Crimp or No Crimp?

Bottle neck rifle cases for bolt guns. I get the part about crimping for tube feed guns, revolvers, auto loaders, heavy recoil guns, etc. Or bullets over compressed charges. Places you don't want the bullet to budge.

So I have at least two different references........Lyman 5oth, which says crimping is required for reasons given above, but otherwise, is detrimental to accuracy.

Then the LEE loading manual, which says accuracy is enhanced by a crimp? The reason they gave was the extra resistance of the crimp will cause pressure to rise to a higher level than just neck tension alone, leading to a more consistent powder burn. But if "accuracy is improved by a crimp" was mentioned once, it was mentioned five times.

So two manuals, two different recommendations for something I would think would be settled science by now. As a newb trying to wade through all this, such inconsistencies wear me out.

 

I use boat tail bullets in .223, .308,.204 rifles and I never crimp. I use these bullets especially so I don't have to. Crimping rifle bullets can create more issue than not. Neck tension is all that the bullet needs. Crimping is intended to remove the bell you added with expander dies. With boat tail bullets you don't need an expander. Just full length size and seat the bullet.

 

I've just finished reloading some 6.5X52 Carcano rounds using a round nose 160 grain Hornady bullet SP. The reason I ended up crimping the bullet is because after reloading with just the neck crimp, I ran some thru my Carcano Cavalry Carbine and had a bullet sink in the neck of the casing. To prevent excessive pressures due to the the bullet entering into the cartridge case, I used the Lee crimp die, but only had it adjusted to make the bullets stay in place, nothing excessive so to speak. BTW all the bullets were at the correct length as recommended by the Lyman reloading manual. Now every once in awhile, depending on which bullet I'm using, (the longer round nose) usually get the crimping die, however, the neck sizing die usually suffices for the other bullets. Note: I never load to maximum velocity, and stay at least 10% below said maximum. I've never seen a significant change in accuracy, from a crimped bullet and one that is only neck sized. Incidentally, I've been reloading for well over 50 years, and never have had an accident with any of my reloads. Obviously some are a lot more accurate than others, which is the reason I reload, with different components to eventually arrive at the most accurate load available to my particular rifle. BTW I have acquired quite a few over the years.

 

I think Lee likes crimps because they offer the Lee Factory Crimp Die, and maintain that a crimp is always beneficial. I don't think so in many cases, but it is in some... it really depends on the application.

As far as a crimp helping the burn characteristic of a specific powder... that's true. H110 (and other slow burning pistol powders) benefit from a good crimp, but other powders not so much. I don't know about rifle powders... I only crimp my rifle rounds out of necessity (lever-action, semi-auto, etc...) not for accuracy or helping the powder burn.

 

In some instances a crimp is beneficial for more than holding bullets in place. I have a 308 Win. that gives me excllent accuracy (7/8" @ 100, which is stellar for me!) and I do not crimp My 30-06 Garand likes a mild crimp, a Lee Collet Crimp just enough to straighten out the case neck. I shoot a lot of 44 Magnums and a heavy crimp is necessary for decent performance. I use slower powders for my magnums and yes, a crimp s beneficial for consistent powder burn. My other bottle necked rounds usually don't get a crimp and some ae difficult to tell if a crimp or no-crrimp is best. The best way to determine your handloads needs is load up 10 with no crimp, load up 10 with a crimp. See which shoots the best in your gun as the results may differ in another gun of the same caliber.

 

When I tested crimp vs non-crimp the Non-Crimp won out on my rifles. The only time crimp is required for a rifle is with Tubular magazines and some times simi-auto. If you do not have enough neck tension on a Simi-auto the bullet can be jammed into the case during feeding. I have found if I run 0.003"-0.004" neck tension, crimp is not required. Now if you crimp into a non canalure you damage the bullet. Best if your going to crimp is that you crimp into the canalure to prevent damage. I normally find that the canalure grove is never where I want it to be.

Lee Recommends because they want to sell you their FCD. That is why they push them. I like they way they work for bottle neck rifle, but not required 99% of the time. btw. I have never bought 1 and don't plan to.

If you go to any long range match, none are crimping there bullets that I know off.

 

I crimp every rimmed cartridge.

