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Thread: Primers Popping !!!

  1. #1

    Primers Popping !!!

    I have a 6.5x47 Lapua and although very accurate, its popping primers on a all to regular basis.

    The load is as follows:- 35.5gr RL15, 123gr Lapua bullets, CCI 450 primers, seated well off the lands - (so no over pressure).

    The rifle groups in the .2's and the rounds are heading down range at 2915fps.

    I'm not getting hard extractions of any sort, but each time the primer pops a small bit of primer metal gets into the bolt, fowls the bolt and results in an inability for any further shots to be fired till the bolt is stripped and primer metal removed.
    Having looked at a number of variables I habe been able to rule out most but am wondering if it could be the firing pin firing to far forward ???

    Any help or thoughts would be much appreciated.

    Kind Regards

  2. #2
    Firing pin too sharp? Tad long?
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

  3. #3
    AS I said on Full-bore - we need a photo or two

  4. #4
    Ask the bloke who built it?

  5. #5
    Quote Originally Posted by LONG RANGE CAPT View Post
    I have a 6.5x47 Lapua .......
    Rob What action are you using? Regards JCS

  6. #6
    Headspace? Or shoulder too far back when sizing? Firing pin pushes cartridge forward, ignites and recoil throws brass back against firing pin?
    Had a friends ruger that did that.

  7. #7
    The rifles an AI AE MK II. Only fired 300 rds all cases are brand new.

  8. #8
    Long Range Capt,

    it's not a handload / cartridge problem, rather a mismatch between bolt face / firing pin / small rifle primer. For some reason, small primers crater and finally pierce (sometimes called 'blank') at much lower pressures than their Large Rifle equivalents. To avoid this, you need a small diameter firing pin that is a very close fit in its hole in the bolt-head.

    You've got an AI Mod AE, I have an FN Special Police Rifle formerly .308 Win, currently but not for much longer 6.5X47L. What they have in common is that they were built as sniper / police / tactical rifles and designed to fire that cap under any rifle and environmental conditions - freezing cold, dirty and wet action after crawling down a ditch ... etc, etc. To do that they have great big heavy, fat firing pin mechanisms that are deliberately a relatively loose fit in the bolt - loose compared to an RPA, Barnard, Stolle, BAT etc target action anyway. Result, you crater and even pierce primers at loads barely above Viht's starting load levels.

    My FN 6.5X47L will shortly be rechambered to .260 Rem, a cartridge that uses the LR primer and I expect its performance and usability to be transformed as a result. The resulting 6.5X47L variation will see a Barnard / Eliseo tubegun rebarrelled to that cartridge, the Barnard action having no problems with small primers.

    This problem affects most factory actions to a greater or lesser degree and also affects similar cartridges, primarily the 6mm BR. It can manifest itself with more mundane SR primed cartridges too if loaded heavily enough, say .223 Rem. Savage Model 12s are the best of the factory rifles, but even they are not immune with loads that generate more than 56 or 57,000 psi peak pressures. Remington 700 actions are variable in this respect - some better (or worse) than others. I've no experience with Tikka and Sako etc continental actions, but doubt if they'll be built as per out and out competition actions on either cost or utility grounds.

    I have one other worry about the 6.5X47L with its small primer. When you get up to .308W charge levels - 42-49gn - the small primer is only marginally powerful enough to give consistent ignition, this manifesting itself in poor performance in cold weather, even hangfires with some powders if cold enough. The new Lapua small primer 'Palma' .308W brass is showing this tendency. It works great in reasonable temperatures with easily ignited powders, but Lapua recommends these cases are not used in 'hunting ammunition'. Although 6.5X47L uses smaller charges so the primer is doing less work, the charge weight is still closer to that of the .308W than .223 Rem. I'll bet that performance (MV and grouping) deteriorates if it gets cold enough even in this country as in the January / February cold snaps with some powders.

    What to do about it? In the USA there is a minor industry in modifying factory rifle bolts and firing pins turning the latter down and bushing the bolt body. Gre' Tan Engineering (Greg Tannel) specialises in this work and turns the customer's bolt around in just over a week for around $85. I've yet to hear of anybody who'll do this work here and if you can find a gunsmith who'll take it on it will be an expensive job, as he'd have to do it from scratch, no jigs set up like Gre' Tan. Also, I'm told that Tannel found out the hard way what length etc of bushing works and what sees the firing pin damaged, so it requires some experience for a good reliable job.

    Otherwise, limit loads and live with the problem. Blank enough primers and you'll damage your firing pin through the escaping gas. You may lose follow-up shots thanks to the little brass disk obstructing striker movement too.

    Or .... forget 6.5X47L and do what I'm doing - ie switch to another cartridge. It's a shame. It's a great little cartridge but the small primer (and flash-hole too as this is undersize at only 1.5mm or 0.059" dia. compared to the standard 2mm / 0.080") limit its applications. It really was designed as a target cartridge to replace 6mm BR Norma in 300M 3-position CISM and ISSF rifle disciplines. I reckon Hornady has got it more right with the very similar 6.5mm Hornady Creedmoor as an all-purpose cartridge and that's what I would weigh up against .260 Rem now when choosing a dual-purpose target and stalking cartridge.

  9. #9
    Distinguished Member Ronin's Avatar
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    Oct 2014
    Lancs / Cumbria Border
    Excellent informative post Laurie (as usual)

    Rob, ive built numerous 6.5x47's using a variety of custom and factory actions - this problem manifested mainly with Remington and Stiller actions who's owners were using "warm / hot loads"

    RL15 may be a factor - it varies in burn rate from lot to lot (like most RL powder).

    Try swapping to Varget, it may alleviate the problem and also use CCI BR primers - they have a slightly thicker cup.

    The problem disapeared (well mainly) disapeared with these changes in the rifles ive experience of.

  10. #10
    Hi there Rob. A frustrating thing . Looking at a powder with a lower burning rate may deliver a a longer pressure curve and subsiquently help to reduce the thrust on the primer. Lauries post as always was concise and full of good sound advise and was absolutely spot on in his assesment . the operational requirements of sniper systems does require that they operate in any situation hence the less than benchrest tight fit twixt firing pin and bolt.
    Hogdon 4350 /Imr 4350 / accurate 4350/ vit n150 may alleviate the problem but is not garenteed. give me a call anyhow or swing into the workshop when passing and we can discuss in length ATB Mike Norris

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