Suppressors Rugged Obsidian piston O ring size and--is it needed?--update

[mark5pt56]

Before reading below, just pointing out that no baffle strikes, end cap, Adapt module, mount was tight, piston was seated properly. And yes the spring was in.

Would anyone know the o ring size for the Rugged Obsidian pistons? I did call them last year and they were less than helpful, wouldn't send/sell them and gave me a size in which I couldn't find. This was for the Obsidian 9 and I just received my stamp for the O .45.

I just got back from the range, trying out the .45 on my HK USP .45T. The sights are adjustable and set dead on at 10, 6'clock hold on a B8 at 25 yards, no silencer. At 10 yards, I can hold a 1" grouping and keep them in the black at 25, so no marksmanship issues. When I first shot with the silencer on, impacts matched, no deviation. Then I noticed impacts started going low, at 10 yards, 3-4" under, shortened it to 7 yards and 2-3". I removed the silencer and noticed the O ring was mangled, was seated in the well prior to. Shot w/o silencer again, sights are still on, same ammunition.

So, maybe that caused the low strikes? Is the O ring necessary for function and what function does it do, at the very least maybe keeping it tight, curious about movement.

I appreciate the help
Mark


Update-Took a chance calling them as last time it was during the whole C19 crap and maybe thats why I couldn't find anything.
Got the sizes and tips on "timing" I did that with the 3 lug and it worked, didn't know one could do it with the pistol pistons.

Anyhow, both are 25 packs, less than $10 each. Viton rings.
.45 is Grainger Item 713D19, 14.5 OD x 1mm
9mm is Grainger iten 713D14, 12mm OD x 1mm

 

[mark5pt56]

For timing on the 3 lug, example with the BT at 25/50 yards, the numbers are the 3 positions mounted with the 3 lug.

The first pic here, bottom is pos 3 although target says "bottom, no suppressor"

No sight change at 50, just wanted to see impact vs point of aim.