doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Help needed on pressures of modern loads?

Still some confusion on proof markings. The "tons" mark (which is actually service pressure rather than proof) was not used until 1954. Between 1925-54, one change that will help you differentiate from those proofed earlier is that chamber length was marked on the later guns but not on the earlier ones. 1904-25, you would have only the shot charge and a nitro proof. There is also a date code that came into use in the early 20's, but it's quite difficult to read on a lot of guns.

If a 16ga gun is has marks of 1 oz, nitro proof, and 3 tons, it should also have chamber length. But I believe the shot charge was dropped when the "tons" came into use, so that would indicate a reproof.

For reloaders, knowing what's in the box is also important after you know what should be . May not seem so crucial at first with one gauge and one or two loadings but it will become very crucial. Don't guess; mark boxes with the loading or gun for which intended or mark the primer of all shells or at least leftovers with colored Magic Marker conforming to a code filed in your head and additionally in your safe, in your reloading area, in your glove cmptmt, and/or in your wallet. Some mark the overshot card on roll crimped shells. Either way, if you use hulls again, the identifier has flown or been punched out--no confusion from old markings.

jack

L Brown (Larry?) If you would not mind continuing the education is the below the correct history of proof marks?

1904 - 1924...... Shot Charge and nitro proof
1925 - 1954...... Shot Charge, nitro proof & chamber length
1955 - 1985+,-... Tons
1985 - Present... BAR

Post 1955 would one of these newer guns have other markings we have discussed, such as chamber length? Never really looked at a newer one that closely.

Questions on the 16 ga are prompted by my lust for a Watson Bros 16 ga. I have had a couple of reservations about the gun 1) Someone extended the chambers from 2 1/2" to 2 3/4" - seller calims subsequently re-proofed and 2) I am not sure if you can use 2 1/2" shells in a 2 3/4" chamber. I am not aware of any 2 3/4" shells that have low enough pressure to use with 3 ton proof.

I can get by #1 by asking for paperwork on when work was done, and They either have or they dont. Maybe I can decipher proof marks to confirm it was re-proofed after gun was reamed.

You folks can resolve #2 for me.

My 12 bore must have been reproofed frequently because it has all above markings except Tons, and by serial # it supposedly was made in early 1900's.

I really appreciate everyone weighing in on this topic. It has been a great and brief education for me.

So please, can somebody tell me if all this means that ALL those Eley shells that Drew has HAVE to be under 8960 psi or not since it says for a service pressure of 3 tons.

Thanks,

Larry

All these folks have low pressure 16ga loads:
Polywad 'Vintager' http://www.polywad-shotgun-shells.com 800-998-0669
Eley http://eleyshotshells.com 512-821-9953 or
http://www.kirklees-guns.co.uk/Eley%20Hawk/Eley%20Hunting.htm
Kent http://www.firearmservice.com 512-821-9953
RST http://www.rstshells.com 570-553-1651

The problem with extending the chambers is removing excess metal and in general, you want .080" at the end of the chambers.

I'm still clueless as to actual service and proof pressures: 10,730/13,920 or 8,960/12,328 (or maybe different numbers meaning the same thing?) We might settle this by asking B&P if the psi on their speed/pressure chart represents SAAMI psi (or roughly needs another 1000 units added) and this a copy of the e-mail I just sent.
Sirs: we've had an ongoing discussion on several Forums regarding converting British/European pressure date to SAAMI psi. Please see this thread http://doublegunshop.com/forums/ubbthrea...;gonew=1#UNREAD
Does the B&P speed/pressure chart indicate SAAMI psi?
http://www.bandpusa.com/files/db_trio.pdf
Thank you. Dr Drew

Revdoc:

You are fortunate just being clueless on conversion.

I am feeling pretty clueless on all of it. Think I got the gist of it.

I realize there are lots of places to get low pressure shells, but aren't they all in 65mm lengths occassionally 67mm. Do you know if I can shoot 65mm shells in a gun chambered 2 3/4" without long term ill effect?

Thanks for heads up on wall thickness for chamber area.

Absolutely no concern shooting 65mm or 67mm shells in 70mm guns. And BTW: most of the B&Ps are 67mm but designed to shoot in 2 1/2" chambers (and 2 1/2" is actually 63mm)

Try this link;
http://www.gunproof.com/Proofing/proofing.html
This is from the Birmingham Proof House & you can scroll down the page & find the marks for 1925, 1954 & 1989. 1904 through 1924 are same as 1925, except length of chamber is not marked. 2½" guns were marked 1 1/8oz & 2 3/4" guns were marked 1¼ oz. 3" or longer were marked with an LC under gauge in the diamond to indicate "Long Chamber".
Incidently the smaller the bore the higher the pressure walls of equal thickness will contain, or for the same pressure can have thinner walls. It is however, as mentioned, easier to load the 12ga to lower pressures than smaller bores, unless exceptionally light charges of shot are used. Many will load 1oz in the 12ga, but not many go down to 13/16oz in the 16ga which would be an equivelent load.

Thanks for all the education and I will check out the variety of links you all provided......

Chicago (Mike)

"If you look in older reloading manuals (or even some newer ones), you'll find the pressure of various reloading formulas expressed in LUP (or lead units of pressure). Those are measurements derived from the old lead crusher system, which the British still use. There's no formula to convert crusher values to transducer values, but an acceptable "ballpark" conversion is: LUP + 1,000 = psi. (Which you can also reverse, if for some reason you want to convert from psi to LUP.) If you add 1,000 to the figures Miller gives above, you come pretty close--especially to service pressure."

I agree to most of what Larry was saying except that in this case do not use the 1,000 conversion from LUPs to PSI, there is no correlation of the two. When Lyman first used the crusher method they called it psi, but found out it wasn't in psi, and eventually this same pressure value began to be listed as l.u.p.
This syestem was used for decades and more and more people wanted to know what the psi was instead of lups. Plus the lup system with the lead crusher was very time consuming and labor intense.
A new system was developed in the 60's using electronic equipment to actually measure in psi. No more aligning lance holes up exactly with the piston in the chamber.
There is no universal difference between the two, in fact some loads are 9,000 lups develop 11,500 psi. On some 12 ga reloads the difference is only 300-1,400 psi. Many of the loads using lead shot developed in the lup system reamin at an accetable level of pressure in the psi system. Now with steel shot the comparison is way higher between the two.
In Lymans 4th Edition of Shotshell Relaoding they give both L.U.P. and P.S.I., in the new edtion they only list psi.

So do not compare psi listings with lup listngs.

If you shoot 16 ga and reload and shoot 70-100+ year old guns there is no better place to learn than on the 16 ga. Reloaders site. They give you information on 2 1/2"-2 3/4" low pressure reloads for our old guns to shoot safely. It cost money, a one time deal, but the information is outstanding and all the loads are proven.