Ok Nobody string me up for this one lol! This is a Formula that seems to calculate accurate barrel life preety darn close YMMV.
C/ Does anyone have the complete (barrel life) equation?
Yes, I do. I originated it on rec.guns years ago. And yes, it's
empirical. Over many years of competitive shooting, I learned from
all the top-scoring shooters their loads and rounds of accurate barrel
life. The key thing here is "accurate" barrel life by their
standards. In highpower competition, accurate barrel life ends when
shots missing where called by about 1/3rd more than when the barrel
was new and in its prime. In other words, when the barrel's grouping
ability is about 33% bigger.
The most common cartridge used until the mid 1960s was the .30-06 with
powder charges about 48 grains of powder. Top shooters would
typically rebarrel at about 3000 rounds; most would not enter the
Nationals with more than 1500 rounds through their current barrel.
Note that this number is based on shots at a rate of one per minute
for 10 to 20 minutes. For rapid fire at one shot every 6 seconds for
one minute, each of these rapid-fire shots is worth two of the
slow-fire ones. If lots of rapid fire is done, then naturally the
barrel life is shorter. I started looking at some fact about this
cartridge I could equate to its barrel life. It just happens than the
cross sectional area of a 30 caliber bore is about 48 square
millimeters (calculated with bullet diameter). It would seem that a
powder charge equaling 1 grain for each square millimeter of bore
cross sectional area means 3000 rounds of accurate barrel life.
Then I looked at other competition cartridges' barrel life as reported
by top scoring competitors:
.222 Rem.; 24 sq. mm, 21 grains, 4000 rounds.
.22 PPC; 24 sq. mm, 24 grains, 3000 rounds.
6mm PPC; 30 sq. mm, 28 grains, 3500 rounds.
.243 Win.; 30 sq. mm, 38 grains, 1600 rounds.
6.5x55 Swede; 35 sq. mm, 42 grains, 2000 rounds.
.264 Win. Mag.; 35 sq. mm, 72 grains, 600 rounds.
7mm-08; 41 sq. mm, 41 grains, 3000 rounds.
7mm Rem. Mag.; 41 sq. mm, 61 grains, 700 rounds.
.308 Win.; 41 sq. mm, 43 grains, 3500 rounds.
.30-.338 Mag.; 41 sq. mm, 65 grains, 1400 rounds.
.300 Win. Mag.; 41 sq. mm, 72 grains, 1000 rounds.
.300 Wby. Mag.; 41 sq. mm, 91 grains, 800 rounds.
This was a most interesting discovery. Cartridges using powder
charges equaling bore area (bore capacity?) got about 3000 rounds of
barrel life. Those using charges twice bore capacity got about
one-fourth of that or around 750 rounds. And those using less got
more than 3000 rounds. I've wondered where the term "over bore
capacity" came from; maybe this is why.
I did some trial-and-error math routines to come up with formulas to
plot a curve that fairly well tracked these numbers. Such empirical
processes have been used since the 1920s to calculate non-linear
ballistic cams used in military mechanical analog computers for aiming
large caliber guns with great accuracy results. So, I figured it
would work for this situation, too.
My formula is:
1. Calculate the bore area in square millimeters using bullet
2. Use one grain of powder for each square millimeter. This is what I
call the reference, or bore capacity powder charge. Example: .30
caliber bore, .308-in. (7.82 mm)bullet diameter = 48 square
millimeters. Bore capacity powder charge for .30 caliber is then 48
grains. A .30 cal. cartridge that burns 48 grains of powder (.30-06)
gives a barrel life of about 3000 rounds of best accuracy.
3. If a larger 30 caliber cartridge is used and it burns more powder,
the accuracy life in rounds for that bore size is reduced. The amount
of reduction is determined by:
a. Divide the increased charge by the bore capacity, then square the
b. Divide that answer into 3000. Example: A .300 Wby Mag. has a bore
capacity of 48 grains. This cartridge burns 91 grains of powder.
(91/48) squared is 3.6. 3000 divided by 3.6 is 833 rounds. Three
competitive shooters told me their .300 Wby. rifles gave them between
800 and 900 rounds.
