So I saw the airsoft industry blow up as a result of "Shredder's Concave Spacer", which was then taken over and produced by Polar Star..reading the reviews, they were constantly given 5 stars and rave reviews. But, after wanting one I waited..and waited...and waited even more for them to be produced and put back into stock on Evike and Airsoft GI. But later I found that there was some sort of 'thing' going on between the two, so the ETA on the nub was not to be known.
Tired of that, and impatient for them to be made coupled with being in school for manufacturing, I decided to make my own.
So, using measurements from a few hopup arms I have for AK's, measures from a handful of random BB's (taking the 'optimal' size of a bb) I was able to make the mock up of it in Solidworks.
Then, after having it programmed it was run on a lathe.
And here's the final product:
I have some of them for sale in the Classifieds section too if anyone is interested