Suppressors subsonic suppressed rounds stringing low after first shot?

[jasper1573]

Hello all, I am new to the art of suppressed shooting and can't figure this one out.

Acquired a suppressor within the last few months. This suppressor shot great when I first received it, and still shoots sub .5 MOA with standard velocity rounds in 308 Win. However, its performance with subsonic rounds has deteriorated in a strange way. When I first received the suppressor, the group size for subsonic rounds at 1050 fps was about 1 MOA at 100 yards. My hand load for that was 9.5 grn Trail Boss and 175 grn matchking. Now, with exactly the same load, it will shoot a few rounds in a 2 inch group, then they will begin to go high and right as much as 12 inches from the original zero. The rounds are stabilized and make nice clean holes

Any idea why this might be occurring?

Tried some 165 grn Sierra hollow point game king bullets today with 9 gr Trail Boss. First shot from cold bore and cold suppressor was in the middle of the target at the bottom of the bullseye. Next shot was 3 minutes low, then next was 5 minutes low, then 7.5 minutes low. I quit shooting after this, let everything cool down and repeated with same results.

What do you think could be causing this strange behavior?

All rounds are stable and makiing clean holes. Barrel is a 11.25 twist. I have also tried 150 grain bthp with similar results.

 

[Buckeye308]

How many rounds has it taken to get this way? I am guessing that something has changed and that you are getting light baffle strikes. Does the suppressor stay nice and tight? Its not backing off? If you look down your suppressor do any of the edges of the baffles look shiny, indicating that the bullet is glancing off of them?

 

[coldboremiracle]

Barrel length? I suspect it will 20+ inches.

 

[jasper1573]

Suppressor stays tight...I have checked it often. I took a look into the suppressor with a flash light...very difficult to see well, but does appear to have some shiny spots. Hopefully this hasn't ruined the suppressor performance with subsonics. The entire suppressor is made with titanium.

Barrel length is 19 inches. I have put approximately 200 rounds through this suppressor.

Not sure what has caused this...initially it did fine with no keyholing issues and excellent accuracy.

Any further thoughts are appreciated.

 

[coldboremiracle]

If the bullets are reaching the paper stable (no keyholing) then I doubt you are having baffle strikes, and if you are getting similar results from 150gr bullets as well then it would seem to be something else. The reason I asked about your barrel length (still waiting) is because I have read and experienced elsewhere that longer barrels are more susceptible to barrel temperature changes due to round count. Your bore heats up with every round and the POI climbs, in your case, but it doesn't necessarily have to go up.

 

[Buckeye308]

How do the subs shoot without the suppressor on?

 

[Killswitch Engage]

i doubt you're getting a heat shift with subsonics. i have shot tons back to back and cant even feel the heat in my can. do you remove the can after each session? if not, you may have a carbon build up issue. if you do, i would suspect its times up differently everytime you put it on and theres a slight misalignment that shows up by a baffle kiss. i have seen it happen and the bullets still strike the target straight but shift way off.

 

[coldboremiracle]

How do the subs shoot without the suppressor on?

This is also a great question, and should shed much light on your problem.

Killswitch; I simply mentioned the heat thing because I have experienced less stringing and POI shift with my 16" VS. my 24" .308. And I have heard the same from others. There may be other factors at work here as well.

 

[RollingThunder51]

Please do the following:

If you reloaded all these rounds, please take 5 of them, measure OAL.
Then pull the bullets off these same five and check the powder throws. Please report back on accuracy.

Please carefully hand feed into the chamber, do not load/use the magazine, ten rounds in a row with a cold barrel (not clean) and report back.

 

[jasper1573]

First, I appreciate all the replies. Yes, I hand loaded all of these rounds. Each one was individually measured for COAL and powder charge weight (9 grns + or - .1 grn), and each one was 2.800 plus or minus a couple of thousandths. The barrel was dirty. Yes, I do remove my suppressor after each use, and I wipe down the back of the suppressor and the threads both inside the suppressor and on the barrel.

I don't think heat is an issue because, as stated above, the suppressor barely gets warm after 5 or 10 subsonic rounds.

I will have to load up some more and report back on accuracy without the suppressor. As I stated in the original post, these original rounds with SMK 175s and 9.5 grains of TB were shooting fine a month ago when I got the threaded barrel back from the mfr. of the suppressor, but I haven't checked accuracy without the suppressor since then.

I will get some rounds loaded up and shoot them without the suppressor and let you all know the results.

Thanks,

Jasper

 

[coldboremiracle]

I don't think heat is an issue because, as stated above, the suppressor barely gets warm after 5 or 10 subsonic rounds.

