To crimp or not to crimp, that is the question.

I'm a newbie at reloading and am currently preparing to load for my Axis and 111 rifles. I'm a little in the dark as to whether I should be crimping or not--the way I understand it crimping is necessary for "dynamic" cycling such as in semi-auto's where cartridges will be "ripped" from the magazine and rammed into a feed ramp. My understanding is this isn't necessary in a bolt action--but all my Savages have the detachable magazines so I'm not sure if crimping is needed or not--and if you can go either way--what the potential bullet movement in the casing, if any, and impact on accuracy pros/cons might be.

I don't crimp for any rifles I reload for,not even my AR's. Never had a problem.

not needed for bolt guns. Handguns, yes.

Crimping also changes the pressure curve as it take more to get the bullet moving

it's real simple, try to see the logic before everyone else tells you it's not necessary.

It's not necessary, most of the time. If you have a hard kicking gun, tubular magazine, straight walled case, a particularly abusive feeding mechanism, or anything else that might cause that bullet to set back in the case, then crimping is useful. If you have a typical bottleneck case and a bolt action rifle, it's almost universally pointless to crimp.

Like blue mentioned, pistols are commonly deserving some crimp on their ammo but even that is a blanket statement that's patently false.

If and only if you have issues with bullet set-back, crimp. If your case neck tension is insufficient to keep the bullets from setting deeper into the case then crimp them just enough so it doesn't happen. If it is sufficient, leave them alone.

FWIW, I do not crimp almost ever. My .45acp rounds don't get a crimp, my .45 Cinderblock rounds don't get a crimp, my 7mm Rem Mag rounds don't get a crimp, my 6x45 rounds don't get a crimp. My .30-carbine rounds DO get a crimp even if quite slight. The .45's don't need it, case neck tension is sufficient. My 7mag doesn't need it for the same reason. The .30-carbine does get a light crimp due to the violence of the feeding system, taper in the case body and short stubby bullet that's prone to set-back. .002" is more than sufficient to keep my carbine bullets from shoving back into the case and prevents some FTF failures.

When crimping use calipers to measure how much you're pinching it and go as little as you can. A couple thousandths is usually more than sufficient unless you're talking about a hard kicking magnum big bore rifle (.458winmag, .444marlin, .45-70) which may need a solid crimp into a cannulured bullet. I would if I still loaded .30-30 use a light crimp on those as well given the typical tubular magazine system.

The effects of failure to crimp when it's needed are pretty spotty. You can see dramatically increased pressures (bullet set-back), or dramatically increased pressures (bullet moving forward to jam into the rifling), or reduced pressures, or incomplete combustion, or bullet wiggle as it enters the rifling. The worst bits you're liable to see based on my experience is a disassembled cartridge sitting in your mag spilling powder everywhere and a bullet floating around your action looking for a spot to jam it up and the other side which would be a probable fail to feed jam caused by a bullet not riding up a feed ramp as designed.

To sum up: There are times when crimp is needed and it's especially useful on straight walled cases or those with heavy and stubby bullets (large bore) with enough inertia to be shoved back into the case under recoil. Magnums often should be crimped. The best rule of thumb is to avoid using it if you don't have to. Variances between crimps make accuracy a little more spotty and can have a dramatic effect on pressures and velocities, especially the extreme spread and standard deviations of such.

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Originally Posted by r3dn3ck

My .45acp rounds don't get a crimp, my .45 Cinderblock rounds don't get a crimp.

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LOL You leave the case mouth belled? Or did you crimp it? just not tight!

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Originally Posted by r3dn3ck

it's real simple, try to see the logic before everyone else tells you it's not necessary.

It's not necessary, most of the time. If you have a hard kicking gun, tubular magazine, straight walled case, a particularly abusive feeding mechanism, or anything else that might cause that bullet to set back in the case, then crimping is useful. If you have a typical bottleneck case and a bolt action rifle, it's almost universally pointless to crimp.

