Gunsmithing Tikka prefit headspace issue?

IronOperator87

Supporter
Supporter
Full Member
Minuteman
  • Jul 22, 2018
    206
    146
    New at this and know just enough to be dangerous. So I bought a new tikka 300wsm and screwed a proof carbon fiber shouldered prefit on, checked the head space with a go gauge then put a piece of masking tape over the back of the gauge for a no go gauge and the bolt closed... hmm so I put 2 pieces of tape on ... didn’t close. Measured both pieces at around .005 - .006 (barrel was torqued at 75ftlbs at this time). So I Forgot about the ptg go gauge, tape, and torque wrench and just cranked the action down tighter and ran 4 rounds through it (I was in the fuck it mode at this point after getting the factory barrel off) Hornady and federal factory rounds had ejector flow and hard/ really hard bolt lifts. I then measured the headspace on the fired brass against the unfired brass and had .006 difference on the hornady and .004 on the federal. Made sense to me because the hornady bolt lift was harder. Is this too much headspace? I know when I reloaded 308 I always went for .002 difference. I tried contacting proof but they are not open on the weekends and have a go/no go gauge set coming in the mail. Am I on the right track thinking it’s a headspace issue? Any Ideas or thoughts in the mean time would be much appreciated.
     
    Last edited:
    Not a very good pic but it’s the best I could do for now
     

    Attachments

    • 0767F665-ED0B-47DC-A3DE-92123AC9F11E.jpeg
      0767F665-ED0B-47DC-A3DE-92123AC9F11E.jpeg
      307.9 KB · Views: 188
    I dont think you have a headspace issue, the heavy bolt lift seems strange as the primer in the picture looks good.
    Have you fired this rifle with this ammo with the old barrel?
     
    No I haven’t. I spun the brand new barrel off and spun the new proof on. The only other thing I could think of is the bullet is jammed into the lands but there are no marks on the bullet from the rifling when loading and ejecting an unfired round.
     
    The primer in the pic doesn’t look bad but there is definitely brass flow into the ejector and extractor on both Hornady Precision hunter 200gr eldx and federal blue box 180.
     
    I wouldn’t want my brass growing .006 on a firing. Cut one open and see if you have signs of incipient case head separation.

    No-Go gauges are Go plus 4-6 thou. I’d say you’re on the upper end of that. If your homemade no-go is 5-6 you’re safe, might see lower brass life. Might not. If you’re reloading bump it 1-2 after it’s fire formed and you’ll be fine.

    did you measure the tape with calipers or an actual micrometer? Calipers can read short a lot from too much operator input.
     
    That is the thing, I have never encountered brass flow into the ejector without flat primers.
    @IronOperator87 post a good clear pick of the bolt face.

    Agreed. I know this is different brass and cartridge but I’ve seen cratered primers when I loaded some hot 308 with almost no brass flow or hard bolt lift(tikka also).
     

    Attachments

    • 6E3C716E-03DE-4A39-B372-53C7327AF337.jpeg
      6E3C716E-03DE-4A39-B372-53C7327AF337.jpeg
      357 KB · Views: 129
    @dustingaunder I did use calipers to measure the tape and when squeezed it was .005 and .006 when not, if that’s what you mean by operator input. I want to shoot factory ammo from this so hopefully I can figure this out. Thanks everyone for your responses so far.
     
    I guess I'll chime in here just to be of any assistance. I would recommend having someone dial that barrel in and take a little off the shoulder and maybe the face to set the headspace back slightly. If you decide you are going to run it as is with heavy bolt lift issues, definitely keep the lugs greased to prevent galling of the reciever and bolt lugs. Once galling happens the bolt can seize and then you'll have to get it fixed. I recommend EWG, Militech, Aim, or an industrial grade molybdenum reinforced grease which you can get at most auto parts stores. I know those barrels are not cheap, so take care of your rig.
     
