Compressed 223 77 TMK Load?

[groc426]

I'm fairly new to reloading, but having struggles with inconsistent loads with 223 77TMK.

My components are:

• Sierra TMK 77gr projectile
• New Starline 223 brass
• IMR 8208 XBR powder
• CCI 450 primers

My load:

• COAL = 2.26"
• Powder = 22gr

My reloading equipment:

• RCBS Rock Chucker Supreme
• Forster Full Length Sizing Die
• Forster Ultra Micrometer Seater Die
• Forster Funnel with Long Drop Tube
• Lyman Case Prep Tool
• Harbor Freight Digital Calibers (tested against precision blocks)
• RCBS 505 Scale and AND Digital Scale (both tested w/ precision weights)

To prep, I ran my brand new brass through the FL sizing die, then reamed and chamfered them.

During the entire seating processes I was getting inconsistent depths. I checked over and over to make sure my die was set correctly and locked down tight. Sometimes I would be off by 0.02" and other times by as much as 0.09". In the end I would adjust the micro dial and get it (close) to the correct COAL of 2.26". My bullets also had ring marks on the top portion of the bullet. I tried to listen and feel for powder crunch, but perhaps because of my inexperience I couldn't really hear or feel for it.

Today I went and shot about 20 of these loaded rounds in my AR-15. Measuring with a Caldwell chronograph my ES was 136 and SD was 42.

I'm wondering, is it possible that I have too much compression with this load? 22gr is the max from Sierra's load data for 8208 XBR. Looking through Rokslide it appears others are using even more powder without issues though.

Any other recommendations what I could be doing incorrectly?

I greatly appreciate the help.

 

[Bowfinn]

I'm fairly new to reloading, but having struggles with inconsistent loads with 223 77TMK.

My components are:

• Sierra TMK 77gr projectile
• New Starline 223 brass
• IMR 8208 XBR powder
• CCI 450 primers

My load:

• COAL = 2.26"
• Powder = 22gr

My reloading equipment:

• RCBS Rock Chucker Supreme
• Forster Full Length Sizing Die
• Forster Ultra Micrometer Seater Die
• Forster Funnel with Long Drop Tube
• Lyman Case Prep Tool
• Harbor Freight Digital Calibers (tested against precision blocks)
• RCBS 505 Scale and AND Digital Scale (both tested w/ precision weights)

To prep, I ran my brand new brass through the FL sizing die, then reamed and chamfered them.

During the entire seating processes I was getting inconsistent depths. I checked over and over to make sure my die was set correctly and locked down tight. Sometimes I would be off by 0.02" and other times by as much as 0.09". In the end I would adjust the micro dial and get it (close) to the correct COAL of 2.26". My bullets also had ring marks on the top portion of the bullet. I tried to listen and feel for powder crunch, but perhaps because of my inexperience I couldn't really hear or feel for it.

Today I went and shot about 20 of these loaded rounds in my AR-15. Measuring with a Caldwell chronograph my ES was 136 and SD was 42.

I'm wondering, is it possible that I have too much compression with this load? 22gr is the max from Sierra's load data for 8208 XBR. Looking through Rokslide it appears others are using even more powder without issues though.

Any other recommendations what I could be doing incorrectly?

I greatly appreciate the help.

The new brass has too much friction when seating the bullet, and it should get better in future firings. Try get some dry lube into the case necks. I use Hornady one shot case lube when I size the brass and make sure to get some in the neck when I spray it. This should help reduce the rings on the bullets. I think the ring is causing some elongation in the bullet and effecting your col

I have the same load as you in my tikka, but I use 205ar primers, 23.5g of XBR, and seat to 2.25ish. I think I first noticed compression closer to 23g. 23.5 is still a light enough compression that it’s doesn’t cause rings for me, or effect col enough for me to care.

 

[T28w]

I loading slightly longer for a bolt gun but same components and I’m mid 23 grains with no compressing. I didn’t fl size cases prior to loading new brass but did lightly lube inside of neck and just ran the ball expander in it to true the case mouth up, then chamfer and debur. How about a photo of how bad the ring marks are?

 

[groc426]

new brass has too much friction when seating the bullet, and it should get better in future firings.

Thanks! I now have some fired brass, so I'll load some more and see how it goes.

 

[groc426]

lightly lube inside of neck

I didn’t do this. I’ll try this and see if it helps.

Here is a photo of the bullet and typical ring I get with these bullets:

 

[Bowfinn]

I didn’t do this. I’ll try this and see if it helps.

Here is a photo of the bullet and typical ring I get with these bullets:

View attachment 925560

That’s a pretty mild ring I wouldn’t worry about it. My guess is it will look better on the reloads, but they will shoot the same. I was expecting something like this.

 

[T28w]

I agree with bowfin, that’s not bad and certainly not enough to cause the variance in seating depths. But rereading your post one thing is that the bullet seater is not base at the tip line measuring the coal. The cbto measurement will be more precise for measuring. I only measure coal the make sure it will fit if a mag, otherwise everything is base off cbto.

Edit. The cbto can be very consistent while coal can and will have some variation from my experiences. So get you gauge to measure cbto and see if it isn’t a lot more consistent.
My first explanation was terrible.

 

[T28w]

May also make sure that the bullet is not bottoming out in the seating stem. That tip looks a little off.