Like blue mentioned, pistols are commonly deserving some crimp on their ammo but even that is a blanket statement that's patently false.

If and only if you have issues with bullet set-back, crimp. If your case neck tension is insufficient to keep the bullets from setting deeper into the case then crimp them just enough so it doesn't happen. If it is sufficient, leave them alone.

FWIW, I do not crimp almost ever. My .45acp rounds don't get a crimp, my .45 Cinderblock rounds don't get a crimp, my 7mm Rem Mag rounds don't get a crimp, my 6x45 rounds don't get a crimp. My .30-carbine rounds DO get a crimp even if quite slight. The .45's don't need it, case neck tension is sufficient. My 7mag doesn't need it for the same reason. The .30-carbine does get a light crimp due to the violence of the feeding system, taper in the case body and short stubby bullet that's prone to set-back. .002" is more than sufficient to keep my carbine bullets from shoving back into the case and prevents some FTF failures.

When crimping use calipers to measure how much you're pinching it and go as little as you can. A couple thousandths is usually more than sufficient unless you're talking about a hard kicking magnum big bore rifle (.458winmag, .444marlin, .45-70) which may need a solid crimp into a cannulured bullet. I would if I still loaded .30-30 use a light crimp on those as well given the typical tubular magazine system.

The effects of failure to crimp when it's needed are pretty spotty. You can see dramatically increased pressures (bullet set-back), or dramatically increased pressures (bullet moving forward to jam into the rifling), or reduced pressures, or incomplete combustion, or bullet wiggle as it enters the rifling. The worst bits you're liable to see based on my experience is a disassembled cartridge sitting in your mag spilling powder everywhere and a bullet floating around your action looking for a spot to jam it up and the other side which would be a probable fail to feed jam caused by a bullet not riding up a feed ramp as designed.

To sum up: There are times when crimp is needed and it's especially useful on straight walled cases or those with heavy and stubby bullets (large bore) with enough inertia to be shoved back into the case under recoil. Magnums often should be crimped. The best rule of thumb is to avoid using it if you don't have to. Variances between crimps make accuracy a little more spotty and can have a dramatic effect on pressures and velocities, especially the extreme spread and standard deviations of such.

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Thanks for the detailed response. If I understand correctly, I guess it's safe to assume the process of cycling a bullet from the detachable box mag (which staggers the rounds) in a typical Savage non very high-recoil (mine are 308, 270 and 6.5 284 norma) it's OK to go with no crimping, yes? Another factor is that I also have an AR10 so at least for the 308 I will be crimping. Which begs another newbie question--since factory ammo manufacturers don't necessarily know what their ammo will end up in--especially for example 223 and 308--is it safe to assume they crimp all of it--or do you need to know what type of bullets are typically cannalured or not? And related to that--should I avoid using brass that has been fired in my AR for reloading and reuse in my bolt-actions?

Thanks in advance.

short answer, yeah you got that about right.

308/243/270/.30-06 are not known for extremely stout recoil and not doing a crimp on them is usually without problem. The AR-10 I would agree on a crimp only because of how the bullets are treated by the feed ramps in AR type rifles (roughly at best). Before you start crimping for an AR-10, make sure you test cycle a few rounds (from full mag, half full mag, almost empty mag) to make sure you don't get any feed jams due to COAL (cartridge overall length). I've had that be a problem before. Once you have the COAL down, a solid crimp will help with the feed related set back.

Most factory ammo that I have come across in the past few years is crimped (either roll or taper) OR uses a sealant or both. Factories will probably use a matrix to make the decision for them. Calculating free recoil in a common arm for X round, count in bullet mass and diameter and length, cannulure depth, etc... and assign some coefficient for each of those and then do some hand-wavey math to see if it crosses the line that says "Crimp it". Stuff like .44's and .458 win mags tend to use cannulured bullets specifically because heavy crimp will be applied to them. Factory crimps will usually be a lot more consistent than hand applied crimp because their machines are so much more massive and precise.

