Do suppressors and/or barrel threads affect POI?

Pond, James Pond · December 19, 2014, 12:42 PM

On rifles, particularly.

Say I've got myself a nice .308 load that is accurate in my bolt action, would threading my barrel and fitting a can affect POI?

I am interested about both steps. The threading and then the can.

This is of interest because if I get the barrel threaded, I want to know if I'd have to re-work my loads, or if I have to do so only if the can is fitted.

Jim Watson · December 19, 2014, 01:39 PM

I doubt the threading will have much effect.
The mass and length of the silencer will.

I can't predict whether the silencer will affect group size, but I would expect it to move POI. So turn the knobs on your scope or sight.

Sharkbite · December 19, 2014, 02:09 PM

Yes...

My FN Special Police is zeroed dead on at 100 without my can (762SDN-6). When i attach the suppressor the same load groups 4.5" low and 1.75" left.

No other change. Just can or no can.

No real change in group size just a shift in POI

Double Naught Spy · December 19, 2014, 02:27 PM

Yes, more often than not.

Some will tighten groups. Some will open groups.

How much POI shift occurs or group size changes will depend on the relationship of the particular rifle and suppressor. It sounds weird, but the same suppressor on two different rifles will not necessarily produce the same result on both rifles.

Tried a suppressor on my 6.5 Grendel. I did not like the results.

Rifle: Alexander Arms 6.5 Grendel Upper
Barrel length: 24"
Optic: Pulsar N750
Suppressor: AAC 762 (don't know which one)
Attachment method: AAC 300 flash hider
Ammunition: Hornady Grendel 123 gr. SST
Range: 100 yards
Average group size/# of groups/# of rounds per group unsuppressed: ~ 1 moa
Average group size/# of groups/#of rounds per group suppressed: 2 moa
Average POI shift suppressed H/V: +2" Right/-3" (low)
Suppressor indexed back to same location Y/N: Y

Comments: Tested suppressor on 2 days, back to back with same results. Basically, it was a significant change to add the suppressor. Opted NOT to hunt with it because of the radical POI change.

wogpotter · December 19, 2014, 03:11 PM

I tested a rifle for this a while back, at least the threading part. I pulled a used non threaded barrel I was familiar with & replaced it with a threaded one that was newer, but of the same weight & length. Accuracy was unchanged & POI only moved about 1"@ 100 yds for a 5-round group.

When I attached a "combination device" (Flash suppressor/muzzle brake/grenade launcher) the POI moved almost 7".

The rifle was a FAL in .308 Win/7.62 NATO. Group size was better with the combo device, but only by a small amount.

Pond, James Pond · December 19, 2014, 03:51 PM

Hmmm.

Well it is impossible to know if threading the barrel will have a positive, neutral or negative effect... until after I've actually done it!!

I've already started another thread on which suppressor to choose. Someone there hinted that getting a .30 cal silencer would do the job on my .223 also.

If so, then at least that way I only have to purchase one and if it does not work on either, I've "only" lost €350, instead of €600...

Snyper · December 19, 2014, 04:55 PM

Just threading the barrel will have little to no effect on POI or groups size

It's when you start adding on objects like a supressor or barrel weights that you start changing the harmonics, and POI as well as group size can be affected

Pond, James Pond · December 19, 2014, 05:02 PM

Quote:

Just threading the barrel will have little to no effect on POI or groups size

It's when you start adding on objects like a supressor or barrel weights that you start changing the harmonics, and POI as well as group size can be affected

That pretty much nails what I wanted to know. Thanks!!
I now plan to get my barrel threaded to match my AR's threading.

So what I may need to do is develop a "suppressor load" to match the suppressed gun and a regular load for when I have no can fitted.

Double Naught Spy · December 19, 2014, 05:59 PM

It may not be possible to develop a "suppressor load" to mimic the POI and group of firing unsuppressed, if that is what you are trying to do. On top of that, you may not need to do so. It just depends on how your rifle and ammo currently perform.

Pond, James Pond · December 19, 2014, 06:11 PM

Quote:

It may not be possible to develop a "suppressor load" to mimic the POI and group of firing unsuppressed, if that is what you are trying to do.

That's not so much the goal as simply developing a load that shoots well suppressed. It does not have to have the same POI as the unsuppressed load, so long as I can maintain/approximate groups size.

