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Thread: R700 5R .223 cratered/blown primers with factory ammo

  1. #21
    Boolit Master
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    I would not put another round in it until the head space was checked. Then I think a known good chamber reamer and confirm nose fits in muzzle then light chamber spin to check for throat removal. Next would be firing pin protrusion, a little suspect marking at base of firing pin stem, internal forward bolt?

  2. #22
    Quote Originally Posted by robg View Post
    Measure the protusion of the the firing pin through the bolt .give everything a good clean then try it again it might be OK .a little crud in the wrong place can cause havoc.
    The firing pin protrusion is .054"

    I did give the firing pin channel a good clean and found one blown out piece of brass in there I was able to blow out, and I soaked the whole bolt in some solvent overnight and it doesn't appear anything more is in there. But again, the problems with light strikes occurred right from round 1 with this rifle, and generally only happens with ammo that has harder primers.


    Quote Originally Posted by HangFireW8 View Post
    What is the firing pin extension from the bolt face?

    A possibility for the blown primers is the chamber neck is cut a bit short, and/or the factory ammo was not trimmed properly. The case mouth pinching the bullet in place can send pressures sky-high. I would check the case length of the cases with blown and cratered primers, compare to other cases, and post the info here.
    Alright, I decided to measure the Sako and the PPU (which were problematic), and the White box and Nosler (which look perfectly fine).


    Sako => 1.761, 1.759, 1.758
    PPU=> 1.762 (neck not square, extreme measure), 1.756, 1.768
    Winchester White Box=> 1.754, 1.759 (neck not square, extreme measure), 1.758
    Nosler=> 1.756, 1.758, 1.759

    So that's not our smoking gun, but it was interesting to see how much more square the necks on the premium ammo was, even the ones I didn't comment on with the PPU/Winchester were off.


    Quote Originally Posted by gnostic View Post
    I'm seeing the cratered and pierced primer. But don't see a flattened radius on the primers or extractor imprint on the case. Aside from the cratered/blown primer, the pressure doesn't look high. Is the bolt sticky when opened? Try the cheap stuff first, I'd replace the firing pin spring to see if a weak spring is the problem. I'd measure the case head expansion, you should have about .007 increase from new, on a normal fired case.
    No bolt stickiness. I have a couple boxes of unfired Sako up where I shoot, i'll check a couple of those with my Hornady Headspace comparator compared to these fired cases and get back to this thread.

    Quote Originally Posted by Gtek View Post
    I would not put another round in it until the head space was checked. Then I think a known good chamber reamer and confirm nose fits in muzzle then light chamber spin to check for throat removal. Next would be firing pin protrusion, a little suspect marking at base of firing pin stem, internal forward bolt?
    I don't have a reamer, what do you mean by the suspect marking? Do you mean the pictures of the galling on the firing pin I posted up in my third post in the thread? I'm not sure what's up with that.


    I couldn't find my preferred Tipton rods locally, so I got the LGS to see if they can special order me one. If the distributor has one in stock it shouldn't take much more than a week or two, i'll give the bore a really good cleaning and then we'll go from there.

  3. #23
    Boolit Grand Master


    Larry Gibson's Avatar
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    "The firing pin protrusion is .054""

    That's within spec but the piercing of the primer indicates the protrusion when firing is too long. The dry fire collar may not be in contact with it's stop surface in the bolt with that protrusion measurement. If it still can go forward under inertia that indicates something else is amiss.

    The cratering may be caused by something as simple as a weak firing pin spring or weak firing pin strike. The misfires also indicate either. That may have been caused by the fouling in the firing pin channel. Have you fired it since the cleaning and removal of the "chip"? I see no sign of any "pressure" problem.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  4. #24
    Boolit Master
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    ^^^ Referring to what Mr. Gibson better explained in more detail. Just pushing forward with finger pressure vs strike protrusion. Yes the marks at base of pin stem, pin possibly going farther than intended post release. Without another identical weapon to compare/mic parts, I think I would buzz pencil very small identifiers on bolt components and give big green a call, hopefully someone still knows how the 700 works there.

  5. #25
    Boolit Buddy McFred's Avatar
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    Reading material RE full pressure and excessive headspace blanking primers:

    http://forum.accurateshooter.com/thr...#post-37402552


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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check