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Thread: Barrel Burnout

  1. #1

    Default Barrel Burnout

    I recently had my Ruger M77 7mm Rem Mag bore scoped because I suspected the barrel may have been burned out because of degraded accuracy. The gunsmith said the throat was burned out and the bore pitted. It was chrome molly made about 20 yrs ago.


    I’ve been thinking about this and it seems a little early in the barrel’s life to have this happen. There have been a maximum of 600 rounds through it. When working up loads I always backed off after seeing signs of excessive pressure, stiff bolt and excessively flattened primers. The loads I have used for it seem to work fine as in easy working bolt and not excessively flattened primers. I always kept it clean except, I did leave it dirty after one hunting season. I almost never fired it without letting it cool except a few rapid fire, four shot groups occasionally.

    I’ve done some research on barrel life in the past and have read typical barrels should last anywhere from 1000 – 5000 rounds.

    So I am wondering why the short barrel life? I figure it takes maybe 100-200 rounds just to break a barrel in and work up loads for it. Then it would be good to fire 50-100 a year through it to stay proficient with it. At that rate it doesn’t take long to reach 600 rounds. Would like to avoid this in the future.

    Any thoughts? What have other folks experienced with barrel life and degradation?

  2. #2

    Default

    That truly was a short life for a 7mm mag, that is interesting and unusual
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  3. #3

    Default alternative thought

    Quote Originally Posted by MontanaRifleman View Post
    I recently had my Ruger M77 7mm Rem Mag bore scoped because I suspected the barrel may have been burned out because of degraded accuracy. The gunsmith said the throat was burned out and the bore pitted. It was chrome molly made about 20 yrs ago.


    Iíve been thinking about this and it seems a little early in the barrelís life to have this happen. There have been a maximum of 600 rounds through it. When working up loads I always backed off after seeing signs of excessive pressure, stiff bolt and excessively flattened primers. The loads I have used for it seem to work fine as in easy working bolt and not excessively flattened primers. I always kept it clean except, I did leave it dirty after one hunting season. I almost never fired it without letting it cool except a few rapid fire, four shot groups occasionally.

    Iíve done some research on barrel life in the past and have read typical barrels should last anywhere from 1000 Ė 5000 rounds.

    So I am wondering why the short barrel life? I figure it takes maybe 100-200 rounds just to break a barrel in and work up loads for it. Then it would be good to fire 50-100 a year through it to stay proficient with it. At that rate it doesnít take long to reach 600 rounds. Would like to avoid this in the future.

    Any thoughts? What have other folks experienced with barrel life and degradation?
    Before admitting a blown barrel, I'd sure go to work with a good copper fouling remover. I've had pretty good luck buying "shot out" guns, then simply cleaning the bore thoroughly to restore superb accuracy.

    BTW- My Rem 700BDL in 7 mag was purchased new in 1972. I can document a little over 6000 rounds through it from my loading log, and most of those were at or near mag with the old surplus 4831. It will still break 2" at 200 yards for three shots with a fair variety of bullets. So something is definitely haywire with yours. I'd bet on copper fouling if you've never used anything but Hoppe's #9 or anything similar.

  4. #4

    Default

    I have a very good friend that works at a well known custom gunsmith who tells me it is not at all uncommon to see rifles in 257, 264, 7mm and some 300 magnum calibers that have significant throat erosion by the time 600 rounds are reached. Stainless is better than chrome moly in this regard but it isn't foolproof.

  5. #5

    Default

    Quote Originally Posted by BrownBear View Post
    Before admitting a blown barrel, I'd sure go to work with a good copper fouling remover. I've had pretty good luck buying "shot out" guns, then simply cleaning the bore thoroughly to restore superb accuracy.
    Yep, I thought of that. I soaked the bore 7 times with wipe out bofore taking it to the gunsmith. There wasn't a trace of copper in it. It was probably one of the cleanest barrels he had ever seen. The next day I took it to the range (as reported in another thread) and was getting 1 1/2" - 2 1/2" groups with occasional flyers, and a 5 1/2" 5 shot group at 200 yds.