If my standard load shoots a nominal 1MOA without the can, but spreads out with the can, I will try to develop a load that brings the group size down again. It may mean turning turrets between one load and another, but that is fine.

Bart B. · December 19, 2014, 06:39 PM

Adding anything to the barrel's muzzle changes its resonant and harmonic frequencies. They both go lower because there's more mass at the muzzle end. Bullets will leave at a different angle the muzzle axis is pointing at upon their exit.

Snyper · December 19, 2014, 10:23 PM

Quote:

So what I may need to do is develop a "suppressor load" to match the suppressed gun and a regular load for when I have no can fitted.

You'll probably want to do that anyway , because if you keep the suppressed loads sub-sonic, they will be MUCH quieter than faster loads

One easy way to do it is use very heavy bullets compared to your regular load

If you want to use the supressor while hunting, you may not be able to slow your loads too much, depending on the game and distances involved

Pond, James Pond · December 20, 2014, 04:06 AM

Quote:

If you want to use the supressor while hunting,

Prohibited anyway, here!

marine6680 · December 20, 2014, 12:18 PM

Did I read correctly and someone was using two different barrels to measure accuracy differences in threaded and non-threaded?

All that does is tell you the difference between the barrels...

As far as threading a barrel, the amount of material removed may cause a slight shift in POI, but probably not enough to notice. If you add a thread protector to cover the threads, than that may cause a little more POI shift.

Most likely nothing will happen to group sizes.

A suppressor will most likely cause a significant impact shift. If the suppressor indexes to the same spot when removed and reinstalled, the POI shift should be consistent in its change, and that can be corrected for. If not, you would have to leave the suppressor on all the time or re-zero every time you installed it.

As far as group size... A well designed suppressor should not affect group size adversely, or very much if it does. Poor designs can creat turbulence that affects the bullet in different ways every shot, which opens up groups. There are also several variables involved, so even a good suppressor can cause issues with some rifles, so trying a different one may be needed in that case.

A 30 caliber suppressor will work with a 5.56, but it will not be as quiet as a dedicated 5.56 can.

Also, the thread sizes will most likely be different... As the 30 cal can uses larger threads, meaning an adapter would be needed for the 5.56 rifle, unless you had the barrel threaded the same... But seeing as this is most likely for your AR, that isn't possible, as it is already threaded.

I would say the best bet is to get a dedicated 5.56 can for your AR, as you can get versions that use the existing A2 flash hider for quick connect/disconnect.

Snyper · December 23, 2014, 04:52 AM

Quote:

Prohibited anyway, here!

LOL
I'm not current on UK's hunting regulations

They just made suppressor hunting legal here, but you still have to go through the same process as buying a machine gun to aquire one

December 19, 2014, 12:42 PM	#1
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	Do suppressors and/or barrel threads affect POI? On rifles, particularly. Say I've got myself a nice .308 load that is accurate in my bolt action, would threading my barrel and fitting a can affect POI? I am interested about both steps. The threading and then the can. This is of interest because if I get the barrel threaded, I want to know if I'd have to re-work my loads, or if I have to do so only if the can is fitted. __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

December 19, 2014, 02:27 PM	#4
Double Naught Spy Senior Member Join Date: January 8, 2001 Location: Forestburg, Montague Cnty, TX Posts: 12,717	Yes, more often than not. Some will tighten groups. Some will open groups. How much POI shift occurs or group size changes will depend on the relationship of the particular rifle and suppressor. It sounds weird, but the same suppressor on two different rifles will not necessarily produce the same result on both rifles. Tried a suppressor on my 6.5 Grendel. I did not like the results. Rifle: Alexander Arms 6.5 Grendel Upper Barrel length: 24" Optic: Pulsar N750 Suppressor: AAC 762 (don't know which one) Attachment method: AAC 300 flash hider Ammunition: Hornady Grendel 123 gr. SST Range: 100 yards Average group size/# of groups/# of rounds per group unsuppressed: ~ 1 moa Average group size/# of groups/#of rounds per group suppressed: 2 moa Average POI shift suppressed H/V: +2" Right/-3" (low) Suppressor indexed back to same location Y/N: Y Comments: Tested suppressor on 2 days, back to back with same results. Basically, it was a significant change to add the suppressor. Opted NOT to hunt with it because of the radical POI change. __________________ "If you look through your scope and see your shoe, aim higher." -- said to me by my 11 year old daughter before going out for hogs 8/13/2011 My Hunting Videos https://www.youtube.com/user/HornHillRange

