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Thread: M77 MKII misfiring

  1. #1

    Default M77 MKII misfiring

    I purchased a 300Wm from a close friend , and it fired one box of remington ammo , I was there when it fired those 20 rds , since I purchased it , it has missfired 14 times in 100 rds . I was thinking primers , but I loaded for several different rifles from that same batch of primers and havent had any misfire . I suspected the bolt was dirty internaly so I gave it a serious bath with brake clean and lubed it with remoil , same result 15 misfires outa 100 . Im leary of takin the bolt apart ,after watchin my smithy put the bolt back togather on my 358 NM . Has anyone had a cci primer problem or bolt problem like this , I have 3 other M77's and havent ever had a missfire.
    Thanks in advance

  2. #2
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    did you save the misfired cartridges? what do the primers look like? the problem should show up there. maybe you could try loading with federal primers for a few hundred rounds, and see if you get any misfires.

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    I would send it back to Ruger. They will fix it for free if it will not fire factory rounds. Make sure your reloads are not defective first.
    Tennessee

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    Default Yes

    Yes, I have had a similiar problem w/some of my bolt guns. I decided it was a combination of the cold (making firing pin fall sluggish), and hard CCI primer cups.

    Take the rifle out to the range, shoot it until it misfires. Once you have a confirmed misfire, pull the bolt out and keep in a warm vehicle between shots. Only take it out to shoot. If it quits misfiring you have grease in the bolt that is freezing. If it doesnt quit misfiring, try winchester primers (soft cups). Another option is to prime some empty brass, pull the bolt and put it in the freezer overnight and see if it make the primers go off. If not, you have grease/oil/etc in the bolt.

    Good luck, let us know how it turns out.

  5. #5
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    We saw this problem posted here back a few months a go with a Ruger SRH and the 454 Casull. It has also been posted here on a few other occasions and CCI has recieved most of the blame. And they may be deserving of all the blame, I don't know.

    You didn't say what if any case prep went into these loads such as uniforming the primer pockets, etc. That can be a culprit, if the pockets are too deep.

    There are about a half dozen reasons why a rifle (or any gun) misfires.

    1. Bad primers. This is most likely casued by contamination with case lube or oils from the hand or improper storage of primers, i.e. humid invironments.
    2. Excess headspace.
    3. Weak striker fall. This as has been pointed out can be from oil and cold weather in the bolt body where the mainspring and firing pin live.
    4. Dragging sear. (the sear realeases slowly) Can only occur on some types of rifles.
    5. Primer pockets too deep. Allows the primer to be seated so deep that the firing pin won't make good contact.
    6. The Firng pin is too short. (a Manufacturers defect) or Broken.

    I'm not defending CCI or any other primer maker but I've got tell you, I just don't see it. Let me tell you how many primers I have used in the past two years (actually about 21 months) since I moved into my house here in Fairbanks.

    Eight boxes of CCI large pistol #300. Two boxes each of CCI-350's and 550's, two boxes of Fed 210's and two of Fed 215. Also one box of CCI-250 LR mag and one box of CCI-200 LR's. About 300 Remington #71/2 small rifle and about 500 CCI 450 SR Mag's. I think 2-300 Fed small rifle something or other. All the SR's were for various 454 Casull revolvers. (Boxes are 1000 each)

    Plus the now opened boxes of primers which have from 100-500 used from them. I do a lot of loading. Of this bunch I have shot about 40% of them the rest sit on the shelf or went to other folks. I have not had a primer misfire in any of these. I got a Remington #91/2 (oh yeah I forgot about them) in my auto primer tube (they aren't nickled and aren't slick) I had to set it off to get it out then had to polish the tube so the would feed. Also I fill cases with water to weigh them to compare capacity. I needed to weigh a new case and put in a live federal primer, filled it with water and let it sit on the scales for several minutes. Then just as a test, I poured out the water and fired it off, just the primer in the garage. Sounded normal. Then did it again with all primers I had that would fit that case. All went bang! I intended to let the water sit over night then try it and also load it and see if the primer would ignite powder. Maybe I'll do that, I'm bored.

