doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Would You Buy an Out of Proof British Shotgun?

650 BAR = 9427 PSI. If that's LUP then I don't think one needs to worry about shooting US shells in the thing. Of course they may have changed the system of measuring when the BAR's were introduced. I did caution that formula was good only for those old British pressures measured in Tons per Sq In. Note that if you run the formula for 3 tons you get a PSI of 8960 or about 618 BAR. A 3� ton LUP converts to 9800 PSI while a 3� ton one goes to 10640. 3 3/4 tons = to 11,480 or about the same as our SAAMI spec. This is getting pretty high. I seriously doubt that any game gun was meant for over 13K PSI for a service load.

FWIW:

The Rottweil shotshell brochure mentions the CIP service pressures for modern CIP standard proof cartridges in bars:

12 gauge: 740 bars

16 gauge: 780 bars

20 gauge: 820 bars

All figures in "piezo-electric"!

Here is a link (hope it works). The info is on page 7 of the brochure under "Playing IT Safe".

Rottweil Shotshell Brochure

Rottweil, as you all know is one of the most respected cartridge makers and make CIP tested cartridges.

All the best

Skeeterbd

Skeeter, the 740 bars 12ga service pressure is 650 bars crusher converted to the transducer measurement. Likewise, 850 bars proof (crusher) is 960 bars transducer. Once you get the transducer measurement, then you can multiply x 14.5 to get psi.

Miller, the old magnum proof (current superior proof) guns have a service pressure of 1050 bars transducer; 1370 bars proof. I don't think those guns are actually meant for 13K plus loads, but they are proofed to that level. The service pressure figure Roger Hancox gives for one of the 850 bars guns: 10,730 psi. (13,920 psi proof.) From those figures, it's obvious that there's a lot more margin between service pressure and proof pressure under SAAMI rules than there is under CIP rules.

According to my "Convert" program the conversion for BAR's to PSI rounded to 3 decimal places is 14.504. Using this factor the above pressure convert respectfully to 740B = 10,733PSI; 780B = 11,313 & 820B = 11,893. It is also noted that "Magnum" cartridges in all three sizes are given as 1050 BAR or 15,229 PSI & reguire guns of special proof for use.

Right. Once the changeover was made from the old tons proofmarks to bars, in the late 80's, there were only two proof levels for British doubles: Standard (850 bars) and Magnum (1200 bars)--for 12ga guns. That's basically the same system still used today, although the guns are now marked with STD under a crown or SUP under 2 crowns. Bars no longer marked. There's also a special proof process for steel shot, with the guns being marked with a fleur de lys and "steel shot". But as far as I can tell, the only difference between the steel shot proof and the superior proof is that 3 steel shot loads are fired in each barrel. But there are also CIP-approved steel shot loads (relatively low velocity and limited to smaller pellets) for guns--even at the standard proof level--that have not passed the steel shot proof.

Proofing is an interesting situation. I am reminded of a Sako rifle brought to me by a new buyer. He was wondering why he could NOT chamber a round in it. It had been proofed but the chamber had NEVER BEEN CUT! As it turns out, Sako only has to actually proof 3 of every 100 guns. Hmmm. At one time I worked for a big box store and problem guns were brought to me. In 6 months, I had 6 Rem 700 short magnums returned with all exhibiting overpressure situations with FACTORY AMMO! Most could not extract the round. The guns were sent to Remington and all returned either fixed or with replacement guns. There was never an explanation. Hmmm. The fat cases with little angle are a promise of over pressure.
Sherman Bells experiment was very interesting with rather little pressure variation between 2 1/2" and even 3" (600 psi as I remember). Also the barrels of Damascus and regular steel bursting finally at 29500-30,500 psi was also very interesting. In the case of doubles, I think there is little danger about which to worry but lots of value about which to worry.

Yes, a Gunsmith friend had a Spanish AyA brought in that had proof marks but the chamber rims had never been cut. Therefore that gun had never had a proof charge fired through it. I can assure you that ALL British guns go through the Proof House if correctly marked. It seems some countries have a slightly different view sometimes. Lagopus.....

Again FWIW!

Please note this is from another website and should not be treated as the final word!


CIP Pressure Chart

Re soft iron shot the charts on page 17-18 of the 2013-14 Rottweil Shotshell Brochure is perhaps of interest.

[url=rws-munition.de/fileadmin/rws/bilder/Service/Download-Bereich/Englisch/issuu_englisch/Rottweil_Shotshells_englisch_2013.pdf][/url]

I think L.Brown was saying the same thing.

All the best

Skeeterbd

A bit more increase than you remember, Pete. Looking back at Bell's article: one 3" load increased breech pressure over 1400 psi when fired in a 2 1/2" chamber. 2 3/4" loads in the short chamber showed pressure jumps as high as 1216 psi. Others at 909, 891 and 787 psi. Others lower than that. Of course the problem would likely come if it were American 2 3/4" factory ammo, which--if at the SAAMI average max service pressure of 11,500 psi--is already about 800 psi over the service pressure for a CIP "standard proof" gun. By the time you add the potential increase for the longer hull in a short chamber, you could be in the vicinity of 2,000 psi over standard service pressure. Not a problem for reloaders, who can hold down the pressure to begin with. I work up a 7300 psi 1 1/8 oz pheasant load in a 2 3/4" Gold Medal hull and don't worry about pressure at all--although I would not want to shoot a round of trap with those in my sub-6 1/4# Brit game gun!

This has me confused as I am not a gunsmith...I have a Grant side lever which had new barrels made by Boss in 1904... Here is what the ledger says about the new barrels....that they have been made for 2 3/4 chambered " American " casings. But this is 1904.... Also for 6 loads.....the proof marks on the new barrel do not show 2 3/4.... I have been on occasion shooting factory target loads at the skeet range of 2 3/4..... Am I walking the line here because of the dates.?..


Boss ledger: