If using for defense or even hunting I would look at other options than using 77grain bullets out of a short barrel. If you have the option and defense really is a priority there's several things to consider.
I keep IMI 77 grain and IMI 69 grain on hand to shoot when I don't have time to reload. It's good ammo and shoots lights out of my SPRish build with a WOA 18 in SPR barrel. I understand wanting to have common ammo to run across multiple platforms.
I was swamped with other things in life and my bolt gun (6.5CM) was in between a chassis swap and several other parts this past fall so I took my SPRis build out for deer season. The ammo was IMI 77grain Razorcore. I ended up shooting a buck at 26 yards (verified with sig kilo 2000). The shot was absolutely perfect behind the left shoulder in the money spot for the lungs/heart. The deer started to run after impact and immediately fell flat on its face after 2 steps, then got right up and hauled ass out. I waited for it to bleed out and after about 45 minutes I got down from my stand. The terrain was very steep (knobs in KY) with a ton of gullies as well. The sun had gone down and it was now dark. I had 5 other people come to assist with a goal of a fast recovery and 3 out of those 5 were experienced trackers (so 4 experienced trackers including me and 2 others to total 6.) One is my father in law that has been hunting this property for 30+ years to include a lot of squirrel and raccoon hunting (he knows the terrain.) We have multiple game cams up and are VERY intimate with where the deer travel, where they bed, and can notice a general shift in activity from week to week starting in August when we start gathering info on them. With all that said.......despite finding some blood that night (which was NOT much) we did NOT recover the deer. I went back out at sun up and got on a blood trail which took 2 hours to track 186 yards worth since the drops (more like specks) were so small. Eventually the blood stopped and depsite 2 other people looking for an additional hour we did not find it. We knew exactly where the game trails, water, and thickets were but still had no luck. The next weekend my father in law was out hunting and was able to recover the head off of the remains due to buzzard activity.
With all that said........I had watched every video that's out there (IMI's testing, BARFcom TMK etc) on any terminal ballistics for the 77 grain SMK and 77 grain TMK. I was confident that at short range the bullet would perform. It did NOT perform anywhere near how I thought it would. I will never shoot another deer with ANY 5.56 round/rifle. The only exceptions
would be:
-I was in danger of starving and 5.56 was my literal only option
-i was doing population management
-even in those situations I would place a head/CNS shot
A lot of people have had other results and I believe a true hunting bullet would have performed better than the SMK.
That's just my $0.02 and others have expertise on others aspects like the BCG issues.
Deer and humans are clearly different with anatomy. Standing broadside on 4 legs vs a person upright presents 2 totally different types of exposure. Even still, if I'm choosing a rifle/caliber to save my life and my families life.....its not 5.56 out of an SBR based on my personal experience.
I'll finish off by leaving a picture of an EXIT wound at 632 yards out of my 6.5CM as food for thought ....147 ELD handload moving 2858 fps (no typo and yes it's a hot load)