December 19, 2014, 03:11 PM	#5
wogpotter Senior Member Join Date: September 27, 2004 Posts: 4,811	I tested a rifle for this a while back, at least the threading part. I pulled a used non threaded barrel I was familiar with & replaced it with a threaded one that was newer, but of the same weight & length. Accuracy was unchanged & POI only moved about 1"@ 100 yds for a 5-round group. When I attached a "combination device" (Flash suppressor/muzzle brake/grenade launcher) the POI moved almost 7". The rifle was a FAL in .308 Win/7.62 NATO. Group size was better with the combo device, but only by a small amount. __________________ Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”? Elderly Hunter: “That's dashed unsporting. Probably Belgium.”

December 19, 2014, 03:51 PM	#6
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	Hmmm. Well it is impossible to know if threading the barrel will have a positive, neutral or negative effect... until after I've actually done it!! I've already started another thread on which suppressor to choose. Someone there hinted that getting a .30 cal silencer would do the job on my .223 also. If so, then at least that way I only have to purchase one and if it does not work on either, I've "only" lost €350, instead of €600... __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

December 19, 2014, 04:55 PM	#7
Snyper Senior Member Join Date: December 16, 2013 Location: Eastern NC Posts: 3,047	Just threading the barrel will have little to no effect on POI or groups size It's when you start adding on objects like a supressor or barrel weights that you start changing the harmonics, and POI as well as group size can be affected __________________ One shot, one kill

December 19, 2014, 01:39 PM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	I doubt the threading will have much effect. The mass and length of the silencer will. I can't predict whether the silencer will affect group size, but I would expect it to move POI. So turn the knobs on your scope or sight.

December 19, 2014, 02:09 PM	#3
Sharkbite Senior Member Join Date: November 4, 2013 Location: Western slope of Colorado Posts: 3,679	Yes... My FN Special Police is zeroed dead on at 100 without my can (762SDN-6). When i attach the suppressor the same load groups 4.5" low and 1.75" left. No other change. Just can or no can. No real change in group size just a shift in POI

December 19, 2014, 05:59 PM	#9
Double Naught Spy Senior Member Join Date: January 8, 2001 Location: Forestburg, Montague Cnty, TX Posts: 12,717	It may not be possible to develop a "suppressor load" to mimic the POI and group of firing unsuppressed, if that is what you are trying to do. On top of that, you may not need to do so. It just depends on how your rifle and ammo currently perform. __________________ "If you look through your scope and see your shoe, aim higher." -- said to me by my 11 year old daughter before going out for hogs 8/13/2011 My Hunting Videos https://www.youtube.com/user/HornHillRange

December 19, 2014, 06:39 PM	#11
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Adding anything to the barrel's muzzle changes its resonant and harmonic frequencies. They both go lower because there's more mass at the muzzle end. Bullets will leave at a different angle the muzzle axis is pointing at upon their exit.

December 20, 2014, 12:18 PM	#14
marine6680 Senior Member Join Date: July 24, 2012 Location: Parker, CO Posts: 4,594	Did I read correctly and someone was using two different barrels to measure accuracy differences in threaded and non-threaded? All that does is tell you the difference between the barrels... As far as threading a barrel, the amount of material removed may cause a slight shift in POI, but probably not enough to notice. If you add a thread protector to cover the threads, than that may cause a little more POI shift. Most likely nothing will happen to group sizes. A suppressor will most likely cause a significant impact shift. If the suppressor indexes to the same spot when removed and reinstalled, the POI shift should be consistent in its change, and that can be corrected for. If not, you would have to leave the suppressor on all the time or re-zero every time you installed it. As far as group size... A well designed suppressor should not affect group size adversely, or very much if it does. Poor designs can creat turbulence that affects the bullet in different ways every shot, which opens up groups. There are also several variables involved, so even a good suppressor can cause issues with some rifles, so trying a different one may be needed in that case. A 30 caliber suppressor will work with a 5.56, but it will not be as quiet as a dedicated 5.56 can. Also, the thread sizes will most likely be different... As the 30 cal can uses larger threads, meaning an adapter would be needed for the 5.56 rifle, unless you had the barrel threaded the same... But seeing as this is most likely for your AR, that isn't possible, as it is already threaded. I would say the best bet is to get a dedicated 5.56 can for your AR, as you can get versions that use the existing A2 flash hider for quick connect/disconnect.