View Full Version : Precision lost when using suppressor
I have been working a load for a Savage 10 carbine .308 with threaded barrel. Barrel is fluted and has 5r rifling. I can achieve consistent 3/4" groups at 100 yds with the 51t AAC muzzle brake. But as soon as I place my AAC sdn-6 on the end my groups open up to 6" - 8" and there is no consistency. It shoots all over the paper. The can is tight on the attachment. At first I thought the large groups were caused by the heat from the can. I thought the heat mirage was throwing the groups so I purchased a gear tab sock to go on the can. I no longer have heat waves from the can but groups are still terrible. I have tried to let the can and barrel cool between shots 5+ mins but still no luck.
I'll post pics when I get home. But has anyone had this bad of luck with the sdn-6 suppressor.
Who installed the AAC hardware, and did they do it correctly? Very generally speaking, I'm no fan of QD mount/can combo for a precision rifle, but I've never seen a rifle open up that much. I'd be on the phone with a reputable gunsmith as soon as possible. Secondarily, I'd be on the phone with AAC. Thirdly, I'd be on the phone with a stocking dealer for Thunderbeast :D...
pretty much what pipes said. AAC doesn't make anything i'd use in a match or on a precision rifle, but i sure wouldn't expect groups to get that big.
I installed the AAC muzzle brake. Ive installed several before. This was installed properly using a shim kit, rocksett and proper torque. It was NOT installed with a crush washer. The ports are set at the 9 oclock and 3 oclock settings.
I bought the SDN-6 suppressor for my 300 AAC BLK 9" upper but wanted to use it for this 308 rifle for 100-300yd hunting. I did expect the groups to open up a little. I did not get this rifle nor set it up to shoot 1/2 MOA as a precision gun. I got it expecting MOA without the can and 1-1/2 to 2 MOA with the can. If I was wanting precision then I would have got a direct thread on suppressor.
Here were my initial thoughts of the terrible grouping.
1. The suppressor's back pressure was causing barrel fouling extremely fast.
The barrel was broken in by Savages break in procedure. So to combat this I tried through cleaning schedules like on my Bench rest competition gun. This did not help. I have also tried shooting the gun with a copper equilibrium barrel break in so see if that would help the groups with the suppressor. It shoots the same both ways.
2. The can was heating up and the heat waves coming from the suppressor was creating a mirage and thus throwing the POI off.
So to deal with this theory I had I got a gear tab anti mirage sock. This did eliminate the heat wave but it did not tighten up the groups.
3. The suppressor was loosing up from the mount.
So I would check the suppressor after each shot. It was still tight on the mount each time. Them I tried just shooting the gun and not checking or touching it each shot so see if that would make a difference. It did not.
4. It could be the scope. The scope that will be on this gun is a Leupold 3-9x40 with larue mount. I thought it could be that scope or mount or the base. So I bought a badger ordinance base, and look off the leupold and put my 5-22x50 nightforce with laue mounts that is on my competition gun on this savage 308. This did not help and groups stayed the same.
5. It could just be me shooting the bad groups.
So I brought a friend along that shoots competition against me and had him shoot it. Groups were the same. Terrible.
6. Last thought was the barrel was heating up. I always kept the barrel cool to the touch. I tried waiting 5 mins between each shot to see if that would help. No luck
Im out of Ideas for the cause of the terrible groups when the can is attached.
Gun itself
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics138.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics138.jpg.html)
Muzzle Brake
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics160.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics160.jpg.html)
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics162.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics162.jpg.html)
Group without Suppressor that I shot
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics153.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics153.jpg.html)
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics154.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics154.jpg.html)
Group Without suppressor that friend shot
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics152.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics152.jpg.html)
Factory Ammo. Federal Gold Match 175 gr Sierra MK without suppressor
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/FederalGoldMatchFactoryAmmo.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/FederalGoldMatchFactoryAmmo.jpg.html)
These are the best groups that I was able to obtain with the suppressor. These groups are about 5" at 100 yds. The other groups were 8-9"
With suppressor attached. The first shot with suppressor attached is ALWAYS to the left a little of POA. The other shots are randomly scattered in no order.
