Modelling Shardcarbines

Self explanatory. How do you guys model shardcarbines? In the codex they are just larger barrelled Splinter Rifles. The Splinter rack rifles you get with the Raider look sort of like larger barelled SR, but they are cases so they don't look right. So what does everyone use? Any clever conversion ideas?

I just shorten regular rifles a bit. Quick and easy, looks fine.

Also You may use ones from Scourges box.

https://thedarkcity.forummotion.com/t258-speedfreeks-s-harlequinade-macabre
In the first post I have a picture of how I made ine by shortening and merging two rifles.
The muzzle isn't double anymore either.

But since the scourges came out, I would use them instead.
Haven't felt like building on mine since the great looking models from GW came out.

I will echo everyone else. I started off by simply shortening the barrel on a splinter rifle; I now use the shardcarbines from the Scourge kit.

I always thought of making shard carbines as double barrel splinter rifles. But now I am in agreement with everyone else. I use the scourge weapons.

I still may do the double barrel thing later.