POI shift as barrel heats up

locknloader · March 9, 2018, 10:00 AM

I was shooting today and noticed that when my barrel heated up my POI started to be way off, after say 40-50 rounds down the barrel of 9mm. I shot about 100 rounds total, the last few were way off low and to the left.

My ammo shoots nice tight groups when the gun is cold, around what point can i start to expect this shift in POI, is it consistent so i can compensate for it?

I usually only shoot 50ish rounds in a range trip and take turns with someone else so i never ran into the issue of the barrel heating up.

Is this more pronounced in handguns or rifles... or same in both?

Thanks!

F. Guffey · March 9, 2018, 10:38 AM

Quote:

I usually only shoot 50ish rounds in a range trip and take turns with someone else so i never ran into the issue of the barrel heating up.

I have two S/As with three complete slides each, for others I have extra barrels.

When it comes to rifles I have little to nothing to gain by getting the barrel hot. I have barrels that came from custom shops that were removed because the rifle "just did not shoot good" ?

When checking the barrels I use 'V' blocks and indicators, some of the problems made no sense so I cut the barrels up in short pieces, I have found a few that were magnificent looking barrels but the bore was not centered etc. The complaint for that barrel was it was accurate until it got warm and after that the hotter the barrel the more predictable what direction the impact would be; meaning the barrel was bending because of the mass being greater on one side than the other.

It was no loss to me because I made a chamber gage out of the big end of the barrel.

F. Guffey

**Unclenick** · March 9, 2018, 01:40 PM

Locknloader,

I hate to tell you, but pistol barrels are too short and the inherent precision too low for barrel heating to affect POI appreciably. That takes a barrel long enough for the heat to warp and/or cause it to contact the stock someplace. If you are right-handed, those low and left POI's are usually the result of a trigger-yanking flinch working its way into your shooting. When I was learning bullseye match shooting I had it happen so invisibly that I could actually aim at the 1:30 edge of a bull and put every shot in the ten ring, yet not feel the flinch in any way and not be able to will it to stop without taking a break to recreate my mindset by dry firing on the bull until it stops.

You may not believe this is occurring, but the way to prove it one way or the other is to have a buddy load your mags with a snap cap or two in unknown (to you) positions in the stack. When you see the low and left shots appearing, run one of those mags and watch what the front sight does when the hammer falls on a dummy. You'll see it dip low and left if this is the issue.

If this is not the issue, then I would suspect some debris in the gun is forcing the muzzle low and left or else a problem with the sight. If the sight is optical, I would check it.

Rachen · March 9, 2018, 02:14 PM

We are talking pistols here, as opposed to rifles. Pistol barrels are short and stubby and I highly doubt that heat generated by rapid firing would have any affect on point of aim.

Now rifles, on the other hand, are an entirely different story. The longer the barrel of the rifle, the more it will be affected by heat. Heck, the barrel does not even need to be affected by the heat of firing to mess up your aim. Trivial things like ambient temperature differences and the residual vibrations from the previous shot will throw your aim out the window. That is the most annoying pet peeve that long range competitive shooters have to deal with. During the War of Southern Independence, Confederate sharpshooters often preferred, and were issued the shorter 2-band Enfields or Enfield musketoons instead of the 3-band infantry standard. The shorter barrel on the carbines were less affected by heat and vibrations and allowed their users to make follow-up shots that were consistently on point. And the Union marksmen also favored Sharps carbines as opposed to the full length rifle for the same reasons.

locknloader · March 9, 2018, 02:29 PM

I am still a newbie so must be my shooting

I had a bad problem when i first started of pulling the trigger to the left, i must be falling back into bad habits. Time to slow down and check the basics again.

Evan Thomas · March 9, 2018, 02:40 PM

It sounds as if your problem could be related to fatigue, and you may want to consider keeping your round count in that fifty-ish range where this problem doesn't show up.

