Seam Sealer Problems

Okay i bought some 3M Fast N Firm Sealer for my bed. The people at NAPA says load it up into a standard caulking gun which i did. Problem is the back is made weird the lips overlap the actual canister should i just push it thru? im affraid it will just crush the canister and ruin a 13dollar tube of sealant.

take that cap off,and the calk gun will slide in about a inch, then seal away

ya you have to pop that cap off it

And if all else fails, cut the tube and spread it with your fingers, lol.