Who "crimps?"
- Thread starter garandman
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Absolutely not, unless there's a specific and good reason for me to do so. Tubular mags, fine. Revolvers, definitely. Auto pistol rounds, a slight taper. But for a 223/5.56mm, or a 308/7.62? No, no reason to.
I would think any semi auto would require crimping, so the cartridge overall length doesn't change as the cartridge is getting chambered, by means of the bullet nose striking the chamber wall.
No?
I do for my .223 but I would like to hear the reasons why you don't ksthomas. I'm new to reloading so I'm a sponge when it comes to information. Is it just not necessary if there is enough tension on the neck to hold the bullet in place without being able to push it in by hand? I'm doing it for a semi auto just to add.
Absolutely not. Most people don't think about this, but it's almost impossible to deep seat a bullet during chambering, due to the fact that most rifle loads are near, or at, 100% load density; there's no where for the bullet to go. The "problem" is generally on the flip side; bullets pulling under chambering in autoloaders. Which they all do to some extent. so long as you've got sufficient neck tension, this won't amount to more than a few thousandths, and doesn't cause any problems. Essentially, an AR (or a Garand, or an M14, or an FAL) is a large, very expensive kinetic bullet puller. With the violent cycling and abrupt stop at the end of the chamber, most bullets will pull, at least a bit. I've seen and measured even M193, complete with crimp AND asphalt sealant, that pulled .002"-.003" after chambering. An uncrimped bullet without the sealant will naturally pull even more. But neck tension alone is adequate to prevent this from causing any problems. And for what it's worth, the majority of my reloading these days goes into Service Rifle Match ammo. It's an overblown concern to most folks these days, and really not as complicated as most people seem to want to make it. Just the nature of these things, and you can't change that.
Garandman and Ultraman550,
I should expand here on what I said in my original post; unless there's good reason. Pistols are one area where the deep seating during chambering CAN be a problem. That's one of the reasons that I mentioned taper crimping them. Revolver bullets, like those in the semiauto rifles, can be "pulled" if not adequately crimped. With the auto rifles, this can (does) occur when the round is chambered. The revolvers, on the other hand, want to pull their bullets when fired, due to the recoil. Yes, revolver loads, paritiuclarly those in hard kicking calibers, definitely NEED a firm crimp to keep them in place. Unlike the rifles, this sort of pulling can cause serious problems in a revolver, including locking up the gun when bullet protrude from the face of the cylinder.
I should expand here on what I said in my original post; unless there's good reason. Pistols are one area where the deep seating during chambering CAN be a problem. That's one of the reasons that I mentioned taper crimping them. Revolver bullets, like those in the semiauto rifles, can be "pulled" if not adequately crimped. With the auto rifles, this can (does) occur when the round is chambered. The revolvers, on the other hand, want to pull their bullets when fired, due to the recoil. Yes, revolver loads, paritiuclarly those in hard kicking calibers, definitely NEED a firm crimp to keep them in place. Unlike the rifles, this sort of pulling can cause serious problems in a revolver, including locking up the gun when bullet protrude from the face of the cylinder.
I guess I think of a light crimp as a way of assuring proper neck tension. I've accidentally bumped an uncrimped round, and had 4-5 thousands of "setback" and crimped ever since.
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I generally don't crimp for my autoloading rifles.
Here is the problem I found with crimping. The walls of different brands of brass have different thicknesses. Winchester brass has thinner walls while Remington and Hornady has thicker walls. When I crimp brass from different manufacturers, I end up with variable tension on the bullet. This causes inconsistent accuracy problems.
Also, it is hard to give an even crimp from lot to lot even when using the same brand of brass. I guess if you are making blaster loads, then crimping wouldn't matter. But I'm trying to go for consistent accuracy and crimping appears to introduce an unpredicatable variable into my reloading process.
Here is the problem I found with crimping. The walls of different brands of brass have different thicknesses. Winchester brass has thinner walls while Remington and Hornady has thicker walls. When I crimp brass from different manufacturers, I end up with variable tension on the bullet. This causes inconsistent accuracy problems.
