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Hot Barrels and Cleaning while shooting
B_Mc
Member Posts: 794 ✭✭✭✭
I was out target shooting this weekend. I shot 7 rounds fairly quickly with very good accuracy. After that i had significant problems holding a tight pattern. I shot 20 rounds in about 45 mins.
What makes the barrel less accurate while it is hot?? OR was it just me??
My other question is does the cleaness of the barrel account for a lot in accuracy??
POI???
What do you mean by bedding???
Are you saying that Remington rifle barrels are no good???
What makes the barrel less accurate while it is hot?? OR was it just me??
My other question is does the cleaness of the barrel account for a lot in accuracy??
POI???
What do you mean by bedding???
Are you saying that Remington rifle barrels are no good???
Comments
Fouling of the barrel can cause accuracy to diminish. As well some barrels shoot better when{edit: warm hot } and some shoot better when cold. I've generally found that heavy barrels will still tend to shoot more accurately than lighter barrels. Especially, ultra-lite/featherweight barrels. That said, there are exceptions to the rule. Some sporter weight barrels have held some pretty good accuracy while heating up from being shot a lot. It's not the norm but it happens. They get broken in right. The barrels steel has no micro-inclusions in the wrong spot...whatever reason they just shoot.
BTW the reason heavy barrels generally shoot better is because they absorb heat and vibration better than a thin barrel. But the first criteria that a heavy barrel shoot well is that that the bore is true and broken in right. And that the steel used is as close to perfectly pure as possible. They won't just shoot better because they are heavier.
I have to have a Long Range rifle that will shoot accurately for at least 60 plus sighters. Individual matches are 20 plus sighters in 33 minutes, most folks shoot faster so the conditions have less time to change. Nice if it will shoot 120 plus sighters so I don't have to clean in the motel at a weekend match.
A NRA Conventional Pistol shooter needs a .45 that will shoot accurately for 90 rounds. A PPC shooter must have a .38 that will go 150, better 210.
Some terms to think about...
Shotgunners shoot patterns or they pattern their shotguns.
Riflemen shoot groups although some groups can be considered patterns but are still referred to as groups.
"After that i had significant problems holding a tight pattern."
This isn't an uncommon occurrence due to the fact that barrels heat up as you shoot and the faster you shoot, the hotter it gets. This heat causes the stresses in the barrel to be relieved and the barrel moves in the stock.
"I shot 20 rounds in about 45 mins."
Remember that heat doesn't necessarily dissipate that quickly and it continues to build as you continue to shoot. More time between shots or groups is helpful. I take several rifles with me when I go to the range so that I can let one cool and still continue to shoot.
When relieved stresses move a barrel, it can make contact with the side or bottom of the barrel channel causing greater variations in your groups. That's why we generally accept that a free-floated barrel will have more consistent accuracy.
"My other question is does the cleaness of the barrel account for a lot in accuracy??"
It can and does cause problems with accuracy. So do about 2 dozen other factors. But keeping a barrel reasonably clean is a plus for accuracy. It's one less thing to worry about.
From Dan Lilja, Lilja Rifle Barrels:
" Stress in steel will tend to come out when the steel is either heated or machined. The heating of a barrel through firing it is often enough to allow some stress movement to occur. In effect what happens is the barrel warps and is no longer "looking" where we thought it was. The bullets don't hit the target where they were intended. If a bar of steel is machined while it contains stress, it will move. This can be noticed in an increase in bore and groove diameters as the outside diameter is reduced. This can mean an increase of these diameters as a barrel is contoured smaller in diameter towards the muzzle. Or an enlargement in the internal dimensions under the flutes of a fluted barrel.
All of the steel used in the manufacture of our barrels is stress relieved by the steel mill as their last operation and again following the rifling operation in a vacuum furnace. In both cases this stress relieving is done through the application of heat.
Rifle barrels made using the hammer forge process contain a tremendous amount of stress. This explains why some barrels on mass-produced factory rifles will walk their shots as those barrels heat from firing."
Best.
It is normally on point with holding pretty tight group. I think that i may have just had a bad day.
But when you say "relieved stresses move a barrel" is this a permanate thing or what?? And what exactly do you mean????
I dont under stand how that affects the accuracy...
EDIT: It is a Remington M700 ADL 30.06 and it was made in 1995.
For best practicality, it would be better to shoot a 3 or 5 shot group, then let that rifle cool for 1/2 hour or so, while you are shooting one or two more different rifles, handguns, shotguns, or muzzle loaders...or air gun. I would also clean the bore after every 20 rounds, then fire a fouling shot.
best.
EDIT:
Something else that you might want to check is the torque of the action bolts. Nononsense can help you out with the required torque, and method in which to do so.
You never did say what model rifle you had, other than being a 700, or what approximate age it was.
Standard Remington barrels are made by the hammer forged method. A mandrel is put into a hole in a short barrel blank and both are put into a machine that hammers the tube around the mandrel giving it the shape of the inside and outside of the barrel.
All of this hammering creates stress in the structure of the metal which has been forced around and stretched along the mandrel. When we heat up the barrel by shooting, the barrel relaxes and moves, shooting to a different point on the target. A tiny bit of movement at the bench can result in larger displacement at the 100 yard target. Stress induced movement is usually not permanent and the barrel returns to its original position when it cools down.
Other variables that can affect your groups include:
Bad rests
Bad hold on the rifle
Bad rifle position on the rests
Mirage
Loose rings
Loose base
Poor quality scope
Something broke in the scope
Incorrect bedding
Barrel touching sides or bottom of the barrel channel
Carbon ring in front to chamber throat
Damaged crown
Changing load components in any way
and another dozen more...
Best.
glabray,
"Steel has to get very hot for stress to be relieved. It can happen in a machine gun barrel, but in a bolt action rifle? Very doubtful."
Steel has to get very hot to achieve permanent stress relief but it can be demonstrated with a very few shots at the range with low cost sporter barrels that have been made by the hammer forge method such as Remingtons. I know this because I have not only done it but can demonstrate it. As you continue to shoot with a hot barrel, the POI actually moves.
Barrel makers all point this fact out and the quote I copied from Dan Lilja states as much.
Best.
"POI???
What do you mean by bedding???
Are you saying that Remington rifle barrels are no good???"
POI = Point Of Impact or where the bullet hits on the target as opposed to where you aimed.
Bedding is usually a two-part epoxy that improves the fit between the barreled action and the stock. It is supposed to enhance accuracy. Bedding is the light tan stuff in this photograph:
Remington rifle barrels are some of the best mass produced barrels in the industry. They can be very accurate so long as you keep them reasonably cool. After all, they are meant to be hunting rifles not Match rifles. Remington does make some extremely good button rifle barrels also that get used in their Military, Tactical and Law Enforcement rifles.
Best.