223 wylde CBTO OR COAL measurements

[DLT]

If there is anyone who has a low round count, 223 wylde chamber in a bolt gun and don’t mind sharing their CBTO with the hornady tool or COAL at just touching the lands and what bullet the measurement is from I would certainly appreciate it. Thanks in advance

 

[Jeff Porter]

I have seen numbers of 1.945"-1.975" for CBTO using my Hornady tool and 77SMK bullets in new Wylde chambers in AR barrels . That is a ball park value. What are you seeing?

 

[Richard Jones]

My touch number on a very new 223 Wylde chamber is 1.879 using a .219 bushing as a comparator. I can't help on the Hornady comparator. That number is for any bullet. I don't measure COAL. Does that help?

 

[DLT]

I have seen numbers of 1.945"-1.975" for CBTO using my Hornady tool and 77SMK bullets in new Wylde chambers in AR barrels . That is a ball park value. What are you seeing?

Thanks for chiming in ! I don’t have a 77smk, I have a 69smk. I don’t know how similar their ogives are but I’m getting 1.890

 

[DLT]

My touch number on a very new 223 Wylde chamber is 1.879 using a .219 bushing as a comparator. I can't help on the Hornady comparator. That number is for any bullet. I don't measure COAL. Does that help?

If I knew exactly how you was measuring in relation to my tool it could be. A .219 bushing slid over the bullet look like it contacts really close to where my tool would.

 

[Liven The Dream]

I have seen numbers of 1.945"-1.975" for CBTO using my Hornady tool and 77SMK bullets in new Wylde chambers in AR barrels . That is a ball park value. What are you seeing?

Jeff,
With you had checked rifles and found .030 different for Wylde Chambers ?? Or so called Wylde ?

 

[Ned Ludd]

Be cautious about comparing CBTO values to make some kind of estimate regarding chamber length. The diameter of the hole in different comparator inserts can vary widely, thus leading to fairly significant differences in measured CBTO values. COAL may be a bit better measurement for such comparisons as long as the exact same bullet is used, but one has to take Lot-to-Lot bullet OAL variance into account.

 

[Laurie]

The diameter of the hole in different comparator inserts can vary widely, thus leading to fairly significant differences in measured CBTO values.

Yes, even from the same supplier. I have two Hornady inserts for some calibres and it took a while before I twigged that they often gave different results. I've now marked up the inserts I use for CBTO measurement with red spots using an indelible write-on-anything sharpie.

 

[Jeff Porter]

Jeff,
With you had checked rifles and found .030 different for Wylde Chambers ?? Or so called Wylde ?

Rifles from the same shop tend to be spot on to a few 0.001" ( I have been through several White Oak Service Rife barrels). I have three form other shops and one from a discount house.. those were what gives me the range but yes, I have seen that much difference.

I could be convinced that the shorter ones were actually stuck in the leade that need some more polishing. I have seen other shooters freak out after 100 rounds saying they were already 0.050" eroded.... But measured the same as my "standard" 1.960" WOA on my tool. My Hornady tool has the curved handle and has some years on it but it repeats for me.

 

[Richard Jones]

If I knew exactly how you was measuring in relation to my tool it could be. A .219 bushing slid over the bullet look like it contacts really close to where my tool would.

Bored out a comparator I didn't need.

 

[DLT]

View attachment 1395893View attachment 1395895

Bored out a comparator I didn't need.

I see. That’s pretty slick.

 

[762plinker]

View attachment 1395893View attachment 1395895

Bored out a comparator I didn't need.

yeah but
that bushing has a RADIUSED MOUTH... so just where do ALL bullets touch ??
grind it shorter and flat with no burrs....then maybe

 

[Richard Jones]

^^^ So it measures at the smallest dia, not at the mouth. So, in theory, ALL bullets touch at the bushing size. Imagine if the very end of the bushing was, for giggles, 1" in diameter. The bullet still wouldn't touch anything until it got to the bushing size, right? If that measurement is repeatable, and it should be, at least within a thou or so, shouldn't matter what size the RADIUSED MOUTH is....

 

[RegionRat]

I have seen numbers of 1.945"-1.975" for CBTO using my Hornady tool and 77SMK bullets in new Wylde chambers in AR barrels . That is a ball park value. What are you seeing?

I am seeing roughly the same as Jeff, probably because I have been a WOA user for a long time too.

In Service Rifle, the 77 grain tends to be used at magazine length and the 80 is the one where we single feed and are more concerned with jump. YMMV