    Quote Originally Posted by dorm View Post
    I have a very good friend that works at a well known custom gunsmith who tells me it is not at all uncommon to see rifles in 257, 264, 7mm and some 300 magnum calibers that have significant throat erosion by the time 600 rounds are reached. Stainless is better than chrome moly in this regard but it isn't foolproof.
    All my rifles in the future will be stainless, including the Finnlight I just got...one good benifit from this

  6. #6
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    Default

    I haven't shot out any barrels but I recently discovered the throat on my 338 WM has eroded about 10 thousandths of an inch. I didn't keep precise records but I estimate I have fired 600 rounds through it since 1993.

    I too would expect you could get more than 600 rounds through your 7mm Rem Mag. How far is your throat eroded? I was able to seat bullets closer to the lands to compensate for my throat erosion. Is that possible in your case?

  7. #7

    Default

    Quote Originally Posted by sep View Post
    I haven't shot out any barrels but I recently discovered the throat on my 338 WM has eroded about 10 thousandths of an inch. I didn't keep precise records but I estimate I have fired 600 rounds through it since 1993.

    I too would expect you could get more than 600 rounds through your 7mm Rem Mag. How far is your throat eroded? I was able to seat bullets closer to the lands to compensate for my throat erosion. Is that possible in your case?
    Not really sure how far the throat was eroded, but the smith thought the barrel was basically toast. And nope, cant seat the bullets any closer. They barely fit into magazine now. Good thought though.

  8. #8
    Member shphtr's Avatar
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    Default Shot Out Barrel

    600 documented rounds is an exceptionally short barrel life for a 7 mag. Even with the sig'ly over bore 7 STW, 7 Dakota, and 7 RUM one would usually expect at least 1000 rounds if given even a modicum of care. Still...it is what it is. Maybe bad metalurgy....definately bad luck! Look on the bright....as in new barrel! Stainless is a good idea. It sounds like you did everything right.

  9. #9

    Default yup

    Quote Originally Posted by shphtr View Post
    600 documented rounds is an exceptionally short barrel life for a 7 mag. Even with the sig'ly over bore 7 STW, 7 Dakota, and 7 RUM one would usually expect at least 1000 rounds if given even a modicum of care. Still...it is what it is. Maybe bad metalurgy....definately bad luck! Look on the bright....as in new barrel! Stainless is a good idea. It sounds like you did everything right.
    I agree that it sounds like time for a new barrel too, but I'd get a rod guide while you're at it. I can't buy bad metallurgy from Ruger as the cause. I've got a 77 in 25-06 that dates back to the mid-70's, and it's lived a very full life shooting thousands of rockchucks, ground squirrels and prairie dogs, shoots that feature real hot loads of slow powders, sometimes firing 20 or 30 in a row quickly with no barrel cooling allowed. I bet it's popped twice as many rounds as my 7mm mag while still giving comparable accuracy.

    If you don't want to rebarrel, I'd look at the crown of your rifle and consider recrowning. I'd expect crown damage to cause accuracy loss such as yours after only 600 rounds or so, but I find it hard to accept that throat erosion could destroy accuracy so quickly or so thoroughly in a 7 mag barrel.

  10. #10
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    Default

    I shoot a lot and have shot out exactly 1 rifle barrel in my life. It was a 30-06 and I shot approximately 5600 rounds through it. Some of the shooting was to see how quickly I could ruin it because I wanted to change cal. I pulled the barrel after the 5600 rounds and it was eroded about 1/3 of the way up the barrel but it would still shoot 1" at 100 yds!!!

    I sure hope your 7 mag would take more rounds. Will the guy let you look using the bore scope? Good luck. J.

  11. #11
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    Default

    One other thought, if you believe the inaccuracy is because of bullet jump, you can set the barrel back by one turn and then rechamber. Not sure how much that would cost but much less expensive than a new barrel but if the barrel is not good, it won't help much.

    I just think the barrel has to be good for more than 600 rounds. If not, that sure sucks. J.

  12. #12

    Default

    I just inventoried all my 7 mag cases. I have about 350. Can't remeber if they were all factory, I may have bought 50 or 100 virgin cases? And I know I have lost a few over the years. Also, I have another 7 mag (S&W M1500, made by Howa), and I've shot that rifle maybe 100 - 200 times. The cases all have been fired anywhere from 1-5 times, so now I'm guessing it's possible that I may have put 1000 rounds through it? (BTW, the S&W is out of commission because of a factory saftey notice that needs to be fixed)

    From reading you guys, I should still be seeing more performance out of this barrel.

