Mike, great series of photo instruction. In your opinion does the insert result in a significant pressure increase?
I have no pressure data but I'm convinced enough that it's a non-issue that I've never bothered to have Tom Armbrust test any. The conventional wisdom is that the Spred-R disc displaces ~ 1/8 ounce of shot but weighs considerably less. Say you start with a given 1 ounce load and substitute 1/8 ounce for a disc. Given a reduced payload with all else being equal the pressure would drop, if anything. The only other mechanism for a pressure increase would be if the disc created an obstruction. But for that to happen it would have to be somewhere down the bore some distance ahead of the advancing shot column and I can't see that happening.