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/46f5f011-282c-4cf5-8337-ba4e90a924d7.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/46f5f011-282c-4cf5-8337-ba4e90a924d7.jpg.html)
Friend did a three shot group without suppressor (tight group little to the left). Them attached the suppressor to shoot a three shot group. Notice the first shot with the can is a little to the left of the original group then the other two are far right.
http://i43.photobucket.com/albums/e400/rhino4x4/Guns/Iphonepics156.jpg (http://s43.photobucket.com/user/rhino4x4/media/Guns/Iphonepics156.jpg.html)
It beats me. What ammo are you shooting? Something really light? Something really heavy? Subsonic?
I share the exact same story as yourself. I have a 9" 300 blackout carbine. And a Savage 10 FLCPK in .308 both which utilize muzzle breaks and a sdn-6 can. My rifle shoots just fine at 100 and 200 yards with 168gr factory loads both suppressed and unsuppressed. MOA - 1.5 MOA. Hope you figure it out and share the cure; whatever it may be
ICANHITHIMMAN
05-26-13, 08:04
So just some thoughts, I don't own a suppressor and have very little experience. Basically I have seen a lot of them and shot a few overseas. But I do shoot a lot of bolt guns.
First off you did not really answer the questions poised to you by jpipes. You said you installed the brake, however you failed to fill us in as to what that means? Was the muzzle cut and threaded at the factory or did you do it? There are reasons I ask this question, if per say you did cut the barrel yourself did you do it from the center point of the bore, or did you cut it using the out side diameter of the barrel?
Next you have not mentioned the bullet or or its weight, nor the primer and twist rate of your barrel and it would also be nice to know your muzzle velocity and altitude? I ask this because depending on the bullet your shooting and the muzzle velocity you have before attaching the suppressor the loss of gas pressure, combined with the barrel length,twist rate,bullet weight, primer and altitude maybe slowing the bullet to the point that it is no longer being stabilized. I only know a few guys shooting suppressors but they all have a few different loads for the suppressor, the bullet is usually heaver and the powders charge reduced but not in all cases.
Jon
Get a chronograph and let us know the bullet velocity both with the suppressor and without. I am sure it has to be significant in order to destabilize the bullet in such a short period.
Also depending on the weight and length of the suppressor the barrel harmonics may be severely altered for the round you are trying to use.
My guess after seeing this before is that the threads are either not concentric to the bore or perhaps the shoulder is not square. It doesnt show up when shooting just the brake because the hole is bigger than it needs to be by a decent amount, but as soon as you put the can on you are now WAY off.
STOP SHOOTING THE GUN WITH THE CAN ON. You are BEGGING for a baffle strike. You may already have a grazed baffle or end cap. The pressure in the can does a pretty decent job at keeping the bullet centered to the bore of the can, but at a certain point it will hit a baffle. You may just be 1 degree(or half a degree of maybe less) off, but at distance it shows up.
You need to get that barrel threading checked out. I wouldnt discount the mount being slightly jacked up either and the can not quite setting up on it just right, but in the 8 51t mounts I have I havent had this issue with any of them(I have 4 that wont quite lock on the last tooth and I need to massage the shoulder of the mount).
ETA: I would say its NOT an ammo issue IMO. 175g SMK's will not destabilize until a REALLY low FPS and even then they transition through transonic into subsonic pretty dang well, not like a 168 which will tumble when it gets into transonic. If the rounds were destabilizing they would be tumbling and key-holing at worst and going through the paper at pretty decent angles at best. They are going through the target square which means they are stable.
Failure2Stop
05-26-13, 10:19
Contact the manufacturer.
Typos brought to you via Tapatalk and autocorrect.
