300 win mag barrel wear
Mike Goldstein
#If you choose the magnum, don't forget to amortize the barrel
#wear into your calculations. Magnums burn so much powder that throat
#erosion sets in prematurely and you'll probably only get about 1000
#rounds out of it. Figure $300 - $400 to rebarrel and chamber in an
#unusual caliber and your're looking at an extra 35 cents a shot just
#for wear on the gun.
My question is can't I just load the 300 win mag to 30'06 levels?
For instance: Instead of given a 165 grain bullet using 67.0 gr.of H380
generating 2,997 fps
use the same 165 grain bullet with 52.0 gr. of H380
generating 2,792 fps.
The latter is a 30-06 load.
Is it safe to use just 52 grains of H380 in a 300 win mag case?
I figure I can always load em up hotter if I need more power, and extend the
life of my barrel.
I guess I should also ask do the barrels of 300 win mags wear out after just
a thousand rounds, or is it just another urban legend?
Thanks,
Mike Goldstein
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Mike Goldstein
Chris Keller
at least 10,000 rounds. I had a .300 Weatherby that had no noticeible wear
after 3000. I shot slow and I used reduced loads, as they were more accurate
than factory ammo in my gun.
In the Weatherby I used 70 grains of IMR 4350, a Federal #215 primer and 180
grain bullets, to approximate a hot 30-06.
I am sure you can do similar things with your cartridge.
If you shoot till the barrel is too hot to touch it will wear out quickly. A
lot of American shooters do this and a lot of them also do not clean their guns
properly.
Chris
Chris----...@aol.Com
Bill VH
(Mike Goldstein) writes:
#
#My question is can't I just load the 300 win mag to 30'06 levels?
#
Why not ? You will get marginally more bullet drop past your zero
range because of lower velocity. But then at 30-06 level you can
find a velocity that gives you great accuracy. Right now I'm shooting
a 25-06 at .250 Savage or .257 Roberts level. While they're not 400yd
varmint loads, any deer I see out to 300yds is MINE.
#
#For instance: Instead of given a 165 grain bullet using 67.0 gr.of H380
#generating 2,997 fps:
#use the same 165 grain bullet with 52.0 gr. of H380
#generating 2,792 fps:
#The latter is a 30-06 load.
#Is it safe to use just 52 grains of H380 in a 300 win mag case?
#
Safe enough. But you won't be getting that 30-06 velocity in a big case.
Try dropping the Magnum load a grain at a time untill you get a more
comfortable velocity. Bet you wind up more like 63 or 64 grains.
#
#I figure I can always load em up hotter if I need more power, and extend the
#life of my barrel. I guess I should also ask do the barrels of 300 win mags
#wear out after just a thousand rounds, or is it just another urban legend?
#
Depends on the level of accuracy you demand. What's worn out to a
Benchrester could be "Ole' Meat in the Skillet" to a hunter.
Bill Van Houten (USA Ret)
Thermopylae had it's messenger of defeat, COME AND GET THEM !
The Alamo had none.
Bart B.
# I guess I should also ask do the barrels of 300 win mags wear out after just
# a thousand rounds, or is it just another urban legend?
Yes, they do. For best accuracy, that is.
Many years ago I came up with a formula to calculate barrel wear.
It's proved very accurate (within 10%) of what top competitive
shooters get with different calibers from 22 up through 30. By very
accurate, I mean a barrel that shoots sub-1/4th inch groups at 100
yards. When this accuracy opens up by about 50%, then best accuracy
is gone. But the barrel may still be quite usable for other than the
most accuracy-demanding applications.
It's simple this; a barrel's best accuracy lasts about 3,500 rounds
when the max load's powder charge in grains equals the same number as
the bore's cross sectional area in square millimeters. For example, a
30 caliber bore is about 45 square millimeters and when the powder
charge is 45 grains you get most accurate barrel life of about 3,500
rounds. Double the powder charge for the same bore diameter and
barrel life is now 25%, or a 30 caliber barrel burning 90 grains of
powder will have an accurate life of about 875 rounds.