    I used to get about 3/4" groups out of the M77 and almost overnight it degraded, so maybe there is another problem or combination of problems? I did have issues with the rear lug screw, which I thought I fixed?

    I'm taking it to another smith for a second opinion, but he doesn't have a bore sight.

    Quote Originally Posted by shphtr View Post
    Look on the bright....as in new barrel! Stainless is a good idea.
    Yeah, I do plan to rebarrel this rifle someday and get a new stock, probably a McMillan, I like the old M77 tang safety action.

    Quote Originally Posted by BrownBear View Post
    If you don't want to rebarrel, I'd look at the crown of your rifle and consider recrowning. I'd expect crown damage to cause accuracy loss such as yours after only 600 rounds or so, but I find it hard to accept that throat erosion could destroy accuracy so quickly or so thoroughly in a 7 mag barrel.
    I cant see anything wrong with the crown, but I don't have a trained eye for that, so, I'll have the smith check that too.

    Quote Originally Posted by OldRgr View Post
    I shoot a lot and have shot out exactly 1 rifle barrel in my life. It was a 30-06 and I shot approximately 5600 rounds through it. Some of the shooting was to see how quickly I could ruin it because I wanted to change cal. I pulled the barrel after the 5600 rounds and it was eroded about 1/3 of the way up the barrel but it would still shoot 1" at 100 yds!!!
    Wow, 5600 rounds, erroded 1/3 the way up and shooting 1"... That is something. I'll take a closer look at this.

    I sure hope your 7 mag would take more rounds. Will the guy let you look using the bore scope? Good luck. J.
    Yeah, he did let me look in the scope and I saw the pitting, but didn't know what to look for in the throat. He pointed out the lines, scratches, grooves or whatever and said it (the throat) should look smooth.

    Quote Originally Posted by OldRgr View Post
    One other thought, if you believe the inaccuracy is because of bullet jump, you can set the barrel back by one turn and then rechamber. Not sure how much that would cost but much less expensive than a new barrel but if the barrel is not good, it won't help much.
    I think that is a great idea and I'll ask the smith about it.

    Thanks for all the help. And if anyone has any other ideas, great. I'll keep you posted on what i find out.

    Mark

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    Default Good cleaning

    I ran in to this very problem with a remington ADL chambered in .270 that I bought back in 1980. I too thought I had shot out the barrel since I had shot thousands of rounds through it. I was in the process of deciding what caliber I wanted to rebarrel it in. I decided to give it an aggressive cleaning and was amazed at how much copper fouling I got out of that barrel. It shoots like new again! I spent the better part of two days running a copper solvent down the tube with a patch, then running a bore brush through it, let it sit for five min to disolve the fouling. I them followed it up with dry patches. When the dry patches came out clean I decided I was done. I would try a through cleaning before I put any money into having another tube installed.

    Just my 2 cents.

  14. #14
    Member shphtr's Avatar
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    Default bore scope evaluation

    Having a bore scope is one thing, but KNOWING what one is seeing/looking at is another. Having a bore scope does not make one an expert. It is my understanding there is a significant learning curve to accurately interrupt what is observed in the scope and it's relevance to the problem at hand. Lastly, what really matters is HOW THE BARREL shoots. It is well recognized that a scoped barrel may look "terrible" and yet still produce acceptable accuracy...and of course the reverse is true. If your rifle's accuracy decrement was rather precipitous I would suspect some other etiology than a "shot out barrel" which should GRADUALLY lose its usual accuracy. Intuitively those are the conclusions that I come up with. Good luck.

  15. #15
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    Default

    I've run into this discussion ALOT over the years and it seems the early Rugers had rough(not inaccurate bores)and fouled fast. First one I came across was a guy I went to work with who was getting rid of his .270 Ruger because it quit grouping and the bore "looked smooth",as in shallow rifling,and figured it was shot out. It was one of the hardest rifles I've ever cleaned up but it worked. I'd definitely go with a good,aggressive clean out before giving up on a barrel. GOOD LUCK!!

