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16” 308 1:8 twist groups open up with suppressor

Black Savage

Private
Minuteman
Mar 2, 2013
17
8
I have a Cadex action with a 16” 1:8 twist CF barrel in 308 from Proof Research with a socom muzzle brake. I took it out yesterday and shot Barnes 168 gr ttsx bt and hornaday precision hunter 178 gr eldx. With out the suppressor the rifle shot tight groups (touching). Once I installed my surefire 300 sps suppressor the groups opened up to 1.5” to 2 inches at 100. Has anyone had similar experience? Next weekend I was going to try my direct thread 30 cal suppressor to see it there is a difference. The surefire didn’t have the same issue on my GAP HRT in 260.
 
Any chance the weight of the can is causing the barrel to touch the stock? Just throwing out ideas
 
Any chance the weight of the can is causing the barrel to touch the stock? Just throwing out ideas
I will check that but it’s in a manners elite prs2 mini chassis stock. There is a pretty large gap but it could be possible.
 
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It's normal that groups open up with a suppressor as it will change the barrel harmonics a lot.
If you reload, you have to do load development with the suppressor you plan to use, otherwise you will likely get shit groups.
My pet load for my .243 win goes from <0.5 MOA to over 1 MOA by removing the suppressor.
 
It's normal that groups open up with a suppressor .....
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Are you using a suppressor cover? If not mirage from the hot can will mess you up big time.
 
A quick glance at the surefire website says that the 300 sps is made for the .300 blackout.
If that's the case, you are fucking that can up, it is designed for a small volume case shooting pistol powders, 20-24 grains of powder, not a rifle cartridge with a slower burning 40+ grains of powder.
Gas volume far exceeds what the can was designed for.
 
A quick glance at the surefire website says that the 300 sps is made for the .300 blackout.
If that's the case, you are fucking that can up, it is designed for a small volume case shooting pistol powders, 20-24 grains of powder, not a rifle cartridge with a slower burning 40+ grains of powder.
Gas volume far exceeds what the can was designed
It’s rated for up to 300wm.
 

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Most of my rifles actually tighten up a little with the can (SiCo Omega) but my 26" medium Palma 1:9 300winmag hates it. Goes from half moa to one and a half. It's the only rifle I have that does that.
 
I will check that but it’s in a manners elite prs2 mini chassis stock. There is a pretty large gap but it could be possible.
I’d be shocked if it was the stock given that setup - about as good as you can get from a reliability standpoint.

Do you have any other loads to try? That’s a relatively light barrel to hang a can off of, it probably changed the harmonics a lot. Bet there’s a new velocity node in which it shoots really well. Maybe a Palma load.
 
So you believe a barrel tuner moving 20 grams of weight 1 mm will tune barrel harmonics, but 500 grams at the end of the barrel won't affect it at all?
Only barrels I've seen that cares little about it are straight truck axles and a few carbon barrels.
You are attempting to quote my beliefs and failing.
I stated nothing about suppressors not changing barrel harmonics.

You specifically stated "It's normal that groups open up with a suppressor ".
Normal would mean typical and expected.
This has not been my experience.

A snapshot of my last 24 months of rifles built and shipped to customers reveals that over 75% of those rifles are being used while suppressed. Most of those rifles are mated to suppressors that were delivered ahead of the rifles. All rifles were test fired (3 consecutive groups) before being boxed to ship. Some with suppressors mounted and some not. The ongoing aggregate for all groups fired and recorded is in the low .3"s (because I suck at shooting groups).

None of my barrels are truck axles or CF.

It is my experience that mounting a suppressor usually changes POI compared to no suppressor, however
we couldn't care less about this since the guns are running 100% suppressed.

I am 100% confident in all of my rifles shooting at least as good suppressed as un-suppressed.
This experience is paralleled by an awful lot of factory rifles that are running suppressed when all parts of the system interface are correctly executed.

I would be confident in stating that if you were to get a poll from the top 20 rifle builders mentioned from time to time on this forum, they would have the same experience as I have shared above.

I am not discounting or trying to refute your experience. I am simply opining that you are painting with a broad brush based on your own sample of experience.

./
 
You are attempting to quote my beliefs and failing.
I stated nothing about suppressors not changing barrel harmonics.

You specifically stated "It's normal that groups open up with a suppressor ".
Normal would mean typical and expected.
This has not been my experience.

A snapshot of my last 24 months of rifles built and shipped to customers reveals that over 75% of those rifles are being used while suppressed. Most of those rifles are mated to suppressors that were delivered ahead of the rifles. All rifles were test fired (3 consecutive groups) before being boxed to ship. Some with suppressors mounted and some not. The ongoing aggregate for all groups fired and recorded is in the low .3"s (because I suck at shooting groups).

None of my barrels are truck axles or CF.

It is my experience that mounting a suppressor usually changes POI compared to no suppressor, however
we couldn't care less about this since the guns are running 100% suppressed.

I am 100% confident in all of my rifles shooting at least as good suppressed as un-suppressed.
This experience is paralleled by an awful lot of factory rifles that are running suppressed when all parts of the system interface are correctly executed.

I would be confident in stating that if you were to get a poll from the top 20 rifle builders mentioned from time to time on this forum, they would have the same experience as I have shared above.

I am not discounting or trying to refute your experience. I am simply opining that you are painting with a broad brush based on your own sample of experience.

./
I think we might have misunderstood eachother here.
What I meant, was that running the same load on the same rifle with and without suppressor will often result in different group sizes and a POI shift.
Like on my Howa, the difference is pretty extreme on groupings, as it seem to put me in the worst possible place in regards to harmonics when I take it off with my favourite load.

From OP, it doesn't seem like he handloads, and I just wanted to present that as a very real possibility for why his group opened up a lot with the suppressor.

For example loose action screws should open his groups up just as much if not even more without the suppressor, so I was only looking for a more reasonable explanation, as I've seen the exact same thing on my own gun, and quite a few others when load deveopment was done for the one configuration.

Tl;dr: throwing a heavy ass can on the end of the barrel can throw you out of your node, with potential of opening up your groups.
 
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I’ve had this same issue with my 300 sps on a 26” MTU profile 6cm barrel. Changing the node didn’t help much. However that can shot phenomenally on a 223 bolt gun 20” no contour barrel and on a 23” 308 no contour.