New Sierra 77gr With.....

[NRAhighpowershooter]

Now Sierra offers a 77gr SMK with a cannelure!!!

[Jicko]

Exactly *sigh*!!!

They may now need to tell us what powder, how much powder to use, and what cases.....

[ocabj]

Yes, this item is already available at retailers. I think Sierra actually announced this several weeks ago, but they did have press release information and samples at SHOT Show.

Click image for higher resolution/quality image:

[pklin1297]

saw that at the SHOT and I'm happy they came out with it! Looking to try it with my next batch to use with my AR to see if I run into any problems with seating depth.

[ocabj]

There really isn't anything to test assuming you already have a load developed for the existing Sierra 77gr Match King. It is the exact same bullet except with the light cannelure. When I say 'light' I do mean light. As far as cannelures go, the cannelure used for this bullet (which is the same exact bullet on MK 262 mod 1), it's neglible. If anything, it's more of a cosmetic item that I am amazed that people are willing to pay extra for.

[Fjold]

I don't like cannelures in match bullets as I set my bullet length to match the throat measurement.

[pklin1297]

I am still learning about cannelures, so please excuse my ignorance. Cannelures are good because they are easier to determine seating depth correct? You would just seat it to where the top of the brass is sitting in the middle of the cannelure? Also, I've read somewhere that you would crimp after you seat to the cannelure location... Is this true? What kind of crimp? Is a crimp even needed for .223?

Thanks!

[ocabj]

Cannelures are required if you are going to crimp the round.

When the military made specs for what would become MK 262, one of the requirements is that the bullet must have a cannelure and had to be crimped. I do not remember where I read this, but Nosler lost the contract to supply the bullets because they wouldn't put a cannelure on the bullet. Nosler actually supplied the bullets for the early run (first version) of MK 262.

Sierra then complied with the requirement by putting on a very light cannelure. Again, the cannelure that is on the Match King is very, very light. I don't think you can put on a serious crimp that is common on actual M193/M855 ammo without compromising the jacket integrity (and accuracy) even with the cannelured version. But from what I remember reading, Sierra simply put this light cannelure to win the contract.

When I have time, I'll try to take a picture of the 77gr MK with cannelure side-by-side with some M855 pulls.

[pklin1297]

Thanks much ocabj!

Would you use a roll crimp or taper crimp with cannelure?

I saw the cannelured 77gr at the Show but couldn't remember how deep the cannelure was. Judging from the picture up top it is rather faint.

[Ahhnother8]

The cannelure is likely positioned such that the case mouth is even with it when the bullet is seated to magazine length. If loading the bullet to touch the throat, the cannelure will likely be above the case mouth.

And, you do not need a cannelure on these bullets. And, you do not need to crimp .223 brass either. With .002 or more neck tension, the bullets will not move. Even with compressed powder loads, the bullets don't move.

FWIW....

Lane

[alpha_romeo_XV]

I got some from Wideners a couple weeks ago. $220/1000 w free shipping. Loaded up 100 and will try them out in HP service rifle match this weekend.

[ocabj]

77gr SMK w/ cannelure on left, 62gr M855 pulls on right.

[pklin1297]

The new cannelures on the 77gr look like they are just lines drawn on the sides of the bullet compared to the old cannelures...

[30Cal]

Meh. It makes sense from a "we want to win .mil business" case. For my use, it's non-value-added at a higher cost.