Local weapon advertised for sale. Considering purchasing as the rifle comes with several mags and 1500 rounds of ammo. I don't care for the 20" barrel. Can it be shortened to 16" and not effect the gas pressure to the point of having operating problems? It has aftermarket Ion RPK stock, is the receiver tanged so a folding stock could be fitted? I had a Sporter-Hunter and was stuck with the oem stock due to the receiver not having provisions for stock upgrade. Overall opinion of rifle appreciated too. Don't get on here much but the site upgrades are excellent. Thanks in advance for comments.