This formula is based on slow-fire applications; rounds are fired at
least 1 minute apart. If rapid fire (one shot every 5 to 10 seconds),
each rapid-fire shot is worth 2 or 3 slow-fired ones 'cause the
increased heat at the throat erodes more metal per shot.
So, you .300 Win. Mag. barrel will loose its best accuracy at around
1000 rounds. But it still may be just fine for hunting applications
up to 300 yards. Test it to find out. You may well get another
thousand out of it depending on your own accuracy requirements.
The blunt truth of this issue is as follows; no insults or slams
intended whatsoever. Someone who doesn't shoot very accuratly will
claim their 30 caliber barrel lasts for ten to fifteen thousand
rounds. But folks who shoot very well know better.
22 and 30 caliber service rifle barrels typically meet government
accuracy specs for about 10,000 rounds. A highpower rifle competitor
who wins a lot of matches will rebarrel his .223 Rem. and .308 Win. at
about 3,000 rounds and his .243 Win. and 6.5 X .284 at about 1,400
rounds. When the 7mm Rem. Mag was popular in competion, they got
rebarreled at about 800 rounds. I had a .264 Win. Mag. I'd used to
win several matches that went from tea cup to wash tub size groups at
600 yards in two shots; shot numbers 648 and 649.
Bill VH
writes:
# I had a .264 Win. Mag. I'd used to
#win several matches that went from tea cup to wash tub size groups at
#600 yards in two shots; shot numbers 648 and 649.
#
Did you, by chance, check the headspace after that catastrophe ? My
brother had a .243 he was shooting with hot loads that went sour that
way. Both our friendly gunsmith and Remington's Factory found excess
headspace.
Bill Van Houten (USA Ret)
Thermopylae had it's messenger of defeat, COME AND GET THEM !
The Alamo had none.
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Mike Goldstein
> ...
Chris,
Please tell me the improper methods to avoid in cleaning a gun. Thanks
for all the info too.
Thanks,
Mike Goldstein
> ...
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Chris Keller
hunting accuracy.
Matches are made and lost on mere hundreths of an inch.
As for hunting accuracy: If it will print a 1-1/2 inch group at 100 yards it
is good for deer to about 400 yards.
The only rifle barrel I ever wore out was on my .308 and it went about 20,000
rounds before the 100 yard groups got unacceptably big. They were up to about
3 inches. By then, the freebore had moved three inches up the barrel, the
lands were rounded, not squarish in profile, and all the original tool marks in
this Model 70 barrel had been polished off by firing and cleaning.
Bain & Davis rebarreled the gun for me at that point, with a Douglas barrel, 26
inches long, a 1 in ten inch twist and zero freebore. This means higher
pressure, but it is very accurate, and since 1996 the freebore has advanced
about 1/4 of an inch. I do less shooting now and the barrel is heavier so it
heats up less.
Chris
Chris----...@aol.Com
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Chris Keller
barrel fouling will draw water out of the air, and the presence of two
dissimilar metals (steel, which is mostly iron) and copper) with water will
cause an electrical reaction and then corrosion. This will reduce barrel life
even if the barrel is not visibly pitted.
I always use a good solvent which dissolves copper. I sometimes wet the barrel
and leave it overnight. Hoppe's #9 is my favorite. It really gets green with
dissolved copper. Once clean and dry a very light coating of oil in the bore
will help to protect from moisture. And if I store the gun I check on it every
few months. If the light oil coat from a clean patch has dried, I re-apply.
If you are in a humid climate check more often.
I sometimes use ammonia as well for this cleaning purpose.
Chris
Chris----...@aol.Com
Ken Marsh
Mike Goldstein <michael.a...@lmco.com> wrote:
#Please tell me the improper methods to avoid in cleaning a gun. Thanks
#for all the info too.
