Asking 4 Help - Sierra MatchKings: 77g vs 80gr (.223 cart.) with CBI barrel

[jhelmuth]

Hey fellow barrel nuts!

Just got my new Criterion barrel in .223 from Jim (NSS) in a 1:8 twist (and 28" length).

I'm going to verify/test her out using 69gr SMKs, but want to work up some longer range loads with either the 77gr or 80gr SMKs (which I need to order).

Any experience you've had with these in similar/same barrel would greatly be appreciated (always cuts down some time, effort, and $ to get there).

Thanks in advance for your feedback.


Jim

[Grit #1]

What chamber do you actually have? Is it a 223 or a 5.56 match chamber? The 77SMK is designed to be seated deep and feed out of a standard AR15 mag. The 80SMK is not and it requires a 5.56 match chamber. The throat is substantial longer in the match chamber than the standard .223 chamber. That said your .223 chamber might have more throat that the Krieger .223 chamber which is the chamber in my AR varmint rig. Very short throat.
Best regards,
Grit

[BoilerUP]

24.5gr Varget and 75/80gr Amax

[jhelmuth]

What chamber do you actually have? Is it a 223 or a 5.56 match chamber? The 77SMK is designed to be seated deep and feed out of a standard AR15 mag. The 80SMK is not and it requires a 5.56 match chamber. The throat is substantial longer in the match chamber than the standard .223 chamber. That said your .223 chamber might have more throat that the Krieger .223 chamber which is the chamber in my AR varmint rig. Very short throat.
Best regards,
Grit


Good info Grit....

Criterion is a child of Krieger, and I'm told that their chambering is similar. Having said that, this CBI is chambered in .223 (nothing special) - not a 5.56. Jim (NSS) told me that the throating would probably be OK for 80g, but no bigger.

Sounds like the 77gr SMK is a better choice.

[jhelmuth]

24.5gr Varget and 75/80gr Amax


Are you shooting these out of a CBI barrel? Tell me more...

[lal357]

i just put a cbi 223 barrel 26" varmint contour (wylbe chamber)on as well took my chamber readings with 75gr. match and amax's as well as 80 gr. amax i will have no problem seating 80 gr heads out some yesterday during break in i shot some junk bullets (75 gr.) thru it shot well most groups @ 100 yds were 3/4-1/2 with no load developement . i'm going to load up some of the same heads as well as 80gr amax heads and see what they will do @ 300yds(range i prefer to shoot at) hopefully next weekend i'll let you know how it does.

[jhelmuth]

The Wylde chamber is throated longer. Since I'm planning to use this in F/TR, the Wylde is not a chamber I could use (that's why I stuck with the std. .223 chambering).

[Grit #1]

You could use any chamber you want in FTR the restriction is caliber 308/7.62x51 or .223/5.56 your choice. I read no where in the rules that restricts chambers.
Best regards,
Grit

[jhelmuth]

Well... I don't control that so while we could debate it, it is not in my control to make that decision.

Having said that, I do not have the .223 Wylde chambering...