Craig thats much more helpful.
It cant be a dry bolt, not if its only partially cycling at 50ms.
Now we know you dont run a QEV, we can rule that out as a problem also.
On an ion, when the bolt isnt coming forward it usually means there is a problem venting the air from in front of the bolt.
So its very likely to be either the front banjo, the small pipe from the banjo to the noid or the noid itself.
Because the bolt is partially coming forward but not properly, you need to ensure the air pathway is not restricted in some way.
Also if you could humour me, and let me know that you've checked the solenoid top, and that the cutout under the top is indeed pointing towards the front of the gun, I can stop going on about it
John