67mm when people want 65 mm

[panoma1]

Birmingham Proof House, normally cites the chamber length of 65mm +2.0mm (even though a true 2.5 inch is only 63.5mm) for chamber length and 20.3mm for chamber diameter, whilst bore is 18.2mm.

 

Even if your cartridge case ends up inside the forcing cone up to almost half way (forcing cones are normally at least 12.5mm long), your are not going to endanger the gun or yourself with a plastic cartridge case that is 0.5mm to 0.75mm thick as the dimensions are not any tighter than what would occur in the true bore of the gun and your chamber/forcing cone area are heavier and thicker than the bore. You may (or may not depending on who you believe) upset the shot pattern, but other than that, little difference will be noticeable.

 

The simple way to be happy is to measure your chamber and forcing cones with a chamber or bore gauge to see what you have as I suspect some may be pleasantly surprised.

Nah! The simple way is to stick with the 65mm cased cartridges I currently use!.........They have served me well over many years! And I'm a great believer in the motto 'if it ain't broke don't fix it' lol!

[Feltwad]

You will find that 99% of these old 12 and smaller gauge sxs hammer guns and hammerless have a chamber lenght of 2.1/2 inch or 65mm these guns then took a rolled turnover which overall cartridge length is less that a 2.1/2 inch with crimp. When using a 67 mm the crimp enters the forcing cone and some make the gun kick heavy .The only old 12 bore guns I have come across with a longer chamber length are those which were used for live pigeon shooting over traps which used a rolled turnover 2.3/4 inch cartridge.

Feltwad

Edited May 8, 2017 by Feltwad

[oldypigeonpopper]

hello, i think if anyone has reservations on the measurement of their guns chamber/s i am sure taking to the gunsmith so that a chamber guage will give the exact size for what cartrige to use and be safe

[propercartridges]

as said before people i can make 67mm carts open measured case but i cannot tell people to buy them and use them in 65mm chambers so its your choice thanks george

[Old farrier]

You will find that 99% of these old 12 and smaller gauge sxs hammer guns and hammerless have a chamber lenght of 2.1/2 inch or 65mm these guns then took a rolled turnover which overall cartridge length is less that a 2.1/2 inch with crimp. When using a 67 mm the crimp enters the forcing cone and some make the gun kick heavy .The only old 12 bore guns I have come across with a longer chamber length are those which were used for live pigeon shooting over traps which used a rolled turnover 2.3/4 inch cartridge.

Feltwad

This ^^^^^^^^^^

 

Just a thought if it's ok to use 2.3/4 inch cartridges in a 2.1/2 chamber gun

 

It stands to reason that it's ok to use a 3 inch cartridge in a 2.3/4 inch chamber gun

 

Think about it !!!

 

Just my thoughts

All the best

Of

[motty]

Round and round we go.

[wymberley]

Said it before here,Eley 2 1/2 inch Gand Prix etc were loaded in 2 3/4 inch cases for years ! That was when many more 2 1/2 inch guns were in regular use.

67 mm carts are fine in 2 1/2 inch guns.

I vaguely remember this although I'm not too sure about, "for years". It didn't make sense to me but I wasn't fussed as I had 2&3/4" chambers. I wonder why they don't still do it. In 12 bore the only thing they now do shorter than 67mm is the 55mm 2".

[wymberley]

Birmingham Proof House, normally cites the chamber length of 65mm +2.0mm (even though a true 2.5 inch is only 63.5mm) for chamber length and 20.3mm for chamber diameter, whilst bore is 18.2mm.

 

Even if your cartridge case ends up inside the forcing cone up to almost half way (forcing cones are normally at least 12.5mm long), your are not going to endanger the gun or yourself with a plastic cartridge case that is 0.5mm to 0.75mm thick as the dimensions are not any tighter than what would occur in the true bore of the gun and your chamber/forcing cone area are heavier and thicker than the bore. You may (or may not depending on who you believe) upset the shot pattern, but other than that, little difference will be noticeable.

 

The simple way to be happy is to measure your chamber and forcing cones with a chamber or bore gauge to see what you have as I suspect some may be pleasantly surprised.

Not quite that simple. If we work on the figures provided, then it will be obvious that it is impossible for the opened cartridge to lay flat when, say, half way down the forcing cone. It's a simple matter of circumferences and explains why often the case mouth can appears in tatters. Yep, it may not endanger you or the gun, but odds on are it'll give you more of a kick than is necessary and exacerbate the wear on the gun.

[Feltwad]

This ^^^^^^^^^^

 

Just a thought if it's ok to use 2.3/4 inch cartridges in a 2.1/2 chamber gun

 

It stands to reason that it's ok to use a 3 inch cartridge in a 2.3/4 inch chamber gun

 

Think about it !!!

 

Just my thoughts

All the best

Of

 

It is unwise to use a 2.3/4 inch case in a 2/1/2inch chambered gun especially if it is a old hammer gun .

Feltwad

[Wilts#Dave]

Blimey, these threads make for heavy reading.