those are roll out distances.

The 40 grain Gb loads were hitting at 20 yards. When we increased loads by 5 grains impact was 40 yards. A change of 5 grains by volume caused a 20 yard change in range.  I think charge sizes are more critical than windage. Weight charges should increase accuracy vs volume loaded charges.

Golf balls and the Fox balls are very uniform.  But if you start casting balls of zinc with varying diameters you also have to ensure the balls are uniform. That is what I am talking about.

Having shot the golf ball and pop can  mortars a bit I don't really think there is any advantage to tight windage in the mortar..  Velocity is low and there is no real need for an increase in velocity.  If you concentrate on keeping every aspect of the loading-shooting uniform accuracy will improve.  I also believe if you increase range accuracy decreases as other factors.

If you game is range, how far can you shoot, then lesser windage might matter in the mortar. 

The one best way I see to improve accuracy in a golf ball mortar is to figure out some way to get the projectile to stick when it hits.

Someone needs to test the windage theory.  Build a mortar with minimum windage do some test firing and and the open the bore up a step and test again and see what happens. Windage for a 1.68 golf ball is .043.  Do it it .004 increments.  Who is going to do it?

[dan610324]

Im not thinking in terms of more velocity , but just that a smaller windage could let you use a smaller charge to reach the 30 yards and maybe also give a little better precission because the ball got less space to "bounce" between the barrels walls

I dont know if it is so or not , but its an idea and would be very interesting to hear if someone have any experiances from this idea .

if I could I would do some tests , but it wouldnt be legal here in sweden

that the balls bouncing and roll away must be a much larger problem with the golf balls than the fox balls I guess as steel is heavier and less flexible , so just changing from golf balls to fox balls would probably give a little better accurazy .

[Double D]

Im not thinking in terms of more velocity , but just that a smaller windage could let you use a smaller charge to reach the 30 yards and maybe also give a little better precission because the ball got less space to "bounce" between the barrels walls

I dont know if it is so or not , but its an idea and would be very interesting to hear if someone have any experiances from this idea .

if I could I would do some tests , but it wouldnt be legal here in sweden

that the balls bouncing and roll away must be a much larger problem with the golf balls than the fox balls I guess as steel is heavier and less flexible , so just changing from golf balls to fox balls would probably give a little better accurazy .

The steel balls seem to roll away pretty good on the hard ground. 

[Cat Whisperer]

Im not thinking in terms of more velocity , but just that a smaller windage could let you use a smaller charge to reach the 30 yards and maybe also give a little better precission because the ball got less space to "bounce" between the barrels walls
...

From my experience, if you have minimal windage the variation between rounds is less.  This is critical for accuracy.  More windage makes accuracy at 30 yards a fleeting dream, although at 100 yards accuracy was good (although influenced more by wind). 

[Victor3]

...a smaller windage could let you use a smaller charge to reach the 30 yards and maybe also give a little better precission because the ball got less space to "bounce" between the barrels walls

I dont know if it is so or not , but its an idea and would be very interesting to hear if someone have any experiances from this idea . 

 This was my thinking when I had Dom bore my Dictator with minimal windage.

 Since I don't have another can-size mortar with more windage to compare it to, I couldn't say how much better it does in powder efficiency or accuracy.

 In scientific terms, one thing I can say is that my Dictator is 'way cool' and everyone who's seen it launch a can agrees. Not a one of them asked about its windage.

[Double D]

From my experience, if you have minimal windage the variation between rounds is less.  This is critical for accuracy.  More windage makes accuracy at 30 yards a fleeting dream, although at 100 yards accuracy was good (although influenced more by wind). 

Exactly the opposite of my experience.  Balls impact with in a foot or two of each other at 30 yards, with in a yard or two at 100 yards and tens of yards at 200 yards.  My mortar with loose windage is much more accurate at short range.

 This was my thinking when I had Dom bore my Dictator with minimal windage.