As far as what you use your brass in, I don't like the dents I see in AR handled brass but it's not a big deal as far as that goes but can reduce powder capacity. AR's with short barrels on the other hand will be very hard on case heads and I would generally give it a tighter inspection protocol than my bolt action brass. I would reserve your bolt action brass for your bolt action and only neck size it (and trim as needed) as long as you can get away with it, it'll last longer that way. Keep AR brass for AR's since you'll have to full length resize.

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Originally Posted by r3dn3ck

short answer, yeah you got that about right.

308/243/270/.30-06 are not known for extremely stout recoil and not doing a crimp on them is usually without problem. The AR-10 I would agree on a crimp only because of how the bullets are treated by the feed ramps in AR type rifles (roughly at best). Before you start crimping for an AR-10, make sure you test cycle a few rounds (from full mag, half full mag, almost empty mag) to make sure you don't get any feed jams due to COAL (cartridge overall length). I've had that be a problem before. Once you have the COAL down, a solid crimp will help with the feed related set back.

Most factory ammo that I have come across in the past few years is crimped (either roll or taper) OR uses a sealant or both. Factories will probably use a matrix to make the decision for them. Calculating free recoil in a common arm for X round, count in bullet mass and diameter and length, cannulure depth, etc... and assign some coefficient for each of those and then do some hand-wavey math to see if it crosses the line that says "Crimp it". Stuff like .44's and .458 win mags tend to use cannulured bullets specifically because heavy crimp will be applied to them. Factory crimps will usually be a lot more consistent than hand applied crimp because their machines are so much more massive and precise.

As far as what you use your brass in, I don't like the dents I see in AR handled brass but it's not a big deal as far as that goes but can reduce powder capacity. AR's with short barrels on the other hand will be very hard on case heads and I would generally give it a tighter inspection protocol than my bolt action brass. I would reserve your bolt action brass for your bolt action and only neck size it (and trim as needed) as long as you can get away with it, it'll last longer that way. Keep AR brass for AR's since you'll have to full length resize.

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great stuff-much appreciated. Just out of curiosity--why would a short barrel carbine be harder on a case neck than a longer one? Except for the gas system and barrel length differences--I don't get how this results in presumably higher case pressures to exit the bullet? Please bear with me--I tend to take as much advantage of those more knowledgeable than me as I can : )

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Keep AR brass for AR's since you'll have to full length resize.

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Oh yeah! Forgot that lesson last week. Picked up some 223 reloads that I thought were for my AR. Got about two miles from the house out in the middle of everywhere and cycled a round....you know just push the button and let the bolt fly... in the chamber....NOT...had a dandy time getting it out. Some lessons are best learned only once and not forgotten.

short barrel AR's are hard on case heads, not case necks. They're hard on case heads because the gas system is shorter than it should be when you start with a chopped down barrel length. We still have to keep the gas system in play and the gas port has to be before the barrel ends so it ends up moving closer to the chamber in short barrel models where the pressures are much higher and viola, you have early opening of the bolt and all the evil that comes with it. The early opening (compared to a proper rifle length AR with a rifle length gas system) causes the bolt to rotate such that it tries to spin the case inside the chamber while there's still pressure in the tube holding the brass against the chamber walls. The brass doesn't want to move (inertia + friction) and is forced to. This stretches and works the brass and eventually will cause a failure. EVENTUALLY either it'll rip a case head off (leaving a case body in the chamber and causing the biggest headache of failure types) or just damage a case so that it splits down the side or succumbs to incipient case head separation. You see this issue a lot with the really short AR-15's that are so popular lately but the problem exists any time you try to shorten an AR gas system and gets worse the shorter the barrel gets and the nearer to the chamber the gas port gets.

