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Barrel Erosion and Boattail Bullets
oneoldsap
Member Posts: 563 ✭✭✭✭
I had a fellow shooter tell me that he thought that boattail bullets were harder on barrels than flatbased bullets . His point was that boattails force gasses to the side and to a point where the boattail ends . Where as with a flatbase the gasses are pushing entirely against the bullet and not to the side and to a point . Frankly I think his point may have some validity ! Any thoughts on this , wouldn,t hurt to sleep on it .
Comments
Sure enough, the boattailed M1 bullet did indeed show more visible throat erosion than the flatbased 1906 or M2 bullets. But a gun shot with boattails still had a longer accuracy life with them due to their better construction with a hard core and better ballistic coefficient.
So the answer is yes, BUT.
When the story first came out, about 80 years ago, one of the national armories, Springfield I think, did some testing.
Sure enough, the boattailed M1 bullet did indeed show more visible throat erosion than the flatbased 1906 or M2 bullets. But a gun shot with boattails still had a longer accuracy life with them due to their better construction with a hard core and better ballistic coefficient.
So the answer is yes, BUT.
But,...(in continuation of what Hawk was about to say) you have to shoot a lot and shoot hot, as in long strings of competition fire, for it to ever matter.
For the guy who uses his rifle hunting and taking it to the range to put 50-100 rounds a year through it, it will take 30 years before that difference makes a difference.
Old wives tail.
quote:Originally posted by XXCross
Note: Gasses and liquids exert the same pressure through-out the mechanism that confines them. Ergo, there is no more pressure exerted against the walls of a barrel irrespective of the bullet type.
Try shooting some serious competition and you'll see that it does matter. Like I said if you don't shoot much it won't matter. But if you do you WILL see a difference.
XXcross,
If gasses and liquids exert the same pressure throught why will equal amounts of powder charge push a flatbase bullet faster than a boattail bullet of equal weights? The boattail has less material touching the barrel usually. I think the truer statement regarding that is the gases want to push at a 90 deg. angle to objects they are pushing. The boattail receiving pressure isn't as efficient as the flatbase at receiving the pressure. For a better, but more expensive to produce design, try the rebated boattail design.
just go shoot and be happy[:D]
who cares. How many folks here have ever eroded a throat to the point they noticed an accuracy decrease?
I haven't yet, but am working on it; F-T/R out to 1000 yards.
When it starts to slide, I will just buy a new barrel.
If you want to play you have to pay.
If gasses and liquids exert the same pressure throught why will equal amounts of powder charge push a flatbase bullet faster than a boattail bullet of equal weights? The boattail has less material touching the barrel usually. I think the truer statement regarding that is the gases want to push at a 90 deg. angle to objects they are pushing. The boattail receiving pressure isn't as efficient as the flatbase at receiving the pressure. For a better, but more expensive to produce design, try the rebated boattail design.
Well lad here's your answer.:
It is true that flat based bullets will chronograph at a slightly higher velocity as compared to bullets with a boat-tail design.all other considerations being equal. (powder charge, bullet weight, ballistic design, etc)
Within the confines of the barrel, the velocity is determined by the rate of expansion of the propellant gasses and the resistance of the bullet against the bore. For all practical proposes there is no significant difference between the two bullet types. Within the barrel the velocities are the same.
The bullet, having exited the barrel, this is where the difference begins to show up. Assuming identical frontal design, it is the vacuum at the rear of the bullet that acts to retard the forward motion. Boat-tailed bullets have a larger area in contact with that vacuum and thus are subject to slightly more drag. This remains true until the projectile goes sub-sonic. The difference isn't great but there is a difference and it happens after the bullet has left the barrel.
I've shot a ton of Lapua's and likely two ton of Sierra's. Judging from the limited amount of sight settings changes required between the two, I'd say the velocities are close to the same.
quote:Originally posted by JustC
who cares. How many folks here have ever eroded a throat to the point they noticed an accuracy decrease?
I haven't yet, but am working on it; F-T/R out to 1000 yards.
When it starts to slide, I will just buy a new barrel.
If you want to play you have to pay.
yep, my match barrels are expensive, but when they start to get a little sloppy in accuracy, I will set them back and have them put on hunting rifles.
"How many folks here have ever eroded a throat to the point they noticed an accuracy decrease?"
I have, I have!
Not once but many times. Some with as few as 15 shots and others in the neighborhood of approximately 200 shots. One experimental barrel and cartridge in particular had 19" of erosion which we checked by milling off half the barrel diameter for the length of the barrel...
The question, while interesting and guaranteed to start an argument, is really superfluous for most shooters.
Best.
JustC,
"How many folks here have ever eroded a throat to the point they noticed an accuracy decrease?"
I have, I have!
Not once but many times. Some with as few as 15 shots and others in the neighborhood of approximately 200 shots. One experimental barrel and cartridge in particular had 19" of erosion which we checked by milling off half the barrel diameter for the length of the barrel...
The question, while interesting and guaranteed to start an argument, is really superfluous for most shooters.
Best.
What were you experimenting with that ate up a throat in 15rounds?? or even 200rounds?? You know, just so I stay away from those chamberings in the future[;)]
Hyper-velocity, high energy wildcats. What some folks refer to as 'overbore'. The barrels were aluminum alloy, slightly harder than most folks are familiar with but I don't recall the numbers.
This was pretty tame compared to the aluminum barrels made to shoot super balls...
The barrels that went 200+ were similar cartridges but made from other grades of ordnance steel with no attention paid to cooling between shot strings. Just simple quests for knowledge.
Best.
who cares. How many folks here have ever eroded a throat to the point they noticed an accuracy decrease?
just go shoot and be happy[:D]
I have with a .300 Win Mag...but only once.