 Since I don't have another can-size mortar with more windage to compare it to, I couldn't say how much better it does in powder efficiency or accuracy.

 In scientific terms, one thing I can say is that my Dictator is 'way cool' and everyone who's seen it launch a can agrees. Not a one of them asked about its windage.

I don't know what windage Dom put in my dictator, never bothered to measure.  But it is clearly more accurate than the golf ball mortar and especially with Round balls. 

Victor I can confirm you scientific fact about the cool factor..

Question for you about can shooting with tight bore.  Do you get a stable flight or do your cans tumble right away.  Ther doesn't seem to be any predictability with mine, some time the cans tumble right away some times they don't

[GGaskill]

Maybe we need to get the grounds crew to soften the impact zone, kind of like the way the Giants would soften the infield when Maury Wills was playing against them.

[Cat Whisperer]

From my experience, if you have minimal windage the variation between rounds is less.  This is critical for accuracy.  More windage makes accuracy at 30 yards a fleeting dream, although at 100 yards accuracy was good (although influenced more by wind).  

Exactly the opposite of my experience.  Balls impact with in a foot or two of each other at 30 yards, with in a yard or two at 100 yards and tens of yards at 200 yards.  My mortar with loose windage is much more accurate at short range.

On the contrary,  I was getting MUCH more variation at 30 yards than at 100 yards.  The wider windage made the burn at small powder charges much more variable.  200?  That would be well into the trees.

That was my frustration with the contest a while back because of the short distance.

[dan610324]

yeah thats exactly what I thought , all my questions on this is because I have been thinking for a while to try to maximize a competition mortar in gb size for fox balls

my thoughts so far would be to minimize the bore to max 1,7" and have a slightly conical chamber that holds the minimum charge to reach the 30 yards . maybe 52 grains or so of ff or fffg powder , maybe even ffffg if it give an good result with a minimized bore diameter

with a minimized bore I think the finer granulations would work better

but so far this is just theoretical thinking

it would be nice to find out how the ultimate competition barrel should be designed

hope some more people will help me and tell me their experiances

now I guess that a slightly conical chamber would be better than an straight chamber , but no real evidence for that yet .

[Double D]

yeah thats exactly what I thought , all my questions on this is because I have been thinking for a while to try to maximize a competition mortar in gb size for fox balls

my thoughts so far would be to minimize the bore to max 1,7" and have a slightly conical chamber that holds the minimum charge to reach the 30 yards . maybe 52 grains or so of ff or fffg powder , maybe even ffffg if it give an good result with a minimized bore diameter

with a minimized bore I think the finer granulations would work better

but so far this is just theoretical thinking

it would be nice to find out how the ultimate competition barrel should be designed

hope some more people will help me and tell me their experiences

now I guess that a slightly conical chamber would be better than an straight chamber , but no real evidence for that yet .

Now I think you are on to something Dan, the chamber.  If you read Muller and Gibbons they both look at chamber shape. Very little mention of windage other than to state the purpose. They do not consider blow by.   I have done two different chambers sizes in my mortars, 1/2" and 5/8"-both straight cylinders. The 1/2" chamber use less powder for 30 yards than the 5/8 to achieve the same ranges.   I think a Gomer  or semi Gomer chamber might work better.  My little take apart mortar lends it's self to this sort of project. Might be some thing to work on this winter.  

Looking at my  chart up thread Fg had a larger spread at 30 yards with a golf ball than with a steel ball.  

I have shoot Cannon and Fg regularly in the GB mortar and now FFFFg.  Cannon and Fg have a larger "fireball" than FFFFg.  That fire ball must be acting upon the ball outside of the barrel.  I think tests with the finer grades might be useful.    Since we know the faster burning powders generate more pressure it would seem logical that they would have greater blow by slower.  

Well I had these neat projects all lined out for this winter, and I don't think they are going to happen.

