I just picked up 2 - 700mm X barrels for my Impact. Being too long to fit into the FX supplied rifle case. I picked up this Document sleeve made by Nozlen on Amazon
https://www.amazon.com/Nozlen-Document-Poster-Tube-Telescoping/dp/B00DGWRHQY/ref=sr_1_2?ie=UTF8&qid=1526670212&sr=8-2&keywords=Nozlen
the case is adjustable in length where you can lock it in 1/2 increments up to 40”. I used a couple of pieces of the heavy foam packing from that Pyramid uses when you buy ammo from them. I put 2 barrels in the case with no difficulty and it can probably hold 2 more without a problem. The best thing was the price is just under $20 delivered. Around each barrel I used some foam pipe insulation to cushion it.
https://www.amazon.com/Nozlen-Document-Poster-Tube-Telescoping/dp/B00DGWRHQY/ref=sr_1_2?ie=UTF8&qid=1526670212&sr=8-2&keywords=Nozlen
the case is adjustable in length where you can lock it in 1/2 increments up to 40”. I used a couple of pieces of the heavy foam packing from that Pyramid uses when you buy ammo from them. I put 2 barrels in the case with no difficulty and it can probably hold 2 more without a problem. The best thing was the price is just under $20 delivered. Around each barrel I used some foam pipe insulation to cushion it.