 

I'm not trying to be a wise guy here, but you're likely to get the same "two different recommendations" (crimp or no crimp) on an internet message board, AND you're likely to get a dozen or more reasons as to why or why not.
I can only tell you what I do. I crimp handgun rounds (roll crimp revolver rounds and taper crimp semi-auto rounds), and I roll crimp rifle rounds for rifles with tubular magazines. I also roll crimp my .45-110 rounds because I'm using compressed charges of black powder.
On the other hand, I've never crimped any of the bottle-necked rifle cartridges I've loaded for bolt action rifles. And trust me, I've loaded for a few real "kickers" - like a couple of .300 Win Mags and my .338 Win Mag. For that matter, even my beloved .308 Norma Mag is no slouch when it comes to recoil. I've just never seen the need for a crimp on a bottle necked rifle cartridge, and I have checked the cartridges left in the magazines of my hard kicking rifles after I've fired a round or two - if the bullets have "pointy" soft lead tips, they get flattened, but they don't get driven deeper into the cases.
Admittedly, the reason I've never seen those bullets get driven deeper into their cases with my hard kicking bolt action rifles might be because I've never used a sizing die that didn't provide adequate neck tension even without a crimp. Also, I have to admit I don't know whether or not a crimp affects accuracy when it comes to bottle-necked cartridges in bolt action rifles because I've never crimped them. I'm a hunter, not a bench rest shooter or some kind of precision rifle competitor. As a hunter, 3-4 bullets in an inch at 100 with a bolt action rifle is "good enough." So I just don't care about whether or not my bolt action rifles would "shoot straighter" if I crimped the bullets in place. The remaining bullets in the magazines don't get driven deeper into their cases when my "hard kickers" go off - that's the most important thing to me.

 

I can't see how unless without a crimp, the bullet moves in the case a bit, changing the pressure - why either way it would make any difference if your crimps are consistent.

 

Lee is selling their FCD.

I never crimp for ceremony's sake, only to solve a defined problem. Had to flare a case? Crimp back to diameter so it fits. Slow burning revolver powder? Crimp for combustion.

I have never had a neck tension issue in bottleneck cartridge that wasn't solved by addressing the cause in sizing. Crimping would have been a lousy bandaid.

 

I crimp all my reloads, straight-walled and bottle-necked.

 

In a bolt gun crimp is an extra step that can contribute to consistency problems. I shoot 308 and 223 and 6mmbr in bolt guns no crimp. In a semi auto absolutely, tube fed lever gun hell yes. Bolt action single fed, why.

 

Pretty easy to test.

A crimp can,and does show improvement with certain cast loads in bolt guns. Same as using fillers. To patently claim yes or no is pretty short sighted. It is sorta like a crutch... but hey,sometimes a crutch is exactly the right tool. If forced to put an actual figure on it,I'd say maybe 10% of the bolt gun loads I use have a real crimp.... meaning more than just snugging up any case expansion from pre seating.

 

Fair, type of bullet was not covered cast does change my answer. A bow tail seated with a chamber seater shows no improvement in my experience.

 

Just test it..... it's one of the easiest to do. Cast or jacketed.

It's similar,to a jam. You're effecting the pressure rise on an XY scale. Another area is your total loaded round neck clearance. With jacketed you "usually" can't reduce clearance.... you can if your making cases from other than that chambering... With cast we change the bullet diameter. That's when crimping can sometimes sneak a little accuracy in.... it's splitting hairs on neck clearance.

And depending on how hard you run the rounds up through the magazine... a crimp can help. But even there,I'd at least try to work on other aspects like changing bullet profiles. Round noses may give up some pure accuracy but dang,get their OAL in the sweet spot and they'll load like greased ball bearings. Then,you won't need a crimp... see,clear as mud.

 

I do not crimp any of my bottle neck rifle rounds whether used in a semi-auto rifle (AR-15, Garand, and M1A), break action rifle, or bolt action rifle. I generally find the accuracy is better when I do not crimp.

But, I will not say I'd never be in a situation where I need to crimp a bottle neck rifle cartridge.

I do taper crimp 357 Sig and 38/45 Clerke. Both are bottle neck handgun cartridges. I have to remove the slight belling of the case mouth.

The only tubular magazine rifles that I have are pistol cartridges and they get crimped anyway.