Owned 3 - still have 1 in the safe 50 Cal MLS 26" Green Mountian Barrel. Like mentioned they need disassembly of the bolt for a cleaning after each range session(no worry if hunting and only firing a shot or two). The T7 hangfires is in direct relation to the spring in the remington conversion/factory equipped 209 ignition. If you switch it out to a 26lb spring you'll get less hangfires, available through Brownells(at least they used to be!). Or you could buy one like cabela's sells, WS used to stock them a few years ago they come with a 24lb spring/solid 209 nipple(no slots like the remmy) but worked flawless in my 700mls. In my green mountain I bought the 26lb spring from brownells and 209 nipples from cabela's, using the factory 209 firing pin. I have had no hangfires that can be faulted on the ignition system alone since these mods.
As to loads if your wanting to use pellets 2x50's under 240 .431hornady XTP with MMP green(.431) sabot has always shot under 2" at 100 in my 700's. Another 250gr SST and packaged sabot over 2x50's. I shoot loose 95gr of T7 under 240 xtp, 100-110gr under 250gr sst for upto deer. For larger then deer I used 300 or 300gr with short MMP .451 black sabot under 110gr of loose T7 or 120 loose Pyrodex RS. I also had good groups with 300gr SW's or SST with crushed rib high pressures (long) sabots under 100-110 T7 loose. I have tried a ton of others but these ones where always 2" or better shooters in my rems.
BTW I only use Winchester 209W primers, never just popped when in the field and rarily on the range. Also when on the range shooting for groups I swab between each shot with 50% windshield fluid and 50% Isopropyol Alky - damp(to wet and you'll have mis/hangfire problems) patch run down in short strokes to the breech, flip over repeat and then dry patch for 2 passes. I found it helps with reducing fouling, cooling for less sabot deformation due to heat and ulitimately better groups. I always started my hunts on a clean bore as all 3 of my 700's shot bang on with no fouling, without the the swabbing between shots #2 and 3 posed no problems but after that I needed a swab to remain consistent in my rifles. I carried some 50/50 solution pre-soak patches in a snuff can when hunting and some dry patches JIC.(though never needed them
) On the breech and nipple I used pink teflon tape, no frozen plugs and less blow back due to a tighter/better seal.
Other then the blow back flaw requiring the bolt disassembly the 700ML has been a great ML and I haven't found to many new sub shooting ML's that are much better on paper (groups). Reason why I have had 3 and still own 1!!
