What caused suppressor end cap damage

[jlow]

Up front, I am not going to reveal the make of the suppressor so that we can keep the discussion on what and how?

This is a 9mm suppressor with a total of 11 baffles. It is attached to a PCC via a 3-lug adapter. Now when you ask how the end cap strike can happen, you will get question about the barrel, the 3-lug adapter, how it is fitted to the barrel, and how the suppressor was mounted.

I am going to say upfront that the problem is likely only in the suppressor. The reason is despite the end cap strike, NONE of the 11 baffles were damaged – ZERO.

If you look at the hole dimensions, a 9mm bullet is 0.3545” in diameter. On average, the baffle holes were between 0.4010” to 0.4040” in diameter, so there is 46 to 49 thousands leeway over the bullet. The end cap undamaged part had a diameter of 0.4135 so a 59 thousands leeway. Where the bullet skin and distorted the end cap, the hole had a diameter of 120 thousands.

So the question is how could a bullet travel past 11 baffles and not damage them but hit the end cap?

I can tell you that this suppressor had only about 150 rounds through it. The first 50 rounds, no damage anywhere. Next 50 I got a slight skim on the end cap. The last 50, I got enough of a it to expand the cap by 61 thousands.

Now if we look at the baffles, I found that they are of a asymmetric design with a keyhole on one side (see attached image from web). My question is could gas associated with this keyhole push the bullet sideways as it is coming out of the end cap to cause the end cap strike? I cannot think of any other way that a bullet can travel past 11 tighter baffle with no hits but hit a larger hole at the end of the suppressor?

 

[Dusty Stevens]

Id check the runout of that hole in the endcap. Those baffles are one of the standards and work well. If you want to test your baffle theory turn them 180 in the suppressor and see if the strike moves to the other side

 

[457ciSBC]

Up front, I am not going to reveal the make of the suppressor so that we can keep the discussion on what and how?

This is a 9mm suppressor with a total of 11 baffles. It is attached to a PCC via a 3-lug adapter. Now when you ask how the end cap strike can happen, you will get question about the barrel, the 3-lug adapter, how it is fitted to the barrel, and how the suppressor was mounted.

I am going to say upfront that the problem is likely only in the suppressor. The reason is despite the end cap strike, NONE of the 11 baffles were damaged – ZERO.

If you look at the hole dimensions, a 9mm bullet is 0.3545” in diameter. On average, the baffle holes were between 0.4010” to 0.4040” in diameter, so there is 46 to 49 thousands leeway over the bullet. The end cap undamaged part had a diameter of 0.4135 so a 59 thousands leeway. Where the bullet skin and distorted the end cap, the hole had a diameter of 120 thousands.

So the question is how could a bullet travel past 11 baffles and not damage them but hit the end cap?

I can tell you that this suppressor had only about 150 rounds through it. The first 50 rounds, no damage anywhere. Next 50 I got a slight skim on the end cap. The last 50, I got enough of a it to expand the cap by 61 thousands.

Now if we look at the baffles, I found that they are of a asymmetric design with a keyhole on one side (see attached image from web)View attachment 1221581. My question is could gas associated with this keyhole push the bullet sideways as it is coming out of the end cap to cause the end cap strike? I cannot think of any other way that a bullet can travel past 11 tighter baffle with no hits but hit a larger hole at the end of the suppressor?

I think you are making the assumption the cleareance is linear all the way through. I would insert an alignment rod and verify the relationship at the end cap before I question the baffle construction.

Are you shooting 9mm Luger out of this 9mm suppressor?

 

[75vmax]

Can came loose.

 

[DirtySteve]

What about the ammo???? Subsonic>?? Handloads??? If the ammo was not going fast enough the bullet could have started to yaw. It would be seriously slow ammo to yaw that much and that quickly. But it is either this or the can was loose...

 

[boltfluter]

Depending on the length of your suppressor, all it takes is for the threads to be off about 1/4 of a degree to the bore and you can get a baffle strike. Suppressor coming a little loose will also do it. I check mine with a good fitting, straight range rod before I fire the first shot. Good luck.

