6.5 creedmoor FL Rcbs Fl do I need to crimp

Semi auto or bolt? Personally the only thing I crimp is for semi auto guns. Also, I have found rcbs dies to have fairly stiff neck tension compared to others I have used.
 
Then no for sure, I shot semi auto non crimped as well but there is some argument to be made for setting back a bullet you don't intend to semi auto but the same is really true if you magazine feed a bolt action.
 
I am of the teachings that a good taper crimp does the job, semi auto or bolt. I shoot high powered stuff like short mags and belted mags, and they come with a heckuvalotta recoil.

It hasn’t happened to me YET, but I also don’t want it to happen to me. Bullet “pull” from recoil. The theory I was taught was that under the report, the momentum of rearward movement, and the inertia of the bullet pressed into the cartridge (the casing being held in place and “tied to” the moving firearm) could cause the case to move backwards faster than the bullet, causing it to pull out slightly under recoil.

So when I was taught reloading, a factory taper crimp was the desired result. This way, if your bullets didn’t have a cannelure in them, you could still get a good grip on it without digging in. I have had phenomenal results in all my work with this.

Your results may vary, of course.
 
I've loaded and shot almost 10,000 rounds with my three 6.5mm CM bolt actions, about 11,000 rounds with two .223 bolt actions, and over 12,000 rounds with two .308 bolt actions all with what I consider good accuracy.
(I've documented summaries of the results in the 110 and Ammo & Reloading forums.)
I have never crimped any of my bolt action loads. I use either BR primers or match primers with my bolt actions.

I have crimped my early 5.56x45 loads for my ARs but found that when I loaded for accuracy, I wasn't pushing Pmax and stopped crimping even them. I do use CCI 400 primers with my ARs to protect against slam fires.
I recently loaded about 300 rounds for my Les Baer Super Varmint .223 (69 grain SMKs at 2780 to 2790 fps) and didn't crimp them. No issues and very good accuracy.
 
The theory I was taught was that under the report, the momentum of rearward movement, and the inertia of the bullet pressed into the cartridge (the casing being held in place and “tied to” the moving firearm) could cause the case to move backwards faster than the bullet, causing it to pull out slightly under recoil.
Click to expand...

Its not a theory, its an observed fact. BUT bullet "pull" is rarely an issue for rifle shooters, it is something revolver shooters need to be concerned with.

With rifles and semi auto pistols the concern is bullets being pushed back into the case, not pulled out from recoil.

This is due to the way the different designs handle the ammunition. Ammo is only "tied to" the moving firearm in revolvers. Because the cylinder chambers also function as the magazine, and rounds in the cylinder are held in place during recoil by the case rim (or headspace ledge if rimless). When the revolver recoils, the case is held firm in the cylinder, and the case is pulled back during recoil, while the bullet is not, and it is inertia that holds the bullet in place while the gun in recoil pulles the case backwards, off the bullet.

This is called bullet creep or bullet jump, because it appears the bullet had jumped forward, but the reality is the case was pulled rearward. The amount of "pull" depends on the balance between bullet mass (intertia) and the recoil force involved. Proper case neck tension is enough to hold the bullet in place when these forces are low. When they are higher, a crimp is needed. At very high levels a heavy roll crimp is needed.

Rifles do it differently. Pull is not the issue, being pushed in (and/or mashed) is the issue. Unlike a revolver cylinder, ammo in a magazine is not "tied to the gun". It "floats" in the magazine. There is some clearance between the round and the front and rear magazine walls.

During recoil, the entire round in a box magazine just "sits there", due to inertia. The rifle moves back under recoil but the ammo does not, UNTIL the rifle contacts it. This happens when the front wall of the magazine, moving rearward during recoil slams into the nose of the bullet, pushing the entire round back, and often (again, due to inertia) pushing the bullet deeper into the case. This also often results in deforming (mashing) soft nose bullets, IF the recoil forces involved are powerful enough to do it.

Additionally, there are two other situations specific to firearm type. One is the semi auto where it isn't just recoil but is also the bullet being slammed into the feed ramp during the loading cycle that tries to shove the bullet deeper into the case. The other is tube magazine rifles. Here you have the combination of the entire column of ammo, lined up bullet nose against the case ahead of it "slopping back and forth" under recoil forces, PLUS spring tension slamming the rounds to a sudden stop during the feeding cycle.

These are the reasons we crimp ammunition (roll or taper and amount used) when NEEDED due to the recoil and operating characteristics of the firearm it is being used in.

When these don't apply, we don't need to crimp. Proper neck tension alone is enough to do the job. A light recoiling repeater, such as the 6.5mm bolt action mentioned, ordinarily doesn't need crimped bullets.

The other thing to remember about crimp, when its done right (and needed) it is a benefit. But when its not done right, it can be worse than no crimp and done really badly (such as in the wrong place) is a disaster that can make ammo unchamberable and unusable.

Hope this helps you understand why some rounds get crimped and others don't.
 
Lake City arsenal says they crimp 30 and 22 caliber service ammo's case mouth into the bullet cannelure to survive rough treatment before chambering so it will function reliably in combat. Case neck inside diameter is a couple thousandths inch larger than the bullet's diameter before bullets are seated so the asphalt sealant is smeared inside before the bullet is seated. Then case mouths are crimped in and the sealant hardens. Bullet pull force is then at least 60 pounds

Ditto for a few commercial ammo companies desired reliability in all hunting environments
 
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