I think 2 factors favor the 209 for dependability: 1) a smokeless MLer, even at best, has less containment of the powder than a closed cartridge, and 2) the breechplug does attenuate the flash from the primer to some degree. I believe RB's attenuates it less than the stock 10-ML2 breechplug. Edge's modified plug which RB makes for people, upon request, also attenuates the flame less. I have a modified plug on an unmentionable 45 smokeless that I shoot duplex loads in(5744 under 2015) that works well with the PR small rifle conversion. 5744 is likely the major reason this works so well. Maybe 4759 would have similiar success. Overall, I think a mag rifle primer in a very modern, efficient breechplug might work very well. RB's current plug is impressive and I understand an improved plug is in the offing. Just some thoughts.