I just installed a muzzle brake on my .300 Win mag. Now there is a big point of impact change. With the muzzle brake on I am about a foot lower at a hundred yds. Is this abnormal? I bored the muzzle brake .02 over size and threaded both on the lathe so everything should me concentric.
Gunsmithing Why am I getting POI Change?
- Thread starter Skeet375
- Start date
Re: Why am I getting POI Change?
Weight on the muzzle can change the harmonic balance of the barrel and result in a POI shift.
Weight on the muzzle can change the harmonic balance of the barrel and result in a POI shift.
Re: Why am I getting POI Change?
Whoa! I should read closer. A FOOT lower!?! Jeez. A small shift I could blame on the mysterious barrel harmonics (not everyone believes in them), but a foot? No sign of strikes in the brake? Did you recut the crown when you threaded the muzzle?
Whoa! I should read closer. A FOOT lower!?! Jeez. A small shift I could blame on the mysterious barrel harmonics (not everyone believes in them), but a foot? No sign of strikes in the brake? Did you recut the crown when you threaded the muzzle?
Re: Why am I getting POI Change?
I ran the center in the bore when I threaded it then I used a steady rest to re-cut the crown with a recessed 90 degree. I can't see anything were it is striking the muzzle brake. I am shooting berger vlds and it seems like they would fly apart if they were hitting. Today I shot it with the muzzle brake on then with it off so its not like my scope is sitting different or the action isn't sitting in the stock the same.
I ran the center in the bore when I threaded it then I used a steady rest to re-cut the crown with a recessed 90 degree. I can't see anything were it is striking the muzzle brake. I am shooting berger vlds and it seems like they would fly apart if they were hitting. Today I shot it with the muzzle brake on then with it off so its not like my scope is sitting different or the action isn't sitting in the stock the same.
Re: Why am I getting POI Change?
It doesn't kick as much right? If so that means less muzzle rise in reoil. Gun shoots lower. Has little to do with harmonic. Harmonic affects accuracy.
It doesn't kick as much right? If so that means less muzzle rise in reoil. Gun shoots lower. Has little to do with harmonic. Harmonic affects accuracy.
Re: Why am I getting POI Change?
interesting........what kind of brake did you use?
interesting........what kind of brake did you use?
Re: Why am I getting POI Change?
With one of my AR's I was getting about 6inch difference between an A2 FH and bare muzzle.
With my GAP with Thruster in 300WM I get no POI change with/without.
This is true for my Kimber 300WM.
Something might be out of whack.
With one of my AR's I was getting about 6inch difference between an A2 FH and bare muzzle.
With my GAP with Thruster in 300WM I get no POI change with/without.
This is true for my Kimber 300WM.
Something might be out of whack.
Re: Why am I getting POI Change?
Barrel is changed,period.POI can change because of that,shoot more and see if the POI is consistant then go from there.If consistant POI,just reset zero and be done.If not,then something most likely is off centric.Just my .02cents.Goodshootin'
~Reagan
Barrel is changed,period.POI can change because of that,shoot more and see if the POI is consistant then go from there.If consistant POI,just reset zero and be done.If not,then something most likely is off centric.Just my .02cents.Goodshootin'
~Reagan
Re: Why am I getting POI Change?
CDixon gave the answer...less recoil, less muzzle rise before the bullet leaves the end of the barrel.
This can be more pronounced in handguns (i.e 45 ACP) where higher velocity rounds (i.e. 185gn SWC) shoot below POA where slower velocity (i.e. 230gn RN) print higher. Seems counter-intuitive until you realize that the few extra miliseconds in the barral under recoil rise do make a difference. And remember, the rise is not necessarily straight up either.
BTW--how are your groups? Better, worse or the same?
ZY
CDixon gave the answer...less recoil, less muzzle rise before the bullet leaves the end of the barrel.
This can be more pronounced in handguns (i.e 45 ACP) where higher velocity rounds (i.e. 185gn SWC) shoot below POA where slower velocity (i.e. 230gn RN) print higher. Seems counter-intuitive until you realize that the few extra miliseconds in the barral under recoil rise do make a difference. And remember, the rise is not necessarily straight up either.
BTW--how are your groups? Better, worse or the same?
ZY
Re: Why am I getting POI Change?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ZY100</div><div class="ubbcode-body">CDixon gave the answer...less recoil, less muzzle rise before the bullet leaves the end of the barrel.
