I am running Noveske barrels (FYI).
C4
Very curious what Garin Lee’s explanation is for the differences you have noted, Grant. He has informed me that the MB and the FH both have the same 3 bearing surfaces.
Now, once you carbon up the MB, yes, maybe it fits tighter because of THAT. Otherwise, I’m curious about the explanation.
Without looking at everything under a microscope and measuring every detail, all I know is that I have witnessed (in training classes and on my personal guns) a large POI shift with the FH’s and NOT with the MB’s (generally speaking). This is why I only run the MB’s.
YMMV.
C4
Have the shifts at least been repeatable?
Yes (at least on my guns). The ones I have seen classes, I cannot answer.
C4
Is 4 MOA typical for the 212a mount?
3-4" I would say. I am sure someone will come along and tell us theirs produces a 1.5" @ 100yds though.
There are TONS of variables with this stuff (specifically the barrel and ammo used) so the shifts could be all over the place.
C4
The dimentions of the bearing surfaces on the flash hiders and muzzle brakes are the same. We use both brakes and flash hiders on the test fire weapons and have not recorded any difference in accuracy from using one over the other.
Thanks for posting. Accuracy difference? I haven’t seen any “accuracy” differences either. POI shifts? Yes.
My adaptors are some of the first ones SF every put out. Maybe they have gotten better over the years (consistency wise), but all I know is that I have NOT had good luck with the 212A’s.
C4
I was referring to the accuracy in our testing protocol for shift and group size. We have changed how the adapters are machined over the years for better control and QC processes of how and where to measure the parts compared to the drawings. I ran this topic by Barry Dueck and he also confirmed the findings since he is the guru master mind here and designed them.
That makes sense. I have not tested your MB’s VS FH’s in years. So my guess is that they have gotten more consistent.
C4
John and Kevin were friends. John designed his barrels such that only AAC products worked correctly.
Or, it could be like AAC and others have said all along, that POI shift is something all manufacturers try to minimize, but Surefire using it as a marketing tool is just that…a marketing tool.
If you read what Garrin posted about how the Surefire suppressors are tested, you’d realize that using the rail gun reduces all rifle & mount related variables. That means if the shots deviate from the standard, they know it’s a problem is with the suppressor and not one introduced by the rifle. Suppressors that do not meet the standard are not released.
Ergo, after a suppressor passes such an inspection and there are deviations mounted on another mount & rifle, the shooter knows the deviations are resulting from the mount & rifle, not the suppressor.
Hanging a weight on the muzzle doesn’t always result in the POI dropping. The weight can change how the muzzle swings which in turn changes where the muzzle is pointing when the bullet exits. The Browning BOSS works by changing the position of a muzzle weight fore and aft just a bit until barrel harmonics are in tune with the load being fired. The weight and design of a suppressor will have a similar affect on barrel harmonics which can change POI
Surefire re-EDM’ed my bore, and verified all bearing surfaces were correct. The bore was in-spec, but a tad bit on the small side within those specs, it was EDM’ed to the exact middle spec called for.
Here is a 25 yard test target shot using PMC XTAC M193 at 25 yards from my 10.5" CHF barrel 212a equipped Noveske equipped with a 2MOA T1 demonstrating POI shift before it was sent in. Next follows a picture of the POI shift once it was returned. This group was fired in low light using illumination from my weapon-light at the same distance, and using an M4S optic. Nothing else changed.
Squares on the top target are 1", “bold” gray squares on the bottom target are 0.5".
Surefire’s customer service time was excellent, and door-to-door was 7 days. I was kept up to speed on everything that was occuring. They next-day aired my suppressor back on their dime along with a print-out of a test-target. My suppressor pouch, original box that the suppressor shipped to my dealer in, and double-sided color copy of my Form 4 were not returned to me.
Have you tried different ammunition?
Yes, I have tried Gold dot 64gr and MK318SOST in addition to the M193. The first time, they all shot to close to the same POI/Shift amount (I seem to be more precise with the M4S RDS than the T1, and groups were a bit larger the first time, so they may have had a slight variance that I could not detect). This time, the Gold Dot appeared to shift about 1/2-1/4" to the left of the XM193, but was within 1/4" vertically of it. None of the ammo I have tried shifts less than the 4-7 MOA seen here. I have as you have seen tried 55,62, and 64gr all of different construction.