The biggest problem is grinding down the crown by rubbing the cleaning
rod against it. What is the crown? It is the edge of the hole at the
muzzle, where the bullet comes out, and the rifling ends.
So, pull the bolt and clean from the breach, and don't pull back the
cleaning tool hard against the crown.
Ken.
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Ken Marsh
Mike Goldstein <michael.a...@lmco.com> wrote:
#My question is can't I just load the 300 win mag to 30'06 levels?
You *can*, but to get 30'06 velocities, you'll have to load to the same
pressures as 30'06. No problem, but that means you'll have to load
*more* powder than a 30'06 load, because a 30'06 load in the larger gas
bottle of the 300WinMag chamber means lower pressure. So, you have to
load more powder than the listed '06 load to get the same velocity.
Then, you'll save some barrel life, but you'll still be generating more
gas and heat than a .30'06.
Enjoy the 300WinMag for what it is, something of a hot-rod, and if you
want efficiency and long barrel life, buy a .308Win. Well, that's another
formula for getting your rifles to last longer- buy more of them, and
spread the shooting around.
Ken.
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Bart B.
# way. Both our friendly gunsmith and Remington's Factory found excess
# headspace.
The 'smith did that fit a .30-.338 barrel to it. Its headspace was
still .219-inch; same as when it was new. It stayed the same as the
bolt lugs were not set forward (or receiver lugs set back) due to the
normal max loads for the .264 Win. as I loaded it at about 53,000 cup.
Any rifle using 'hot' loads with pressures in the 58,000+ spectrum
will probably gain a bit of headspace. How much depends on how soft
the bolt lugs and receiver are and the amount of lug contact things
started with. And probably only one in a million rifles will shoot
accurate with loads this hot.
Bart B.
# hunting accuracy.
Point taken, but doesn't that depend on how far one will accept
missing where they call the shot? Praire dogs at 400 yards, for
example.
# As for hunting accuracy: If it will print a 1-1/2 inch group at 100 yards it
# is good for deer to about 400 yards.
1-1/2 inch groups at 100 yards doesn't mean 6 inch groups at 400 yards
if that's what you're assuming. Group sizes have never been linear as
range increases. Muzzle velocity and ballistic coefficient spreads
cause them to have more vertical shot stringing that's more pronounced
as barrel wear increases.
Charles
# 1-1/2 inch groups at 100 yards doesn't mean 6 inch groups at 400 yards
# if that's what you're assuming. Group sizes have never been linear as
# range increases. Muzzle velocity and ballistic coefficient spreads
# cause them to have more vertical shot stringing that's more pronounced
# as barrel wear increases.
I once did a test in my back yard with a pellet rifle, both with BBs and
pellets. The group expansion was pretty linear up to about 50 feet. Then
it seemed the pellets tumbled and the groups went to pot.
BB's did that at a shorter distance.
I am sure the same principle applies to rifles in some way but I have
never extensively tested it.
Charles.
Ken Marsh
Charles <cst...@interpex.com> wrote:
#I once did a test in my back yard with a pellet rifle, both with BBs and
#pellets. The group expansion was pretty linear up to about 50 feet. Then
#it seemed the pellets tumbled and the groups went to pot.
#BB's did that at a shorter distance.
This is similar to my lifetime introduction to ballistics.
#I am sure the same principle applies to rifles in some way but I have
#never extensively tested it.
Kinda-sorta. Remember, your BB's were subsonic from the beginning, most
centerfire rifles are not. The closest thing I can think of- Centerfire
rifle bullets experience some destabilization when going from supersonic
to subsonic, but that's WAY out there (on the order of 600-1200 yards,
depending on the cartridge).
Ken.
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Bart B.
