Your opinion please........

[Ben]

I have a Ruger # 1 stainless 308 Win. It is one of my favorite .30 cal. rifles ( and I have MANY ) and is an extremely accurate cast bullet rifle. My favorite load is 18.5 grs. IMR 4198 with a g/c'd Lyman 311290 sized .310 ". My alloy is WW's with 2 % tin.

http://castboolits.gunloads.com/showthread.php?t=96037

I realize with stainless steel, I should have a LONG barrel life.

In your opinion , how many of these rounds would have to go down this barrel before I notice any appreciable loss of accuracy ? I'd be interested in seeing your opinion to this question.

Thanks,
Ben

[gray wolf]

I am not sure about cast bullet life with lead bullets, But I know with standard
loads and J bullets there are formulas that can be used to help answer your question.
I believe it has to do a lot with heat and barrel cooling between shots. Some powders are hotter that others. I also think that barrel throat erosion happens way before actual barrel
barrel wear happens.
I looked up the data once and was depressed to find out that 270 Win. barrel life was about 12 to 1,500 rounds with standard ammo. I think it is less with cast and softer loads.
Look at 22LR, 50,000 rounds is not uncommon, but not with high power rifles.
Ok now that my guess at the question has been given I will bet that many folks will say they get many, many rounds down the barrel, and that's good.
I would also like to know the correct answer to this OR at least get some good opinions.
My answer here does not reflect an expert answer--only what little I know about it.
But I do think some of my thoughts are valid.

Sam

[Ben]

Sam :

Thanks for taking the time to respond, you make some very valid points ! Thanks,

Ben

[waksupi]

Shooting cast only, this will only be a concern to your great great great grandchildren. I bet you will never have a noticable loss of accuracy in your lifetime.

[HORNET]

Heat, pressure and shock (including thermal shock) are what usually kill barrels. The load that you listed shouldn't run very high as to pressures and, if you don't shoot it fast, it shouldn't get hot very fast. That stainless barrel should be fairly resistant to that, so wear might enter into it. Some of the boys in the ASSRA will swear that the Antimony in wheelweights will wear out a barrel faster than straight Lead/Tin mixes, but they're still talking about tens of thousands of shots. Check the throat wear every thousand rounds or so and adjust the overall length accordingly and let us know how it's doing in ten years or so.

[felix]

Ben, the Hornet man Rick is correct. Pressure has nothing to do with it per se, but the heat generated by the pressure at the throat area does, and big time at that. Forget the lead versus copper thing. Yes, check every 1000 rounds or earlier when shooting 40-60K. 60 grains of powder at 60K is many more times more damaging than 25 grains of same, assuming the same location of 60K in the barrel. But, 4198 is much faster that 4831, so the 40K in your 308 would be a lot closer to the throat. The only way to check things is to measure the seating distance to the lands for the same accuracy from the new barrel start. Hopefully, you don't run of neck or boolit length for the duration of fun with that gun. ... felix

[Glen]

The most systematic comparison I can recall seeing was one done a number of years in which a serious bullseye shooter set up two 1911 .45 ACPs identically (match barrels), and then used one as a hardball gun, and the other to shoot only cast bullets. The accuracy capability of each was measured periodically by shooting a handful of groups from a Ransom rest, and the condition of the bore was monitored with a bore scope and by slugging. The history of rounds shot by each was meticulously recorded. As I recall, the hardball barrel had lost match-grade accuracy after about 5000 rounds, and showed significant wear on the lands/grooves. The test on the cast bullet gun was terminated after something like 150,000-200,000 rounds because the author wanted to publish his article. At that point, there was no loss in match grade accuracy, and no significant wear on the bore.

The comments about pressure and heat above are very good points, and admittedly, .45 ACP bullseye loads don't generate the same levels of pressure and heat that a centerfire rifle load is capable of, but the bottom-line is that if you pace your shooting and don't over-heat your barrel I doubt you'll ever see any measurable impact on accuracy from using the cast bullet load you describe.

[felix]

Glen, thanks! Because the heat generated is so low in the ACP (load and action type), I would guesstimate heat had no effect on the outcome. Maybe a lube thing more than anything. Too bad the test did not include moly coated bullets, at least for grins. ... felix

A way to tell is looking for micro throat cracks, which WOULD indicate heat effects! ... felix

[Mk42gunner]

I think heat has more to do with interior barrel wear than anything else--we all know that steel gets softer after it reaches certain temperatures.

I have no idea how many thousands of rounds you will be able to put downrange before the barrel wears out, but I am sure it will be fun to try.

I think you will be more likely to damage the bore by overcleaning than by shooting with your referenced load.

Robert

[Char-Gar]

Ben.. I would not hazard a round count as that would be a SWAG figure. But, like others, I don't believe you will live long enough to wear that rifle barrel out with that load or see any appreciable wear that can be compensated for as Felix said.