The temp of the suppressor is not what I'm talking about, its the bore itself that Im referring to. A cold bore will throw bullets a different place than a warm or hot one. As we all know, a cold bore shot VS. the following three or four will land in different places. And also as we have learned, subsonic loads are exponentially more susceptible to conditions like wind, temp, humidity, ect. so it stands to reason that the temp of the bore would have a much bigger part to play than with your supersonic loads. Dedicated SS rifles typically have short barrels, mainly because it doesn't take much barrel to get a bullet up to 1000ish FPS, I also believe the short barrel helps by fewer shots to warm a smaller barrel mass up to shooting temp, resulting in more consistent shooting throughout the string. I look forward to hearing back on your results with/without the can.

 

[RollingThunder51]

I did, it seems, a poor job of explaining.
It takes more than a spoonfull to get great groupings with subsonics at 100 yards+.
I have found thata number of folks end up with a dirty chamber that progressively moves an un-crimped bullet farther back into the case with every stroke of the bolt.
The very best targets I get are with my uncrimped loads.
That is why I am curious to see what happens when you gently hand feed each of the ten rounds into the chamber.

I would also like to know/see the following:

1. What rifle
2. What can
3. QD/direct?
4. crown issues
5. pic of the groupings on the target

First rounds you loaded headed off high to the right.
Second rounds you loaded headed off low.

It may very well be that your bullets are being reseated.
Try running the rounds through your rifle without firing them and check OAL again.

 

[Guest]

Hello all, I am new to the art of suppressed shooting and can't figure this one out.

Pull the can, shoot 10 rds like was said earlier. If everything is good the issue is with the can or it's mounting. If your can comes apart, take it down and see whats wrong inside. A problem inside with a mono or stack, can cause what your describing on target. Not all can issues are just mounting or ammo.

 

[Killswitch Engage]

I did, it seems, a poor job of explaining.
It takes more than a spoonfull to get great groupings with subsonics at 100 yards+.
I have found thata number of folks end up with a dirty chamber that progressively moves an un-crimped bullet farther back into the case with every stroke of the bolt.
The very best targets I get are with my uncrimped loads.
That is why I am curious to see what happens when you gently hand feed each of the ten rounds into the chamber.

I would also like to know/see the following:

1. What rifle
2. What can
3. QD/direct?
4. crown issues
5. pic of the groupings on the target

First rounds you loaded headed off high to the right.
Second rounds you loaded headed off low.

It may very well be that your bullets are being reseated.
Try running the rounds through your rifle without firing them and check OAL again.

i agree that if in fact a bullet is being pushe back in the case that is an issue but....how and why? i have cycled shit tons of rounds through my mag fed bolt guns. i have many times chambered from a mag and ejected the round measuring oal and concentricity wondering what happens to a precision round being stipped out of a mag....results? nothing. they were the same length and concentric as when i started. this is with non crimped ammo with .002-.003 neck tension. i highly doubt this is happening. further more i want to know really what all the bullshit voodoo is with subsonic loads. i simply load my 175,178,220,55gr etc subs into a case, throw in my powder charge and seat it to normal length. i get great results as in under an inch at 100yds. i dont drill flash holes, i dont lube bullets, i dont lube my bore, and i dont crimp. results are what they are. am i lucky? i am not lucky at anything else so i doubt it.

 

[Killswitch Engage]

Here's my last 175smk subsonic load at 100yd. 10gr of trail boss. Ol remmy brass and wlr primer.

 

[RollingThunder51]

All true, but you are not experiencing the issues the OP is. So......for you none of this matters.
I have seen a good number of boxes of ready made subsonics where a gentle tap sends the bullet back into the case, even easier for reloaders and used cases.
I have seen a good number of bolt actions that handle squared away crimped rounds, but when confronted with a non crimped round settles it back at random lengths.
I have seen a good number of position sensitive powders that work wonders in sub use, but require a gentle tip back prior to feed to work.

For the OP, I have no idea what his chambering looks like, nor armature of his can is, the attachment method, the barrel profile, the quality of his reloads, the accuracy of his scale, etc. etc.
Hell I am not sure this isn't a gas gun, with a crap early QD and a broken latch system....
You are not lucky, you are shooting .308....try that with other calibers and you will quickly find yourself SOL...
Even with the simplicity of Trail Boss and .308 this guy has issues...so we try to help him.

 

[WileyG]

Are you loading a magazine and racking the rounds in or shooting by loading one at a time?

 

[Killswitch Engage]

All true, but you are not experiencing the issues the OP is. So......for you none of this matters.
I have seen a good number of boxes of ready made subsonics where a gentle tap sends the bullet back into the case, even easier for reloaders and used cases.
I have seen a good number of bolt actions that handle squared away crimped rounds, but when confronted with a non crimped round settles it back at random lengths.
I have seen a good number of position sensitive powders that work wonders in sub use, but require a gentle tip back prior to feed to work.