Paul

 

[jlow]

Depending on the length of your suppressor, all it takes is for the threads to be off about 1/4 of a degree to the bore and you can get a baffle strike. Suppressor coming a little loose will also do it. I check mine with a good fitting, straight range rod before I fire the first shot. Good luck.

Paul

I have thought about a rod, but if the rod is going to work, it is going to have to be a close fit to your barrel or it would wobble around. But pushing a tight fitting rod down your barrel can't be a good thing?

Not arguing, but asking.

 

[boltfluter]

Jlow,

I have made several rods out of brass stock that worked quite well. I made mine with a slight taper about an inch from the tip so it would naturally go to center.

Paul

 

[tobnpr]

This (if you can find one in stock)

https://geissele.com/16-9mm-suppressor-alignment-gage.html

You could also call Meyer Gage Co. and have them grind one for you.

 

[jlow]

This (if you can find one in stock)

https://geissele.com/16-9mm-suppressor-alignment-gage.html

You could also call Meyer Gage Co. and have them grind one for you.

So I have seen the Geissele ones (which are out of stock), but if you read it, it says "The Geissele SAG is manufactured from hardened steel that has been ground 0.002” under nominal bore diameter. " thus my question about pushing a tight fitting rod down your barrel...

I can see a brass one that boltfluter mentioned but...

 

[tobnpr]

^^^
Yeah, I get that- but I think of it no differently than a solid pilot reamer, and it ain't spinning in the bore.
If it's sized properly, shouldn't be a problem.
But, that's the issue. Two tenths isn't enough IMO, it'll risk binding if the bore is just slightly oversize.

Hardened steel isn't a problem if it's correctly sized for the bore, Dave Manson has stated he'd in fact prefer a solid pilot over a bushing if he had the barrel in front of him to be able to grind the pilot to exactly the right size.

Boltfluter's idea is fine, but I know I couldn't turn a skinny rod like that a foot long between centers without a follow rest (which I don't have) to keep diameter consistent and keep it perfectly straight.

Why not a grizzly rod with correct pilot, or a range rod?

 

[jlow]

Just an update. I found out talking to folks on a forum dedicated to this firearm that the problem has to do with the tapered barrel and so does not have a 90 degree shoulder for the 3-lug to torque on to. That apparently can cause concentricity issues.

The fix is an adapter which you first put in so that it sits against the taper on the barrel and gives you a 90 shoulder to screw the 3-lug against.

What I can tell you is without the adapter, when you tighten the 3-lug onto the barrel, I have never been able to reach a hard stop, it seems to want to keep going in even though visually the end of the 3 lug was already up against what looks like the end of the stop of the barrel. The 3-lug was never lose as I had Rocksett on it and I confirmed tightness when I initially removed the 3-lug.

Fast forward with the adapter in place, very easy to reach a hard stop.

On top of this, when the whole thing was mounted together again, using the same RDS that had been zeroed at 25 yards, my POI was more than 3 feet to the right and one foot low again at 25 yards….

 

[Dusty Stevens]

Its so very important to have any kind of muzzle device threaded onto the barrel with very concentric threads. They should be set up just like chambering. The end cap is a long ways in front of the muzzle and it doesnt take much at the muzzle to be off a lot that far out

 

[tobnpr]

and so does not have a 90 degree

Well, duh....
Seems we never bothered to ask what the firearm in question is, doesn't get any more basic than that.

I just assumed it was an AR in 9mm, or a pistol already threaded for a can.

Can't have a suppressor that's not seated on a substantial, 90 degree shoulder that's faced perfectly parallel to the bore. It can be an internal shoulder seated on a squared muzzle, or more commonly on the barrel itself- but there's no getting around it.

 

[Clous]

I shoot a tapered Sig can against a 90 degree shoulder and haven’t had any problems. I do however have video of a popular can flying off a 338 that only hit the end cap. Been three weeks and they haven’t come up with an explanation. This wasn’t new either. Probably had 100 rounds through it.