doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 70 mm ammo in 67 mm chambers?

Anyone have specific information or experience about use of nominal 70 mm hulled shotshells in 67 mm chambers?

We know of CIP permissibility of using CIP 67 mm hulled shotshells in 65 mm chambers. What I have never seen is any specific information about use of actual 70 mm hulled ammo in 67 mm chamber guns. These would seem closely identical situations, given identical chamber pressures.

I am asking because I have a totally original Sauer M2 hammer double with true 67 mm chambers, short forcing cones, tight chokes, etc., typical of various higher quality Germain doubles I have owned. This gun locks up quite tight and patterns nicely with 24 and 28 gram loads in 67 mm ammo (Remington Promo loads and reloads in same 67 mm length hulls). It is my current favorite bird gun.

However, of 16 gauge shotshells readily available in USA stores, only Remington black hulls and USA Fiocchi hulls are 67 mm, even though they are marked "70 mm". Winchester and Federal hulls are 69-70 mm. While I can and do shorten Federal hulls to 67 mm for reloading, I would like to use 70 mm hulled factory ammo on some hunting trips. These would be 28 or 32 gram field loads at 1200-1250 fps, most likely Federal.

Thanks,
Niklas

NP - hull length is not definitive of the shell. The pressure of the loaded hull and the match of that pressure to the design working pressure of the gun is much, much more important. Unless you are satisfied that you have identified the intended working pressure of the gun and the pressure of the load, simply put, don't use it, no matter the hull length. For example, I use my own low pressure reloads in 70 mm hulls with 7/8 oz shot charges in 65 mm chambered guns on a regular basis. The guns all have current Brit 1 1/8 oz proof, so I know the working pressure. I do all my own reloads, so I can keep pressures well below the proof pressure. I will shoot correct length CIP factory loads in these guns, but not longer. I will NOT shoot any SAAMI loads unless the factory is willing to tell me the pressure - some factories' pressures are known, most are not.

A longer hull is likely to raise the chamber pressure somewhat. The higher the pressure of the load, the more you are likely to see a bigger change. Note that shot charge weight and dram equivalent/muzzle velocity do not tell you anything about the chamber pressure. Pressure can be known only from a formulation that specifys hull, primer, powder type, powder charge, wad, and shot charge and lists a measured pressure. If you are not reloading, then you must rely on the factory for pressure information.

Further note that high pressure can be detrimental to hinge pin and hook, locking mechanism, and action. High recoil can be very damaging to wood.

This question and the response should be permanently available on this BBS! Both the question and the answer are clear, concise and informative.
David

I agree that it's a very good discussion of the important points.
Should be in the FAQ section. If there's a space problem, maybe it's time to delete the Chambers-Thorny-Joe thread. Plenty tired of looking at that mess!

Rocketman,

Nearly all the shotshells I shoot are of correct length for the chambers, are light loads, usually 24 grams, and have chamber pressures below CIP limits. My question is not about loads to be used in high volume shooting, as in trap, skeet, sporting clays. It is about occasional use of USA factory loads for hunting, in 70 mm hulls, 28 gram loads mostly, with Federal and Winchester being the most likely. This could happen on trips far from home. With Fiocchi I am OK, but, I never see them in stores where I might need them. Remington black hulled 28 gram ammo is also OK in the gun in question but seldom seen in stores. For these four shotshells we have some pressure data via the 16-gauge low pressure loading group. So, it really is about 67 vs 70 mm hulls with Federal and Winchester 16 gauge ammo.

I long know all the things you note and agree with them. I am looking for specific experience and data for use of 70 mm, USA-made hulled shotshells in 67 mm 16 gauge. FYI, I never use 70 mm hulls in 65 mm chambers but, I do follow CIP and use 67 mm hulls for both target (24 gram) and hunting (28-30 gram) in 65 mm chambered 16s.

Decades of experience with Sauer and Merkel 67 mm chambered 16 gauges leads me to expect I will see no evidence of excessive pressure. However, I have never needed to use 70 mm hulled USA-made ammo in them. I have used various USA 70mm shotshells for many seasons hunting in old Merkel gun that had chamber lengthened to 70 mm -- no problem. Gun still tight after 15 years of hunting, shooting 3-5 boxes per season. Will not be lengthening chambers in Sauer M2 hammer gun from about 1920.

Thanks,
Niklas

I've been shooting 2 3/4 inch American shells in 2 5/8 inch chambered 12-gauge Ansley H. Fox doubles for 41 years and my Father and Grandfather were doing it with even a twist barrel Parker Bros. of 1890 vintage, a Vulcan Parker Bros. of 1902-vintage and a Damascus barrel Remington of 1896-vintage for half a century before that. Those three guns, all fairly heavy 30-inch barrel guns, have probably digested a boxcar load of Federal Hi-Powers and Super-X type shells among them.

That said, for clay target shooting I use 7/8 ounce loads at 6300 psi, but I'm certainly not opposed to the use of a Super-X where called for in guns of suitable weight.

Thanks Researcher!

Think I will do informal experiment next time I am trap shooting. Will alternate between Remington black promo (67 mm hulls) and Federal (70 mm hulls) 1,0 oz loads. The Remingtons are listed as 1220 fps and the Federals at 1165. Always before, I notice in 70 mm chambered 16 that the Remington loads recoil distinctly more. SO, if the Remingtons still recoil more, I will consider the effect of the 3,0 mm longer Federal case to be negligable. Shoulda thoughta doing of this before!!

This old hammer double weighs about 6 1/4 lbs, so, not many loads with more than 28 grams of shot will be fired in it, maybe none. It does have 75 cm barrels and wonderful triggers, now both at same let off effort.

Niklas

Niklas, I can't imagine it would hurt a Sauer. I shot 1 1/8 oz American pheasant loads in a pre-WWII Sauer 16 for years, before I knew about stuff like different pressures for European vs American guns. That being said, the key issue is the service pressure for which the gun was built vs the pressure generated by the load in question--which, as indicated above, will likely go up (but probably not much) when fired in a slightly shorter chamber.

We all have been shooting longer shell than sometimes the old chamber allowed. If the cone do not allow the shell to open fully the pressure built up will far away superior to the normal pressure of the shooted cartridge. The gun will kick hard, sometime the rib will start to separate from the barrels. Make the cone longer, remove the step in the cone design for the paper shell will lower the pressure but will make the steel thinner.
Shooting the proper lenght and low pressure cartridge as in the old days will be better for the gun on long term. RST cartriges could be find easily in short lenght. They will take care of your old gun. Check with RST.

darnation

RST good cartridges, but, not sold in stores in USA hunting areas. Can only mail order -- too slow when need to buy ammo where hunting. Would only need enough cartridges to finish hunt.

IF at all possible, I take all ammo I need, ammo I load myself with same hull length as chamber, 67 mm, or USA factory ammo with 67 mm hulls (Remington or Fiocchi). Cannot always do that or have used all ammo I take.

Will not be altering cone or chamber length on nice old Sauer that gives really nice patterns.

Niklas