    From my experience primer misfire is a function of, in this order;
    1. Gun malfunction. (See above)
    2. Contaminated primer.
    3. Case primer pocket.
    4. Defective primer. (Way down on this list)

    Rifles I have fired in the past two years.
    Dakota, Kimber, Winchester, Sako, Tikka, Remington, Montana (MRC), Ruger, Marlin, Browning A bolt and old Safari, Weatherby, Sauer (202), HS Precision, Blaser, some Customs, Merkel, Chappuis, H&H, Watson Bros., Jeffery, and a couple of Griffin & Howe originals.

    Some of these rifles had problems, none failed to fire ever. Mostly (99%) were with handloads. I don't know what to make of primer failures.

    I'm not much help with this one.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Default My Theroy

    It all seems to coincidental to me. If there had been mutiple threads on this site and others saying my rifle/pistol is having misfires with various primer brands, I would say load technique or firearm... But every misfire story I expierience or hear involves a CCI primer. I dont think the primers are deffective (atlest in my case), but I do think their cups are hard! Maybe too hard to cause ignition with a marginal strike.

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    Is that a 3-position safety bolt? Look at the back end of the bolt, the cocking assembly, and see if it has a small hole right across it. If so, then you have a similar rifle as mine, a Ruger M77 MK-II. The bolt is taken apart by hand as follows:

    1. Get a finish nail that fits in the hole below the cocking piece on the bolt (the end of the bolt, behind the handle). Find a nail that fits just less than snugly (not tight).

    2. Remove the bolt from the gun, and insert the nail in the hole, making sure it does not drop out.

    3. Grab the bolt with one hand (don't drop the nail), and with the other hand turn the cocking piece counterclockwise, until it comes out of the bolt.

    You should now have two pieces in your hand, the bolt with handle attached in one hand, and the cocking piece with the firing pin attached. Don't remove the nail, just leave it there.

    The firing pin is under pressure, and you don't want to take it apart. Spray a cleaner/lubricant on the cocking piece, clean it well, and then just a tiny bit of lightweight synthetic oil on the bar by the hole and nail.

    Look inside the bolt, and make sure the firing-pin hole is clear and round in shape. Make sure that there are no rub or strike marks by the firing-pin hole. Clean the inside walls of the bolt, and lubricate it just a little.

    Clean the firing pin, oil it with some synthetic gun oil, put a little dab of gun grease on the threads, as well as another dab of grease on the bolt near the small notch used by the cocking piece. Then thread the cocking piece/firing pin back into the bolt. If the bolt/cocking piece are properly tightened, the cocking piece will lock on the notch of the bolt, and it will click ON. At that time, remove the nail.

    That's all there is to it. If you have strong hands, you don't need a nail to take it apart and then to reassemble the bolt. You can do it with bare hands, but the nail makes it much easier.

  8. #8

    Default M77 MK II misfiring

    Thanks to all who have responded , Ray sounds easy now to take that bolt down , I will do it asap. Murphy .. I have tryed everything you have suggested , I loaded new winchester brass , I took the rounds that misfired and compaired the primers that fired under magnifing glass and I dont see a difference , I sized the misfired brass and measured the depth of the primer pockets and compaired them to ones that fired , No measureable difference . I too have loaded to many rounds this year (06) to count , and I have only used cci primers for the last 20 years ( since I live 80 miles from there factory ) Yes hear in Gods Country , oops ..... thats maybe another thread . I did prime 100 pieces of brass and sit out on the porch at 44 deg. and 15 misfired , this is puzzling to me . when it first started we were out shooting some test loads for the 325 ( shooting primers from the same batch loaded in the 300wm ) it was right at 30 deg. that morning. and I thought there was factory grease in the bolt that was causing the misfires . I will open this bolt and see what I see , Im going to town tomorrow and will swing by my smithy and let him look at the bolt . I will let you all know .

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    I am holding out for your final discovery.

    I just bought a M-77MKII and now you have me wondering at some sort of manufacturing flaw. It does happen.

    My wife had a brand new in the box 3903 S&w 9mm pop-gun. The firing pin was broken in two pieces from the factory. Go figure...