This also seems to work when using powder charges less than bore
capacity. The .222 Remington was the winning cartridge in benchrest
matches until the PPC family came along. It burned about 21 grains of
powder in a barrel whose bore capacity is about 24 grains. So,
(21/24) squared is 0.7656. 3000 divided by 0.7656 equals 3918 rounds.
Top benchresters in the ‘50s and ‘60s rebarreled their triple-deuce
stool guns at about 4000 rounds.
But this empirical formula has limits. The old .22 rimfire long rifle
burning 1 grain of powder in a bore whose capacity is 24 grains would
calculate to give a barrel life of some 1,728,000 rounds. But the top
international shooters I've talked to rebarrel their $4000 Anschutz
free rifles at about 25,000 rounds. And then there are thousands of
folks who claim a .22 rimfire barrel will never wear out.
And bore material and manufacturing processes can make a difference,
too. Most top-quality 30 caliber barrels get about 3000 accurate
rounds for the .308 Win. There's one make that gets about half that;
but they've been used to win the Nationals and other big highpower
matches more than once.
The intended firearm use and accuracy expectations comes to play, too.
Take the M1 and M14 service rifles. Their typical combat barrel life
established by arsenals is about 10,000 rounds with service ammo.
It's accuracy requirements was (as I remember) about 3.5 inches at 100
yards. Compare this to top competitive highpower shooters
requirements of no more than 1/4th inch at 100 yards. That's what it
takes in highpower to stay under 1/3rd MOA at 200 yards, ½ MOA at 600
yards and 3/4ths MOA at 1000 yards.
If anyone can shoot a hole through this theory, I welcome that shot.
This is more or less an emperical process based on accurate barrel
life in several calibers as reported to me by lots of folks plus a
couple dozen barrels I've worn out. All I did was study the data and
determine what math would give a best-fit formula. And if someone has
a better method, I'd like to know what it is.
And if your experience differs with this data, that's fine. Make your
own barrel life determinations based on what you observe using your
own accuracy standards. I don't expect everyone to have the same
standards, but it helps when they're realistic for the shooting
discipline. We all get to decide the most we want to miss where we
call the shot on the targets of our choice; animal (game & varmints),
mineral (metallic silhouette) or vegetable (paper targets).
So According to this Fig Kirby your 7mm Allen Mag is as follows
7mm. 41 sq. mm, 118 grains
118/41 = 2.88 squared = 8.29 Then Didvide that bye 3000 = 362 rounds
Now just for [censored] and giggles lets figure the 122 grains that you say you can gain with it re-throated
7mm. 41 sq. mm, 122 grains
122/41 = 2.98 squared = 8.88/3000 = 337 Rounds Whew unless this formula is really jacked up ..That is a bbl SMOKER [img]/ubbthreads/images/graemlins/shocked.gif[/img] Now before I get jumped...I know Kirby has his own figures on these Carts..His figs are for a sporter weight rifle use to 700 yards on deer size game..I believe his figures are about right + or - a few rounds :-)
and as Kirby stated powder choice will play a big role in throat erosion Kiby I must say has takin all thse factors into consideration.. and designed these carts for optimum bbl life...Man I still want one Kirby..that 7mm Allen Mag has reall peaked my interest...AGAIN LOL!
String you up? Why? Everyone is entitled to their opinions, right or wrong.
I just don’t see the point in posting something, before the ink is dry on the first posts about the new 7mm Allen Mag., that seems to, in effect, tell someone that he has pretty much wasted his time, money and materials and that what he is saying is probably not true. Then at the end you edit it as though you didn’t really mean it and that Kirby’s statements are right, by his figures, + or – a few rounds.
Ever think what statements like yours, based on mathematics mostly, could possibly do to someone that has put as much as Kirby has into research, experimentation, investing his time and money and then sharing it with anyone that wants to read about it? I guess not. You can’t un-ring a bell.
I, for one, do not buy what your figures are saying. I do however, believe that Kirby has some very powerful and well designed cartridges for the modern hunter wanting the best possible long range solution to his hunting needs.
