Your question has been asked here before. Do a search on smokeless brass shotshell and you will see several discussions. From these and others it appears that using heavier cards that seal better is important so the pressure has time to rise before the column starts moving.
Here is a post from Stoney Mike that I saved from the SASS Wire back in 2001 (I haven't tried this myself) (Also note that the old Rem-UMC hulls are about the same as the MagTechs):
"Well here goes, These are the loads I've used all season in my 97 and Baikal Mule eared SXS.
I use Remington-Umc all brass hulls. They take a regular rifle/pistol primer. I use CCI Magnum pistol. Never had a light strike or misfife of any kind.
I use Titegroup in my 45Colt pistol and Rifle so it looked and the Hodgdon web site and found a handicap load using Titegroup that looked good.
It took some tweaking to get it right but now I'm set on 22 gr of Titegroup, on top of that an 11,guage, 1/4 overpowder wad from CircleFly wads. Then a half inch fiber cushion wad also from CircleFly. and another 1/4 card wad. This is mainly to take up space in the hull. I them use a Win AA RED wad. A regular white wad will be too long even without the last card and the red would be too short, trust me this is the combiation that works the best for me. I use 1 1/8 ounce of 7 1/2 shot and then another 1/4 heavy card and a slight
crimp, Just enough to hold the card and cycle good, It doesn't take much.
I have a set of dies for the All brass hulls from CH 40. Somebody out there emailed their address and phone to me , now I lost it. You need a RCBS reloader special #5 or a Rockchucker to use them as they are quite a bit bigger than regular dies.
You need the 1/4, harder card at the end instead of the thin overshot card.
unlike blackpowder you need pressure to get a good burn. I tried the thin over shot card glued in with various things but the primer was blowing the wad befor the powder ignited and the shot and wad barely left the barrel.
If anyone has anymore questions please feel free te email me or post a reply and I'll answer the best I can. As the shooters is Southern Wisconsin can attest. I use these every week.
I hope I covered all the bases,
Best Regards, StoneyMike"