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Thread: Primer strike force

  1. #1
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    Primer strike force

    Primer Strike Force
    I have an article by Charlie Dell about some primer tests that he conducted to determine if bullet velocity and/or accuracy was affected by the force of the hammer strike. His conclusion is that there was no connection. I'd never thought about it, but it struck a chord; Ricardo ("The High Speed Internal Combustion Engine" found that the size/voltage/strength of the spark had nothing to do with the characteristics of the burn in the cylinder. If it lit, it burned.
    Then I found this. In the Gun Digest Treasury, Deluxe 4th edition, "Reloading for Varmint Hunting" by John Lachuck, page 313, he writes: "Accuracy depends to a surprising degree upon good primer action. Superior automobile performance requires a hot spark."
    He then goes on about firing pin springs etc., then: "Frank Snow discovered that short-action bolt rifles shot better when heavy firing pin springs were installed. Coincidentally, ballistician Edward M. Yard found that a heavy blow of the firing pin causes increased flash energy from a primer."

    I have but can't find a reference to Remington testing for this. Several to many other references have been made to the "fact" that firing pin strike force affects velocity and/or accuracy.

    If so, this is an easy and quick fix to increase accuracy. I see the firing pins and springs being offered for sale in the gun magazines, the assumption seem to be that they increase accuracy.

    I'm interested in hearing from anyone with experience in this matter.
    Thanks;
    joe brennan

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    Again, as with the chronograph thread, my methods aren't scientific enough to make pecific satements. That being said I believe consistant primer ignition is important, as is consistancy throughout the rest of the shooting event. Poor or blocked strike makes for problems. At the same time we know that sometimes a cool primer or a hot primer can alter the perfromance of a load. There is a lot on this in Charley Dell "The Modern Schuetzen Rifle" as I'm sure you know. There is more found in the pages of Precision Shooting, Handloader, etc.

    The Highpower and Benchrest crowd can probably give you specifics.

    BTW- You ask good questions.
    Last edited by Bret4207; 01-01-2007 at 06:29 PM.

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    Another question with conditional answers. It's hard to prove too. When you use Savage 110 actions, you can adjust both strike depth and impact force. You can see this very plainly. The problem is that 99% of the time, when a shooter does have this problem, it is misdiagnosed.

    Another thing that masks this problem and makes it hard to see is that some corrective actions a shooter makes, can solve other problems at the same time. So credit for the accuracy improvement is attributed to something else. Here are some of the ways a cast shooter can and will compensate for it trying to get consistency. And this list is not all inclusive as these are just common things we discuss regularly.

    1. Change to another or a hotter primer.
    2. Change to a faster or bulkier powder.
    3. Failure to adjust to 1 or 2 forces them to use filler. (Ever wonder why one guy needs it and another does not?)
    4. Seat bullets into the lands so that pressure must come up before the bullet can begin moving forward.
    5. Choke for the same reason.
    6. Fire form new brass with jacketed first or use high presure loads once their headspace is reduced from cast.
    7. Neck size cases only.
    8. Drill out flash holes.
    9. Harden the bullets so they take longer to begin moving forward.
    10. Increase case neck tension or crimp.
    11. Or just accept accuracy limits as a problem with cast, or this particular gun, or this particular bullet, or that they are having a bad shooting day. Etc.

    This was why removing end play in revolvers made so much of a difference for me. You are establishing consistent headspace! If the cylinder isn't held in the same place all the time, you get different impact and depth and therefore ignition. Then you force yourself to have to go up to the list above, to try and compensate again.

    This is also the biggest reason why pistol primers are more consistent than rifle primers. Pistol primers have a softer cup that just makes it easier to impact consistently. Can this impact be overdone? No on impact, Yes on depth. And firing pin shape can make a difference on how much of both you need too.

    It's all starts with ignition, ignition, ignition.
    Last edited by Bass Ackward; 01-01-2007 at 11:30 AM.

  4. #4
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    Joeb, I don't know about force of a primer hit, but it does have to be entirely consistent for the BR guns to shoot. ... felix
    felix

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    Red face Suspicion

    I have experienced the accuracy improvement by replacing a weak firing pin spring in one of my rifles. On the other hand, I have replaced springs "just in case" in identical rifles (except for cartridge/caliber) and seen no change in the accuracy.

