Please correct me if I'm wrong but to take advantage of the 7.62x39s ballistics a barrel should be 16inches long. How much will a 20 inch barrel add in terms of distance and how much will a 12 in. subtract?
Just curious because I'm waiting for a Saiga with a 16in barrel to be converted and wonder how shortening the barrel would change the effective range?
Misc

I don't have the exact information that you're looking for, but I will tell you this.  The 7.62x39 is almost identical in case capacity to a wildcat called the .30 Herrett.  It was designed by Steve Herrett and Bob Milek for use in the T/C Contender with a 10" barrel.  I've used one for hunting for several years now and I've got a nice 11-point buck on the wall next to that was taken with it.

You might try contacting Sierra Bullets tech support by way of e-mail.  They're quick and I know a couple of the guys there; they give very good, factual information.

Hope that helps a little,
Robert

I buddy of mine and I were shooting 7.62x39mm's one day . He had an 18" SKS I had my (Ex) Mini 30 . w a 16" Barrel .

(I dont have the mini any more nor do I own an SKS so it could be 18" Mini and 20" SKS whatever is standard for each , 2 inch barrel length differance .)

The SKS was plugging an I beam we were shooting , while the Ruger only dimpled it , the exact same steel and ammo , which was Wolf not steel core Chinesse . A very deep nearly thru dimple , but the differance was clear . Why is not so clear as we didnt have a crony .

It "may" have something to do w/ Rugers comprmise bore dia. or the 2" differance OR who knows but it was interesting as hell . Between that and the 4 + " groups at 100 yds , it went to the curb .

Quoted: I buddy of mine and I were shooting 7.62x39mm's one day . He had an 18" SKS I had my (Ex) Mini 30 . w a 16" Barrel . (I dont have the mini any more nor do I own an SKS so it could be 18" Mini and 20" SKS whatever is standard for each , 2 inch barrel length differance .) The SKS was plugging an I beam we were shooting , while the Ruger only dimpled it , the exact same steel and ammo , which was Wolf not steel core Chinesse . A very deep nearly thru dimple , but the differance was clear . Why is not so clear as we didnt have a crony . It "may" have something to do w/ Rugers comprmise bore dia. or the 2" differance OR who knows but it was interesting as hell . Between that and the 4 + " groups at 100 yds , it went to the curb .

Could have been some of that top secret Soviet voodoo at work!

VOODOO , it worked on me . I'm standing there w/ my scoped synthetic stock mini30 . This$ 89 SKS is clearly drilling this I beam AND MY gun was NOT .  

This was a couple of years ago so I dont remember exactly but my buddies chiding and out right gaafaa may have got on my nerve as well .

I was working on one of my great theories (smaller , lighter) .........

Conventional wisdom was confirmed and I bought an M1A