"I have read that oil left in the bore will cause wrinkles in the steel as the first bullet passes down accumulating that oil in front and by hydraulic action from the pressure of a fluid...."
Regarding oil left in the barrel: Who has not fired two shots before sighting his rifle, or going hunting to get the oil out of the barrel? I push a 2x4 through it but have not always done so. That very thin protecting film clinging to the bore after weeks or even one day can never cause hydraulicing as there is no obstruction ahead of it; so plastic deformation in the barrel steel caused by the supple copper shanks of the bullet will be very unlikely.
Oil in the chamber is a much more dangerous liability.
I believe the user would have rejected an intrinsic inaccurate design.
The risk is at the crown. A microgroove barrel like the JM Marlins have are very accurate for having large number of release points in the crown. A two-land bore must only have the slightest out perfect concentric release of the bullet and the effect on accuracy will be great.
If I remember correctly one of the companies building the Springfield rifles did extensive testing of the 4 vs 2 groove question before they made the change from 4 grooves to two. They could find no differences in accuracy. Now days in-house company testing may be taken with a grain of salt (or two). Back then, and building products for the war effort, I think they would not build them were the two groove barrels substandard.
Same rate of twist of the rifling will give same spin rate to the bullet no matter 2 or 4 groove. The risk for non perfect muzzle departure is just high on a 2 groove muzzle. That is the reason why those two Marlins with the microgroove barrels are so extra-ordinary accurate - the risk for crown blemishes on a land are spread into many more degrees.
Added: Of course if the crown is perfect both should be accurate if all else in the barrel-action-stock combination is straight and square and concentric.
Interesting. My instinctive feel is that if the crown is perfect (NB) and the bullet base squareness is perfect (no boat tail bullets here) and the bullet and bore diameters is a perfect seal there should be no mechanical difference in the muzzle exit dynamics.
I would suggest one of each. Good learning in there.
During WW2, US rifle barrel makers (not all) went to making barrels with 2 grooves to increase production. These can be found on 1903 Springfields and Savage made #4 Enfields.
Now old husbands of old wives have spun tales that 2 groove barrels are 1 - less accurate and 2 - have shorter life. These tales, over the years, have been accepted as fact in many camps. The link below should put some light on the 2 groove barrels after a 16,000 round test.
"the 2 groove barrel out performed the 4 groove edition by a notable margin."
So now I have a decision. I will shortly buy 2 #4 as new barrels, so what do I get - both 2 groove or both 4 groove ? Or.....one of each and do my own testing ?
I have read that oil left in the bore will cause wrinkles in the steel as the first bullet passes down accumulating that oil in front and by hydraulic action from the pressure of a fluid. I don't know either yay or nay about this but do have experience with hydraulics and know that a fluid cant be compressed as a gas can be, therefore I'm leaning towards it being a truth. Does anyone have any insight to this ?
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"I have read that oil left in the bore will cause wrinkles in the steel as the first bullet passes down accumulating that oil in front and by hydraulic action from the pressure of a fluid...."
Regarding oil left in the barrel: Who has not fired two shots before sighting his rifle, or going hunting to get the oil out of the barrel? I push a 2x4 through it but have not always done so. That very thin protecting film clinging to the bore after weeks or even one day can never cause hydraulicing as there is no obstruction ahead of it; so plastic deformation in the barrel steel caused by the supple copper shanks of the bullet will be very unlikely.
Oil in the chamber is a much more dangerous liability.
I believe the user would have rejected an intrinsic inaccurate design.
The risk is at the crown. A microgroove barrel like the JM Marlins have are very accurate for having large number of release points in the crown. A two-land bore must only have the slightest out perfect concentric release of the bullet and the effect on accuracy will be great.
If I remember correctly one of the companies building the Springfield rifles did extensive testing of the 4 vs 2 groove question before they made the change from 4 grooves to two. They could find no differences in accuracy. Now days in-house company testing may be taken with a grain of salt (or two). Back then, and building products for the war effort, I think they would not build them were the two groove barrels substandard.
Same rate of twist of the rifling will give same spin rate to the bullet no matter 2 or 4 groove. The risk for non perfect muzzle departure is just high on a 2 groove muzzle. That is the reason why those two Marlins with the microgroove barrels are so extra-ordinary accurate - the risk for crown blemishes on a land are spread into many more degrees.
Added: Of course if the crown is perfect both should be accurate if all else in the barrel-action-stock combination is straight and square and concentric.
Yes, regarding accuracy, once the spin at the required twist is imparted (all else being equal) there should be no difference ?
Not altogether different than a small hand or a large hand throwing an elliptical US football as long as the correct spin is put on the ball.
Interesting. My instinctive feel is that if the crown is perfect (NB) and the bullet base squareness is perfect (no boat tail bullets here) and the bullet and bore diameters is a perfect seal there should be no mechanical difference in the muzzle exit dynamics.
I would suggest one of each. Good learning in there.
2 groove vs 4+ grooves
During WW2, US rifle barrel makers (not all) went to making barrels with 2 grooves to increase production. These can be found on 1903 Springfields and Savage made #4 Enfields.
Now old husbands of old wives have spun tales that 2 groove barrels are 1 - less accurate and 2 - have shorter life. These tales, over the years, have been accepted as fact in many camps. The link below should put some light on the 2 groove barrels after a 16,000 round test.
http://www.remingtonsociety.org/remingtons-wwii-experience-with-2-groove-rifling/
"the 2 groove barrel out performed the 4 groove edition by a notable margin."
So now I have a decision. I will shortly buy 2 #4 as new barrels, so what do I get - both 2 groove or both 4 groove ? Or.....one of each and do my own testing ?
Oil in the bore
I have read that oil left in the bore will cause wrinkles in the steel as the first bullet passes down accumulating that oil in front and by hydraulic action from the pressure of a fluid. I don't know either yay or nay about this but do have experience with hydraulics and know that a fluid cant be compressed as a gas can be, therefore I'm leaning towards it being a truth. Does anyone have any insight to this ?