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Thread: K98k mainspring question.

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  1. #1
    Member Fruler's Avatar
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    K98k mainspring question.

    I purchased a K98kicon earlyish this year and have not had any extreme problems with it, besides a little rust in the bore, which cleaned out easily. The bolt is a little stiff, which I attribute to the Mauser action. (I'm used to Enfields) When I shoot new Prvi or S&B 7.92 ammo I have no problems at all... I shot a box of each when I purchased the gun... They all shot fine, no hard primers or anything like that. Normal impact depth on primers.

    I purchased several hundred cartridges of Czechoslovakian 1948 7.9 ammo... 65-70% of the time I have no problem shooting it but sometimes some require 4 strikes to go boom. When I looked at the primers of the brass that I shot, the ones that only required one strike, I see just a very small, shallow indent... Smaller than what I see on my spent Prvi or Sellier brass. I would also like to note this is Berdan, corrosive primed of course... The ammo has German WW2 style primers, (single, offset flash hole...) The primers are made of steel so they're magnetic. Some came on German stripper clips, some didn't. All came in German WW2 made cardboard paper type boxes, which I found interesting.

    I have a few questions which I will put below.

    1. Will it be worth my time to put in a heavier pound rated spring? I'm looking at Wolff springs...

    2. Should I go heavier than the factory rate spring or should I just get a factory rated spring of normal poundage?


    3. If I get a heavier spring, wouldn't it require more force turn up the bolt?
    (to unlock the bolt.)

    I prefer to shoot milsurp ammo, if I can find it at a reasonable price these days. With new factory ammo I have zero problems. It could be that I have a weak spring, the primers are super hard, ammo is showing its age... Probably a combination of all those things and more.

    Any advice is very much appreciated, as it always is. Thanks guys. Good day.
    Last edited by Fruler; 07-16-2019 at 08:34 PM.

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  3. #2
    Really Senior Member Daan Kemp's Avatar
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    Clean the bolt thoroughly, oil lightly, before replacing the spring. It should improve the functioning.

    Not all ammunition are made the same. 1948 is 70 years ago, erratic functioning should be expected. Your Czechicon ammo probably has hard primers; if they really are steel they will be very hard I think.

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    Member Fruler's Avatar
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    Quote Originally Posted by Daan Kemp View Post
    Clean the bolt thoroughly, oil lightly, before replacing the spring. It should improve the functioning.

    Not all ammunition are made the same. 1948 is 70 years ago, erratic functioning should be expected. Your Czechicon ammo probably has hard primers; if they really are steel they will be very hard I think.
    Thanks... Excellent advice. I stripped the bolt completely as you said and cleaned it. I found a thin layer of rust starting at the bolt face, that stops at the two gas relief ports machined into the bolt... The rust is inside the bolt body, not on the outside... Outside is still in the blue. I'm actually not too surprised of this finding really... The bore was a bit rusty when I bought it. I attempted to clean out the bolt rust with various methods and have had limited success so far. I may try boiling the bolt body in water next.

    The previous owner of the rifle claimed he hadn't shot it in many years but when I purchased it he said he fired blank ammo through it to confirm function recently... So his story changed somewhere between first speaking to me and me purchasing it. The rust looks to me like it's been there for decades... But I'm not a rust expert, it's certainly not newly formed though.

    As for the ammo, I assume the primer is steel, it attracts a magnet... But I'm not an expert in the the field of metals... I do know it's brass cases. I don't expect perfect ammo from 1948, sorry if I wasn't clear on that. I just want to be sure my rifle is performing the way it should be and I want to attempt to eliminate as many variables as possible.

    I have removed the barreled action from the stock before and there is no rust on the underside of the barreled action. The stock is in great shape in terms of proper fitting.

    Thanks for your reply, I wouldn't have stripped the bolt if you didn't speak up.

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    Member Fruler's Avatar
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    Quote Originally Posted by Steve762 View Post
    In the 98's and 48's that I have replaced the firing pin spring in the factory rated springs worked fine. It is an inexpensive fix. Cleaning the interior of the bolt and the firing pin, spring and collar of any grease and crud helps too. Note: Wolff has springs for 98's and 48's be sure to order the correct one.
    Thanks Steve762.
    By 48 you mean yugo m48? So you say go with original spec factory rated springs? Yes, the springs are tempting to me because of the price. I've read reviews where people go heavier and shoot surplus ammo that once gave them problems and they no longer have to perform double strikes.
    Thanks.

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    Quote Originally Posted by Fruler View Post
    Thanks Steve762.
    By 48 you mean yugo m48? So you say go with original spec factory rated springs? Yes, the springs are tempting to me because of the price. I've read reviews where people go heavier and shoot surplus ammo that once gave them problems and they no longer have to perform double strikes.
    Thanks.
    That's probably because the original spring was weak to begin with, or gummed up. OEM spec springs are plenty strong enough to ignite the hardest of primers. Just break down the striker assembly and you'll see, especially if you let it slip.
    Last edited by vintage hunter; 07-17-2019 at 08:12 PM.

