KAC e3 question

[Direct Assault]

I have been building an ar pistol and all I have left to buy is a bcg. I have read that a KAC e3 bolt will not work in a mil spec barrel extension but I have a Rainer ultra match barrel and an extra e3 bolt lying around (don't know why) so I threw it in to see exactly how the e3 bolt fails to work with a mil spec barrel extension. Much to my surprise the e3 bolt slips right in and locks up perfectly. Wtf? I didn't feel any binding or excessive play so I don't get it. I wouldn't have the balls to squeeze the trigger but the e3 bolt DOES fit and lock. Can someone tell me why it won't work? I've done some googling and have just seen people saying it won't work at all and you need an e3 extension. Im not calling anyone out but I am a bit of a KAC fanboy and if I can use an e3 bolt in all my rifles I would.

 

[Jefe~]

I would like to know the "Why's" to this one myself. I have an SR15 E3

 

[Scotts556]

I believe it has to do with the lugs being more round than square.

 

[Mike_Honcho]

I thought the issue was the other way around - KAC extension with a standard bolt.

 

[Direct Assault]

The story goes "a milspec bolt can be used in a E3 barrel extension in a pinch but an E3 bolt will not work in a mil spec barrel extension at all"
I'll take some pictures to show what I mean about the E3 locking in fine.

 

[Direct Assault]

E3 bolt




Lugs fit fine


Locked in

 

[Direct Assault]

Nobody? It closes on an empty chamber though. I do not have go no go guages to test it

 

[brcook03]

It may not hurt to shoot an email to KAC and ask them. They should be able to give you the engineering reasoning behind why it shouldn't be done.