ForTehNguyen
05-26-13, 11:17
another issue is when you attach the suppressor it must be attached in the exact same spot and ratcheted to the same spot or else your new zero will be different. People prefer direct threads for bolt guns because it always tightens down the same every time.
VooDoo6Actual
05-26-13, 12:03
another issue is when you attach the suppressor it must be attached in the exact same spot and ratcheted to the same spot or else your new zero will be different. People prefer direct threads for bolt guns because it always tightens down the same every time.
I index w/ paint marker my indices on Can's for this very reason.
You said you installed the brake, however you failed to fill us in as to what that means? Was the muzzle cut and threaded at the factory or did you do it? There are reasons I ask this question, if per say you did cut the barrel yourself did you do it from the center point of the bore, or did you cut it using the out side diameter of the barrel?
Next you have not mentioned the bullet or or its weight, nor the primer and twist rate of your barrel and it would also be nice to know your muzzle velocity and altitude? I ask this because depending on the bullet your shooting and the muzzle velocity you have before attaching the suppressor the loss of gas pressure, combined with the barrel length,twist rate,bullet weight, primer and altitude maybe slowing the bullet to the point that it is no longer being stabilized. I only know a few guys shooting suppressors but they all have a few different loads for the suppressor, the bullet is usually heaver and the powders charge reduced but not in all cases.
Jon
I bought the gun from buds guns in late November/early December. It had the barrel threaded directly from savage and its a gun savage recommends a suppressor for (so I would assume they would thread the barrel correctly). I do not know anyone locally that could thread a barrel or check it. Local shops have no clue and will not mess with suppressors. I would have to send the barrel to ADCO firearms and have them check it.
The bullets are all 175gr Sierra Match king. I have tried two different batches from sierra to see if that made a difference. I have tried a few different powders and like the Hodgdon Varget and IMR4895 best. I think varget has a little better group. I have tried Winchester LR primers, Federal Match primers, and CCI LR prmers. All are about the same but gun likes the CCI a little better.
The altitude is 990 feet. I have tried shooting in 55-90 degree weather to see if that makes a difference.
I did chrono when first making the loads, but only without the suppressor. My loads depending on the powder were high 2500 to mid 2600. The varget was a hair over 2600 fps, spread was less than 20. The reason I went with varget is because it was close to the factory load fps, same as factory POA to POI and availability of the powder. I did not try it with the can attached.
Ive shot 183 rds down range with this rifle (about 75 suppressed). I have checked the baffles for a baffle strike. I do not see one. I have looked down the bore with the can attached and baffles do clear the bore.
Failure2Stop
05-26-13, 15:14
Contact the manufacturer.
Typos brought to you via Tapatalk and autocorrect.
Failure2Stop
06-27-13, 11:55
reopened for update
I have a few updates. I sent the suppressor back to AAC and they tested it and said all was good and the suppressor improved the accuracy with there tests. So they sent me a new 51t brake to see if that would help. It did not.
So I purchased another 51t mount and tried it on the savage. I still had terrible accuracy problems with it. Meanwhile I purchased a remington 700 with stainless 5r barrel and it shoots 1 moa with or without the can.
So I know it is the savage gun and I contacted savage customer service twice and talked to two different people. Savages says they will not guarantee the guns accuracy with any muzzle device attached to the gun nor with any suppressor attached. I asked savage to check the concentric of the threads to the bore. Both times they said the wouldn't check that and they would only shoot the gun to test for accuracy with nothing attached to the threads.
So it sounds like I'm shit out of luck with savages factory threading so I took it by a local gunsmith to retread the barrel. I'll let you know if it shoots better once I get it back from the gunsmith.
Thanks for the update. Pretty disappointing that Savage won't even look at the threading given that they were the ones who performed the work. Guess I'll keep that in mind. Good luck with the rifle. Hope it works out.
Sounds like you got your answer and a lesson in Savage's customer service. I'd sell that Savage and never look back.
it doesnt sound like the threads were cut concentric to the bore. baffle strike perhaps?
sell the savage OR get it rethreaded.
they're supposed to be user replaceable barrels. take it off and pay a gunsmith $50 to cut half an inch off, rethread and recrown it for you.
or just buy a new aftermarket barrel to put on it.
