I just found a small pamphlet in my files, produced in December 1944 by the "Office of the Chief of Ordnance" that lists the M21 as standard. Having thought about this and finding little difference between the M21 and Mk. II Practice grenades and also in light of the M21's in the fibre containers dated 1944 being no more than Mk. II bodies. I now believe that the M21 was nothing more than a redesignation of the Mk. II Practice grenade to M21 practice grenade to avoid confusion between live grenades and practice grenades. Makes perfect sense to do that to avoid confusion. Can you imagine ordering practice grenades and having someone not read the whole designation and send by mistake live Mk. II grenades for the Mk II practice grenades. OOOPs, oh dopey me......
I have never found anything in writing (other than on BOCN) that mentions varnishing the corks in place.
Great, thanks very much. Maybe the varnish on corks will be found in another pamphlet or manual. But I think we are on the same page with most of this. You may be correct. What you say about name change is also something I was thinking, and this could be the one of the answers. You're also right about that there is little difference of the MkII and M21, "especially" when looking at my photos in post #19. This is because 3 of the grenades shown in are all the same grenades, the same shape & the same maker, "C" Crane Co. (this is just by chance I have 3 Crane bodies)
My Theories...............I hope it makes some sense
The one "M21' shown, the dark blue grenade that has just a perfect round hole, no threads, this is the same body as the light blue "MkII" that has a threaded filler hole, and the same body as the other MkII light blue trainer shown, that has a "very out-of-round hole"
That MkII light blue blue trainer with the "out-of-round hole" has had it's original threaded hole "drilled/reamed out" to conform with what I believe is the other change made to MkII practice grenades.
Besides just re-naming the grenades "M21", I think the new specs for M21's called for just an un-threaded hole. Maybe the procurement paperwork or something else might prove this when found.
So I think besides re-naming the MkII's to eliminate confusion and possible accidents or delays in training, that they also called for all blue trainers to just have an un-threaded hole.
So my theory of what was done with practice grenades in the 42-45 time frame is that some of the regular threaded hole MkII practice grenade bodies had their threads removed by drilling/reaming to conform with new "M21 standards", and thus theoretically a MkII practice could become an "M21" by drilling/reaming the threaded holes. (not all were able to be modified, and this is why you see WW2 blue trainers both threaded MkII, and un-threaded holes M21)
I have seen quite a few WW2 era blue practice grenades with the out-of-round, and usually off-center chamfered edge holes like I've shown.
I have mentioned this drilling /reaming of threads and the out-of-round & off- center holes before but no one commented on this, but I really think this is what was done. I certainly think we did not start at a time of war some new type of production to start making special "lower quality" or "special training grenade" bodies with just a hole, as I've heard others suggest... ESPECIALLY if they re-used old WWI bodies like the other M21 shown, and they still called it an "M21"...... then I don't think they were making any special lower quality training bodies during the war.
Does what I'm saying make any sense?
During WW2 I think for all training grenades, no matter the name they were called MkII or M21, we used and then modified just regular threaded hole bodies. If these grenade bodies were never pulled off the production line to use as trainers, then they would have been used as a regular explosive-HE grenade. I say "No special lower grade bodies" specifically made for trainers during late war years of WWII. This is of course only "during" the war. After the war they obviously specifically made some new M21's trainers ....The RFX M21's.
So it looks like to me, at least the Crane company who already was making regular HE bodies at the time, and probably....or maybe obviously, judging by my one non-threaded hole body, Crane probably still made bodies with threaded filler holes, and they just pulled some grenade bodies off their production line before they were threaded, and these would have already conformed to the "new" M21 specs. Then obviously they supplied some of these new "M21's" to the Gov as we have seen from the fiber containers ...........................................................................................and then I buy a couple from a guy who found them in a dumpster over 40 years ago, and they make me think and type a lot, and then also make people hate me for making loooooooong posts. haha, funny how things work out. :tinysmile_eyebrow_t :tinysmile_cry_t4:
cguru:
