Pressure signs from suppressor?

[WoolyBugger]

I just got my first suppressor (Unknown Reaper) and went out to rezero with my same hand loads I’ve been using the past 900 or so rounds on my gun, felt a slightly sticky bolt towards the end of the 10 round zero. After this I waited a couple min and went into a shooting drill and after a couple shots I started getting sticky bolt that progressed to heavy bolt lift and I stopped, ejector swipe on my brass.

Next day I went out to see if removing the can when I started to get sticky bolt lift would remedy this. I shot a 10 round string, waited approx 2 min then started another string. After 3 shots on the second string I had a slightly sticky bolt, next shot was very sticky. Removed the can instantly and quickly fired 2 shots, no hard bolt lift no ejector swipes on those 2 rounds

I’m not shooting a particularly hot load in my opinion. 6.5cm 140gr eldm 41.5gr h4350 Peterson brass. I’ve never noticed ejector swipe and have never had an even slightly sticky bolt.

Is this common? Is there a reason why the design of the reaper would have this happen over a different kind of can? Again this is my first one so I have nothing to compare it to and I’m fine putting this on a hunting rifle that won’t go through long strings but I will be using this particular gun for NRL and prs this summer. I would lighten the load but I’m just at power factor minimum for nrl so I’ll just put a brake back on if I have to.

 

[Ope]

Going by Hodgdon’s data the max load for 6.5cm 140 Eldm h4350 is 40gr. What data are you using? I’m no expert but it seems like you could be close to pressure without the can but adding the can pushed it over and now you’re getting signs.

 

[WoolyBugger]

Going by Hodgdon’s data the max load for 6.5cm 140 Eldm h4350 is 40gr. What data are you using? I’m no expert but it seems like you could be close to pressure without the can but adding the can pushed it over and now you’re getting signs.

Hornady book has max at 41.5. When I did load dev I shot several loads over this out of curiosity to see where I got pressure signs at didn’t have anything at 43 gr. Also have been over book max on 147s for curiosity’s sake without any signs of pressure. Not saying you’re wrong but just seems odd

 

[Ope]

I had a slightly sticky bolt, next shot was very sticky. Removed the can instantly and quickly fired 2 shots, no hard bolt lift no ejector swipes on those 2 rounds

Hornady book has max at 41.5. When I did load dev I shot several loads over this out of curiosity to see where I got pressure signs at didn’t have anything at 43 gr.

Well that is odd then. I wouldn’t think the can would make that much of a difference unless the load was pretty close to pressure anyway, but that doesn’t seem to be the case here. Hopefully someone will come along and have an answer for you. I have a Reaper as well so I’m interested in what’s causing it.

 

[RockAndSage]

The possibility of it being the suppressor doesn't make any sense to me, at all. Peak pressure occurs before the bullet moves much, and continuously drops all the way to bullet exit. Pressure at muzzle is typically about 15-25% of chamber pressures, depending on barrel length and cartridge.

 

[WoolyBugger]

The possibility of it being the suppressor doesn't make any sense to me, at all. Peak pressure occurs before the bullet moves much, and continuously drops all the way to bullet exit. Pressure at muzzle is typically about 15-25% of chamber pressures, depending on barrel length and cartridge.

What are your thoughts? Abnormality in my hand loads potentially?


Also looking back I mis stated when I got the pressure. Here is the second string from yesterday. Pressure on shot 6 and 7. Can off for 8 and 9 no pressure signs. These speeds are pretty normal, about 7 fps lower than what I use in my ballistic solver

 

[vonb]

The difference in velocity I see b/t shooting with the can on vs off is about a 40 fps increase when shooting with the can. You could already be at peak pressure with the can off. Then, when you add the can, it puts you into dangerous territory.

 

[WoolyBugger]

These are from my first string of fire yesterday. Extra .2 gr of powder to get to power factor for nrl was testing these loads. No pressure signs.

 

[RockAndSage]

I wouldn't say it's impossible the suppressor isn't changing pressure, but I'm definitely saying it doesn't make any sense. Would suggest running at least 10rds with the can off, then put it back on to see if pressure signs return. Maybe doing the same thing with a box of factory ammo to see what happens. And I would definitely appreciate knowing your results.

That said, it does sound like something's up with the ammo. Maybe back off a half grain or so and see what happens.

EDIT: just saw that it was loaded for power factor. Not sure what to do.

 

[WoolyBugger]

I wouldn't say it's impossible the suppressor isn't changing pressure, but I'm definitely saying it doesn't make any sense. Would suggest running at least 10rds with the can off, then put it back on to see if pressure signs return. Maybe doing the same thing with a box of factory ammo to see what happens. And I would definitely appreciate knowing your results.

That said, it does sound like something's up with the ammo. Maybe back off a half grain or so and see what happens.

EDIT: just saw that it was loaded for power factor. Not sure what to do.

I’ll do that next time I can get to the range and post results. If these loads that make power factor aren’t going to work out I’ll just shoot factory ammo.

 

[5MilesBack]

I saw the same thing with my Tikka 243 8 twist and 108gr ELDM UM loads. Without suppressor there were no pressure signs. Put a Nomad TI XC on it and the first two rounds blew primers, had hard bolt lift, and heavy extractor marks on the brass. I pulled some bullets, lowered the powder, re-seated the bullets and shot them again without any issues.

 

[WoolyBugger]

I saw the same thing with my Tikka 243 8 twist and 108gr ELDM UM loads. Without suppressor there were no pressure signs. Put a Nomad TI XC on it and the first two rounds blew primers, had hard bolt lift, and heavy extractor marks on the brass. I pulled some bullets, lowered the powder, re-seated the bullets and shot them again without any issues.

So what is it about a can that will take an otherwise safe load and do this? More back pressure?