This can be more pronounced in handguns (i.e 45 ACP) where higher velocity rounds (i.e. 185gn SWC) shoot below POA where slower velocity (i.e. 230gn RN) print higher. Seems counter-intuitive until you realize that the few extra miliseconds in the barral under recoil rise do make a difference. And remember, the rise is not necessarily straight up either.
BTW--how are your groups? Better, worse or the same?
ZY</div></div>
This sounds very plausible Try it with and without the brake If you get a 12" POI change there's likely your answer
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ZY100</div><div class="ubbcode-body">CDixon gave the answer...less recoil, less muzzle rise before the bullet leaves the end of the barrel.
This can be more pronounced in handguns (i.e 45 ACP) where higher velocity rounds (i.e. 185gn SWC) shoot below POA where slower velocity (i.e. 230gn RN) print higher. Seems counter-intuitive until you realize that the few extra miliseconds in the barral under recoil rise do make a difference. And remember, the rise is not necessarily straight up either.
BTW--how are your groups? Better, worse or the same?
ZY</div></div>
This sounds very plausible Try it with and without the brake If you get a 12" POI change there's likely your answer
Re: Why am I getting POI Change?
Wouldn't the muzzle brake also decrease the projectile's velocity by allowing pressure to escape from the sides? I imagine this would contribte to a lower point of impact when using a zero established with a higher velocity round. Maybe it's not responsible for all 12" of the drop in POI, but possibly some.
Wouldn't the muzzle brake also decrease the projectile's velocity by allowing pressure to escape from the sides? I imagine this would contribte to a lower point of impact when using a zero established with a higher velocity round. Maybe it's not responsible for all 12" of the drop in POI, but possibly some.
Re: Why am I getting POI Change?
Since you re-cut your crown I would check it. No muzzle brake I have ever used changed POI that much.
Since you re-cut your crown I would check it. No muzzle brake I have ever used changed POI that much.
Re: Why am I getting POI Change?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: boudin</div><div class="ubbcode-body">Wouldn't the muzzle brake also decrease the projectile's velocity by allowing pressure to escape from the sides? I imagine this would contribte to a lower point of impact when using a zero established with a higher velocity round. Maybe it's not responsible for all 12" of the drop in POI, but possibly some. </div></div>
^^^^This was a joke right?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: boudin</div><div class="ubbcode-body">Wouldn't the muzzle brake also decrease the projectile's velocity by allowing pressure to escape from the sides? I imagine this would contribte to a lower point of impact when using a zero established with a higher velocity round. Maybe it's not responsible for all 12" of the drop in POI, but possibly some. </div></div>
^^^^This was a joke right?
Re: Why am I getting POI Change?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">It doesn't kick as much right? If so that means less muzzle rise in reoil. Gun shoots lower. Has little to do with harmonic. Harmonic affects accuracy. </div></div>
I'm not a gunsmith but the break doesn't work till after the bullet has left the barrel. Or am I off base in my thinking?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">It doesn't kick as much right? If so that means less muzzle rise in reoil. Gun shoots lower. Has little to do with harmonic. Harmonic affects accuracy. </div></div>
I'm not a gunsmith but the break doesn't work till after the bullet has left the barrel. Or am I off base in my thinking?
Re: Why am I getting POI Change?
Did you pull the optics/rings or bases when you recrowned and threaded the barrel? Maybe this would explain the change in POI
Did you pull the optics/rings or bases when you recrowned and threaded the barrel? Maybe this would explain the change in POI
Re: Why am I getting POI Change?
I cleaned up the muzzle brake and found a slight copper scuff mark on the top right at the end. I opened up the bore a little more but I haven't tried it yet. I am surprised the bullets were holding together and didn't disintegrate and they shot pretty good. The brake is one I made that is really similar to Hollands quick discharge brake. The recoil is so much less it amazes me.
I cleaned up the muzzle brake and found a slight copper scuff mark on the top right at the end. I opened up the bore a little more but I haven't tried it yet. I am surprised the bullets were holding together and didn't disintegrate and they shot pretty good. The brake is one I made that is really similar to Hollands quick discharge brake. The recoil is so much less it amazes me.
Re: Why am I getting POI Change?
Skeet375 when i had my brake installed I had a POI shift, cant remember if elevation went up or down, but the shots were impacting a few inches right at 100 yards but the impacts where consistent and in the same spot.
The rifles zero was re-evaluated and was back on track shooting lights out within a few rounds.
My understanding is that some do experience change in POI, some do not.