I went through months of issues with AR's. I was not taught to reload for them, I learned the hard way, by having one idiot problem after another and then sitting down and reasoning out the "why" of each failure until I got a pretty solid idea of what was going on. Wait till you start working with powders that are great in a bolt gun but wretched failures in a gas gun. Then it gets interesting.

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Originally Posted by wbm

Oh yeah! Forgot that lesson last week. Picked up some 223 reloads that I thought were for my AR. Got about two miles from the house out in the middle of everywhere and cycled a round....you know just push the button and let the bolt fly... in the chamber....NOT...had a dandy time getting it out. Some lessons are best learned only once and not forgotten.

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this describes about a dozen different trips out to the desert for me. Driving 8 hours back home with nary a shot fired because I was a dolt and didn't test locally made the lessons very hard to forget.

One thing I did not see mentioned...I may have just overlooked it. Neck tension on semi outo rifles can play a roll. Some brass is very soft, some reloading techniques and abusive handling may require crimping to keep the automati feeding from jaming the projectile too deep in the cartridge causing the mentioned overpressure. Redneck mentioned a phenomina that was happening on a particular dpms 308.

another one bites the dust.

Wow....
this is a tough room.

I'm back to the AK board to practice my Russian.

Have nice day, y'all....

Kinda getting away from the thread but not too much. Any of you guys remember the hurah that the honcho at Speer Bullets and the honcho at Lee Dies got in years ago? Seems Lee did some "research" about crimping and came up with an add that said crimping improved accuracy....even on bullets that did not have a crimp ring. Since Lee just happened to be pushing their die sets that included their crimping die (at extra cost of course) they spent lot's of advertising money to "prove" their point. Speer took exception and said that crimping bullets without a crimp ring did not improve accuracy and deformed the bullet. Well it finally got out of hand and Lee put in print that Speer bullets were bad and no one should buy them. Speer countered with Lee dies were junk and no one should buy them. Lessons learned? You can be right in the wrong way and/or wrong in the right way.

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Originally Posted by r3dn3ck

short barrel AR's are hard on case heads, not case necks. They're hard on case heads because the gas system is shorter than it should be when you start with a chopped down barrel length. We still have to keep the gas system in play and the gas port has to be before the barrel ends so it ends up moving closer to the chamber in short barrel models where the pressures are much higher and viola, you have early opening of the bolt and all the evil that comes with it. The early opening (compared to a proper rifle length AR with a rifle length gas system) causes the bolt to rotate such that it tries to spin the case inside the chamber while there's still pressure in the tube holding the brass against the chamber walls. The brass doesn't want to move (inertia + friction) and is forced to. This stretches and works the brass and eventually will cause a failure. EVENTUALLY either it'll rip a case head off (leaving a case body in the chamber and causing the biggest headache of failure types) or just damage a case so that it splits down the side or succumbs to incipient case head separation. You see this issue a lot with the really short AR-15's that are so popular lately but the problem exists any time you try to shorten an AR gas system and gets worse the shorter the barrel gets and the nearer to the chamber the gas port gets.

I went through months of issues with AR's. I was not taught to reload for them, I learned the hard way, by having one idiot problem after another and then sitting down and reasoning out the "why" of each failure until I got a pretty solid idea of what was going on. Wait till you start working with powders that are great in a bolt gun but wretched failures in a gas gun. Then it gets interesting.

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Hmmmm interesting stuff since I haven't reloaded for an AR yet. I have a 16" 5.56 carbine that I recently bought a Stag 16" 6.8 spc upper for with the specific intent of reloading for it to fine tune the ideal load for. I also have an LRT SASS with 18" bull barrel--would the mid-length system be less prone to this type of failure?

BTW--just got back from my LGS and the reload guy (says he's been doing it for over 51 years,he's kinda like Levon Helm in "The Shooter") tells me of a guy who just bought a Bushmaster AR and stuck his reloads in without resizing the brass--apparently blew it to pieces--but Bushie for some reason agreed to give him a new rifle no charge.