Also, it is hard to give an even crimp from lot to lot even when using the same brand of brass. I guess if you are making blaster loads, then crimping wouldn't matter. But I'm trying to go for consistent accuracy and crimping appears to introduce an unpredicatable variable into my reloading process.
Interesting point.
I crimp each individual round "by hand" with a feel to the depth of crimp. I've gotten to where I can do a pretty consistent crimp depth by feel. And both my precision rifles (1 semi, 1 bolt) hover at half MoA.
Oh, forgot to mention one other problem I found with crimping. I've noticed the necks of my brass grow longer with crimping. This results in more frequent trimming and also more material removed when trimming.
Sounds like some of you are way better than I when it comes to crimping. LOL
What kind of crimp do you use? I have the Lee and Dillon crimp dies.
Sounds like some of you are way better than I when it comes to crimping. LOL
What kind of crimp do you use? I have the Lee and Dillon crimp dies.
Garandman,
Neck tension and degree of crimp are two entirely different topics. You can absolutely have inadequate neck tension of a bullet that's been firmly crimped, just as you can very easily have more than enough neck tension on a round that's been "undercrimped." No the same thing at all here. The best argument against crimping when it isn't needed, for my shooting anyway, is that it tends to degrade accuracy. I've seen some marginal ammo (substandard or downright unacceptable accuracy) that benefitted from crimping. In good ammo that was shooting decently, I've only seen it hurt the end result.
Neck tension and degree of crimp are two entirely different topics. You can absolutely have inadequate neck tension of a bullet that's been firmly crimped, just as you can very easily have more than enough neck tension on a round that's been "undercrimped." No the same thing at all here. The best argument against crimping when it isn't needed, for my shooting anyway, is that it tends to degrade accuracy. I've seen some marginal ammo (substandard or downright unacceptable accuracy) that benefitted from crimping. In good ammo that was shooting decently, I've only seen it hurt the end result.
I share the sentiment expressed by the OP. I crimp all rounds to be used in a semiauto, albeit lightly. I use the Lee FCD for this. The only rounds I DON'T crimp are for bolts or my Ruger #1 and are segregated from my general stock.
Although I am NOT a precision shooter like many on this forum, I like my ammo as accurate as I can get it but I have not noticed any decrease in accuracy or anything else between crimped/uncrimped. I know I speak sacrilege here. Guilty.
I also do my best to load ammo dependable enough that I can safely say that if my weapon fails me, it won't be because of my ammo. YMMV
Although I am NOT a precision shooter like many on this forum, I like my ammo as accurate as I can get it but I have not noticed any decrease in accuracy or anything else between crimped/uncrimped. I know I speak sacrilege here. Guilty.
I also do my best to load ammo dependable enough that I can safely say that if my weapon fails me, it won't be because of my ammo. YMMV
MK 262 is crimped from the factory as part of the specification. That can't be by accident. I have seen serious setback with AR platform rifles. While I may not crimp for a bolt gun, my ARs are hard on ammo and crimping seems logical to keep the bullet exactly where I put it.
I also use the Lee die. Even with my 6.5 Creed bolt gun. As I say above, I get half MoA accuracy, that even if the gun is capable of more, I am not. If I noticed crimping was degrading accuracy, I'd stop. But with the crimp, I have that little extra level of assurance of maintaining CoL.
I've also noticed my 6.5CM bolt gun is VERY senstitive to overall length. 2.820" is perfect in my 2.844" chamber. 2.835" and 2.840" evidenced a significant increase in group size.
I appreciate the clarification and professional input. I certainly count myself as one with much yet to learn. I always FL size, which I'm guessing pretty much assures proper neck tension. Yes?
Again, F/L sizing and neck tension are completely independent of one another. You can F/L size using a body die that will not even touch the neck, leaving it completely unsized. Neck tension is set primarily by the amount of constriction (to a certain point) that the case neck imparts on the bullet. That, in turn, is set by having the dies properly sized to begin with (we're speaking of its I.D. here) and then not mucking it up with an oversized expander or mandral, should one be involved in setting the finished I.D. of the processed case. Bushing dies handle this nicely, and allow for complete control of exactly how much constriction you're applying. I like 'em, and I use 'em.
