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Thread: to crimp or not to crimp...

  1. #1
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    Default to crimp or not to crimp...

    something I have been curious about and thought I ask.. How many crimp thier rifle bullets.. I shoot a 416 wby with 400 x bullets and typically keep the long so they just fit in the magazine(its a Weatherby so I dont have to worry bout where the rifling is). I keep my die backed out a bit so as not to crimp the bullet in and really have never noticed any issues.. My mag only holds 2 down so as an experiment at the range I always kept the same one in the mag to see if the recoil pushes the bullet in deeper, it does but very minor and doesnt seem to affect accuracy.. Just curious what others do.. Oh and also even if I wanted to crimp on the crimp groove of an x bullet it would be really short for the reccommended COL and probably be a really compressed load..

  2. #2

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    Recoil can push bullets back into the case or pull them out. If the bullet isn't held firmly enough it can be pushed back into the case when it hits the top of the chamber, while stripping it from the magazine into the action; This can cause a jam. If the bullet is pulled out far enough, it can be jammed into the rifleing and if it's not fired the bullet can remain in the rifle as the round is extracted causeing powder to be spilled in the chamber and action and a major cleaning is required. While crimping does work the necks somewhat, I believe that the additional confidence in positive feeding/extraction is worth it; so does the military. Cannelures aren't always in the proper location for each individual caliber. Crimping doesn't have to take place in the cannelure you can taper crimp the neck into any part of the bullet shank making the COAL your choice.
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    I crimp for

    Tubular magazine
    Heavy recoil
    Auto cartridge
    Handgun

    Because I understand those are the reasons a crimp might be required.

    I don't crimp if there's no crimping groove.

    I don't think crimping is bad even where it may not be needed, provided the bullet has the groove and the OAL is satisfactory. I note that FLs are crimped for all cartridges.

    I don't have auto rifle, or a heavy recoil rifle (since I sold my 338.) Sometimes I crimped for the 338.

    Right or wrong, that's how I choose whether to crimp or not.

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  4. #4

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    Quote Originally Posted by Smitty of the North View Post
    I crimp for

    Tubular magazine
    Heavy recoil
    Auto cartridge
    Handgun

    Because I understand those are the reasons a crimp might be required.

    I don't crimp if there's no crimping groove.

    I don't think crimping is bad even where it may not be needed, provided the bullet has the groove and the OAL is satisfactory. I note that FLs are crimped for all cartridges.

    I don't have auto rifle, or a heavy recoil rifle (since I sold my 338.) Sometimes I crimped for the 338.

    Right or wrong, that's how I choose whether to crimp or not.

    Smitty of the North



    Right or wrong, dat's how I does it.
    Pretty good summary. About 40 years ago I picked up a C&H tool for adding cannelures when and where I want them, whether for bullets that don't have them or have them in the wrong place. I don't use it all that often, but when I need it, I really need it.

  5. #5
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    Default Lee and crimping...

    Check out what the Lee catalog says about crimping and their factory crimp die. Their take is kinda interesting.

    I've got to break down and buy the Lee reloading manual - it may have some interesting stuff in it but I've never seen one.
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    I pretty much agree with Smitty. Maybe to clarify my position, Handgun: auto pistol rounds headspace on the case mouth and need a slight taper crimp. The will get pushed in the case under recoil. Revolver headspace on the rim and the bullets can pull out under recoil. The need a heavier roll crimp.

    As for rifles, two rules; Bullets must have a crimp groove or cannelure (or TSX groove) to crimp and anything in the 375 H&H category or heavier needs a crimp. Anything in a tubular magazine should also have a crimp.
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    Default to crimp or not to crimp...

    I have a lee universal crimp die that I use for my 6.8 SPC regardless of if there is a crimp ring just to keep bullets from getting shoved back into the case when being loaded. Seems to work well.

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    I crimp only when necessary. Some auto handguns. 45acp and 40S&W yes, 7.62x25 no. Light crimp on 41 and 44mag for revolver, 38/357 just straighten out neck. I have 3 tube fed rifles, 25/20, 32/20 and 454casull. The 25/20 and 32/20 have never had a problem with bullet movement. The 454 is a compressed load and has never moved so I don't crimp my tube fed rifles. I even have a 35Rem auto that I don't crimp My 338 and 358N have never moved so no crimp. I haven't crimped on my 416Rem yet but I haven't shot it much and I may start crimping it. I don't like crimping as it's hard on the neck but sometimes you have to.

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    I don't crimp for my 375H&H...haven't for many years. I exclusively load the TSX for it, and the cannelure and rings don't line-up right for my seating depth to the lands. That said, I've had no bullet creep whatsoever with three in the magazine. The same goes for all of my other bolt action rilfes. I do crimp for my autoloading 223's, using a Lee factory crimping die.

    Handgun cartridges are another story...especially my 454 Casull

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    Default to crimp or not to crimp...

    I let each individual load determine whether or not I crimp. No did an experiment with my ar-10... Uncrimped gave me 1" groups for 10 out of 20 rounds in a mag, with the other 10 being "fliers" out to 2.5 inches. When crimped with a Lee FCD, I got 20 out of 20 in 1.75". While not as individually as accurate as the first 10 uncrimped rounds, it was more consistent with crimped. I'll take the slight loss of occasional accuracy for the known 1.75 group for all crimped rounds in the mag.

    I didn't get as in depth on my .223 AR, but IIRC, the results were similar, and I crimp those as well.

