doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Forcing cone alterations=out of proof?

Roy, I don't disagree. However, it depends on how much steel there is at the end of the chamber, and how quickly the barrels begin to taper beyond the chamber. If there's a rapid taper (to reduce weight) combined with a long forcing cone, you could end up with a situation where barrel walls are of questionable thickness at a point where pressure is still fairly high.

I don't think it matters what the members of this Forum think.
The way I understand British Proof Law is that the Proof House will inspect a firearm and determine whether it can be Proofed or Re-Proofed and what they determine is Law.
If the Proof House is telling you that removing metal from theforcing cone takes the firearm out of proof, then I don't know what recourse you have under British Law.
Knowing or not knowing whether something was done is not the issue, it's whether firearm is considered in Proof(safe to my understanding).
Of course in the USA, British Proof Law does not have any Legal bearing.
From an Engineering perspective, at least my Engineering, anytime you alter the pressure retaining components of a firearm, you alter the design and call into question whether the firearm is safe.-Dick

"Personally I think its time we started from scratch again ,but that's not going to happen so we just muddle along as best we can hopping we get it right most of the time." Good idea Gunman, I feel like the British Proof Houses stance on removing anything "substantial" isnt a very substantial rule.

I guess I can see why the proof houses feel this way. They probably see hundreds of barrels a year fail that seem perfectly fine, obviously due to any number of conditions not related to removing "substantial" material, most are probably new barrels made of poor steel. In America its like talking to a cardiologist or oncologists, they will tell you everyone dies from cancer or heart attacks depending which one you are asking. If you ask the proof house modifying barrels makes them out of proof and therefore dangerous.

Has there ever been a major case where the proof house has provided evidence in a lawsuit that a barrel has been modified and out of proof? Living and growing up in America, shooting thousands of guns that have never been subject to a government proof, I guess I just dont get the point of the proof house. I suppose it gives me a warm and fuzzy feeling knowing that I am buying a gun that is in proof, but from a manufacturing standpoint it seems like a total waste of money and time, but thats jmho.

Channing

One other factor here is that the London and Birmingham Proofhouses apparently disagree as to the impact of forcing cone alteration on a gun's proof status.

A long time ago I knew a fellow that wanted long forceing cones on his Browning super 28 gauge. They hit air befor the reamer was all the way in. Out of proof?
bill

I'd suspect the forcing cone work was done well and safely, so it may come down to the perceived value of the proof stamp. If there's a question, I'd think send it to the proof house nearest the origin of the gun and let them use their expertise to either reproof it or provide documentation that the gun was still in proof.

Guys,
I really don't know why we are discussing this subject at all.
It as been proven beyond all reasonable doubt that lengthening forcing cones only lightens your wallet, that is not good and neither is lengthening forcing cones.

With all due respect, I'm going to disagree with you on this. My testing showed me that there was a small but measureable increase in the quality of the patterns in 12ga testing I did many years ago, comparing SAAMI spec cones to 1 1/2" and 3" long cones. My testing of .410's with SAAMI spec cones vs. 3" long cones showed a significant improvement in patterns with 3" shells.

It may be in the eyes of the buyer/seller as well. I bought a lovely Brit BLNE from a Seller of good reputation. The cones had been lengthened. I asked if it affected proof, and was told no. Couple years later when I was trying to trade the same gun with the same dealer, I was told value was diminished cuz the cones had been lengthened and it was out of proof...Heated discussion commenced..........

The chamber body itself tapers at a rate of about .005" per inch. Shotgun bbls having less taper than this over the chamber area are few & far between, thus lengthening a chamber is virtually guaranteed to reduce the wall thickness at end of chambder. The cone tapers by .070 �a thou or so over the length of the cone (to a std bore dia) There are not many bbls which will be thinned by cone lengthening unless it is a very long cone. Also the further down the bbl the lower the pressure. I cannot conceive of any ordinary cone lengthening creating a Danger Spot.
As to pressure, it has for years been standard practise to record max pressure 1" from the breech to ensure that max was always read. Pressure rises very rapidly, but it also falls rapidly. I nighly suspect that giveen proper equipment that would read the pressure curve from max to beyond the cone that change in max pressure from cone length would be essentially undectable. What would be more probable is that the presssure would simply be just a tad slower in falling with the short cone, vs the long one, but not likely anything to get up on your Tricycle about.
As to patterns the biggest aspect here would be of easing the shot from chamber to bore with the least deformation. Modern plastic wads have taken care of very much of this. With old style card & filler wads due to their lack of obturation a long cone often did more harm than good by allowing gas leakage, so its a good bit of a wash here.
The .410 in 3" is of course such an unbalanced & ridiculus load it does indeed "NEED" all the help it can get.