3 Attachment(s)
300 Blackout Suppressor - fixed the bastard...
The inaccuracy of my Blackout with Sub-sonics has been the subject of much head scratching. I built up a load that cycled well and was pushing 240 SMK's at 1020 fps. My suppressor is an over-barrel one built by Goodwin Prototyping and it looked nice enough, and was quiet, but every time I spun it on, and tried it, the POI was low and left, 7:30 on the clock. I initially sent it back to them as I suspected I was getting internal strikes, and to have the rear bushing redone. They sent it back with a note to say there was no evidence of strikes, and a new busing was fitted.
Today I finally got around to debugging it myself, as it was still giving me a very low left POI. I should point out that without it, I coud zero with subs or supers and the groups varied only in elevation, no windage factor.
I fired a group and got a string of hits from the POA on down to the left. I the unscrewed the suppressor half a turn and got two hits high and right... Here's the target. Ignore the .22 stuff.
Attachment 21726
This pretty much convinced me I was getting internal baffle strikes so I decided to pull the suppressor apart. Some heat on either end with the blowtorch took care of the loctite they'd used and I was able to pull and inspect the baffle assembly. Here's what I saw...
Attachment 21727
Quite obvious copper smears in there...
It looked like the bore through the baffles was slightly over 8mm. I ran a 8.5mm drill through from both ends, cleared out the swarf, reassembled and shot and a reasonable group but it was still low and left. At least the group size was encouraging but still being interfered with by the suppressor. I then opened it up with a 9mm and test fired. With no scope adjustments, the POI was immediately back to near centre. A few clicks brought the group up to the aiming point.
Here's the target, the 5 shots about 8" away at 7:30 are after the first rebore. The ones about 1" away at 5:00 are after the 9mm rebore and with no scope adjustment between those groups.
Attachment 21740
Damned thing has been bugging me for ages but I'm happy I've got it sorted now.