    I also crimp all handgun rounds, at least to remove the bell.

    I do not crimp my '06, 35 whelen, since I've found no accuracy benefit or setback due to recoil.
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    I shot the same load out of a RUM crimped and uncrimped using the Lee FCD. The uncrimped shot about a 2" group and 100 yards and the crimped under 1". Big difference. I noticed the tip of the Etip bullets were dented and worried about them moving around.

    Something I wondered about. Will a Lee FCD help offset inconsistencies in the neck diameter and length? Say you have some brass that is not trimmed to exact lengths or has a thick neck. A little crimp with the Lee Die might just even out the pressures and make varied neck tensioned loads a bit more consistent. Just a thought.

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    I certainly appreciate all the replies its been a good read and some very good info.. So not to ask a stupid question but will give it a go.. Does crimping change pressure.....

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    Quote Originally Posted by Bear View Post
    Does crimping change pressure.....
    Well the simple answer is yes it absolutely changes pressure. It increases bullet pull tension holding the bullet there longer giving better more consistent ignition and usually slightly increased pressure but mostly a very different pressure curve. It's just like seating long to be agents the lands gives you more initial pressure, often better accuracy but peak pressure comes sooner and you get less total pressure volume under the curve. Weatherby used a long freebore so he could push the bullet faster by getting more volume under the curve. He turned the peak into more of a hump so with different powders he got high pressure for longer pushing the bullet faster, he was a big velocity guy.
     
    Thatís over simplified but your simple answer is yes it will change pressure. There are guys out there that could write a novel about in what way or how pressure changes and the effects of those changes though so not as simple a subject as it sounds.
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    I waited a couple days to let the folks who know more about this than me speak up. I crimp everything. Some of it for the reasons already stated. gas bolt stuff, AR-xx, I dont want the BCG pushing the bullet down in the case. Lever stuff, I don't want recoil pushing bullets down in the case. Revolver stuff, I crimp just enough to keep the bullets from walking out longer under recoil. I don't own any handguns that aren't revolvers.

    I don't have anything else. I do have a bolt action rifle chambered the same as my AR-10, but I am only willing to make one load for both rifles in that caliber. So for that one my seating depth is for best accuracy in the bolt gun, but I crimp them all so I can run them in the AR-10.

    My next rifle will most likely be a 270 because my dad really likes antelope meat. I'll probably get a Lee Factory Crimp Die for it when I buy one. I am not sure how much difference it makes, but if nothing else even with decent neck tension each of my handloads should be a tiny bit more weather proof with a kiss of crimp on them.

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    Quote Originally Posted by ADfields View Post
    Well the simple answer is yes it absolutely changes pressure. It increases bullet pull tension holding the bullet there longer giving better more consistent ignition and usually slightly increased pressure but mostly a very different pressure curve. It's just like seating long to be agents the lands gives you more initial pressure, often better accuracy but peak pressure comes sooner and you get less total pressure volume under the curve. Weatherby used a long freebore so he could push the bullet faster by getting more volume under the curve. He turned the peak into more of a hump so with different powders he got high pressure for longer pushing the bullet faster, he was a big velocity guy.
     
    Thatís over simplified butyour simple answer is yes. There are guys out there that could write a novel about in what way or how pressure changes and the effects of those changes.
    Good post AD:

    I like the way you splained it.

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  16. #16

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    Quote Originally Posted by ADfields View Post
    Well the simple answer is yes it absolutely changes pressure. It increases bullet pull tension holding the bullet there longer giving better more consistent ignition and usually slightly increased pressure but mostly a very different pressure curve. It's just like seating long to be agents the lands gives you more initial pressure, often better accuracy but peak pressure comes sooner and you get less total pressure volume under the curve. Weatherby used a long freebore so he could push the bullet faster by getting more volume under the curve. He turned the peak into more of a hump so with different powders he got high pressure for longer pushing the bullet faster, he was a big velocity guy.
     
    Thatís over simplified but your simple answer is yes it will change pressure. There are guys out there that could write a novel about in what way or how pressure changes and the effects of those changes though so not as simple a subject as it sounds.
    GOOD EXPLANATION ! While the pressures will rise after the bullet has been crimped in the case, the overall pressures will be under the maximum rated chamber pressure for that caliber providing that the round is loaded to loading manual specs. The manuals take into consideration that ammo is crimped from the factory and will most likely be crimped when reloaded, and maybe even waterproofed. This is one reason that many people can reload powder charges in excess of manual specs increaseing velocities, they don't crimp or waterproof ammo.
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    I have a light .38 special load that a heavy crimp really increases the accuracy. I imagine due to better ignition and better burning because of increased bullet pull.

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    I crimped some of my 375 Ruger loads today that I usually do not crimp using the Lee factory die. I fired four non crimped and four crimped. Same point of impact at 100 yards. So, should I crimp it because it doesn't hurt and it can only help with bullets in the mag during recoil? Or, do you not bother?

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    Quote Originally Posted by Daved View Post
    I crimped some of my 375 Ruger loads today that I usually do not crimp using the Lee factory die. I fired four non crimped and four crimped. Same point of impact at 100 yards. So, should I crimp it because it doesn't hurt and it can only help with bullets in the mag during recoil? Or, do you not bother?
    I would crimp because it's a heavy recoiling cartridge, but you might get away without doing it.

    I would want a crimp groove if I did.

    Smitty of the North
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