Longer practice sessions are tempting -- we all want to improve as fast as we can -- but they can be counterproductive if they force you into bad habits. It's not true that "practice makes perfect" -- rather, "perfect practice makes perfect."

anymanusa · March 9, 2018, 07:25 PM

I have a 21" barrel FAL that may be doing what you describe FGuffey. Thanks for the post.

Yosemite Steve · March 11, 2018, 02:29 PM

Unclenick is probably spot on. I was doing the same thing. My 10mm with hot loads would begin to wear on me after three clips and my accuracy would begin to fail due to anticipation of recoil. Try alternating from left to right and back again every clip. It will force you to concentrate on your grip and your trigger pull more and greatly improve your skill. Make sure you are doing everything right. Finger placement, focus on the front sight, relaxed squeeze, breathing, stance, etc. If you do it with your other hand you will have to think about what you are doing more and you will probably shoot better! Then carry what you learned over to your habitual side. Switching hands teaches us better coordination and control in everything we do.

JeepHammer · March 11, 2018, 06:39 PM

While ALL barrels will shift impact *IF* you get them hot enough,
(Practically, we are talking hot enough to make the barrel steel malleable)

I have to go with Uncle Nick on this one.
I can't see a 9mm barrel of any kind being long enough to shift enough you can tell it in freehand groups...
Low/Left sounds like a grip/stance/trigger control issue as you get tired/bored.
(And trust me, no one gets tired/bored faster than me shooting handguns)

From a metalurigic & machining standpoint, there is no possible way to drill, rifle a barrel blank in EXACTLY it's thermal expansion center AND have the metal grain lines in exactly the correct place.
Just plain impossible...

You didn't say what pistol...
There is crap like Hi-Point where the barrel is flopping around like a broke neck chicken, and nothing more than carbon will shift the barrel...
There are barrels with a big old lug on the bottom, a big chunk of steel that expands with heat and bows the barrel, there are barrels that are front end bushed to keep them in place,
Bushing & barrel expand at different rates and the POI shifts...

Some barrels have WAY too big of bores and when they thermal expand the bullet more or less rattles down the bore.
(Beware 'Cheap' barrels, low cost up front usually ensures inaccuracy)

March 9, 2018, 10:00 AM	#1
locknloader Senior Member Join Date: August 28, 2017 Posts: 164	POI shift as barrel heats up I was shooting today and noticed that when my barrel heated up my POI started to be way off, after say 40-50 rounds down the barrel of 9mm. I shot about 100 rounds total, the last few were way off low and to the left. My ammo shoots nice tight groups when the gun is cold, around what point can i start to expect this shift in POI, is it consistent so i can compensate for it? I usually only shoot 50ish rounds in a range trip and take turns with someone else so i never ran into the issue of the barrel heating up. Is this more pronounced in handguns or rifles... or same in both? Thanks!

March 9, 2018, 01:40 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Locknloader, I hate to tell you, but pistol barrels are too short and the inherent precision too low for barrel heating to affect POI appreciably. That takes a barrel long enough for the heat to warp and/or cause it to contact the stock someplace. If you are right-handed, those low and left POI's are usually the result of a trigger-yanking flinch working its way into your shooting. When I was learning bullseye match shooting I had it happen so invisibly that I could actually aim at the 1:30 edge of a bull and put every shot in the ten ring, yet not feel the flinch in any way and not be able to will it to stop without taking a break to recreate my mindset by dry firing on the bull until it stops. You may not believe this is occurring, but the way to prove it one way or the other is to have a buddy load your mags with a snap cap or two in unknown (to you) positions in the stack. When you see the low and left shots appearing, run one of those mags and watch what the front sight does when the hammer falls on a dummy. You'll see it dip low and left if this is the issue. If this is not the issue, then I would suspect some debris in the gun is forcing the muzzle low and left or else a problem with the sight. If the sight is optical, I would check it. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 9, 2018, 02:40 PM	#6
Evan Thomas Senior Member Join Date: July 7, 2008 Location: Upper midwest Posts: 5,631	It sounds as if your problem could be related to fatigue, and you may want to consider keeping your round count in that fifty-ish range where this problem doesn't show up. Longer practice sessions are tempting -- we all want to improve as fast as we can -- but they can be counterproductive if they force you into bad habits. It's not true that "practice makes perfect" -- rather, "perfect practice makes perfect." __________________ Never let anything mechanical know you're in a hurry.

