Are 67mm cartridges ok for 2 1/2 inch chambers?

[Guest cookoff013]

the cip regard 65 and 67.. the same.

 

but this is where the kicker really is, if you measure new unfired cases, you`ll find most ~1.5mm shorter than advertised.

70mm, being 69-68mm.

65mm - 63.5mm

67mm - 65.5mm or so.

 

so the cip recomending 67mm hulls for 65mm chambers spot on.

[WelshAndy]

This is what you need

 

http://www.justcartridges.com/xtreme.html

[JohnfromUK]

I have several 2 1/2 chambered guns, including two with (nitro) Damascus barrels. I was advised by the maker of two of my guns that the chambers are actually approx 2 5/8" and that 67.5 mm, 67mm and 65mm are all OK provided the load is below the proof load (often 1 1/8oz). 70mm is NOT alright and nor is anything over 1 1/8oz, whatever the case. The thing to look out for is that if the gun has short chambers AND abrupt forcing cones, the opened cartridge can sometimes just not quite clear the cone. You see this as damage on the fired case - like a chewed edge to the opened end and pressures are raised. Long term damage due to raised pressure (the gun shooting loose) can occur if done regularly - and there is a (small) risk of short term damage (bulge - or very rarely worse).

 

I knew someone who went on a simulated game day and fired a lot of the cartridges provided through a fine old English gun without realising they were 2 3/4" He ended up with a sore shoulder, a headache, but when cleaning the gun, he thought it was a bit loose. Took it to a gunmaker and ended up with an eyewatering bill to rectify the situation. What we don't know was the state of the gun before this all happened (slightly loose guns with rapidly loosen if overstressed) - and what the loads fired were since 2 3/4" (70mm) cartridges often carry a heavier load.

Edited May 3, 2013 by JohnfromUK

[brent52]

if it says 2/12 on the box thats what it's for, whats the problem ?

[Wildfowler325]

Aaa just hold them through

[simmans]

just to further confuse the picture , I use gamebore super xls no 8 in my damascus barrelled hammer gun 

.. case says 65mm with arrows indicating the unfired length

 

my callipers measure 63.70 mm overall fired length 55.67mm unfired

 

more confusion... these are subsonic and sound like a **** in a cullender.

 

BUT the vintagers club here t in melbourne say it is fine to use 67mm

thanks 

george

 

 

[DUNKS]

What I would suggest is that you get a couple of the cartridges shot in a gun with 70mm chambers. Then measure the shot cartridges accurately. Put a well fitting hardwood or steel plug in your chamber and also measure. I think you may be surprised  I have several old guns with 65mm chambers and they are all 67.5 at least. Only one a 1885 SXS is exactly two and a half and the forcing cone is very sharp.

Also I have measured a lot of fired cartridges and nearly all are shorter than stated  67s are usually only 65.5.

I have some Eley first which are 67.5 and fired they measure 66.25.

[Lloyd90]

Seems a bit all over the place. 

Before I know any better I went to get some carts for fox in a gunshop, I told them the gun I was using and they sold me some 3” SG carts for my gun with 2 3/4” chamber ... I fired a couple with no issues although recent noticed this and wasn’t impressed to find out... 

How many newbies about there would be as aware of such an issue? 

I always thought if the cart was too long then it would stick out and the gun wouldn’t shut. 

 

[Gunman]

A lot will depend on the profile of the chambers in your gun. Many older guns had what can be called "roll over " chambers , that is a very short cone into the barrel that on view looks more like a step . If so I would try to avoid cases that when fired open up to over 65 mm . This may depend on the cartridge and the crimp and not all gases are the same .

If the chamber has a "normal" tapered cone then there is no real problem .

It may be wise to have the chambers plugged , that is correctly measured , as again older guns often had tight chambers , so may need to have be slightly opened up or re profiled to modern profile . I have done this on numerous occasions usually to help with extraction problems and providing the chamber is not deepened beyond the specified depth it will not affect proof status . 

[wymberley]

Sometimes an indication that something is not quite right is that the cartridge mouth is tatty or 'feathered'.

[Dougy]

5 years old +, i bet the cases have shrunk since this thread was started. 

 

[simmans]

yes well shrunk bit like me really!

 

My westly richards hammer gun is chambered for 2 1/2 but when measured with a 20mm dowl shows the chambers to be 67.98mm

B&P sub sonic 1oz loads are 67mm when  fired despite the packet saying 2 3/8 inches so guess ok  and should be within my three tons pressure limit, or close.

the only problem that arises is there aint no pigeons in Oz!..  good for all varieties of snakes though

 

cheers

george

 

 

[simmans]

14 hours ago, Gunman said:

A lot will depend on the profile of the chambers in your gun. Many older guns had what can be called "roll over " chambers , that is a very short cone into the barrel that on view looks more like a step . If so I would try to avoid cases that when fired open up to over 65 mm . This may depend on the cartridge and the crimp and not all gases are the same .

If the chamber has a "normal" tapered cone then there is no real problem .

It may be wise to have the chambers plugged , that is correctly measured , as again older guns often had tight chambers , so may need to have be slightly opened up or re profiled to modern profile . I have done this on numerous occasions usually to help with extraction problems and providing the chamber is not deepened beyond the specified depth it will not affect proof status . 

Many thanks your comments Gunman.

you are correct on the roll over chambers , they look just like a ridge 

I have just noticed on the B&P packet  "do not  use in damascus barrelled guns , but my westley is damascus and is nitro  proofed to 3 tons so should be ok.