Dynatex Timed Fuses

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Bought two Dynatex/Dynatec timed grenades a few weeks ago. They were fine when they arrived, but incredibly dirty (to the point where the shotgun to 9mm adapter head ceased up. I dissembled them the way I did with my existing one to just remove any dirt and use a brass brush on a Dremel to get rid of the years of carbon buildup on them. Timings on each were between 4 to 6 seconds. I thought this was a bit long too, and probably down to how old and how much dirt was in each.

 

After reassembling them the fuses were all over the shop - between 2 to 13 seconds long. I thought at first the lube I'd added might be interfering with the timing, so I removed it all and cleaned the inside with alcohol before leaving them in a bag with silica gel for 48 hours to ensure all the moisture was out - didn't work.

 

I then realised that the Dynatex is an old design and it's possible it's been revised internally to the point that the large plastic part (the only real component apart from the spring and 2 o-rings) was a different spec. I measured my existing one and the two new ones - one of the new ones was 38mm wide, whilst the other two were 37. I then spent about 2 hours trying different springs with the different internal cylinder thingies find a combination that worked. I now have one grenade that takes 13 seconds to actuate, one that takes 2.5 - 3 seconds, and another that takes 5.

 

Finally I checked the holes drilled into the sides of the plastic were clear and even went as far as to try and remove the firing pin before discovering that I think it's riveted in place. I don't think it has much to do with the timing mechanism though despite the video below.

 

Has anyone run into such an issue before? If so, how did you sort it? The system is so simple I just can't work out what's wrong - there's nothing broken and the seals are in good condition. Nothing stuck in the pinhole where the air moves in etc.

 

Here's the disassembly video I used. He describes a 'jet nozzle' that can be removed, but I see no such nozzle - just a hole under one o-ring that allows air to slowly seep in. Either all three of mine are an old design or his is. He also has a single o-ring whereas I've got two on each of mine, so clearly ours aren't the same.