Pressure signs with suppressor

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freediver111

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Jan 23, 2014
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John Day, OR
I’m shooting a 300 wsm, 212 eld x, Norma 2x fired brass, and 65.5 gr of H4831sc. Tikka action with a 22” benchmark barrel. FL resize of brass and using an expander mandrel for the case mouth.

I just got my TBAC U7 about a month ago and prior to the can it was moving 2780 fps. Now I’m getting 2820 and in my case it’s not reliably having a sticky bolt lift, but it seems like out of 30 rounds fired I had tighter bolt lift on about 10 cases. In addition to the tighter bolt lift on roughly 30% of the cases, I have slight swipe marks on the brass.

I really hesitate to mess with it much as it’s shooting absolutely lights out. Max load with 4831 and 212 gr bullets is 66 gr, so obviously I’m close to max.

I did try 10 rounds at 65 grains and velocity dropped 10-15 fps average, but no change in tighter bolt lift/brass swipe. There were none of these issues prior to the can. Thinking more back pressure, maybe some carbon build up. I did clean the throat/chamber prior to testing the 65 gr loads but didn’t make it better. I should also note that bullet seating depth tests put my best load at .09” off the lands, so not jamming the crap out of these at all.

Thoughts on maybe taking it back to my smith and just increasing the freebore a touch with a reamer? I won’t do anything now as I’m headed to MT with a combo tag next week. While I don’t like to play with pressure signs, this thing is shooting amazing so I also hesitate to mess with it much. It shot one ragged hole with a 3 shot group, and softball sized group at 800. It’s becoming one of my favorite rifles that I’ve had built, and it’s actually shooting better with the can. But with mild pressure signs. Maybe I’ll try trimming the cases down just a touch more? Not sure. It’s odd to me that prior to the can I had zero issues with pressure.

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I'm interested in your findings as well. I have a rifle that has similar issues but I have not shot it without the suppressor yet. I gave up on mine for hunting season and went with a different rifle. A chamber cast looked like things are in spec.

Have you checked your head space? Can you drop a new projectile in a fired case without opening the neck up with the sizer?
 
huntsman22 said:
It ain't the can.......
Click to expand...

So no can, no pressure signs, but with can I get pressure signs. But it isn’t the can? I don’t think the can is a problem, but it seems like it’s magnifying something.

I’m not discounting that it could be something else, but I’ve had this rifle for 8 months and this is the first time in hundreds of rounds I’ve seen an issue….with can on.

At this point I’m hunting with it. Long term when I get back from the hunt I’ll try some things lowering charge, deeper cleaning, or seeing if the chamber is fully in spec.


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Suppressors always add backpressure. Some more than others. I get a sticky bolt on my Tikka when shooting with my Griffin Sportsman.

I'd work back some loads and see how that does once you return.
 
Ever figure anything out? Had a similar experience today. Load I’ve shot for quite some time all with no pressure issues assudden has swipe, ejector marks and sticky bolt.
Only thing I’ve changed is one more firing on the brass (3rd firing adg brass) and had the suppressor on.


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WMWILLIAMS said:
Ever figure anything out? Had a similar experience today. Load I’ve shot for quite some time all with no pressure issues assudden has swipe, ejector marks and sticky bolt.
Only thing I’ve changed is one more firing on the brass (3rd firing adg brass) and had the suppressor on.


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Click to expand...

You pointed out the other issue I was curious about with the OP. Sometimes things seem to get sticky with more firings on the brass too.

Following to see what you guys figure out. Be interesting to see what happens with a charge lowered until velocity duplicates prior velocity.
 
wind gypsy said:
You pointed out the other issue I was curious about with the OP. Sometimes things seem to get sticky with more firings on the brass too.

Following to see what you guys figure out. Be interesting to see what happens with a charge lowered until velocity duplicates prior velocity.
Click to expand...

I talked to my gunsmith today and he thinks it’s probably because the amount of firings on the brass. Probably completely stretched to the chamber now so no energy is being waisted stretching the brass. I didn’t have a chrono with me today so idk if velocity was the same or not. This load is 53.5 grains h4831sc adg brass 215m primer and 153.5 Berger out of a 6.5prc. On virgin brass it was 2860fps. (22” proof carbon barrel)


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This seems fairly minor as far as overpressure is concerned, I wouldn't mess with it if you're leaving in a week unless it's something that you feel would screw with your shot confidence. Personally I'd shoot it for the hunt and then try to dial it back a bit later on
 
Not directed toward anyone particular:
Like others have said, suppressors have a little pressure contribution. And it's a growing pain pretty much all new suppressor owners or new reloaders undergo

An unsuppressed load that shows no pressure signs, can very well show pressure signs just by adding a suppressor. The resolution is the same as you would take with any hot loads

camelcluch said:
Bolt was extremely heavy on mine. Maybe a bad batch of ammo. I also had a big loss in accuracy.
Click to expand...
Bad luck. You aren't the first with hotter than desired factory ammo I suppose. In your case I would just find other ammo to shoot.


To OP specifically, I would just back the charge off more until pressure goes away, and check accuracy. You say you don't want to "mess with it much", but to me, changing the freebore is messing with it a lot more than altering the load slightly.

Not to mention that 0.09" freebore is already plenty, so I'm not sure that you will see much pressure reduction until you add a significant amount of freebore.
Either way you will lose some speed. So the powder is easier to try first
 
I have experienced this with one specific factory ammo and working up reloads (hard lift/swipe) for one gun. I never took it in, but my gun smith suspected a tight/dirty chamber for this specific gun (chamber looks clean).
 
Good info. Thanks. That was about the fourth box of eld-x I shot through it. I was still getting consistent speeds (2823 fps 300 wsm) but will try something different. At this point I will clean the gun throughly and try some different ammo.
 
I ran one brand of suppressor on a rifle and it caused cartridges to completely blow the primer. This never happened before when not using a suppressor on this rifle. I switched to another and it completely went away.

So to answer the question, it can definitely be related to the suppressor, rifle and cartridge combo you are shooting. You can try a different suppressor and it may resolve itself, but if you are seeing pressure signs I would advise not using the suppressor or use a lighter load.

The thing to remember is if you are seeing pressure signs in good weather shooting at the range, it can become much worse when you are in wet weather, hotter weather, etc. on a hunt. Why ruin your hunt or risk injury in the backcountry when your rifle is clearly telling you something is wrong?
 
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