Does neck tension/crimping improve accuracy?

[TomVan]

I understand the need to crimp in pistols, semi autos and tubular action feeds but in a bolt action rifle, will a crimp help improve accuracy?

[Bart Solo]

I understand the need to crimp in pistols, semi autos and tubular action feeds but in a bolt action rifle, will a crimp help improve accuracy?

NO.

[Iowegan]

In rifle ammo, crimps are only needed to hold the bullet in place during cycling or recoil, just as you stated. In a bolt action, a crimp will often impair accuracy.

Neck tension is quite a different subject. The bullet needs to be firmly seated (neck tension) so the powder will ignite properly. Loose or worse yet, inconsistent neck tension will result in non-uniform chamber pressures, thus inconsistent velocities. Of course this is will show up down range as poor groups.

A good way to insure uniform neck tension is to carefully inspect your brass after it has been sized. Examine the case mouths and look for splits, potential splits, and thin areas. When you are seating bullets, if you detect an unusually light or heavy pull on the press handle, you probably found a bad case.

Being an old bench rest shooter, I get anal about cases. If one doesn't look right I'll throw it in the cull box or the trash can.

[sgtt]

The only absolute I have encountered in reloading is that there are no absolutes.  99% of the time it will detract from the objective.  There is that rare exception when the best load I have encountered for that particular rifle will have a crimp.

[Loader 3009]

Lee Collet Dies are responsible for shrinking my groups to less than 1/2" in .223, .22 Hornet, .308, and .22-.250.  I use no crimp in these calibers.

[Reed1911]

In most cases crimp will decrease accuracy. Especially if the bullet you are using has no cannelure. Bullet makers spend a lot of money ensuring that the jacket is as perfect as possible, and when you crimp the heck out of it really tends to disrupt things.

There are some cases when using a crimp will increase accuracy, but you have to look at it from the view of one specific load W/O crimp VS the same load with crimp. The only scenario that comes to mind is the use of either a slow powder and short barrel; or too slow for caliber and standard barrel. In these cases, crimp will usually improve accuracy. Again, that is just a comparison of those loads to one another.