Extending barrel
 

If I put a longer barrel on my AK (RPK Conversion) Will I need to modify anything so it doesn't negatively effect my fps? or will it give me more fps because of it?

How long is the RPK inner barrel?

definately wont give you more FPS

Depending on how tight it is you should be ok with a type 0 cylinder or a bore-up kit especially if you use a tighter barrel. If its a stock barrel, 6.08+, than you should be able use 590mm without drastic negative affects. I do believe you need a 590mm barrel for the RPK. I would not use a 6.01mm due to barrel suck, stock might the best way to go on this one. If you need to bump your FPS a little add a spacer on your spring guide, tweak your compression or use a stronger spring.

mateba, you have that reversed.

A tightbore inner barrel has less internal volume than a larger bore inner barrel would, and as a result, you're more likely to require a bore-up kit on a STOCK inner barrel, and less likely to require a bore-up kit if you use a tightbore.

Of note: I've used a Systema M120S and PGC M130 spring on a 590mm 6.03mm inner barrel before and tested performance with both a Systema Type-0 inner barrel as well as a Systema Bore-Up kit and noticed zero difference in performance.

ok

So if i get a 6.04 PSG-1 barrel my Fps shouldn't go down by more than like 20 Fps?

Tightbore should add about 10fps to your velocity. Is just a general rule of thumb though.

Incidentally, I cut a stock barrel to 330mm and installed it in my MP5-SD (stock had a 229mm) and saw my velocity go from 365fps to 387fps simply because of that extra 100mm of inner barrel.

Hmmm, a 590mm barrel is only a 140mm upgrade, so i guess ill get the PSG-1 and hope there is little or no negative effects.

Be aware that there are two PSG-1 inner barrel lengths: 590mm and 650mm.

Ya, Im trying to figure out what i could fit with the extension im getting (http://airsoftglobal.com/product_inf...oducts_id=4595)
so ill decide once I know that.

If you get the 650mm, you will HAVE to get a bore-up kit and an M120 or stronger spring to power it.