Taper crimp or ?

[Trueblue]

So, getting setup on my Dillon 550 to reload for 6.5 Grendel.
Coming from a bolt rifle background, I would trim necks, and use .002 neck tension.
Not trimming necks for a short range(3-400yard) AR, buy was wondering about neck tension of .003-.004 vs crimping. Also, seemed to be a difference in the type of crimps used, such as taper crimp or a crimp like what Lee factory crimp die uses. So, what is the consensus on this? Do most of you crimp or run tighter neck tension, and if you do crimp , what type do you use?

[Sticks]

.003 neck tension and no movement of bullets in an AR cycling for me .

From what I have gleaned, there is a little bit of everything being done. Loaders preference.

[Zeus]

I've never crimped an AR15 load......thousands and thousands of them have functioned as expected. Give it a shot if you like.....but if your neck tension is messed up then crimping won't help.......

[Jakal]

What Sticks said...

[Klem]

True Blue,

Sticks is right, there does not seem to be a consensus on what is better; crimping or neck tension. I imagine it's so close that it depends on what your load/rifle likes.

That said, I did a test between the two and for my rifle neck tension is more accurate. You can see by the data that it's so close that it really doesn't matter. On a single-stage press neck tension is one less stage you have to go through so it saves time as well. With your Dillon progressive there's no time saving so it's not an issue.

4-rd groups at 100yds, bench-rested. No groups discounted. The taper crimp die I used is a Redding.

[Trueblue]

Thanks for the replies.
Going to run with .003 neck tension and see if that is enough.
The 6.5 Grendel doesn’t have much recoil.

[hikfromstik]

I just ordered a Lee factory crimp die for my 223 . I would have a much faster round here and there on my magnetospeedV3 , so I figured I was getting a bullet pushed back and increasing pressure . Sure enough the crimped helped . That 1 inch high flier disappeared . I use a .286" bushing in my Redding type S die for 6.5 Grendel . It holds enough that I don't get any bullet push back . So either will work in my experience.

[Crusty]

My rounds are working fine at .002" neck tension and there is no movement of the bullets. I don't intend to ever drop my ammo out of an aircraft so I don't see any need for a crimp.

[centerfire]

My rounds are working fine at .002" neck tension and there is no movement of the bullets. I don't intend to ever drop my ammo out of an aircraft so I don't see any need for a crimp.

Same here. I find tension uniformity more important than the amount of tension. I tension with a neck mandrel turned to .2625. It gives me slightly more than .002 tension if all the brass is annealed the same. Crimping changes the uniformity.

[Mad Charlie]

"Crimping changes the uniformity"

Yes, it does.

[Klem]

I might add that my experience is of bullets moving forward due to not enough neck tension, not being pushed back. The rounds were being cycled as normal and when coming to a sudden stop in the chamber the bullet continues forward slightly under inertia, like one of those kinetic bullet-pulling hammers. This lead to the occasional bullet going forward so much that it came to a stop in the lands. Took me ages to figure out why the occasional vertical flyer.

[centerfire]

I might add that my experience is of bullets moving forward due to not enough neck tension, not being pushed back. The rounds were being cycled as normal and when coming to a sudden stop in the chamber the bullet continues forward slightly under inertia, like one of those kinetic bullet-pulling hammers. This lead to the occasional bullet going forward so much that it came to a stop in the lands. Took me ages to figure out why the occasional vertical flyer.

Yes, that is what I understood you to mean. Heavier bullets need more tension.

[centerfire]

It's worth mentioning that the ID of the sized case compared to the OD of the bullet is the interference not the actual tension. The hardness of the brass determines the tension. There is a correlation between the interference fit of the brass and bullet and neck tension but the actually tension will change with the metallurgy of the brass.

I loaded a dummy case, marked at the bullet junction with a marker, with .0025" of interference and cycled the case from a magazine using the BHO 20 times in a row. The brass was brand new, trimmed to 1.510 and neck sized with a mandrel. After 20 cycles into the chamber there was no visible or measurable (with a comparitor) changes in COAL. There is slightly more inertia on the second cartridge in the magazine when firing the rifle as opposed to cycling from the top of the magazine with the BHO but 20 cycles should be enough to identify any COAL changes. The hand cycled cartridge was pretty knackered looking despite not changing length.