CAG36C barrel/hopup issue + cylinder question

[Spa]

Just a quick question on what may be causing this problem. My G36C shoots fine and everything just after shooting 100 rounds it jams and no BBs are fed through. To fix the problem I usually take the mag out and full auto fire, put the mag back in full auto fire, and some bb's fall out then the guns begins to work properly again.
I think the problem could be shitty BB's or a shitty Barrel. The barrel is not stock and i believe it is also from a crappy company make.
Any suggestions may help, thanks.

My second question is, What is the real difference between a stock brass cylinder and a "upgraded" cylinder that is chrom and shiny?
My friend asked his brother who is a mechanical engineer and he said absolutly nothing, but I also heard that the metal helps "lubricate" the oring better then brass. Brass is also more maluable then the "upgraded" cylinders, but could friction from the pistons oring cause it to bend over time?
So, the question is what are the pros and cons with the difference in cylidner material.

Thank you for your considerations, input and help.

Spa

[hutch1970]

Spa, what brand is your barrel? Did you change it out yourself? What brand bb"s are you using? Was the hop-up replaced? What are your aeg repair skills like? When was the last time you cleaned your barrel? Is your magazine locking in positively? Your answers to these questions might help somebody to help you. As to your cylinder question, please browse the modification section. The subject has been debated.

[Spa]

well hutch i cant find it in the mods section even after i searched

I did fix the jam problem though:P just a dirty barrel and its a KW or KM barrel.

Another question that poped up (yes i did look but nothing) was what are the pros/cons/differences between a metal nozzle and a plastic nozzle? and to metal nozzles come with orings or slots to put orings in them?