Barrel thread question

I posted this on mcb but I got no response. I have had this marker for several months now, but I am not 100% sure what barrel threads it is using. I have compared the threads to the pictures on Doc's barrel guide and to me it looks like the prerelease impulse threads, but I couldnt find anything about a carter marker using these threads so I am not positive. Since I dont have a shocker barrel to cut down I wanted to get a second opinion before I picked one up for it.

Here is the barrel:
http://www.fusionowners.org/cartercomp.jpg

Here is the pre impulse barrel picture on Docs website:
http://www.docsmachine.com/tech/preimpulse.jpg

And here is a picture of the complete marker:
http://www.fusionowners.org/cartercomp2.jpg

Thanks for any help/confirmation anyone can provide

I expected the carter guys to jump on that. That shoulder at the end kind of defeats a good part of the threading. That barrel may have been a conversion from a different thread.

If you look closely at the impulse threads in the second picture you can see the same shoulder, The shoulder and measurements is what is making me think it is that barrel type. If the marker was rethreaded, I cant imagine why someone would go with that particular thread. The barrel its self has been bored for freak inserts, but still weights in at 11 ounces. The entire marker is actually lighter on the scales then my pump mag, but because of the barrel it feels significantly heavier.