    New at this and know just enough to be dangerous. So I bought a new tikka 300wsm and screwed a proof carbon fiber shouldered prefit on, checked the head space with a go gauge then put a piece of masking tape over the back of the gauge for a no go gauge and the bolt closed... hmm so I put 2 pieces of tape on ... didn’t close. Measured both pieces at around .005 - .006 (barrel was torqued at 75ftlbs at this time). So I Forgot about the ptg go gauge, tape, and torque wrench and just cranked the action down tighter and ran 4 rounds through it (I was in the fuck it mode at this point after getting the factory barrel off) Hornady and federal factory rounds had ejector flow and hard/ really hard bolt lifts. I then measured the headspace on the fired brass against the unfired brass and had .006 difference on the hornady and .004 on the federal. Made sense to me because the hornady bolt lift was harder. Is this too much headspace? I know when I reloaded 308 I always went for .002 difference. I tried contacting proof but they are not open on the weekends and have a go/no go gauge set coming in the mail. Am I on the right track thinking it’s a headspace issue? Any Ideas or thoughts in the mean time would be much appreciated.
    .006" case length difference between virgin and fired brass is not unusual. It only stretches that much once, after that you're only bumping back .001-.002". When firing virgin brass the longer headspace can cause false high pressure signs in the form of ejector swipe marks. If the primer hasn't flattened, it's likely a false pressure sign. The swipe mark is caused by the case slamming back into the bolt face.

    A word about the relationship between barrel torque and headspace. The greater the torque, the greater the headspace. The barrel tenon threads are stretching. At 100 ft/lbs it is about .002". So, you increased torque past 75 ft/lbs to an unknown higher level - you just increased headspace. It may not be much, but if you thought you were "squeezing" the headspace smaller, you've got it backwards.

    Take your now once fired brass, measure cartridge base to shoulder. Adjust your sizing die to bump back .001-.002", reload, shoot, and check for any new pressure signs. Best practice is to index the case so that the ejector is not sitting on top of the prior ejector swipe - mark the swipe with a sharpe. If there are two swipe marks, one is new.

    If you call Proof and explain the bolt closed on a Go Gauge w/tape, they might offer to take the barrel back and take a thou or two off the shoulder which will reduce headspace (or ask you to try a real No-Go gauge). Ideally, when chambering/fitting a barrel, the bolt closes on a Go gauge, and does not on a No-Go gauge. I've seen factory rifles which do close on a No-Go. It doesn't mean that they have dangerous headspace, just that the brass is growing more and subsequent brass life will be decreased. It's why hand loaded ammo may work in one rifle, but not another.
     
    • Like
    Reactions: IronOperator87
    @Praeger So I guess the threads are already stretched so removing the barrel and retorqueing wouldn’t help? The headspace on the fires brass was .006 and the tape/ no go gauge measured .006 so maybe it didn’t stretch much if at all.
     
    @Praeger So I guess the threads are already stretched so removing the barrel and retorqueing wouldn’t help? The headspace on the fires brass was .006 and the tape/ no go gauge measured .006 so maybe it didn’t stretch much if at all.
    The threads aren't permanently stretched unless you went full gorilla with a 4 foot breaker bar. You can remove the barrel and re-install at the correct torque - it may not have made much of a difference, just wanted you to understand the mechanics. All screw threads stretch. It is how they apply tension relative to the level of torque applied.
     
    • Like
    Reactions: IronOperator87
    So I spun the barrel back off yesterday cleaned both mating surfaces thoroughly and torqued it back on to 75ft/lbs and that seemed to help. Measured headspace with tape and go gauge... it seems i lost .002 and fired brass from first time won’t close in chamber. Won’t be able to try it until this weekend though. Thanks for the help @Praeger !
     
    • Like
    Reactions: Praeger
    That's why hand loaded ammo may work in one rifle, but not another.
    [/QUOTE]

    I have a switch barrel setup that was done by Gordy Gritters, the ammo for that barrel 22-250 will ONLY chamber in that barrel.
    As far as the tape trick, I had my 243 barrel (same rifle) that I could close the bolt wit 2 piece's of masking tape yet the gun Smith I took it to put his go/no go gauges in and the bolt wouldn't close with the no go. I mentioned the tape trick and he said that it's not accurate.