Get the barrel to a smith that understands how to cut threads for a can.
Morgan at Dallas Shooting Supplies is who I recommend.
He has 20k in his setup for doing barrel threading.
He is fast and reasonably priced.
Just my two cents...
Silencers CAN add to accuracy with some rifles. I used a MK-11 in the military that shot about 1-1.5MOA without the suppressor and .75MOA with it attached. I also shoot a SDN-6 now that has been hit or miss on different mounts. Some provide for the same or better accuracy...some worse. I think the mounting interface has to do a lot with accuracy results.
I have noticed a lot of serious long range shooters will either use a thread on can or a QD mount that is essentially a thread on system. This provides for a more consistent interface. And as it pertains to long range shooting/accuracy consistency creates the potential for accuracy. The 51-t mounts are not consistent. I have had to hand fit two while two others fit from the factory but to different tensions. I am very happy with the SDN-6, but my next can will be a thread on model.
Suppressors just add another variable to the mix that will either contribute to accuracy or detract from it based on the other characteristics of the weapon.
I'd think it may have something to do with the stock and bedding. If everything is nice and tight in the muzzle that can't cause it. Concentricity is IMHO on/off type of thing: it shouldn't cause such a spread. Either the accuracy is closer to what it is without the can or you grazing the baffles and you are way off in all possible directions. (I would look at the end cap for any bullet marks though.)
If the rifle is just about free floating in normal shooting, the added weight of the can could possibly cause a barrel to touch the stock when fired. Such a disturbance to the barrel harmonics would cause groups like that. I would check that in normal shooting stance with the can added. If no problem there I would double check the bedding and see that there are no underlying problems there.
IZinterrogator
07-27-13, 05:36
I'm also thinking something along the lines of stock or bedding. The targets are lacking something that should be expected if the was an issue with the threads, or the way the mount was installed, or grazing the baffles: keyholes. Those bullets are leaving the suppressor flying straight and true to a different point of aim every time. Somewhere, that action is shifting in the stock when the extra weight of the suppressor is mounted on it.
OrdnanceLocker
07-28-13, 10:35
Anytime you add a suppressor you're increasing your FPS by 15-30 as well as changing your barrel harmonics. So what may have worked well for a load before may not work as well now. Have you tried different loads if your reloading, or factory ammo? Also, I'm in no way saying you're a bad shooter, but have you considered that it might be the operator and not the firearm? Some guys when they use a suppressor as a result of less recoil will relax their position on the rifle. Just to food for thought...
Add: In regards to your can loosening. In the future I'd go with Surefire, Thunderbeast, or Mack bros and it will fix that issue for future purchases.
I finally received my rifle from the gunsmith. He cut 1/2" from the barrel and rethreaded the barrel. He said the factory threading was off by .015 from the concentricy to the bore. The gunsmith said factory tolerances should have been .003 max and that I was lucky to not have a baffle strike. I shot the gun and it shot the same with and without the suppressor. I was able to achieve 3/4 moa accuracy with factory ammo.
I am now happy with this gun. Thanks savage for your great customer support :eyesroll: and shitty barrel threading. Guess I'll be buying a remington from here on out. At least it shoots well after paying to have it rethreaded.
Glad you got it straightened out. Doesn't surprise me at all coming from savage. It isn't the first time I've heard of it. I haven't seen it on a remmy yet. Doesn't mean it can't happen though.
brokeenthusiast
09-29-13, 18:18
An alternative solution if your bore is concentric and still seeing the issue could be the mount being loose from the suppressor. I have an 18t mount and it can loosen up after some shooting unfortunately. I have not had this done yet but I think it would be beneficial, Accurate Ordinance put a set screw in their quick detach mount.
http://accurateordnance.com/cgi-bin/imcart/read.cgi?article_id=19&sub=4
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