As far as the accuracy question and military ammo, that's more a matter of tradition . . . and the utter impossibility of getting the military to change something once its been carved in stone. When they first started loading the 77 SMKs, the bullets were uncannelured. This came to the attention of the bean counters, who promptly demanded that it be cannelured and crimped. What resulted is what you see on this ammo today; a barely perceptible cannelure that technically meets the legal definition/requirement, but doesn't do as much damage to the bullet as a "real" cannelure would. It's all about accuracy, and it's readily known to those involved that this does indeed degrade the potential accuracy of the rounds. Essentially, the most accurate a bullet is ever going to be is when it leaves the sizing die in the final station of the press. Virtually ANYTHING done after that (and includes tumbling, polishing and most certainly, applying a cannelure) causes a measurable loss of accuracy. Simple as that.
As far as the accuracy question and military ammo, that's more a matter of tradition . . . and the utter impossibility of getting the military to change something once its been carved in stone. When they first started loading the 77 SMKs, the bullets were uncannelured. This came to the attention of the bean counters, who promptly demanded that it be cannelured and crimped. What resulted is what you see on this ammo today; a barely perceptible cannelure that technically meets the legal definition/requirement, but doesn't do as much damage to the bullet as a "real" cannelure would. It's all about accuracy, and it's readily known to those involved that this does indeed degrade the potential accuracy of the rounds. Essentially, the most accurate a bullet is ever going to be is when it leaves the sizing die in the final station of the press. Virtually ANYTHING done after that (and includes tumbling, polishing and most certainly, applying a cannelure) causes a measurable loss of accuracy. Simple as that.
Good info. Is there any research or a guide as to how much a cannelure degrades accuracy and how?
Its interesting to me as I used both MK 262 Mod 0 and Mod 1 overseas and I had issues with the Mod 0 projectile getting pushed into the case on chambering. I did not have those issues with the Mod 1 version.
Its interesting to me as I used both MK 262 Mod 0 and Mod 1 overseas and I had issues with the Mod 0 projectile getting pushed into the case on chambering. I did not have those issues with the Mod 1 version.
I'm sure there is, but good luck on getting any of it released. You'd be dealing with the government if you're getting info from LCAAP, and private entities dealing with BHA, Sierra, Federal or others involved here. Most consider such testing info as strictly proprietary, and are hesitant (that means "NO!") to release stuff like this.
These types of orders always require certification, and the cert will call out testing standards and performance specs. So long as the end result meets those specs, everything's good and the order ships. Aside from this, you have daily QC accuracy firing of the lot as it's being produced, which results in its own set of records. While I've seen (thousands) of such tests, there is no direct comparison of those regular QC tests and the end results of the certifications. Might be an interesting comparison, though.
These types of orders always require certification, and the cert will call out testing standards and performance specs. So long as the end result meets those specs, everything's good and the order ships. Aside from this, you have daily QC accuracy firing of the lot as it's being produced, which results in its own set of records. While I've seen (thousands) of such tests, there is no direct comparison of those regular QC tests and the end results of the certifications. Might be an interesting comparison, though.
No. And sort of yes. A bushing die is one which uses interchangeable bushings to set a given neck diameter on your resized cases. They are available in N/S and F/L formats, from both Redding and Forster, among others I'm sure. These are the two that I normally use. But yes, they can be had either way. Now you see what I meant by saying they were independent issues.
Pistols get a taper crimp. Everything else gets enough neck tension to hold it in place, including both semi autos and my 300WM. I certainly would never crimp a bullet that doesn't have a cannulare ring on it. Doing so it just deforming the jacket and doesn't really do much for accuracy.
To the definitive, all encompassing statements somewhere up in the thread:
Sometimes it's required, sometimes it ain't. When I load brand new 77gr SMKs for my AR15, nope, no crimp required. Brand new 55 or 62 grain FMJ bullets? Nope.
