Thread: Suppressors and carbon fouling - what's your got to fix ?

have a 7mm RM, did most of load development with out suppressor. Then for final load fine tuning and POI added the can.
Groups have gradually gone from 0.5 - 0.7 moa to 1.5+ moa . I'm pretty sure its due to carbon build up in throat area.
Be very interested to hear comments from others and any smart ideas for getting rid of carbon build up due to suppressors.

What brand of bore cleaner are you using and how long are you leaving it in the barrel to do its job ?

I was leaving this out for now to get ideas with out my bias.
I have a very rigorous cleaning process using bronze brush, followed by Hoppes & patches (heaps of times !!) then Boretech Eliminator till all Cu is removed, then hopes to neutralise then oil to finish and store.

I tend to follow the "run a bore snake through it after every hunt and leave it the hell alone other than that" regime, works fine for me, 260 rem cloverleafs/ragged holes still after probably 200+ rounds since load development was done, 270 has held .6moa for a fair few rounds so far also, both suppressed, both 20" barrels

Apart from cu build up haven't the old days of corrosive primers gone? Unless its military or cheapo ammo? Spent powder residue gets blasted out we each shot? So how necessary is it to clean like Sadie after each round of banging, not taking moisture into account?

Hi chainsaw,
I think your first mistake is to do all the load development with out the suppressor.
Adding the suppressor may have changed your barrel harmonics and opened up your group.
I always do all my developments with supressor on.
As for cleaning, to remove carbone I use bore tech C4, it is none toxic and does not smell. Then the gunslick foam left in the bore between 1 hour to 1 night depending on how much my barrel fouls out. I am not a big fan of bronze brush and what I use above seems to do the trick with out them.

All this is only valid provided you have a good bedding in your stock, and that your suppressor is mounted properly and does not bind on the barrel for exemple if it is an over barrel.
If you can not get descent groups with the suppressor on, you might have a problem with the way it is fitted, or the added weight at the end of your barrel may make it touch the stock during firing giving you irregularities on target.

Good luck.

thanks for info & suggestions all. The ammo is hand loaded - Fed brass, Fed magnum primers, 2217 powder & AMAX pills.
Friwi the groups have opened up progressively - initially tight with suppressor added similar to no suppressor, just a different POI (as you'd expect). But over time the groupings had got worse. I thought it might be brass aging (work hardened) so tried annealing = no improvement. Went back and tried some factory Hornady SST ammo which had grouped tight (0.75 moa) but this also was also now 1.5 moa. To my way of thinking this rules out the brass and variations in my hand loads & takes me back to the possibility of carbon build up the throat area (or something else). I've checked other variables like bases or scope rings being loose and same for bedding screws. All are torqued to correct settings.
So any other suggestions for dealing with carbon fouling (especially throat) would be appreciated.

Do the groups revert to ~0.6 when the can is off?

nope

Anyone got a borescope that would stop the argument right away

As @Tommy said does it revert with the can off to tight again (relatively). I had this issue with a hardy gen 4 can on t3 7 rm when I ran it in with federal blue 150s groupings got worse - the load had a High degree of carbon in it and was causing actual carbon dags on the internals. Sent everything to Hardys for them to concur the approach was the suppressor and take everything else out of the equation. The gun was off to fiordland in 3 weeks at the time and I didn't want to fuck around.

Dan looked at him himself and agreed with the issue was the buildup in the internal baffles re bored it slightly wider came back and was shooting less than a half MOA.
Don't know if this is you're issue but thought I'd share my experience.

Sorry about the edits bloody iPad after a few whiskeys is murder...

Originally Posted by Marty Henry

Anyone got a borescope that would stop the argument right away

Yea but it needs batteries

If you want to get rid of carbon build up in throat then hit it with autosole


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Originally Posted by Tommy

Do the groups revert to ~0.6 when the can is off?

Originally Posted by chainsaw

nope

That sounds more like copper build up to me or something is loose elsewhere.

Originally Posted by gadgetman

That sounds more like copper build up to me or something is loose elsewhere.

Yeh carbon build up at the throat, in my 6.5AI takes around 100 shots so I know that I need to dung it out around then I use JB's or sometimes Autosol. Prefer JB's. You can pick up the carbon issue if you have a Stoney Point (Hornady whatever now) seating depth gauge. You will find you cannot get consistent readings and they are also shorter than normal. Once cleaned the readings become very consistent again (around 1 thou of each other depending upon your technique). I also know when my AI is building up - I load with the projectiles touching the lands and I can feel the change with the bolt being a bit "notchy" when pushing it fully fwd b4 closing. Cannot say the C build up has dramatically affected the accuracy at the time (in theory it should have some effect) whilst Cu build up certainly does.