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    Member Fruler's Avatar
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    Quote Originally Posted by Steve762 View Post
    --Yes, 48 = Yugoicon 48's.
    --A new factory spec spring and a clean oiled bolt interior should be all you need.
    --Problem with new springs of standard or extra weight is the increase in trigger pull weight over your old spring.
    --Also, check to see if firing pin is bent.
    --Old bore brushes of various calibers on a pistol cleaning rod is a good way to clean the old grease out of the interior of the bolt. I finish with a pipe cleaner at the bolt face.
    --Any solvent that cuts old grease should work. Soak the bolt if necessary.
    --Old ammo is old ammo. Not all of it will fire.
    Regards, Steve
    Goodness... All you chaps were so helpful. I used a .17 caliber brush, a .22 caliber brush and a .357 steel brush. Rust is gone in all the easy to reach place inside the bolt body. Rust was a bit stiff but I took my time. I also used old thin twine that I found under the boot of my car. Used it to clean the firing pin hole, for lack of proper words.

    Inspecting the spring I found an almost enamel like, beeswax looking finish. I believed this was very dried and caked on cosmolineicon or something of the sorts. I obviously wasn't the first owner of this milsurp, not telling how many hands it's passed from... It's amazing people don't take the time to do a proper job of it, to make it free of that bugger. So the spring is clean now too.

    Should be properly finished cleaning by tomorrow, when I have more time. Will do a follow up and shoot this weekend to see if there's any improvements.

    If nothing is improved, I haven't lost anything. The bolt will at least be cleaner-ish. If I don't have improvements with firing pin spring strength, I will look into a new spring. I have a bit of money tied up in this ammo, so I'd like to be somewhat happy shooting it. The small indentations on the Czechicon primers have me thinking it's got to be the rust and Cosmo on the spring. Cheers.
    Last edited by Fruler; 07-18-2019 at 08:43 PM.

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    Contributing Member Doco overboard's Avatar
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    Next time you strip the bolt, have a look at the firing pin flange to make sure that it's not interfering with the corresponding recess inside the bolt. Sometimes the flange can become peened or malformed over a little bit that it interferes with proper function. Increased friction from the dispersed metal around the flange to internal bolt safety lugs and then combined with cartridge fit between the different types of ammo could maybe be a possibility for part of the problem.
    Also the cocking piece should be a nice fit on the tail of the firing pin and not overly tight. If it's binding, on the tail of the FP or when the cocking piece itself travels forward it could slow the pin down a small bit as it travels through the bore of the shroud. Could be some hardened or caked grease/oil lurking around those areas too.

  10. #8
    Member Fruler's Avatar
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    Quote Originally Posted by Doco overboard View Post
    Next time you strip the bolt, have a look at the firing pin flange to make sure that it's not interfering with the corresponding recess inside the bolt. Sometimes the flange can become peened or malformed over a little bit that it interferes with proper function. Increased friction from the dispersed metal around the flange to internal bolt safety lugs and then combined with cartridge fit between the different types of ammo could maybe be a possibility for part of the problem.
    Also the cocking piece should be a nice fit on the tail of the firing pin and not overly tight. If it's binding, on the tail of the FP or when the cocking piece itself travels forward it could slow the pin down a small bit as it travels through the bore of the shroud. Could be some hardened or caked grease/oil lurking around those areas too.
    I checked it last time I took it apart. Firing pin is nice and straight with very little wear marks. Thanks.

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    Member Fruler's Avatar
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    I got all the rust out of the bolt body, it took me some time to do but I enjoyed it... Kind of relaxing. I went and shot the rifle last night, I took the Czechicon surplus and newly made Prvi partizan ball. Prvi fired with no problems of course. Still having problems with the Czech ammo... Still not sure what steps to take, if any... This will be something I'll have to think about. I believe in the first rule, "do no harm." I will probably keep the Czech surplus in the bottom of my ammo can and save it for a rainy day. I will be sticking with the newly made Prvi Partizan and Sellier and Bellot 7.9 ammo for the foreseeable future.

    I learned a great deal from this thread and I would like to thank everyone who contributed their time and knowledge. Thank you.

  12. #10
    Advisory Panel browningautorifle's Avatar
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    Quote Originally Posted by Fruler View Post
    Still having problems with the Czechicon ammo
    One time consuming test for this ammo would be to take 100 rds of boxer brass and prime them up, use the powder and bullets pulled and installed straight across from the 1948 ammo... If all of them light with an immediate earth shattering kaboom then it's the primers and not your rifle.

    That's what it usually is anyway.
    Regards, Jim

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