Starting to shoot my 40/65 with a Douglas 1:18 twist .410 diameter barrel for hunting.  I want to shoot black powder and that is a new game for me.  Today was my first session using 400 grain Snover (.410), Lyman 403168 210 gr (.410) and a harder bullet .412 300 gr gc.  The .412 bullet chambers easily.  Finding cast bullets for a .410 barrel is not the easiest thing but many are .406 or .408.  Three questions. Using 20:1 alloy how much below .410 can I go without problems using black powder?  Second question is how hard of an alloy will bump up without causing problems.  Third question, if I have to go with a gas check bullet will .410 work or do I need to be slightly larger at .411 or .412?  Bullets for the 405 Winchester are mostly gas checked at .412.  The ones I shot today did fair for my first attempt at guessing what powder charge to try using Goex ffg.  I switched to a front aperture instead of a flat post after shooting these and could see my target more precise with the aperture.  The 210 grain bullets shot a very respectable 10 shot group and they were loaded with very little compression.  I am hoping to find a 300 grain plain base flat nosed bullet but so far the only ones I have found are gas check.  I am going to try the ones I have again next week with very little compression and now that I can see the sight picture better am hoping the group will shrink in size.  Between breech seating the 32/40 and shooting black powder in the 40/65 I am staying very busy not only at the range but at the reloading bench.  That is a very good thing!     Tom

Grumpybear, my problem is that most places such as the one in your link have tons of bullets sized less than my .410 bore.  I know that a .408 bullet in a .410 bore using smokeless won't work worth beans but have no experience with the black stuff I am now using to pollute the clean California air.  Will . 408 bullet work and even better, since I am hunting and not wiping between shots is it better than a bore size so that it chambers easier.  I used duplex loads today and the bore stayed very clean.  When I changed to a different bullet I ran a wet patch and then a dry and started again.  Tom