223 Rem OAL problems

[JDM66]

I recently picked up a Sako 85 varmint in 223 and want to work up a load. I decided on 77g SMK and got out my Hornady measuring tools to get CBTO and got 1.830 that translated to COAL of 2.230. I want to bump back 0.010 from lands which will give me 2.220 as my COAL. Both the Lyman and the Alliant reloading information warns to not go below 2.260 as pressures will be too high. Is there something I'm doing wrong or are some rifle chambers on the short side. I'm very confused. Thanks

 

[MikeMcCasland]

What is the twist rate on your 85? Sako makes them in 1:14 all the way to 1:8.

The fact that you can't get 77 SMK to 2.26 would indicate you've got very little freebore to work with, which would be odd on a gun with a twist rate that would stablize a 77gr bullet.

Twist rate issues and chamber aside, you could still run it at 2.220, you'd just need to make sure you start at book minimums and work up in ~.2gr increments. Chances are you'll find pressure signs before book maximums.

If it turns out you have a 1:14 - 1:12 twist barrel, save yourself some time and use those 77 SMKs through an AR (what they're meant for to begin with). A 1:14 - 1:12t would be right at home with a 52gr SMK.

 

[rangerlong]

Yes, sometimes chambers have throats that are too short. I can’t say whether this particular gun is designed that way, or it’s a defect. If you have a slow twist barrel sako may have optimized the chamber for shorter bullets.

I agree you can start at minimum charges and load right to the lands, if your barrel twist will stabilize the 77gr.

 

[JDM66]

The rifle is 1in8 twist. I just took measurements using 80g and also tried 75 g and they are also under specs the 80g was 2.370 for COAL Lyman manual states 2.550 OAL and the 75g was 2.220 COAL book says 2.390 This is really strange.

 

[MikeMcCasland]

The rifle is 1in8 twist. I just took measurements using 80g and also tried 75 g and they are also under specs the 80g was 2.370 for COAL Lyman manual states 2.550 OAL and the 75g was 2.220 COAL book says 2.390 This is really strange.

Sounds like they're using the same reamer for varmint barrels that they are for faster twist stuff. It's not a massive problem; just less than ideal as far as bullet location in the neck, and powder capacity.

You'll probably end up with slower velocities than properly chambered setups, but otherwise it should be fine.

If it really bothers you, make a dummy round with the bullet you want to shoot seated to the depth you want it at, and take it to a smith and have them throat it the way you want.

I'd probably clean the throat out to make sure you're not hitting some debris, and double check the twist rate with a cleaning rod and a patch though...

 

[rangerlong]

I have a Savage in 6mm creedmoor that was very difficult to chamber, and pushed bullets deeper into the cases.
It went back to savage for repair.

I think I’d call Sako if it’s still under warranty.

 

[NighthawkCG]

When you say 'measuring tools', which ones specifically? The tools to measure your CBTO, COAL, distance to lands, and headspace are all different. Can you elaborate on what you used to get that measurement? What did you measure as well (a fired case, a loaded factory round, etc)?

 

[JDM66]

I used the Hornady OAL striaght rod with the 223 modified case and 77g SMK bullet and Hornady bullet comparator