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I have since learned that the forward assist is best left as a decoration

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In another life in a far away place I saw Marines killed, in part, because of that decoration. Early on M16's would fail to go to battery. LOTS!. The next move was to push the decoration and the next was to take out a cleaning rod get up on one knee and try and clear the weapon. Terminally bad move!

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Originally Posted by wbm

In another life in a far away place I saw Marines killed, in part, because of that decoration. Early on M16's would fail to go to battery. LOTS!. The next move was to push the decoration and the next was to take out a cleaning rod get up on one knee and try and clear the weapon. Terminally bad move!

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Bummer--what happened--they launched a round into the face or something?

Redneck, I think after your condescending attitude towards someone that is possibly less knowledgeable than you it is kind of easy to skip over your lengthy post. I reread you post and I still don't see the "lengthy" discussion on neck tension. I did see the part about work hardning but you left out the part about "neck tension" with regards to softer newer brass like winchester or anealed brass, especialy when using dies that are designed for competition reloading where the neck tension by design is only .001 or .002. So I will rephrase myself. There are neck tension issues other than what R3DN3CK mentions that can make crimping a good idea in rifles like the AR 15 and the AR 10(DPMS308). Have a beer brother, I'm on your side and have no entension of stealing your thunder.

Anyone else want a vacation while I have the ban button warmed up?

Holy Exile Batman!!!!!

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Bummer--what happened--they launched a round into the face or something?

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No. Just problems with the weapon.

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Originally Posted by MrFurious

Anyone else want a vacation while I have the ban button warmed up?

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Think I'll go root around in the fridge and see if I have a cold Coors left. This could get interesting. :o

Naaa...I already took care of the two hot-heads - one permanently and one for a week accordingly.

I know my vote don't count for squat--but I sure as heck got a lot out of pickin redneck's brains and kinda hope he could be back to contribute again--MrFurious you might remember the initial reaction to gary on the Axis list and he's now the star there. : ).

What did I miss?

A pissin contest.....and some discipline applied to those that did wrong. :yield:

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Originally Posted by wbm

Kinda getting away from the thread but not too much. Any of you guys remember the hurah that the honcho at Speer Bullets and the honcho at Lee Dies got in years ago? Seems Lee did some "research" about crimping and came up with an add that said crimping improved accuracy....even on bullets that did not have a crimp ring. Since Lee just happened to be pushing their die sets that included their crimping die (at extra cost of course) they spent lot's of advertising money to "prove" their point. Speer took exception and said that crimping bullets without a crimp ring did not improve accuracy and deformed the bullet. Well it finally got out of hand and Lee put in print that Speer bullets were bad and no one should buy them. Speer countered with Lee dies were junk and no one should buy them. Lessons learned? You can be right in the wrong way and/or wrong in the right way.

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It appears that some of the 6.8 guys are not crimping, don't know if that's a risky thing or not. correct me if I'm wrong, but doesn't crimping increase the tension of the grip of the neck on the bullet, and therefore changes the case pressure build-up and bullet release characteristics? I don't generally notice crimp/non-crimp info on load tables.

I never crimped for the 308s in my Rock River LAR-8. I had the 16" mid-length, and never had an issue with setback.

Like it was somewhat mentioned before, you can take a dummy round with no powder or primer, and cycle it hard, repeatedly in the action. If you take before and after measurements of the OAL, you would be able to see if your tension is more than likely enough to keep the bullet in place.

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Originally Posted by richhelton

I never crimped for the 308s in my Rock River LAR-8. I had the 16" mid-length, and never had an issue with setback.

Like it was somewhat mentioned before, you can take a dummy round with no powder or primer, and cycle it hard, repeatedly in the action. If you take before and after measurements of the OAL, you would be able to see if your tension is more than likely enough to keep the bullet in place.

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I get the logic of that--but it still is leaving out the pressure issue from fire/recoil, which in my mind is a bit of an unknown if you're not doing a live-fire.