To crimp or not ?

Discussion in 'Hand loading your Sako' started by Bucktote, Mar 31, 2021.

  1. Bucktote

    Bucktote Well-Known Member

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    Reloading various calibers it came to my attention that in 308 cartridges crimping the necks is recommended. Does crimping cause higher pressures ? as the projectile seems to have to overcome the neck wall resistance in microsecond time before starting travel up the barrel.
    All my rifles have not had any problems without having shot reloads not crimped. The only crimped loads were factory loads and I see no advantage to the crimping , am I missing an important step ? Also I have experienced full sizing with small base dies having 6 out of 20 casings not chambering prior to priming & charging. I removed the decapping pin & ran them thru a neck resizer 2 or 3 cycles with success in chambering the cases. Is this a common problem while reloading ? I always dedicate brands of casings to different rifles of the same caliber to prevent chambering issues ( 30/06 = Sako Federal cartridge , Weatherby = Win/ west) etc.

     

  2. icebear

    icebear Sako-addicted

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    If a reloaded round is not crimped, there is a danger that the combination of recoil and inertia could push the rounds in the magazine forward, in turn shoving the bullet a ways back into the case, thereby reducing the volume and increasing the pressure. If the bullet fits tightly into the neck and the round does not have a lot of recoil, this is unlikely. It is, however, a known and documented issue with Magnum rounds and I have seen it happen even with lower-powered rounds if the bullet didn't fit tightly enough in the case.
     
  3. stonecreek

    stonecreek SCC Secretary Forum Owner SCC Board Member

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    With proper neck tension there are very few instances in which a modern, bottlenose round for a bolt action rifle requires crimping the bullet in. It is useful in some semi-autos and in rifles which use tubular magazines where the bullet rests against the round in front of it. As far as heavy recoiling magnum rounds, I have Sakos in .375 H&H and .416 Remington and I DO NOT crimp either of them. Never had a problem.

    Regarding pressure, crimping can make a small difference in handgun cartridges which use relatively fast-burning powder. It makes no measurable difference in the typical centerfire rifle cartridge.

    As far as accuracy, ask any benchrest shooter if he has ever used crimped-in bullets. He'll laugh himself off of his chair.
     
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  4. icebear

    icebear Sako-addicted

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    I agree.

    This may be why crimping was recommended in the instructions for reloading .308, which is almost the same thing as 7.62 NATO, a widely used military caliber. And military ammo is ALWAYS crimped.

    There's no point in crimping any cartridge that is going to be used in a single-shot rifle. The only real need to crimp reloads is to prevent the bullets in the rounds in the magazine from creeping under recoil, and that obviously isn't an issue in a bench gun. In the old black powder days, shooters with Ballard rifles and the like would sometimes come to the line with a primed cartridge case, pour in the powder, push in the bullet by hand or with a hand press, and then take their shot.
     
  5. stonecreek

    stonecreek SCC Secretary Forum Owner SCC Board Member

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    Many bench shooters still do much the same thing today. They will have a tight necked chamber, turn the neck of their brass to perfectly fit the chamber, then never resize the brass at all.
     
  6. Bucktote

    Bucktote Well-Known Member

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    Thanks Icebear & Stonecreek,
    I do not have a .308 but my friend an X Army Ranger, and my son do & I was researching for them. one has a semi auto & the other has a bolt action rifle. I guess the semi auto rounds need to be crimped and the bolt action not. Neither shooters are bench rest shooters, so I guess sub moa are not critical. I think however getting the most out of a cartridge is still desirable as we owe a quick kill if we are going to hunt any game animal. Delayed kills are what I dislike about bow & arrow hunting. I feel that it gives too much negitive fodder to talk about by the anti hunting crowd.
     
    Last edited: Apr 14, 2021 at 1:08 AM
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  7. dgeesaman

    dgeesaman Well-Known Member

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    Benchrest shooters might use a variety of neck thicknesses, but the overwhelming majority full length size the brass each time and maintain .002-.004 of clearance between the loaded round neck and chamber neck diameter. If there are any shooters who still only neck size their brass, they’re not competitive. Competitive benchrest shooters take impeccable care of their brass and reuse the same cases many times if the primer pockets support it.

    The reasons why I would not crimp in a competition rifle are simple: 1) it’s completely unnecessary in a single shot rifle 2) it’s an added variable to manage. For the best possible tune and accuracy, reduce the variables as much as possible.

    Another data point: I do not see PRS shooters crimping their loads and they load from magazines. As long as the neck tension is not too light, and the loaded magazines are not handled roughly, the lack of a crimp has not caused issues.

    Semi auto and roughly handled bolt actions are where I’d start crimping.
     
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  8. ricksengines

    ricksengines Sako-addicted

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    After over 55 years of handloading I can only say that I crimp when the cartridges are being used in tubular feed rifles. This prevents the bullets from being pushed back into cases that are stacked one on top of the other. This occurs from recoil and in rare instances can cause detonation in the tube feed magazine. Otherwise crimping is not necessary and con only be done when bullets have a crimping ring on them.

    rick
     
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  9. paulsonconstruction

    paulsonconstruction Sako-addicted

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    If your firearm type or situation gives you a need to crimp, the bullet you use MUST have a crimping cannelure as rick mentioned.
     
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  10. Bucktote

    Bucktote Well-Known Member

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    Thanks for the info. gentlemen, I'll pass it on to the 308 guys. by the way I am seeing much rifle casings for sale on GB, some prices are reasonable if any one is interested.
     
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  11. stonecreek

    stonecreek SCC Secretary Forum Owner SCC Board Member

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    As you can tell from my previous post, I have very limited use of crimping.

    But when crimping must be done most people do it the wrong way -- by simply setting the seating die low enough that the crimping ring engages the case neck at the end of the bullet seating stroke. This is so wrong: When set up this way the bullet is simultaneously pushed deeper and the neck of the case crimped against it. This cannot help but scar and/or deform the bullet. It also increases the bullet's resistance to seating, thus the pressure applied by the seating stem has to be greater and may deform the ogive of the bullet.

    The proper way to do it (with a seating die with a built-in crimp ring) is to back the die off so that it does not engage the brass. The seating stem is then set at the right depth and the bullets seated.

    In a separate operation the seating stem is backed off (or removed entirely) and the die is re-set lower to provide the amount of desired crimp. In this manner the bullets are not moved as the crimp is applied and therefore no damage to the bullet occurs (provided you've seated it in the right place to begin with.)
     
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  12. Bucktote

    Bucktote Well-Known Member

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    Good Info. Stonecreek, Thanks,
    While we are in the reloading section I ordered & received .243 casings from
    Rockwell Workshop advertising on GB. (TEXAS VENDOR) The casings were cleaned, sized and in great condition. I deprimed them, trimmed to length, champhered necks, cleaned primer pockets, and every one of them chambered in my Forester. I cannot be happier with this vendor and can give them my sincerest thanks!!
     

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