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

Don,

That is the reason Chuck and I need you to blow up a couple of guns for us!

Roy,
This whole situation is becoming more troublesome with each passing day.
Today I received news of 3 freshly sleeved guns from a highly respected specialist all failing proof with bulges behind the chokes.
Understandably the specialist asked for an investigation and the Proof House has offered to do the subsequent tests using old proof cartridges from a previous supplier. I have an interest in this as I have several guns in the log jam from this situation and I am crossing my fingers that all will be well.
It would appear from this development that the London Proof House has tacitly admitted that there is something amiss with their proof loads although the are admitting nothing verbally.
The problem with what you suggest is that the Proof Houses are very much a self contained, self regulating institution. If they brought in outside help, they would probably see that as an admission that they are not up to the job, something that I doubt they would be prepared to do.
Furthermore, if they had been at fault, they might be at risk of becoming liable for all the damage they are currently causing. Again, not something they are likely to relish.
It would appear that this current difficulty is centered in London, I have heard from 2 sources that Birmingham were unaware of London's problems.
Give me strength!

Toby,As I understand the proof regulations,the U.K. proof houses were established by act of parliment. Surely this means they have a responsibility to report to a parliment. For example, who whould take action if the weapons failing proof were military issue? Is this an avenue worth exploring in order to expedite resolution?

OK. I will do it. I will have be careful that I can work around available time. But, basically, yes, I'll do the testing.

One input is only inconvenient, not problematic. How many strain gauges do you think? Breech pressure, barrel pressure just in front of the choke section, the start of the choke section, and muzzle?

I don't think so, as these principles were at work back when shotguns lacked shot protection. The venturi effect is, unfortunately, counter-intuitive to "common sense," which is why it was so long to be discovered.

Don,
I'm not sure how much you want to expand the research. But I'm leaving that up to you.

One nagging question I have and probably many others is the comparision of steel vs lead on the choke area stress. Then further comparisons of smaller vs larger shot size in both lead and steel. All testing should probably be done with like loadings from same mfrs when doing the shot size comparisons, of course.

I also have a chronograph if you don't have one.

If I might add a little to the thoughts. In one of the appendices to The Modern shotgun bu Burrard he reported on some tests which had been conducted in England. A heavy pendulum gun qa fitted to record max pressure, velocity & recoil. Two bbl extensions were very carefully fitted & lapped to identical diameters, one cylinder bore & one full choke. Loads of several varieties of powder were tested from the heavier of the bulk smokeless down through a fairly light dense powder & If my memory is correct I believe black as well.
Bottom line was that though small, statistically significant readings showed the full choke to give higher velocity & lower Recoil readings. Velocity was of course the "Observed" velocity over 20yds. Load in all cases was the normal 1 1/16oz with 3 dram measure or equivelent depending upon powder. The conclusion drawn at the time was that the choke "Checked" the velocity but the shot remained closer together as the exited the muzzle
& drag was less for a short distance allowing them to more than regain the loss.

Now, if we can take it the Remington tests recorded velocities close enough to the muzzle to eliminate the possibility of the results being skewed by outside influence, then obviously their conclusion, though reasonable, was not factual.
But, Something caused the lowered recoil & it wasn't the "Speeding Up" of the shot. So what's left. Note the comparsions are strictly between the F choke & Cyl for Each load, everything else being identical. Maybe, just Maybe we need to look to the wadding. Could the wadding have been checked enough to slow the ejection of the gases just enough to give the lowered recoil??
I am going to go out on a limb & "Predict" you will find a point of a slight pressure spike when you run your tests. You may have to move the strain gage around a few times to find the right place, but it'll be there. Normally this will not be enough of a spike to bulge a bbl as the check is slight, & the load is moving so rapidly at the time it takes a bit for the gases to "Catch up". I do seem to recall seeing high speed pics of the charge as it leaves the muzzle & the wad was snugger against the shot from a cylinder than from a full choke, which indicates the wad was delayed by the choke.
From further back in this thread I recall it being mentioned the proof house had quit using shells supplied by the trade & started loading their own. Maybe its not the shot at all, maybe they are using stiffer & heavier wads & these are making enough difference to create the bulge in sme cases.

Thank you Don. I leave it to you and Chuck to design for best possible data.

Pete

A couple of years ago the Birmingham Proof House were having an abnormally high percentage of failures in 20 bores. Not choke damage but just burst barrels and cracked actions as would be expected from proof overloads. I don't know if Smallbore has any knowledge of this. I submitted a 20 bore with damascus barrels at around that time. The barrels were o.k. but the action was bent like a banana. Lagopus.....

That might hold true with a muzzle loader over loaded by a small amount....but don't think you can't reek havoc on a cartridge gun with an over load of black powder.