Seam Sealer Dual Caulking Gun

[C10 - C90 Bill]

I decided to go with the 3M 08307 Self Leveling Seam Sealer on my '72 C-10. But of course you need the Dual Caulking Gun in order to use it. As many will know they ain't cheap so I went checking around. Seems like the average price is about $70 and you can find some for a lot more, but I found what looks like a pretty good one at Amazon for $34. Got it today and it looks great, but noticed that there are 2 different size round push plates on the ends of them. The small plate is fine, but the large plate is a little too big for the 3M tube.

You would think that they all would be standard, like the old Single Tube caulking guns are, but I found out today they are not. I'm either going to have to return it or modify it to work. Luckily there are 2 Screws holding the large plate on and I believe I will be trying to grind it down to make it a little smaller.

Wondering if anyone out there has ever run into this problem and also want to warn others to be aware of this if you buy one.