Skeet375 when i had my brake installed I had a POI shift, cant remember if elevation went up or down, but the shots were impacting a few inches right at 100 yards but the impacts where consistent and in the same spot.
The rifles zero was re-evaluated and was back on track shooting lights out within a few rounds.
My understanding is that some do experience change in POI, some do not.
Re: Why am I getting POI Change?
Not a joke. A question actually, but your response sent me searching for an answer for myself and as it turns out, no it would not decrease velocity. However, in some instances it has been found to <span style="font-style: italic">increase</span> muzzle velocity if it is not cut excessively oversize. I guess that makes a little more sense. Thanks for the clarification.
Not a joke. A question actually, but your response sent me searching for an answer for myself and as it turns out, no it would not decrease velocity. However, in some instances it has been found to <span style="font-style: italic">increase</span> muzzle velocity if it is not cut excessively oversize. I guess that makes a little more sense. Thanks for the clarification.
Re: Why am I getting POI Change?
Skeet375 if you chuckup the barrel in your chuck and have it running straight then run a boring bar so you are only cutting on one side you won't have the bullet hitting the brake.
Skeet375 if you chuckup the barrel in your chuck and have it running straight then run a boring bar so you are only cutting on one side you won't have the bullet hitting the brake.
Re: Why am I getting POI Change?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skeet375</div><div class="ubbcode-body">I just installed a muzzle brake on my .300 Win mag. Now there is a big point of impact change. With the muzzle brake on I am about a foot lower at a hundred yds. Is this abnormal? I bored the muzzle brake .02 over size and threaded both on the lathe so everything should me concentric. </div></div>
How did you set up the muzzle end? steady rest, thru headstock? did you indicate the muzzle in on the bore?
If it was set up concentric as you say you would not be getting strikes on the brake. So we need to evaluate the problem with the instal.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Skeet375</div><div class="ubbcode-body">I just installed a muzzle brake on my .300 Win mag. Now there is a big point of impact change. With the muzzle brake on I am about a foot lower at a hundred yds. Is this abnormal? I bored the muzzle brake .02 over size and threaded both on the lathe so everything should me concentric. </div></div>
How did you set up the muzzle end? steady rest, thru headstock? did you indicate the muzzle in on the bore?
If it was set up concentric as you say you would not be getting strikes on the brake. So we need to evaluate the problem with the instal.
Re: Why am I getting POI Change?
Grabbed the action in the chuck, dialed in the barrel just ahead of the action ran a center in the muzzle. Turned my tendon, threaded, setup the steady rest moved center away indicated bore with indicator rod. re cut muzzle with a recessed 90 degree crown and lapped the burr off with roundheaded brass screw and lapping compound. When I built the muzzel brake I did it all in one setup in the lathe. I did drill the bore through, but new drill bit and centerdrilled first. Bored out the internal tread portion and singlepointed the treads. I just didn't give myself enough clearance in the hole. Now that its opened it up to .328 I am shooting to the same POI and in one ragged hole.
Grabbed the action in the chuck, dialed in the barrel just ahead of the action ran a center in the muzzle. Turned my tendon, threaded, setup the steady rest moved center away indicated bore with indicator rod. re cut muzzle with a recessed 90 degree crown and lapped the burr off with roundheaded brass screw and lapping compound. When I built the muzzel brake I did it all in one setup in the lathe. I did drill the bore through, but new drill bit and centerdrilled first. Bored out the internal tread portion and singlepointed the treads. I just didn't give myself enough clearance in the hole. Now that its opened it up to .328 I am shooting to the same POI and in one ragged hole.
Re: Why am I getting POI Change?
I came late to class, sorry. Was your original hole in the brake .310 (.308 + .02). If so man that was tight. Glad to hear you got it figured out.
I came late to class, sorry. Was your original hole in the brake .310 (.308 + .02). If so man that was tight. Glad to hear you got it figured out.
Re: Why am I getting POI Change?
We really need pics of the finished brake and report on how well it reduced recoil.
We really need pics of the finished brake and report on how well it reduced recoil.
Re: Why am I getting POI Change?
I hope this image works. It was taken before I deburred it and filed the baffles flat. Originaly the hole was .01 over and now I opened it up .020 over. If I had to guess the recoil has got to be close to 50% less.
I hope this image works. It was taken before I deburred it and filed the baffles flat. Originaly the hole was .01 over and now I opened it up .020 over. If I had to guess the recoil has got to be close to 50% less.
