misfires with Rem 7 1/2 primers

Discussion in 'Reloading Forum (All Calibers)' started by uncle-buck, Jun 9, 2019.

  1. uncle-buck

    uncle-buck

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    I recently loaded 20 brand new, never fired Lake City 5.56 cases using Remington 7 1/2 bench rest primers. Shot them today and had 5 misfires (out of 20 rounds) in a Savage 10 bolt gun chambered in .223 Rem.

    Pulled bullets and dumped powder from the 5 dud rounds and loaded the empty, primed cases into an AR-15. Four of the five primers went off.

    Any ideas what may be causing the misfires in the bolt gun?

    Am seating the primers about 0.006" below the bases of the cases and it looked like they were getting good strikes. (see attached photo below)

    Thanks for any suggestions.
     

    Attached Files:

  2. DaveTooley

    DaveTooley Silver $$ Contributor

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    Not sure if this is your problem but primers have to seated firmly to the bottom and then a slight crush doesn't hurt. This sensitizes the primer by seating the anvil against the priming compound. Because you had 4 of 5 go off I'd say you helped with the sensitivity when you hit them again..
     
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  3. jepp2

    jepp2 Gold $$ Contributor

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    4 of the 5 have light strikes. What is the case head to datum length?
     
  4. Martin52

    Martin52

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    The headspace on the new brass may be slightly short for your bolt gun chamber but ok in the AR.

    Measure the fired cases then re-size for your bolt gun chamber and try firing again.
     
  5. Uncle Ed

    Uncle Ed

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    You should go by feel making sure the anvil contacts the bottom of the primer pocket with a slight primer crush.

    [​IMG]

    I also use Remington 7 1/2 primers in my Savage .223, Ruger .223 Ranch rifle and in my AR15 and have never had a single Remington primer fail to go off.
     
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  6. Dusty Stevens

    Dusty Stevens COVFEFE- Thread Derail Crew Gold $$ Contributor

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    Seat by feel not depth. Slight crush and theyll go off every time
     
  7. Bill K

    Bill K Silver $$ Contributor

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    You could be bumping your shoulder back too far in the bolt rifle, or your primers are not seated solid against the flash hole, or your rifle has a weak fire pin spring. Start eliminating each and see if you find the one causing the problem.
     
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  8. 243winxb

    243winxb

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    The velocity of the firing pin is being slowed by something. Old gummed up oil? Soak in kerosene overnight. .

    Broken firing pin?

    Its not head to datum, head space. My Savage 223 will fire primers with the shoulder cut off the brass.

    A bullet seated into the rifling, with low neck tension, will absorb the pin strike, as the round moves forward.

    The extractor stops forward movement of the round.

    The firing pin strike will make my Axis head to datum measurement shorter by .006"
    Found this out when a CCI 400 primer was defective. It fired on the 4th strike, after reseating it a few times in other brass.
     
    Last edited: Jun 9, 2019
  9. uncle-buck

    uncle-buck

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    Appreciate all the replies, guys.

    I will check headspace in the rifle and practice seating and igniting primers to develop "feel" for the slight crush a couple of you referred to.
     
  10. DaveTooley

    DaveTooley Silver $$ Contributor

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    I've been reloading for 40 years and building rifles for 36 years now. I have never heard of a primer failing because it was "crushed" to death. I don't know how your seating primers but my guess it with a tool that has a stop. Remove it. You'll feel the primer bottom out then with a little more pressure you feel the seating of the anvil. I pretty much flatten all of mine when seating.
     
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  11. mikecr

    mikecr

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    WOW, talk about an extreme in striking. My 223 head spacing does not change one bit with primer firing. This is normal, desired, and by design.

    You do need relative speed though, so make sure there is nothing slowing striking.
     
  12. 243winxb

    243winxb

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    Use a dead primer. The 2nd strike set shoulder back even more, using the same piece of brass.

