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3.7 inch AA Mk6 Probert


Well-Known Member
Premium Member
thought you might like to see a 3.7 inch Mk6 Probert proj. It makes an excellent door stop!
Very nice!
Just what I'm after to put in my 3.7 inch case!

hope you mean a 3.7 inch Mk 6 case - they were different to the standard 3.7 inch case - taller and with a more tapered shoulder. I got rid of the case as they crimped over the driving bands and as it was a fired case, the neck had been pushed out and the shell wouldn't sit happily in it (like a 76mm Scorpion)
Ahhh,mine is a 1949 dated MK 1 case.

Always thought it was a MK 6 for some reason,don't know why!

Are primers for these cases easy to come by?

hi Andy, the primers aren't too difficult to find as long as you know what you are looking for - MkII no 11, see atached photo from the 3.7" handbook. Dave
I never seen mk6 shell and case..... wonderful.
the case is a 4,5in AA adapted to 3,7in shell (94x857)??

best regards
That is as I understand it but I didn't have a 4.5 inch AA to compare the 2. I think the necking down process also included tapering the shoulder more than on the 4.5 but perhaps others have more knowledge of this.
3 "/ 70 Probert Mk 34 Mod1

As a comparison


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Thanks so much for the photo. I am a long time collector over 50 years of it but very new to the computer age. My 1st replay thanks again for photo , my scrap binder is now in vol.7 ebay[love them/ hate them] used to be a good sourse of photos, i now have a much better one boc
3/70 some information

see attachments;

search web with ; [FONT=Arial,Helvetica][SIZE=+2]3"/70 (7.62 cm) Mark 37

this will lead to the British version etc.
I've lost control of the type size !

Type Fixed Weight of Complete Round
(see Note 4) 36 lbs. (16.4 kg) Projectile Types and Weights HE Fuze NC101 - 15 lbs. (6.8 kg) Bursting Charge N/A Projectile Length N/A Propellant Charge 11.2 lbs. (5.1 kg)
Cartridge weight (empty): 9.8 lbs. (4.4 kg) Cartridge 76.2 mm x 662R Muzzle Velocity 3,400 fps (1,036 mps) Working Pressure 22.5 tons/in2 (3,547 kg/cm2) Approximate Barrel Life N/A Ammunition stowage per gun
(see Note) 1,000 rounds Notes:

1) These weapons had 161 ready rounds per gun in two hoppers (100 and 38 rounds) and in the transfer system. The figure listed above is the quantity per gun stored in the magazine.
2) HE Fuze NC101 was normally a VT (proximity) type round. It could be used in a contact mode by "paralyzing" the VT mechanism via a wiping action.
3) Besides the HE NC101, there were also a non-fragmenting round for AA practice and an inert training round.
4) "US Naval Weapons" has a complete round weight of about 61 lbs. (27.7 kg). I believe this to be incorrect.
5) Although munitions were a joint development, the USN and British cartridges were slightly different.


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On tuesday one of my contacts phoned me. He buys and sells all sorts of stuff, militaria being one thing he's into, although he's not a collector. He told me he had found a "big shell case, it says 3.7" GUN VI on it". I wen't over today to pick it up, only to find that it had been cut off below the neck. Why is it always the good ones?
For those of you who like the technicalities about how these things are meant to work, I was sent this a while ago:

I was taught, and went on subsequently to teach at the Army School of Ammunition, the aim of Probert rifling was to extend the barrel life by allowing greater wear at the neck of the chamber. The system worked by separating the roles of imparting spin and forward obturation to two separate bands. The forward driving band, up by the bourrelet was designed to engage the rifling and the rearward obturation band to provide the gas seal. This second band was very deep to allow for significant erosion at the case mouth. The leed was very long (about 7 between the end of the chamber and the C of R) on a probertised barrel to allow for this. The 3.7, being fixed QF, could not take up wear by ramming so would be condemned very quickly if rifled in the conventional manner. The tapered muzzle section swaged down the driving bands to clean up the projectile, but this was not the main aim of the Probert system..
After years of searching and 2 very helpful people on BOCN I finally got one today, thanks to both of them.
Just looking out for a primer now.