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Discussion Starter · #1 ·
Ive been biudling my M1A for a while now. I originally went with the Smith Ent vortex kit and Fisher can. Ended up getting bad baffle strikes and broke a bolt lug. I drilled a relief hole in the gas plug, and had Smith install one of their new CQB 14 barrels. It runs beautifully now with one potential problem. The POI shift is bad. Like 8 inches south at 25 feet.

I spoke with Smith ent. and he said this was normal for the M14 platform. He recomended using 147 Grain instead of the 168 I was using.

My question is should I just go as light as I can? Like 110 Grain Hornady? Would match grade shift less than bulk surplus?
 

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In the gilded halls of Valhala
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Discussion Starter · #6 ·
Dont care about decibel level. Im just looking for less poi shift. 8 inches at 25 feet makes me worry about baffle and end cap strikes. The way i understand the less grains the easier it is to stabilize?
 

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I don't know much about sound suppressors, I've fired a couple of rifles with them and none had a huge shift in POI so I find it unusual that anybody would say that it's normal with the M1A platform.

But I also find it unusual that anybody would pay a $200 annual tax stamp fee for a $1000 suppressor and not care about how well is suppresses the report of the rifle.

Based on what I know about ballistics, if the suppressor was installed correctly and it's sized for a .308 caliber bullet then there is no way that it would shift the POI that much. The bullets have to be striking the suppressor somewhere to cause that kind of shift at that short range.

But if the reduction in sound doesn't matter then you could always drill a half inch diameter hole through the center of the suppressor, there's no way the bullet would hit it then. DI5
 

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Discussion Starter · #8 ·
Its a one time tax stamp, not yearly. And i dont really care about decibel level in my suppressors. As long as they eleminate flash and mask location theyve done their job for me.
 

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Its a one time tax stamp, not yearly. And i dont really care about decibel level in my suppressors. As long as they eleminate flash and mask location theyve done their job for me.
I wasn't trying to be picky about decibel level. by your own admission you want to mask location?

that sonic "CRACK" will defiantly give away your position.
 

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Discussion Starter · #11 ·
Mask, not conceal. Its really difficult to trace a sonic crack back to the shooters location. Thanks for the replies though everyone. Ill just get a few boxes of varying weights and see how it goes!
 

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The POI shift you are experiencing is not from the ammo, but from attaching a nearly 2 pound weight to the end of your barrel. I like Smith's products but their suppressor is listed at 30 ounces, and nearly 22 ounces for the aluminum bodied "light weight" version! A comparable Surefire FA762K weighs 19 ounces, and their mini 762 can should weigh around 15 ounces.

However, if you can, test this by attaching an equivalent load with lead weights on a looped steel cable hung off the front sight post. You should see similar POI shifts with the same weight pulling on the barrel. If you don't see a dramatic shift then I would suspect you still have a concentricity issue where the bullet is too close to the baffles, but not striking them.

If you do find the same POI shift with the weight method then the best suggestion I can give to help reduce it is to use a stock system like the JAE or SAGE with a barrel tensioner. This will allow you tune the POI shift and support the barrel closer to the muzzle which should reduce POI shift dramatically in this case.
 

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It can't be the muzzle weight. Using some simple trig, the angle required to create an 8" deflection at 25' is a little less than 1.5 degrees (use 1.5 to make the calculations easier). Extending the range to 100 yards, the vertical deflection comes out to almost 8 feet. That's a lot of vertical impact error. Calculating the other direction, the barrel would have to be bent about 0.4" along it's 16.25" length in order to create a 1.5 degree angle. It's not possible to bend the barrel almost a half inch with just two pounds of pressure at the muzzle.

I think that there is an alignment problem with all that stuff hanging off the muzzle and the bullet is hitting something.
 