    (Savage Axis 223)
     
  13. Ggmac

    Ggmac Gold $$ Contributor

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    Is this the same rifle you were having misfires with maybe a year ago ?
    Have you played with the mainspring at all , meaning trying to lighten the bolt lift ? Just want to eliminate other possibilities besides improper primer seating or excessive shoulder bump .
     
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  14. sundance

    sundance Silver $$ Contributor

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    I had light hits on primers in my 20 P with CCI 450. Bat B action. Got a new spring from Bat. Problem solved.Bat recommends changing the spring every 1500-2000 rounds. Your mileage may vary.
     
  15. Uncle Ed

    Uncle Ed

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    mikecr

    In the reloading manuals they tell you to never use cases used with reduced loads again with full powder loads.

    This is because with each firing the case becomes shorter every time the firing pin hits the primer, meaning the case shoulder is pushed back.

    If the reduced load cases are used with full power loads it is possible that you will have a case head separation.

    The amount of shoulder setback varies but I know some of my milsurp rifles can make the case over .001 shorter each time the firing pin hits the primer.

    Below a 7mm Mauser long in the tooth just under maximum headspace with factory loaded ammunition. Notice how far the primers have backed out of the primer pockets. In this rifle you have long headspace and short factory cases and still have good firing pin hits.

    My guess is the OP did not seat the primers properly and they moved and blunted the force of the firing pin hit.

    [​IMG]
     
    Last edited: Jun 10, 2019
  16. SBS

    SBS Gold $$ Contributor

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    Had some of the same problem when using military .223 cases a couple of years ago. Turns out I wasn't swaging the primer pockets deeply enough and the primers got tight before they had bottomed out. Headspace was min. and the lot of primers worked fine in commercial cases and with other caliber rifles.
     
  17. onelastshot

    onelastshot Gold $$ Contributor

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    It sounds as though the primers were not seated properly; the first strike seated the primer and the second strike set the primer off. The fact that four out of five fired on the second strike supports this theory.
     
  18. Texas10

    Texas10 Gold $$ Contributor

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    If that doesn't work, additional information on the particular firearm might help diagnose your FTF issue.

    FWIW I had a new Savage 223 that a No-go gage would chamber in. It shoots fine, but it is a few thousands long in headspace. Add that to using some new brass and hard cup primers and there'd likely be some misfires.
     
  19. divingin

    divingin

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    Had a factory Rem700 that was the same way. Just a slight bit of resistance closing on a NoGo gauge. Have since replaced the barrel.
     
  20. Uncle Ed

    Uncle Ed

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    Having collected milsurp rifles and just because the bolt closes on the NO-GO gauge doesn't mean the headspace is excessive. Normally there is approximately .003 between the GO and NO-GO gauges and you have .007 more before the rifle fails the field gauge.

    Pacific Tool and Gauge offers three lengths of headspace gauges per rifle caliber. In order from the shortest to longest, they are: GO, NO-GO, and FIELD:

    1. GO: Corresponds to the minimum chamber dimensions. If a rifle closes on a GO gauge, the chamber will accept ammunition that is made to SAAMI’s maximum specifications. The GO gauge is essential for checking a newly-reamed chamber in order to ensure a tight, accurate and safe chamber that will accept SAAMI maximum ammo. Although the GO gauge is necessary for a gunsmith or armorer, it usually has fewer applications for the collector or surplus firearms purchaser.

    2. NO-GO: Corresponds to the maximum headspace Forster recommends for gunsmiths chambering new, bolt action rifles. This is NOT a SAAMI-maximum measurement. If a rifle closes on a NO-GO gauge, it may still be within SAAMI specifications or it may have excessive headspace. To determine if there is excessive headspace, the chamber should then be checked with a FIELD gauge. The NO-GO gauge is a valuable tool for checking a newly-reamed chamber in order to ensure a tight and accurate chamber.

    3. FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gauge, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin.
     

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