I also believe enough in the Allen Magnums that I have invested several thousand dollars, and waited a long time, and one of those Nesika actions Kirby mentioned for the 7mm Allen Mag. is mine, and he has another action I sent him that will be re-barreled in 270 Allen Mag.
I will dearly love to see how many rounds I can put down the tubes to prove your figures wrong. If you’re right, the poor gun will be worn out before I even get it out in the fields and hunt with it.
Time will tell, but I can guarantee you that I will document every round as well as the accuracy. Stick around and we’ll see how they perform.
I guess I might as well send back some of the 200 grain Wildcats since I will only need 4 boxes, with some left over.
And Kirby, I will make you an offer and take that worn out 270 Allen Mag off of your hands even though it has 300 rounds through it and is probably worn out.
My money is on Kirby and the Allen Mags and I for one, would not hesitate to order another.
ss7mm No hard feelings man..I edited because I had more to say...those figures are done on BR requirements...not a hunting rifle...I was not bashing Kirby..NOT AT ALL! Hell I can't wait to get one of his AM done up for myself. I never said these figs were set in stone ...but they do seem to be accurate for BR shooters. I remember whan Kirby fisrts started this venture...I was excited..well still am :-) I think thse carts are going to be a huge success! are they going to produce BR accuracy after 4-500 rounds ...doubt it...but for hunting I don't think you could get any better.
Go ahead and run the Formula and base it on BR performance requirments...if you find it to be way off then I will delete it. I guess I should have started a new topic for this formula...but somebody asked what bbl life was to be expected out of thse huge carts.. not totaly accurat..as I stated in my first post this is comparing apples to oranges... Kirby's AM's are Hunting Carts not BR.
Long range D t
I will just make a couple of points.
You are extrapolating a long way from where you have any data. With only three peices of Wby 300 data which has a water capacity of aboout 100 gr you happily go into the 120 gr range where you have no data. You acknowledge that metallurgy has made considerable progress since some of your data was collected and there are now 5C and 3 grooves.
What it takes to win at benchrest and what it takes to make a kill on an elk are two different size groups. If a gunsmith can build a 0.2 MOA gun that will finally need to be re barrelled at 1.0 MOA then the spread of accuracy is greatly different from benchrest and affects the end point of your prediction.
Right now I am working on a barrel that will no longer hold under 1.0 MOA with the same bullets that it would shoot when it was new. But I can "trick" it by going to 160 Accubonds and 175 SMK and it shoots just as tight of groups as it did when it was new. Bench rest shooters cannot rely on "tricking " thier gun with longer bearing surface bullets. They have to win. (Actually it seems to me that Benchrest shooters do more standing around visiting with each other than shootings and that who wins is secondary to getting to talk to everybody). This gun would never shoot under 0.5 mainly because I never shoot under 0.5. So according to your theory it would need to be rebarreled before it was even shot. In fact according to your theory ever gun I have ever bought or would ever buy would need to spend its entire life with the gunsmith because of my shooting skills.
I hope this wasn't insulting. I am trying to barbcue some ribs and have to keep running outside. If I burn them I am really going to be mad at you because that is $23.00 of really good ribs out there.
Any Way back to the important stuff
Kirby - my time frame is something like this. My son will have to decide in March of 2006 where he is going to college and that will determine tuition costs. Tuition costs determine if I can retire. If I retire then I will need a really fine new elk gun. I will think about what you said about the extraction problems and see what can be done. My heart is set on a single shot bolt action.
Now before this gets into a huge ******* match, lets end this right now!!!
I appreciate the kind words and support from ss7mm, I also appreciate the comments of LRDT. No offense taken.
I do have a response for LRDTs post and I will make it in several different points:
1. As you have stated your predictions are based on BR rounds. Now I am not a BR nut but I do know they have a certain about of rounds they have to get down the bore in a relatively short amount of time. When conditions are correct, or favorable, at least in long range BR shooting, the qualifying rounds get sent down range as quickly as possible. This is why rounds such as the 6.5-284 lead the pack in popularity, because they are easy to load, easy to tune the loads and also relatively easy on the barrel.