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I do have my doubts as well that its barrel deflection alone that is causing such a massive POI shift, I think the lug may be pulling out of the bedding or some other stock fit/interference may be created by the weight addition. If he tests the theory by adding weight to the muzzle, this can be ruled correct or incorrect very quickly. I just felt I should post since the ammo selection is not the issue at hand in my opinion.
 

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Discussion Starter · #15 ·
Thanks guys. I will try the different ammo and the weight test. I really hope its the extra weight Ive been looking into lighter suppressors anyway. The mini7 comes to mind.
 

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Am I reading this post correctly? You sight the rifle in at 25 feet and then put your suppressor on and your POI shifts 8 inches? At basically 8 yds you shouldn't need to aim the thing; just point and shoot. Why are you shooting at such a close range?



Ive been biudling my M1A for a while now. I originally went with the Smith Ent vortex kit and Fisher can. Ended up getting bad baffle strikes and broke a bolt lug. I drilled a relief hole in the gas plug, and had Smith install one of their new CQB 14 barrels. It runs beautifully now with one potential problem. The POI shift is bad. Like 8 inches south at 25 feet.

I spoke with Smith ent. and he said this was normal for the M14 platform. He recomended using 147 Grain instead of the 168 I was using.

My question is should I just go as light as I can? Like 110 Grain Hornady? Would match grade shift less than bulk surplus?
 

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perhaps he meant yards not feet. He seems like he knows his stuff, and is in killeen so that tells ya something.

However i thought all our boys were provided with suppressors.

Either way, i think rammac is the one you need to listen to. Putting it in a sage won't do anything. The barrel tensioner can only make it shoot lower so that won't help you at all.

and its also a bad fix when something is VERY wrong.
 

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I didn't mean to shut this post down or say the OP doesn't know his stuff. I'm sure all you boys from Texas are shooters as most Texan's migrated from Tenn. GI1 I was just trying to get my head around the problem. I don't use suppressor's, but the thought has crossed my mind. I thought suppresors enhanced accuracy not messed it up.
 

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I can tell you from personal experience that the weight of a suppressor can cause a 6 o'clock poi shift and often does. And if the SEI can really weights 30oz.... good god almighty that's the weight of a good high caliber bolt gun can, not a can for a battle rifle.

That being said, the length of the barrel makes the barrel sag a far less likely culprit. Short barrels are more stiff and its more difficult to have that much of a poi shift.

Is the shift repeatable? you said you had baffle strikes - is this the same can?

The problem must be somewhere either in the mounting system of the can itself. Are you sure that the mount is concentric to the bore?
 

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I don't know much about sound suppressors, I've fired a couple of rifles with them and none had a huge shift in POI so I find it unusual that anybody would say that it's normal with the M1A platform.

But I also find it unusual that anybody would pay a $200 annual tax stamp fee for a $1000 suppressor and not care about how well is suppresses the report of the rifle.

Based on what I know about ballistics, if the suppressor was installed correctly and it's sized for a .308 caliber bullet then there is no way that it would shift the POI that much. The bullets have to be striking the suppressor somewhere to cause that kind of shift at that short range.

But if the reduction in sound doesn't matter then you could always drill a half inch diameter hole through the center of the suppressor, there's no way the bullet would hit it then. DI5
It's a one time stamp, and yes its reasonable to say that one might not be too concerned with the DB level. The m14 rifle is loud, even with a suppressor. The goal with any supersonic round is to make the report hearing safe. Once that goal is achieved, additional suppression is less important since you still have to combat the sonic crack.

I wasn't trying to be picky about decibel level. by your own admission you want to mask location?

that sonic "CRACK" will defiantly give away your position.

That's not true at all. the muzzle report is very quiet. The sonic crack is created along the entire flight path of the bullet, not just at the shooter. Therefore, anyone who hears the crack is going to feel like the sound originated from the part of the bullets flight path that is nearest to their location. It makes it very difficult for human ears to distinguish the direction of origin. Not only that, but it masks the flash very effectively.
 
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