Rifles & Suppressors - Compensating for the Change in Point of Impact

[Anthony]

Hello Everyone,

I am currently planning out a long range purchase of two different rifles with a list of accessories for each. One is an enhancement of my Colt AR-15 in 5.56mm NATO that I have owned since 1993 and the other will be a semiautomatic 7.62mm/.308 rifle. In the latter case I have narrowed it down to an Armalite AR-10 or DSA SA-58 FAL.

It is my intent to eventually buy two suppressors that can be used on each of these rifles as well as any future rifles that are able to use them and have had the necessary mounting modifications.

I have read many reports and talk to other user who have told me that the point of impact when firing the rifle with and without the suppressor attached can vary as much as four minutes of angle. Further, some suppressors do this more than others. As I plan to use a combination of optics as well as iron sights on both rifles this concerns me greatly.

Without firing the rifle exclusively with the suppressor attached, what methods would allow me to most easily compensate for any change in the rifle's point of impact resulting from the attachment of the suppressor?

What has worked best for my fellow THRs?

Is there a particular brand and/or model of suppressor that is known for not adjusting a rifle's point of impact at all or at least less than competing brands?

Before anyone suggests Surefire I can tell you that they do not sell their suppressors to civilians due to a California state law forbidding it. I already asked them.

Thanks for your input.

 

[Zak Smith]

On bolt rifles, JET suppressors seem to affect the POI less than some others.

It also depends on barrel profile, etc. A shorter and thicker barrel "may" have less deflection than the same suppressor on a longer and skinnier barrel. I have had up to 6" of deviation can on / can off.

Document your sight / click settings with the suppressor on and off for each rifle, and adjust them appropriately.

IMO, though, it's probably best to decide to the suppressor on. Less things to potentially go wrong.

-z

 

[Anthony]

So you're suggesting something along the lines of zeroing and shooting the rifle exclusively with the suppressor attached or (in the case of the AR-15 & AR-10) dedicating a separate top half and its sights to the suppressor being attached?

 

[Zak Smith]

If you have repeatable sight adjustments which are also easy to look and determine their (reliable) settings, then there's no reason why you couldn't just dial to the "suppressor" zero and back. The problem comes in when adjustments are not exactly repeatable, or you can't look at the sight and determine its absolute adjustment (e.g. EOTech).

For simplicity, it's often easier to "always" shoot with the 'can on or off.

 

[Anthony]

Yes, that would definitely be an issue in this case.

 

[444]

Dupe

 

[444]

"what methods would allow me to most easily compensate for any change in the rifle's point of impact resulting from the attachment of the suppressor?"

The only method I know of is to adjust your sights to compensate for the change in POI. Or using a reference point on your scope reticle to hold off: mildots or the lines on an ACOG or whatever.

I can only give you my own experience. I have never seen a suppressed centerfire rifle being fired other than the one I have. I have an AAC M4-2000 suppressor that I use on AR15 rifles. My suppressor moves my POI straight down at 6 o'clock about two minutes.
Depending on what you are doing with the rifles, I might not do anything about it other than aim a little bit higher at long range. For example, most of the shooting I do with my AR and suppressor is either defensive type training/practice, or shooting at steel targets at longish range (longish for a carbine, 200-500+ yards). I am not shooting tight, bench rest groups on paper. I am not shooting little 4" plates at hundreds of yards. I am doing stuff more like trying to make a headshot from the low ready from 15 yards in less a 1.5 seconds, and the difference in POI isn't a big factor. If I am shooting at a pepper popper at 200 yards, we are talking about 4 inches low. That isn't going to hurt much. From 200 on out, I just hold a little higher than I normally do. I hit the steel just fine. Actually, I shot the suppressor on steel for a couple months before I ever shot the gun/suppressor on paper. I was hitting my targets without changing anything and didn't even realize it was shooting low by a couple inches.
Now, Zak is doing some really precision shooting. That shift in POI makes a difference in some of the stuff he does. Obviously, if you are doing real precision shooting, you need to know how much the suppressor is effecting your POI and do something about it. And again, you adjust your sights or adjust your sight picture in the optic. This is the reason they put target turrets on tactical scopes: so you can adjust your sight dope for the conditions you are shooting in.

 

[Rem700SD]

In general, figure that the heavier the can, and the thinner/less rigid the bbl, the bigger the POI shift. I've held the surefire, and they're pretty light. Jets are titianium, iirc, so they are light as well. I've had good repeatable zero with the suppressors that I have used. I never shoot them w/o supressors so I've never bothered w/ POI shift. My advice would be to use dedicated suppressors/uppers for the rifles. Barring that, just track the POI shift on each weapon and write it on each rifle, preferably on a laminated data/ballistic card.
Using cans on your ARs will cause increased blow back, which causes your gun to get dirtier, but it's not much more than a nuisance. One thing of note is that the FAL class has an adjustable gas system, which gives you more options regarding suppression.
Hope that helps.

 

[Anthony]

Wonderful points, 444 and Rem700SD.

Rem700SD: How and what types of suppression options does the FAL's adjustable gas system give you?

444: Using an optic's reticle to compensate for the change in the point of impact had occurred to me. Especially the Horus system that seems to be gaining quite a bit of popularity in the last few years. My understanding is that it seems very complex initially, but a piece of cake once you learn the system.

 

[Zak Smith]

Horus H25
[ link to LARGER image ]

I would not necessarily want to have to apply a 2-dimensional translation to every shot, because it is complex visually, but it could be done if you're not in a hurry.

 

[GarrettJ]

I have found that some guns are more prone to shifting the POI as well. Also, heavy, slow (like subsonic) bullets tend to have a greater POI shift with/without the can. I have a Contender that I use with a long, heavy subgun can. The POI shift is terrible.

I would just get a dedicated can, but that is not very feasable for me right now. I currently live in a no-silencer state, and have to store my cans elsewhere. If I want to shoot my gun at home, I have to do it without the can. I have considered having a barrel weight made up to simulate the weight of the can. I imagine it would be possible to get close to the same POI with the barrel weight vs. the silencer.