How does the Sig Sauer MCX SPEAR-LT .300 Blackout 9" compare to 5.5" or 6.75" 'Rattler'?  I will be shooting suppressed exclusively, almost exclusively subsonic, and believe they all have 1:5 barrels so bullet stability with long heavy options should be fine.

How does handling vary?  How different is muzzle blast either unsuppressed or in terms of flame cutting a Titanium baffle?  What are reasonable accuracy expectations at 100 yards?

I won't be shooting for Social Media accuracy claims but, I also need to be able to shoot smallish critters reliably.  Mainly beavers and dogs (~20lbs and up, 12" tall and up).  Will this work well for feral hogs in terms of humane lethality at 100 yards?  I have tried using a shotgun with "Coyote" loads which work well around water where poisonous snakes are an issue but, I find it to be generally too long and too heavy; however it is effective inside 50 yards on beavers and snakes and I have confidence if I'm attacked by dogs again, it would take down a 100lb dog or pack of 3 or 4 'bird dog' sized ones in-bound as a pack.

On a related thought, I have been looking at a B&T APC9-SD SBR for a similar role.  Pretty different options but, 9mm 147gr versus 7.62mm ~208gr at similar velocities so, a little difference in penetration depth against something like a ~100lb feral hog but, probably a wash or slightly favoring the larger 9mm hole on dogs.  Beavers and snakes are probably a wash in terms of one being better than the other.  General thoughts and experiences here?

TIA,
Sid

I speak from shooting an 8" suppressed .300blk. I shoot 90% subsonic suppressed, and does everything I need from it out to 100yds.

For my uses, property pest control, hunting, I like the middle ground barrel wise. 6.75 is pretty short and shines for <25yds. 9" IMO is unnecessary for subs, and can get an occasional supersonic speed in my experience.

Subsonics out of 9" barrel going supersonic?  I used to seeing lower velocity numbers out of longer barrels due to extra bore friction or something like that.  If I wanted supersonic velocity, I would use a 16" rifle, today probably my 300H'AMR or 6.8SPC.

Do you reload?

If not, you need to examine your preferred factory sub load to see what its performance will look like out of extremely short barrels.  Many are designed for use in 8”-10.5” barrels and as such can lose enough velocity in anything shorter that you fall outside of the velocity envelope where their projectiles will provide reliable terminal performance.

I can’t recall exact numbers, but 190gr Hornady Sub-X out of my 5.5” Rattler chrono’d slow enough that it wouldn’t have reliably expanded at the muzzle or at least much past it.

Frankly, supers are a much better choice for shooting living things with 300BLK outside of some very niche applications.  I’m not saying subs won’t kill stuff, they just won’t do it anywhere near as well.

Yes, I even get the occasional "crack" out of my 8" barrel. However, it's not often. About 1 in a hundred rounds. Just thought it was worth mentioning.

Now I could see lower velocity out of something like 16-20" barrel with subs. I used to have a chart but deleted from my files some time ago.

A Rattler is an amazing backpack/car gun. That's what it was built for. It makes compromises to get that short though.

If you're going to be shooting suppressed 100%, and you have a specific suppressor you're going to leave on the weapon, I'd go for the 9" since you said you might need it for hogs.


As another poster said, most of the factory ammo loads are designed for 8-10" barrels for 300 blackout.

Don’t have an Sig, but I did switch my 9” .300 to a 6”. I probably would have gone 6.5-7” if I’d been able to find one. I like it, as even with the can it still feels short!