    til later

  16. #16

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    Montanarifleman, are you going to have it rebarreled or rechamber and if so what are you thinking of doing? Will you go with 7mm Rem mag or something else. I think there is a lot more to accuracy with a barrel than just how smooth the bore and throat might be, such as concentricity (How centered is the bore in the barrel), uniform depth/width of grooves, uniform height/width of lands, and the amount of lands/grooves. Also, it is very important how stress was relieved in the barrel after cutting the rifling along with how the rifling was cut and how centered is the crown. Another consideration would be how even is the leade-cut. When they cut the chamber, the head of the reamer cuts the leade( distance between the Ogive of the bullet and the rifling). Now if you are considering having your rifle rebarreled with a custom barrel and the smith does the chambering and if the reamer's been re-sharpened and some do because they cost a lot to manufacturer and this is done at least once in a reamer's life there can arise a problem. Sometimes the Leade-cutter doesn't get sharpened evenly and some parts of it cut deeper into the rifling "forward" than the rest, giving it an angled-oval look. Now this causes the bullet to not enter the rifling centered. this produces a little yaw when the bullet leaves the bore, opens up the group. Of course this does not happen often but when it does your groups are big and generally someone has spent a lot of money for a rifle that will not shoot good groups no matter what. Pick a good smith that has a good reputation for detail and attention to his work and I would really like to know what you decide to do when you rebarrel your rifle, like what barrel you will use and cartridge you choose.
    A GUN WRITER NEEDS:
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  17. #17

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    Beartooth, A lot of good info there, I really appreciate it. Right now I am going to see if I can get this barrel firing well again unless this other smith thinks the barrel is shot, like a bulge or something. The next time I take it to the range I'm going to swap out scopes, I have two Identical ones, and one is in almost new condition. The next step would be to put a new stock on it which I would rather do than reinforce, pillar and bed this one. I would like to get a McMillan with an aluminum bedding block. If this doesn't work and the crown is ok, I'll probably abandon this barrel for a new one, I was consdering going to another caliber but will probably keep it in the 7 mag. I have been liking the idea of getting a 300 RUM or 338 RUM or both someday, but for that, I think I will start from scratch.

    If I do decide on a new barrel, you will probably see a new thread for opinions on good barrels I have been thinking about Lilja barrels but have heard some conflicting reports on those, sometimes you get a real shooter and sometimes not, I heard about a guy in Livingston who supposidly makes a real good barrel. Would like to keep this a Montana project if I can, but quality is most important.

    You're absolutley right, I need to get a good smith, so I'm going to be doing some research. You mentioned you had friends down here who made rifles and if you or they have any recommendations I would be glad to hear from you. You can PM me. I'll be asking all the shooters I know around here.

    This will probably be a drawn out process, especially since I am getting my 300 WSM together and want to concentrate on that as soon as I can pay off my Nightforce scope. Hope to get it up to speed by antelope season. Right now I basically have a 200-250 yd rifle to get me through the spring bear season.

    I'll keep you all posted on the progress

  18. #18

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    tradbowkill and 300S&W, I thoroughly cleaned the barrel as mentioned in an earlier post. All the copper was removed, before being bore scoped and taken to the range, Thanks for the $.02

    shphtr, I tend to agree, if it was barrel burn out, one would think it would be a gradual process, another guy I talked to thought it might be a bulge in the barrel. It looks like there are a few possibilities.

  19. #19

    Default

    Last year I had a rifle that suddenly lost accuracy. I thought it was clean, but I thought wrong. I got a lot of crud out of it and it shot better, but not what I was used to. Even though I couldn't see anything wrong with the muzzle, I invested in an 11 degree target crown cutter, and what a difference after recutting the crown. The throat of this barrel is so eroded that with some lightweight bullets I can't even get them to touch the lands and still be in the case. But it will now shoot a third of an inch at 100 yards with W748 and 50 gr. Hornady SX's. Technically it needs a new barrel. In practical terms it is still serviceable. One thing about a crown cutter is that all you need is different arbors for different calibers, so it's useful for all your rifles. It's worth a try when nothing else seems to work. I still haven't decided who to send it to for a new barrel when I can't get it to shoot under an inch anymore. Good luck.

  20. #20

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    Check Livingston out first because I have heard the same that there are some real good gunsmith's in Montana, I mean really good gunsmith's the "A-Class" type.
    A GUN WRITER NEEDS:
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    THE HIDE OF A RHINOCEROS

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