# You *can*, but to get 30'06 velocities, you'll have to load to the same
# pressures as 30'06. No problem, but that means you'll have to load
# *more* powder than a 30'06 load, because a 30'06 load in the larger gas
# bottle of the 300WinMag chamber means lower pressure. So, you have to
# load more powder than the listed '06 load to get the same velocity.
I'm surprized that you're saying the same case loaded to the same
pressure with the same powder and bullet will produce different muzzle
velocities. It's confusing to me.
Having noticed that 5 cartridges loaded to the same pressure, say
52,000 cup (.300 Savage, .308 Win., .30-06, .300 Win. Mag. and .300
Wby. Mag) all produce different muzzle velocities with the same
bullet; each larger one about 100 fps faster than the previous one.
So, if you want any one to shoot bullets a few hundred fps slower, you
gotta reduce the pressure. That's done by reducing the powder charge.
If you check loading data with pressure listed and find a .30-06 and
.300 Win. Mag. shooting the same bullet with the same pressure, the
Mag will push it out a few hundred fps faster.
Ken Marsh
Bart B. <bar...@aol.com> wrote:
#I wrote:
## You *can*, but to get 30'06 velocities, you'll have to load to the same
## pressures as 30'06. No problem, but that means you'll have to load
## *more* powder than a 30'06 load, because a 30'06 load in the larger gas
## bottle of the 300WinMag chamber means lower pressure. So, you have to
## load more powder than the listed '06 load to get the same velocity.
#I'm surprized that you're saying the same case loaded to the same
#pressure with the same powder and bullet will produce different muzzle
#velocities. It's confusing to me.
Me too, since that is *not* what I'm trying to say. :O I guess I
wasn't clear.
What I'm trying to say is, if you put a listed 30-06 charge in the
larger 300WinMag case, same bullet, you'll get lower velocities than if
you put it in a 30-06 case. The reason, you have lower pressures in the
larger case.
<snip stuff I agree with>
Ken.
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Bart B.
# The biggest problem is grinding down the crown by rubbing the cleaning
# rod against it. What is the crown? It is the edge of the hole at the
# muzzle, where the bullet comes out, and the rifling ends.
reminds me of the M1 Garand (7.62 NATO) barrels I wore out when
shooting on US Navy Rifle Teams. I cleaned the bore after every 50 to
100 rounds.
When new, the bullet's copper wash (smear? fouling?) would extend all
the way out to the crown; both on top of the lands as well as in the
grooves. Cleaning these barrels was done from the muzzle with a solid
steel rod. None of us kept the rod perfectly centered and in time the
barrel metal wore away a bit.
One could easily see where the copper wash stopped. After about 1,000
rounds, the wash stopped about 1/16th of an inch behind the crown. At
5,000 rounds the wash stopped about 3/8ths inch back. In other words,
the bore and groove diameters had increased as the metal was rubbed
away by the steel cleaning rod. The bullet no longer touched the
barrel those last few fractions of an inch. And some barrels would
have the worn out area uneven around the bore such as a lot of wear at
the bottom but hardly any at the top. We called this the "blunderbus
syndrome" as the barrel was microscopically belled a few
ten-thousandths of an inch where the cleaning rod wore away the
muzzle.
Accuracy through 1,000 yards was the same throughout the barrel life
of about 3,000 rounds of best and 5,000 rounds of very good. And
sight settings for zeros at all ranges remained the same for each lot
of ammo.
Some folks on the Navy Rifle Teams got cleaning rod guides that
clamped on the muzzle and kept the steel rods from touching the bore,
but they had no effect. Accuracy with barrels cleaned this way was no
better than Garands cleaned without a rod guide.
We came to the conclusion that the reason wearing away the crown had
no effect on accuracy was that the crown's condition stayed the same
from shot to shot. Yes, the bullet impact will shift a bit when more
metal is lapped away at the crown, but not enough to be noticed
throughout the barrel life.
In talking with members of other service rifle teams, they noticed the
same thing. Wearing out the crown either uniformly around the bore or
more at one point didn't seem to cause accuracy problems.