March 11, 2018, 06:39 PM	#9
JeepHammer Junior member Join Date: February 27, 2015 Posts: 1,768	While ALL barrels will shift impact IF you get them hot enough, (Practically, we are talking hot enough to make the barrel steel malleable) I have to go with Uncle Nick on this one. I can't see a 9mm barrel of any kind being long enough to shift enough you can tell it in freehand groups... Low/Left sounds like a grip/stance/trigger control issue as you get tired/bored. (And trust me, no one gets tired/bored faster than me shooting handguns) From a metalurigic & machining standpoint, there is no possible way to drill, rifle a barrel blank in EXACTLY it's thermal expansion center AND have the metal grain lines in exactly the correct place. Just plain impossible... You didn't say what pistol... There is crap like Hi-Point where the barrel is flopping around like a broke neck chicken, and nothing more than carbon will shift the barrel... There are barrels with a big old lug on the bottom, a big chunk of steel that expands with heat and bows the barrel, there are barrels that are front end bushed to keep them in place, Bushing & barrel expand at different rates and the POI shifts... Some barrels have WAY too big of bores and when they thermal expand the bullet more or less rattles down the bore. (Beware 'Cheap' barrels, low cost up front usually ensures inaccuracy) Last edited by JeepHammer; March 11, 2018 at 06:44 PM.

March 9, 2018, 02:14 PM	#4
Rachen Senior Member Join Date: May 10, 2006 Location: Weekend cowboy Posts: 542	We are talking pistols here, as opposed to rifles. Pistol barrels are short and stubby and I highly doubt that heat generated by rapid firing would have any affect on point of aim. Now rifles, on the other hand, are an entirely different story. The longer the barrel of the rifle, the more it will be affected by heat. Heck, the barrel does not even need to be affected by the heat of firing to mess up your aim. Trivial things like ambient temperature differences and the residual vibrations from the previous shot will throw your aim out the window. That is the most annoying pet peeve that long range competitive shooters have to deal with. During the War of Southern Independence, Confederate sharpshooters often preferred, and were issued the shorter 2-band Enfields or Enfield musketoons instead of the 3-band infantry standard. The shorter barrel on the carbines were less affected by heat and vibrations and allowed their users to make follow-up shots that were consistently on point. And the Union marksmen also favored Sharps carbines as opposed to the full length rifle for the same reasons.

March 9, 2018, 02:29 PM	#5
locknloader Senior Member Join Date: August 28, 2017 Posts: 164	I am still a newbie so must be my shooting I had a bad problem when i first started of pulling the trigger to the left, i must be falling back into bad habits. Time to slow down and check the basics again.

March 9, 2018, 07:25 PM	#7
anymanusa Junior Member Join Date: November 9, 2008 Location: Beautiful South Posts: 8	I have a 21" barrel FAL that may be doing what you describe FGuffey. Thanks for the post.

March 11, 2018, 02:29 PM	#8
Yosemite Steve Senior Member Join Date: December 27, 2017 Posts: 460	Unclenick is probably spot on. I was doing the same thing. My 10mm with hot loads would begin to wear on me after three clips and my accuracy would begin to fail due to anticipation of recoil. Try alternating from left to right and back again every clip. It will force you to concentrate on your grip and your trigger pull more and greatly improve your skill. Make sure you are doing everything right. Finger placement, focus on the front sight, relaxed squeeze, breathing, stance, etc. If you do it with your other hand you will have to think about what you are doing more and you will probably shoot better! Then carry what you learned over to your habitual side. Switching hands teaches us better coordination and control in everything we do.