[DragoonDrake]

On a similiar thread to Glenn. I know a guy that bought a new Kimber 45ACP yearssss ago. The barrel finally cracked and he figures that he had between 275,000 and 300,000 rounds through it. He only shot lead.

[45 2.1]

With that load you would see the throat lengthen slowly and your great grandchildren will have a well polished barrel in that rifle. Change the alloy so the antimony content is about two to three percent and you will have better accuracy and longer (basically unlimited) barrel life.

[felix]

It is a never ending thing to determine the proper metal mix and match for making jet engine parts. Yep, it's heat damage versus mechanical damage. Performance curves become really interesting when heat with an alloy are recorded to the point of failure. It's even more interesting to look at the smoke stacks (water vapor, really) when live chickens are thrown into the engine's intake. Pure white becomes off-white in a jiffy. Tree huggers make Pratt and Whitney and everyone else use graveyard dead chickens/geese/ducks nowadays. ... felix

[felix]

Larry, what is the pressure of Ben's load as indicated. Anything in your notes anywhere close? ... felix

[Tatume]

Barrels used for high power rifle competition have a typical life of anywhere from 2000 to 7000 rounds. Usually they can be set back a thread for another 2000 - 3000 rounds of competive accuracy. This assumes a high master shooter who expects across the course accuracy in the 97 - 98% range, or better. These are maximum or near-maximum loads with jacketed bullets.

A barrel that is removed from competition will usually be sufficiently accurate for a lifetime of hunting, again with jacketed bullets.

I doubt that a gun that is used with cast bullets and typical cast-bullet loads will ever show a significant decrease in accuracy attributable to wear or use.

[old turtle]

It will take a long time for the lead (forcing cone) anyway the beginning of the rifling to wear out with cast bullets. The even better news is that when it does you can just have the barrel set back a thread or two an have at it again. This is th area of a barrel that wears out and leads to inaccuracy. Assuming you do not mess up the muzzle or mess the barrel with improper cleaning

[old turtle]

Tatume beat me to it. My feelings also. He is right on.

[HangFireW8]

Heat has been touched upon, but I'd like to mention the related factors of rapidity of fire, and bore ratio.

Firing high pressure loads quickly, one after another, in an increasingly hot barrel will yield a lower lifetime than allowing the barrel to cool thoroughly between shots. One thing I really like about cast boolits is that I can bang away like a .22LR with my hunting rifles with nary a care for barrel temp. When I'm done it is just warm to the touch, not too hot to hold.

Bore ratio is kind of obvious when you think about it, a 220 Swift or 7mmRemMag is not going to have the lifetime of a 222 Rem or a 7x57. You have to load a few percent more powder just to get up to the same level of performance as the smaller chambering, which means you have more gas rushing through the same-size throat.

Friction in the bore is less of a strict mechanical wear-n-tear issue than a temperature issue. Jacketed bullets have greater friction, while the 1/10,000th of an inch extra bore and rifling wear that generates is not a big issue in the entire lifetime of the barrel, the heat that it generates pushes the barrel temperature up the temp curve faster to the point where throat erosion occurs sooner.

OK, so I know the issues of temperature and mechanical wear are linked at the hip, my point in the last paragraph is simply letting the barrel cool down between shots will compensate for a lot of the wear difference between jacketed and cast. But not all the difference.

-HF

[mpmarty]

Prime example of ratio of bore to case capacity is the .264 Win. Mag. That thing ate barrels at an alarming rate.

[1Shirt]

Just a wild guess, but would bet with your load Ben, that 10-15 thousand just might be very much on the conservative side. Lots of words of wisdom in the replies, but gotta love the response from Felix as one of the best I have seen in awhile!
1Shirt1:coffeecom

[Bret4207]

I always thought of barrel wear as erosion. Works about like water in my mind. Gentle waters/loads erode rock slowly, polishing the rock over a long period of time. Spring flood waters/hotter loads with their higher volume and speed and rocks and dirt do it faster. Some yahoo with a jackhammer/cleaning rod can do a lot of damage muy pronto.

I'm betting cast will offer basically unlimited shooting, in this lifetime anyway.

[HangFireW8]

I'm betting cast will offer basically unlimited shooting, in this lifetime anyway.

If I wear out a barrel with cast, I'll say to myself, "that's a job well done".

BTW Felix, any truth to the "don't use frozen chickens" story?

-HF

[felix]

HF, I have no idea about things done today to check out engines. Back in the early 70's it was all live birds, and all kinds of sand, big, little, and all points in between. The military engines had other kinds of tests which I was not privy to (no active security clearance at the time; goggle explosion proof motors for an idea ). ... felix