    I suspect several things may be at play here...1) Your rifle (handgun, too) and loads, and shooting technique must be accurate/good enough for you to see the difference. If you have a rifle that consistently groups into 1.5" or so, or marginal loads/technique, I rather doubt you will see the change with a spring change, unless of course the spring is so weak that you experienced mis-fires in the first place. 2) If you have a reasonable firing pin strike (whatever that is) then the improvement, if any, may be detectable with a BR level rifle only. If you change to a harder primer with the same spring, then the strike may not be hard enough and you could detect an accuracy improvement with a stronger spring. A softer primer of course would not show any change with that same spring. 3) If your shooting technique is in the slightest sloppy, then the delay time between sear release and firing pin strike (lock time) might be long enough for you to have an accuracy decrease due to rifle movement. In that case, very little change will be noted with any other change. With proper techniques (follow through, etc) you might see a change with a spring change. On the other hand, a shorter lock time (shorter strike length w/ a stronger spring) may very well show you a decidedly marked increase in accuracy. It isn't for nothing that most BR guns are built on Remington actions or custom actions. Yes, the Remington action is stiffer than most, but equally important, if not more important, is the fastest lock time of the commonly available actions. And 4) The scope you are using may be playing into the accuracy of your rifle. I once had a Tasco (trashco?) 6x18 on a .223 that consistently showed groups of 1" while a different scope (Weaver KT15) on that same rifle, EVERYTHING else being the same (same day, same range session, same loads, etc) would group into <3/4". A primer or firing pin spring change on that rifle with the Tasco in place wouldn't show any improvement. FWIW....Pilgrim

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    Boolit Grand Master Char-Gar's Avatar
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    It has always been my understanding that a weak firing pin strike will degrade accuracy. I thought that was given.

    Then we have primer "brisance", which is determined by the primer compound. Brisance is a way of measuring how fast a primer releases 100% of it's energy. Brisance does not speak to how much energy is in the comound or the heat of the energy released. While not entirely accurate, I feel it helpful to think of brisance in terms of rate or speed.

    I have no scientific evidence to back it up, just experience, but I have changed to a new or stronger firing pin spring in several rifles and have seen an improvment in accuracy. I have also noticed that low brisance primers make it easier to find a good accurate load. While not 100% true in all cases, I still find it helpful to start with a low brisance primer.

  7. #7
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    Bass, I do not understand your point #9 "harden bullets so they take longer to begin moving forward". Not diagreeing just don't understand. Could you explain? Thank you. Duckiller

  8. #8
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    Quote Originally Posted by Duckiller View Post
    Bass, I do not understand your point #9 "harden bullets so they take longer to begin moving forward". Not diagreeing just don't understand. Could you explain? Thank you. Duckiller

    DK,

    Sure. If you harden your bullets, it creates more friction. It will take more pressure to get them to engrave or size down, right? The longer any delaying action you establish, the more pressure gets up, and the pressure from the powder expansion establishes ignition instead of the primer blast itself.

    Same thing with increasing bullet weight. Increases inertia. I didn't have that one listed.

    The list was not meant to be all inclusive, but to show how everthing is interwoven into the total cast picture and how you have to think in order to find the correct answer to the actual problem.

    How about increasing friction by not using a slipery lube like LLA? Or that slippery lube can reduce friction below a point where you get poor ignition after it builds up in the bore. Could be then thought of as a lube flier until the excess is purged out of the bore.

    All of these things can contribute to solving a problem created in another area, like the primer impact senario which I believe is real. "Consistent" ignition is the key.

  9. #9
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    Certainly, positive, consistant ignition is an important factor in any accurate load. It also should be noted that replacing a weak spring with a stronger one increases the speed firing pin travel and reduces locktime, allowing the shooter less time to alter the sight picture and muff the shot.

    SS
    NRA Life Member Since 1981



    "The very atmosphere of firearms anywhere and everywhere restrains evil interference - they deserve a place of honor with all that's good"-- George Washington

    II Corinthians 4:8-9. We are hard-pressed on every side, yet not crushed; we are perplexed, but not in despair; persecuted but not forsaken, struck down, but not destroyed."

    Psalms 25:2 O my God, I trust in thee: let me not be ashamed, let not mine enemies triumph over me.

    [SIGPIC][/SIGPIC]

  10. #10
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    In the BPCR crowd, it is a well know fact that when a Sharps rifle breaks a firing pin (a dog legged affair), it can still fire but there are "fliers". A lot of shooters wonder what's happening to their rifles/loads then find the pin has broken, and when replaced, the accuracy is back. This to me shows how much a primer strike does change point of impact.
    Gus

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    Wink

    ---The depth of firing pin strikes are adjustable on Mosin Nagants, as far as primer difference the average shooter would see no change--- Mag

  12. #12
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    I had some experience with this in the new made Winchester lever guns with the rebounding hammers. With the rebound working the gun would mis fire about every 10 shots and groups would be srtung up and down over 6" at 100 yards. Replacing the rebound system with the old style stopped the mis fires and cut the groups to right at 2". I have also noted this with muzzleloaders. HOWEVER, this was with BLACK powder. With smokless in the 1886 the groups did not show near the same dispersal effect. With smokless the change in group size was less than 1" at 100 yards. I never tried to find a scientific answer. but for black at least firing pin force is a factor.

  13. #13
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    BP vs WP makes a lot of sense because BP is extremely dependent on the proximity of its grains to one another. A different primer hit between shots should be very obvious, unless the BP is packed quite tight enough to ignore external vibration right before ignition. ... felix
    felix

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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