I wouldn’t go that far. An extension that large needs to be clamped to the barrel for support, which is impossible to do on an Auto-5 since the barrel reciprocates. Nordic Components, where I got mine, suggests not more more than a 4 round extension on these shotguns.

I bought the 3 round version, and let me tell you, 8 rounds of buckshot is like a mag dump from a submachine-gun with a 72 round magazine.

How to Configure Your MXT Extension Kit - Nordic Components Inc.

 

Thanks.

 

I keep a 2 shot mag ext. on my A5 that I made out of a
piece of a metal chair leg, a washer and an A5 magazine cap. Has worked for over 25 years.
To the op. You don't want that........Even if you found one it would be cumbersome and might break off.

 

Thanks. You mean I don't want which, a 3 round or 4 round extension or a sling adapter?