For the OP, I have no idea what his chambering looks like, nor armature of his can is, the attachment method, the barrel profile, the quality of his reloads, the accuracy of his scale, etc. etc.
Hell I am not sure this isn't a gas gun, with a crap early QD and a broken latch system....
You are not lucky, you are shooting .308....try that with other calibers and you will quickly find yourself SOL...
Even with the simplicity of Trail Boss and .308 this guy has issues...so we try to help him.

I understand what you are saying and I agree. I hope the op figures out his issue. I have had pretty much the same results as my 308 subs with my 300blk with aa1680 and 223. I was just curious as to some of the voodoo I seem to hear about. Good luck op and keep us posted.

 

[Pappasniper]

Are you loading a magazine and racking the rounds in or shooting by loading one at a time?

Why does this make a difference? Curious,n reading and learning here.

 

[jasper1573]

Again, I really appreciate all the info and advice...you all are a good crowd to converse with.

So I did as was directed...I loaded up some rounds with the original load that worked well originally, 175 grn SMK, 10 grn TB, WLR, and Win brass. I fired 5 rounds without the suppressor...nice group of about an inch with one flyer a couple of inches away, but that was a problem with the trigger mechanism, that is, my trigger finger;-) No issues with tumbling...nice clean holes at 100 yards. All rounds were carerfully single fed.

Next 5 rounds through the suppressor...again, nice group of 4 rounds at about an inch or slightly more with one flyer a few inches away, but not 7-8 inches as before. Now I am beginning to think it was all operator error.

So I loaded up 10 more just as before, but before going out to shoot I put my stock between my legs and gave a little pressure to the suppressor to ensure it was good and tight. On the first group today I had only snugly hand tightened without wedging the stock between my legs.

So I go out and shoot...first two rounds about an inch and a half apart and grouping as before. Next three rounds fly 7-8 inches high and right, and I begin to think to myself, "self, you tightened that can down differently this time." I loosened the suppressor, then snugly re-tightened using only my right hand on the suppressor as with the first 5 rounds. The next 5 rounds grouped at about 1.5 inches...if I throw out the flyer, the four were within 1 MOA.

Now to explain...I gave my rifle to my gunsmith/machinist to do a little work on the threads so that the suppressor didn't work itself loose with standard velocity rounds, and he did some machinist's trick so that when I tighten the suppressor down, there is an offset space now and that causes the suppressor to stay in place without working loose. Before he did this work, I had been accustomed to really cranking down on the suppressor with the stock between my legs.

Apparently, since the new thread work, I have been cranking down way too hard on the suppressor and likely putting it off center. With the suppressor snugly tightened with only one hand on it and one on the stock, the issue is resolved.

Good gracious, who would of thunk it?

Jasper

 

[jasper1573]

1. What rifle...Rem 700 5r
2. What can...Hooper Ordnance made here in AL
3. QD/direct?...DIRECT
4. crown issues...No, nice crown done by a top notch machinist...shoots great with standard velocity rounds
5. pic of the groupings on the target...sorry, I didin't take a pic, but grouped at about 1.5 inches

First rounds you loaded headed off high to the right.
Second rounds you loaded headed off low.

The first rounds were SMK 175s while the second set were SGK 168s and 165s...maybe the difference.

It may very well be that your bullets are being reseated.
Try running the rounds through your rifle without firing them and check OAL again.

I didn't do this once I figured out it had to do with the suppressor torque at the threads...that is, my uberstrength tightening.

By the way, I did run the last couple of rounds through the gun magazine-fed to see if it made any difference...no it didn't...the last two grouped with the three rounds before them.

 

[Killswitch Engage]

I don't what kind of "machinist" trick this threading job consists of but it sounds bad to me. I could thread a can on my rifles as tight as I want and if the shoulder is cut square to the bore it isn't going to make any difference. It will only go as far as the shoulder will let it. Now this could be something to look at with cans that mate up to beveled degree shoulder like ops inc it something. Apparently you have retard strength and are deforming the can is about all I can figure.

 

[jasper1573]

I don't what kind of "machinist" trick this threading job consists of but it sounds bad to me... Apparently you have retard strength and are deforming the can is about all I can figure.

Yes, I am not too fond of the idea of it being different than before. I don't know about my strength being that great, but I certainly don't have to crank down on it as before. I will continue to shoot some rounds through it to ensure this is indeed the issue, but for now, it seems that this was a matter of torque.

 

[WileyG]

Why does this make a difference? Curious,n reading and learning here.

It could have been an issue of recoil setting bullets back in their cases if there wasn't enough neck tension or the mechanics of chambering (actually just before the round lines up with the bore) could have set the bullet back due to same issue.

Sounds like he found the issue though and that's good to know. Hopefully it can easily have a permanent fix.