Originally Posted By: NiklasP
Tobais,

I have several older Husqvarna hammer doubles, made before WW2, and ALL have measured 65 mm chambers, in both 12 and 16 bore. I also have several older, also pre-WW2, Germain 16s that have measured 67 mm chambers. What later Husqvarna doubles have for chamber lengths, I have no personal information about because I have never found one that handled as well as older top lever hammer doubles.


I have measured quite a lot of HVA and they are normally 67 to 68mm long.

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Per CIP regs, 67 mm ammo having proper service pressure for gun in question is considered totally OK for use in actual 65 mm chambers. I have done this for years with 16 bore Remington Game Loads,16 bore Fiocchi Game loads and Venuezalian Imperial 16X67 ammo, all having actual 67 mm hulls, even though Remington and Fiocchi are marked on hulls as 70 mm. Do some simple calculations of how much last 2 mm of modern, skived, plastic hulls will constrict forcing cone, even short, 10 mm cones -- think you will conclude that there really is no problem at all.


The problem is quite simple: a gun stamped 65mm (or 2 1/2") normally have chambers that are 67-68mm long. But if you stumble along a gun that is from before 1900 you can suddenly find guns that is stamped 65mm which have shorter chambers - 64-65mm. I have a Churchill BLNE from the first years Churchill made guns – chamber length 64,5mm. And a John Wilkes (1893) also 64mm. Both guns stamped 2 1/2". So the use of a margin was something that each maker did after their own ideas. During 1895-1897 there was a discussion in UK if the chamber should be exactly as long as the shell or if there should be a few mm "flight". And in such guns 67,5mm shells doesn't work properly, test and they give you a nasty punch in recoil and normally they have poor quality when you look at the performance.

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I have also Husqvarna hammer double made after books say Husqvarna went to 70 mm hulls, BUT, it also has 65 mm chambers. Maybe 70 mm story is only for internal hammer doubles??

Niklas


Nope, that is the same thing you can see on cartridge boxes from Eley: For 65mm chambers, shell length 67,5mm..... There were no "67/67,5 or 68" mm chambers stamped on guns. There were just 65/70/76 - nothing else, only indicating for what maximum length of the shell used should be. What the chamber in reality was - is something totally different.
And then you have the trick with the mouth.... When we used cartridges with overwad they had to little resistance when they were opened, so the gunmakers made the mouth of the chamber smaller than it should be - to withhold somewhat harder. Today we use cartridges with no overwad (that has a opening resistance that is twice the old overwad cartridge) in chambers that are to short in some cases together with the fact that the chambers is to narrow. Are you surprised that there sometimes are problems? Not normally, but the problems do show up form time to time.
I wrote an article in Vapentidningen (www.vapentidningen.se) about this. That's why I put a very short version of article on my site, since there were a lot of questions regarding this.

Best regards
Tobias