The blow back question does not apply to mine there isn't any, it is without dought the easiest cleanig muzzle loader I have ever own [thats some where around 25 not counting the ones I built for other people] I did make one modification on the forarm. as with all guns barrel harmonics enter into what it likes to shoot good groups with, my particular gu shoots best with the 200gr SW and a 100 or 110 gr 777, I have gotten 3/4 inch groups when every thing was just right[especally the wind it shoots anumber of bullets under 2 inches and has grouped the 250 Gold Dot and the 300 gr Gold Dot well enough that the average for them is less than 1.25 inches which I considerreasonable for a 4 power scope and 110 gr 777; I like to experiment and so I try a lot of things to condense it a bit what it did not like was MMP12 impossable to load MMp HPH 24 [my favorite sabot] too tight large groups Crush Rib with the right load with shoot XTP 230,250 & 300gr 250 & 300gr SW 250 & 300gr Gold Dot. It did not shoot 180gr Gold Dot or the 230gr Gold Dot well [around 3.5 inches] it likes 777 and pyrodex [ which is all I have tried in it but it likes 777 best. I plugs up the touch hole in the breach plug if you try to shoot the Win 777 -209 or that dirty old Rem made for muzzle loading and it is really difficult to clean out but the regular win 209 for reloading shot shells works just fine and cleans easy.
Now I can only tell you about what I have tried, I can clean it in under 5 minutes if the water is already boiling; I tried just field cleaning it and can do a good enough job that way but with out the boiling water and a bit of brushing it seems to lose that fine edge of accuracy. Also there was some bullets I had to go clear down to 90 gr to get a round an inch group.
If you have any other question I will try to answer them if I can. Lee