doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Proof failures

I'm willing to machine a couple barrels to screw together. I would hope we could find a tightly choked barrel for this. Sounds like Pete may have something.

I really think porting after something like 18-20" in the first barrel is a good idea to reduce gas pressure as low as possible to negate any effect on the strain measurement, since this debate is about the stress effect of the shot column on the choke.

Don,
do you mean to say that: if the pressure drops in the choke, there will be, effectively, no expansion (no change in strain value) of the barrel at the choke?

Toby,Over the past 2-3 years we have seen many posts reporting abnormal failures of guns during proof testing in the U.K. This is causing consternation on the part of gun owners,in particular those considering sending valuable guns for reproof. The failure of the proof houses to issue a statment on this issue,is in my opinion damaging their otherwise excellent reputation.
Resolution of this issue is very important to the British gun trade and their customer base.If the Proof house and the Gun trade have not already embarked on a joint study to resolve this issue they would in my opinion be well advised to do so.
The University of Aston, in Birmingham, is but a stones throw, from the Birmingham Proof House; surely this highly respected technical University would have the expertise to advise and resolve this matter.

Don,

The wads from some steel/hard non-toxic shot are tapered so that the side petals of the wad are significantly thicker toward the base of the wad than toward the top. Could this positively affect at least the start of the flow of shot under Bernoulli's Principle?

Respectfully,
Mark

Don, if "the pellets act independently as fluid particles", as you said earlier, how do we explain the ruptured chokes so prevalent when steel, and especially hevi-shot, is used in conjunction with very tight chokes. We say, "because of bridging", right? Well, how can a substance acting as a fluid be subject to bridging? If all those little balls, acting so independently as fluid particles, are able to bridge, occasionally, to the point that the barrel, in the choke area, is violently ruptured, then I say we cannot use the Bernoulli Principle to predict the flow characteristics and resulting pressures, within and without the shot column.

As I understand it, even the Bernoulli Principle is subject to modification because of the difference in viscosity of the substances being examined. In it's simplest form, Bernoulli's Principle governs an inviscid flow. Where does lead shot fall, as far as viscosity is concerned, and steel shot, and tungsten/iron shot? And, could a number value for viscosity can be assigned to the different types of shot? More questions.

And, again, how does a "liquid" (or a mass acting as a liquid) bridge and burst chokes if there is a reduction in pressure? The gas pressure may have reduced, but the forces acting on the barrel at the burst point certainly have not. I can accept that there can be a reduction in pressure AFTER the shot has passed the taper, and maybe even a velocity increase because of it, but cannot yet accept that the shot exerts no strain on the tapered area of the barrel.

How in the world can we even compare the dynamics of small shot, as it passes through the taper, with that of much larger sized shot? There IS a difference in it's behavior at that point, or there wouldn't be all the burst chokes and barrels due to the larger hard shot, as compared to the smaller.

Still chewin', Stan

Don,
Unfortunately, my device only has the capability of one input at a time. You could still get statistical information.

That last sentence was a hint... I'm willing to machine all the parts and provide the device, Pete is onboard with supplying the guns. I'm thinking you're the right person with the right credetials for the testing.