However, when I load pulled 55gr FMJBT bullets w/o a crimp, I ended up wasting a day at the range and tossing a bunch of rounds because they got jammed back into the case by the feed-ramp. Using CFE223, that ball powder settles in nicely, and doesn't take up anywhere near as much case capacity as Varget does.
Those require a light crimp. Could I get another neck sizing die and tighten up the neck to really squeeze the pulled bullets? Sure, but it would cost me more than a $9 Lee crimp die, which does just as good a job.
So, better answer: It depends.
Sometimes it's required, sometimes it ain't. When I load brand new 77gr SMKs for my AR15, nope, no crimp required. Brand new 55 or 62 grain FMJ bullets? Nope.
However, when I load pulled 55gr FMJBT bullets w/o a crimp, I ended up wasting a day at the range and tossing a bunch of rounds because they got jammed back into the case by the feed-ramp. Using CFE223, that ball powder settles in nicely, and doesn't take up anywhere near as much case capacity as Varget does.
Those require a light crimp. Could I get another neck sizing die and tighten up the neck to really squeeze the pulled bullets? Sure, but it would cost me more than a $9 Lee crimp die, which does just as good a job.
So, better answer: It depends.
Attachments
That's a fair point. I crimp bullets without a cannelure, and get half MoA. But I can def see the danger of deforming the jacket. I'm gonna try some uncrimped in my 6.5CM bolt gun and see what happens.
Garandman,
Goes back to the point I mentioned earlier that there is literally NOTHING that you can do mechanically to a bullet once it comes off the press that will increase its accuracy. Nothing. The bullet is at its absolute peak accuracy potential when it comes off the press, and every step, every process every bit of handling from that point on, merely reduces the accuracy, or has the potential to do so. Crimping, either with or without a cannelure is one such mechanical operation. In the case of uncannelured bullets, the deformation caused by crimping is just a bit more immediate.
Goes back to the point I mentioned earlier that there is literally NOTHING that you can do mechanically to a bullet once it comes off the press that will increase its accuracy. Nothing. The bullet is at its absolute peak accuracy potential when it comes off the press, and every step, every process every bit of handling from that point on, merely reduces the accuracy, or has the potential to do so. Crimping, either with or without a cannelure is one such mechanical operation. In the case of uncannelured bullets, the deformation caused by crimping is just a bit more immediate.
I have a featherweight Mod 70 338 Win Mag which I crimp. I learned a long time ago that the recoil causes bullets to back out and can cause sticking in the magazine. It can even cause more serious problems like causing the bullet to be jammed into the lands which can raise pressures or cause problems when unchambering the rifle, dumping a load of powder and having to tap the bullet out with a cleaning rod.
Good explanation. I guess technically, I don't crimp, except by mistake - i.e., over pressure into the crimp die. Mostly, I'm just making sure there is sufficient neck tension at the case mouth.
When I say "light" I mean "almost inperceptible." But your point is well made, and worth investigation on my part.
M40 A1,
Exactly the same thing applies there. Done correctly, meplat uniforming won't effect accuracy one way or the other. It will uniform BC, and that can result in decreased vertical at LR, but it's not really an increase in accuracy per se. Part of the trade off is a measurable reduction in BC, but you are bringing the SD of the samples down somewhat, and that's where the reduced vertical comes from.
The same thing applies for pointing. You're adding another mechanical operation here, and there's always a potential downside to this. And over done, yes, it will definitely damage accuracy, and measurably so. The key to both of these is understanding what you're doing, and not overdoing either.
Exactly the same thing applies there. Done correctly, meplat uniforming won't effect accuracy one way or the other. It will uniform BC, and that can result in decreased vertical at LR, but it's not really an increase in accuracy per se. Part of the trade off is a measurable reduction in BC, but you are bringing the SD of the samples down somewhat, and that's where the reduced vertical comes from.
The same thing applies for pointing. You're adding another mechanical operation here, and there's always a potential downside to this. And over done, yes, it will definitely damage accuracy, and measurably so. The key to both of these is understanding what you're doing, and not overdoing either.
