Sierra 77gr SMK: cannelure vs. no cannelure

[sentry1]

Is there a difference in use/performance between the two when used in an AR? I've shot plain 77 gr SMKs in my AR and had great results, but I've found that the cannelured SMKs are easier to find at times.

Does the cannelure affect the accuracy of the bullet, and if so, significantly enough to be noticed in a 16" AR, or even a Remington 700 varmint rifle? For my intents and purposes, we can ignore bench rest levels of accuracy.

 

[rjacobs]

I've shot both. Couldn't tell a difference. I just bought 1k non cannulared if that says anything. If you heavy crimp and need to seal your bullets the cannular is obviously necessary. A light crimp and no sealant you don't need it. I don't think there is an accuracy difference personally.

 

[sentry1]

I've needed to put a heavy crimp on second hand, resized 55 gr FMJBT bullets, but I've never had that issue with SMKs, they feed just fine even without a light crimp.

 

[dbateman]

I run 77smk with a cannelure because I found them easier to find as well.

I did think about the effect on accuracy as well but I don't think it is that big an issue after its been pushed into the riffling and forced out the other end.
They seem just as accurate as none cannelure projectiles.

 

[leid]

OP,
Long ago, I rolled a heavy M193 type cannelure on 70gr. Speer bullets with a CH tool then roll crimped the case to them to see what effect it would have on my pet load: group size doubled. Putting a heavy cannelure on a bullet then crimping the case to it does nothing to enhance accuracy. Probably one of the reasons why the M118/M852/M118LR cartridges don't use cannelured & crimped bullets. The original Black Hills MK 262 MOD 0 ammunition used the 77gr. SMK without cannelure. So did all of the 77gr. SMK MATCH ammunition I have used in the past but I don't know about the latest MATCH loads. BH did not want to use a cannelured & crimped bullet because it could possibly have a negative effect on accuracy especially if executed poorly. When DOD required BH to further weaponize the MOD 0 cartridge to MOD 1 spec by using a cannelured & crimped bullet (I believe around 2002-2003), a very mild cannelure was put on the 77gr. SMK bullet to keep any degradation of accuracy to a very minimum. I prefer using the non-cannelured 77gr. SMKs for handloading because I don't crimp anyway. But the cannelure may help the bullet fragment enhancing terminal performance if that is part of your goal. I tested an 18" 1x7.7 full-heavy Krieger to 750yds. in trigger-pull conditions & accuracy was virtually the same between the factory BH MK 262 MOD 1 cannelured 77gr. SMK load & my non-cannelured 77gr. SMK handload. So I would think it is pretty much a wash accuracy-wise unless you are on a bench looking for the smallest 5.56MM groups way out yonder. And you would probably want to use an over-mag-length 80gr. SMK or VLD load for that purpose anyway. HTH.