Well Jake I looked around and can't find any mags for 2 3/4", only 3".
AK-74 AK-47 SVD 7.62x39 5.45X39 7.62X54 magazine clips inert ammunition
And I saw a post on Saiga forum were someone else (unless it was you) had the same problem, on person said they had to open the gas port a little but gave no details.
So if your not a member there you might want to sign up and ask over there.
Sorry I couldn't help any more then that.