That said, I am not building BR rounds. If that was the case I would shoot a 25-284 with Richards 156 gr ULD RBBT bullet with its BC of +.8 which would out perform the 6.5-284 substantially at 1000 yards when the later is using a 140-142 gr VLD.
The Allen Mags are designed for one reason, to give the big game hunters as much controlable performance in velocity, trajectory and limited wind drift as possible without excessive recoil and in a rifle that is portable. They have all done this and done so very well.
If you are a tinkerer, in that you are always looking for that new load that will take .1" off your group average, then please consider the Allen Mags NOT FOR YOU because you will burn the barrel out looking for a good load.
But if your looking for the ultimate in performance in a round that will delieversub 1/2 moa consistancy in a big game rifle and offer legit 1000 yard performance and power for deer size game, these are on the top of the performance pile.
2. As big game cartridges in big game rifles, these are not intended to be fired like a BR rifle is. YOu develope your load, which should take no more then 50 rounds to be honest in one of my Extreme Sporters, and then you practice from time to time to stay proficent and use the rifle hunting big game where it will actually be used very little for actual field shooting as most on this board would agree that the actual big game season is pretty boring as far as shooting goes. Generally only a few shots a season are taken. Used in this way, 1000 rounds would easily last 8 to 10 years depending on how you practice and how much you hunt, and finally, how good of a shot you are.
3. I was after performance. I wanted to offer true 600 yard reach in a sporter rifle with very minimal hold over or dial up. These rounds do that. Using a standard mil bot scope on one of these rifles and sighted in 2 1/4" high at 100 yards, the second dot down will be a dead on hold from 600 to 650 yards depending on which Allen Mag you have and how hard you are driving the pressure.
To acheive this, we need horse power. If you want a car to get great gas milage you get a little four cylinder and be happy with having to have a 1/2 mile to pass a fellow driver on the road. If you want power you get a big block that can break the tires loose when you down shift at 50 mph!!!
There are trade offs, just like rifles, big engines have larger appitites and shorter lives. Just how things are.
But if you take care of both your engine and your rifle, you will have that power at your fingertips for many years to come. Luckily, rebarreling your rifle costs about 10% what an engine rebuild would run and to be honest would cost less then buying a new factory rifle these days.
So while I would say for BR shooting your statements may have some credit, for these rounds used the way they were designed, its like apples and oranges.
You get the barrels hot on these rounds and keep shooting and yes you will smoke your barrel in 400 yards. You keep the barrel cool and clean and you will get several times this amount of shooting.
There are certainly prices to pay for extreme performance, barrel life is one but used correctly it is not such a sad story as you portray it to me.
I mean saying a 243 only has a 1600 round barrel life seems a bit extreme to me personally, unless you shot those 1600 rounds in the same week [img]/ubbthreads/images/graemlins/grin.gif[/img]!!
No offense taken by your post, but I will say that in the last five rounds out of my 270 Allen Mag, two were center hits on rockchucks at 1098 and 1114 yards and one was a miss by only inches at 1255 yards. Now this barrel is coming up on 300 rounds down the bore, what will I see when the barrel lets loose in another 50 to 60 rounds???
I'll let you know when she stops producing minute of rock chuck at 1K.
Many told me I was wasting my time with the Allen Mags saying the performance was not worth the shorter barrel life. Fortunately for me most of those people failed to consider anything but stricty the barrel life of the barrel and never realized that there are ways to increase barrel life by using special rifling design, powders and throat designs, combined with heavy for caliber bullets. This is why the Allen Mags work as well as they do, because we did some homework on paper and then tested the hell out of them on the range and they work.
DO they have the barrel life of a 280 Rem, NO!
Can a 280 Rem drive a .950 BC 200 gr bullet to 3200 fps, Not that I have seen yet. When that happens we will be in business for extreme range performance and long barrel life!!
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
Any time you are ready my friend we can design your rifle. We can always work on the cost with different options to get you what you want. By then you will have an entire host of Allen Mags to choose from!!!
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.