Miss fires

  • Friend of mine just had a dasher built on a surgeon action and is having a ton of miss fires. He went with hydro formed brass and on the first firing had only 3 or 4 miss fires. Yesterday we went to a match and it was horrible 3 or 4 miss fires per stage. Some would fire on the second try and some wouldn’t. This was the second firing on the brass, with the same lot of primers and other components. He’s had the action for a while now and it has never given any trouble with miss fires with previous barrels so I don’t think it’s anything to do with the firing pin assembly or action related. I told him to go compare some of the brass he shot yesterday with brass he has sizes and ready at home to see if he was pushing the shoulder back to far, and check that the primers were seated fully. Other than that I’m out of ideas. Any suggestions as to potential causes he can check would be greatly appreciated.
    He’s running CCI 450 primers and 32.5 gr of varget with the 105 hybrids at 2950.

  • @bull81 Sounds to me like he's setting shoulders back too far. Either that or primers are being put in inconsistently. Could be cocking piece drag on the action or some other thing robbing inertia from the firing pin. Could be the wrong sear in the trigger, dragging on the cocking piece.

    Could be about 50 things, actually.

  • Well it’s the same trigger that’s always been in that gun, like I said it shot fine as a 6.5 with the same primers. He just measured the shoulder set back and is .0015 from the fired case. He’s gonna load up 5 each with no powder or bullets with 450’s, 400’s, and 205’s and shoot them then measure shoulder set back to see which primer is setting it back the most. Kinda like I did when I was having problems with my TL3 and the lake city brass. I think the brass is softer than optimal and absorbing to much power from the firing pin, that’s what was going on with mine that time.

  • @bull81 said in Miss fires:

    shoulder set back and is .0015 from the fired case.

    Did he have the ejector out when the cases were formed, and have a HEAVY jam on the bullet? Otherwise there is nothing to say the case being fired is representative of the chamber dimensions. It will take 3-4 firings before a case takes on the proper dimensions of the chamber. If he's firing a case one time, and then setting it back one and half thousandths from there... he's undoubtedly ending up with 5 thousandths or more of headspace from actual chamber dimensions.

    Even with the ejector plunger removed, and a heavy jam on the bullet, I can usually take a once fired formed case and chamber it back in that same rifle. Even another firing on it with only neck sizing, and it will usually go right back in there. So you have to remember about the tendency of the brass to spring back, and not fully form initially.

  • What trigger is it? It is possible that it has come out of adjustment and is robbing inertia.
    Any chance he popped a primer somewhere along the way and has debris in the bolt body holding the firing pin protrusion short?

  • @tscustoms
    It’s a timney Calvin elite. I don’t think he’s ever popped a primer but the first thing I had him do was pull the bolt apart and check for anything blocking or restricting the firing pin. It all looked good and was clean. I really think it’s something brass related. I’d not considered what @orkan brought up about not being fully formed to the chamber, so that’s something he can look at. I’ll ask and see if he has a spare trigger he can try if not I have one I can let him borrow and see if it improves.

    Forgot to mention he checked the firing pin protrusion and it is at .060

  • Id definitely try another brand of trigger. The Surgeons have an aversion to Timney's.

  • @tscustoms
    Never heard that before thanks for the heads up, I’ll definitely let him know.

  • Remove firing pin assembly & ejector from bolt and close the bolt on a fired piece of brass -- does the bolt just fall closed?

  • @tan_90
    No he checked that right off the bat.