[Double D]

Another issue that we haven't talked about in regards to accuracy and the is weight.    I wonder how much the weight of the mortar effects accuracy.

[dan610324]

nothing I guess
the ball have most certainly already left the barrel long before the barrel starts moving
unless you got an extremely light mortar and heavy ball
just remember that for each force you the same force in the oposit direction

I guess most mortars are approximately 5-10 times heavier than the ball
with that much larger mass it takes much longer time until the mortar moves than the ball

but as usual its just me trying to think logical

I had an idea of a powder chamber that is 1/2" in diameter where its connected with the bore
2,5" deep + the full radius in the bottom
1/4" diameter at the bottom of the conical part

I guess that would hold approximately 50 + grains , thats also just a guess

[dan610324]

just one question DD
could you please check the both movies with the fox balls
85 grains fg vs 85 grains ffffg to see how much difference there is on size of the fire ball

I guess its a much larger fire ball from the fg powder

all powder burning on the outside is wasted powder

so a really tight bore and a much smaller amount of a finer powder I would say is much more cost effective at least
and it hopefully also give a higher accurazy

the question now is :  what is the best chamber shape ??

[Cat Whisperer]

nothing I guess
the ball have most certainly already left the barrel long before the barrel starts moving
unless you got an extremely light mortar and heavy ball
...

BUT, if it's immoveable (ie: very heavy) it won't move much and the 2nd shot will be spot on.

[Double D]

just one question DD
could you please check the both movies with the fox balls
85 grains fg vs 85 grains ffffg to see how much difference there is on size of the fire ball

I guess its a much larger fire ball from the fg powder

all powder burning on the outside is wasted powder

so a really tight bore and a much smaller amount of a finer powder I would say is much more cost effective at least
and it hopefully also give a higher accurazy

the question now is :  what is the best chamber shape ??

85 grains of Fg Steel Ball


85 grains of FFFFg steel ball.


As soon as the ball move in the bore recoil starts moving the mortar.  A heavier mortar will resist recoil and should be more accurate.

The finer grain powders are faster burning and increase pressure with out increasing velocity. The ideal powder would be one that burns all up just as the ball leaves the muzzle. 

We  did notice shooting the full chamber with steel ball that 85 grains of Fg had a longer range with less recoil with both steel and golf balls than 85 grains of FFFFg with either ball.

I agree a tighter bore might shoot better.  So somebody step up and do the test.

[Victor3]

Question for you about can shooting with tight bore.  Do you get a stable flight or do your cans tumble right away.  Ther doesn't seem to be any predictability with mine, some time the cans tumble right away some times they don't

 Same here.

 One factor is that the ones I've only filled partially flip more than the ones filled right to the top. I guess that's to be expected since air can grab the open end of the can in flight to disrupt whatever stability might have been there to start with.

 If you fill to the top though, you don't get that neat whistling sound. 

 I notice that the short soda cans tumble less often than standard length ones.

 I generally use FG or cannon in my can mortar. I do think that a light (ice or P of P filled), cylindrical projectile like a can might be more stable in flight using an optimum charge of FFFFG. That way it would be more of a 'pop' to the base of the can without as much disturbance as a slower burning powder might produce as the projectile left the bore.

[GGaskill]

If someone has a good source of 16 ounce beer cans, please fill a few about one quarter full of lead, place leaded end in bore against the charge, and see if they flip over once and fly heavy end forward.  I have seen this happen once but usually the cans tumble end over end which significantly reduces the range.

[Parrott-Cannon]

The kenetic energy of the recoil is:

Ke - Recoil = (MassP+ 0.5*MassPc)^2 * Vp*Vp/MassW

Where:

      MassP - Mass of the projectile
      MassPc - Mass of the powder charge
      Vp - Velocity of the projectile
      MassW - Mass of the weapon

The recoil energy is a loss to the chemical energy contained in the powder charge and reduces the the muzzle velocity - a lower projectile mass will increase the velocity.