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    Floatplane,Tailwheel and Firearms Instructor- Dragonfly Aero
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  10. #10

    Default M77 MKII Misfiring

    Well I took the 300 WM into my Smithy and told him what was going on , Befor I could blink he had the firing pin spring out and a new 24 # spring installed , There 21# from Ruger , He said he has seen more of the Ruger's than any other manufacturer misfire and its due to a light pin spring . I didnt think 3# would make that much difference . But it did ...... It fired 100 primers tonite without one misfire , Once agian Thanks to all .

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    Quote Originally Posted by FLEMC1 View Post
    Well I took the 300 WM into my Smithy and told him what was going on , Befor I could blink he had the firing pin spring out and a new 24 # spring installed , There 21# from Ruger , He said he has seen more of the Ruger's than any other manufacturer misfire and its due to a light pin spring . I didnt think 3# would make that much difference . But it did ...... It fired 100 primers tonite without one misfire , Once agian Thanks to all .
    Glad to hear that the problem is over. I have never had a single misfire from my Ruger M-77 MK II. When put my rifle away, I take the tension off the firing pin spring as follows:

    1. (WARNING point). I make sure the magazine is unloaded, and then the chamber is empty. Visually inspect the chamber by looking at it, or by looking through it out the barrel-after removing the bolt.
    2. Move the safety lever to FIRE, squeeze and hold the trigger down, and then close the bolt while the trigger is pressed.

    When you do this, there is no much tension left on the spring. However, the warning above is extremely important. One must never for get to empty the magazine and the chamber, and then visually inspect the chamber to make sure it's empty

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    RayfromAK:
    I do the same thing myself.

    My habit is to put my little finger into the chamber, to make absolutely sure it's empty, then hold the trigger and close the bolt.

    My reason for doing so is, I can glance at the bolt and see that the chamber is empty, which it is, unless I'm gonna shoot. I seldom even use the safety.

    I'm glad to hear there is another good reason for doing it. (taking "the tension off the firing pin spring").
    Smitty of the North

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    Quote Originally Posted by Smitty of the North View Post
    RayfromAK:
    I do the same thing myself.

    My habit is to put my little finger into the chamber, to make absolutely sure it's empty, then hold the trigger and close the bolt.

    My reason for doing so is, I can glance at the bolt and see that the chamber is empty, which it is, unless I'm gonna shoot. I seldom even use the safety.

    I'm glad to hear there is another good reason for doing it. (taking "the tension off the firing pin spring").
    Smitty of the North
    That's a good idea, too. Whatever habit one can develop to make sure the chamber is empty, and to do the same every time, is what safety is all about.

  14. #14
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    Quote Originally Posted by RayfromAK View Post
    That's a good idea, too. Whatever habit one can develop to make sure the chamber is empty, and to do the same every time, is what safety is all about.
    Yeah, I agree. One little mistake, can sometimes spell disaster.

    I keep thinking about those guys up there by Lake Louise. They could have been safe gun handlers most of the time, but just one time, someone slipped up. What a sad situation.
    Smitty of the North

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    Quote Originally Posted by TomM View Post
    Yes, I have had a similiar problem w/some of my bolt guns. I decided it was a combination of the cold (making firing pin fall sluggish), and hard CCI primer cups.

    Take the rifle out to the range, shoot it until it misfires. Once you have a confirmed misfire, pull the bolt out and keep in a warm vehicle between shots. Only take it out to shoot. If it quits misfiring you have grease in the bolt that is freezing. If it doesnt quit misfiring, try winchester primers (soft cups). Another option is to prime some empty brass, pull the bolt and put it in the freezer overnight and see if it make the primers go off. If not, you have grease/oil/etc in the bolt.

    Good luck, let us know how it turns out.
    Checking through old posts, I found this thread. I just had the same problem of a Ruger MkII 300 WM not fire with reloads. Did a lot of reading and I do believe that the CCI mag primers (250) are harder than others. What wasn't mentioned here is if there were light strikes present on the "non fired primer". In my case yes. I cleaned the bolt(didn't seem too dirty), then loaded the same bullets with federal large rifle primers....boom boom boom. I think I will still replace the firing pin spring with a heavier one though. Nice to find answers here! Thanks.

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