90gr TNT and 8208 XBR

[Oso Polaris]

I am loading for a Howa Mini with a magazine length of 2.415" (Oregunsmith's bottom metal). Based on my rifle's chamber, the COAL (max) is 2.263" (OAL Gage) with a corresponding CBTO (max) of 1.669" (Sinclair bullet gage). My initial load development was 29.5gr - 31.5gr XBR with a CBTO load length of 1.644" (2.20" COAL). This seated the base of the bullet approx. 3/4 into the neck. At approximately 30.5gr, the powder volume level located at the base of the neck (neck/shoulder junction).

I am planning to extend the seating depth (shorten the jump) to 1.660", which would place the bullet 2/3 into neck. Decrease bullet jump = increase gap/space between the bullet and powder (i.e. decrease case fill) In perfect world I like to have good case fill and also ability to play with bullet seating depth. Out of curiosity I wanted to know how much powder would fill the case with my current CBTO. At 32.8gr the case was completely full with no loose powder felt when shaking the cartridge and not compressed. This is +1.3 gr above max loads...theoretical exercise.

My Question: Most are loading for AR15 with 2.20" COAL for the 90gr TNT. Are you simply living with the extra space in the cartridge or is there a better solution?

Edit: As I come back and revisit this post from late last night (after work), I realize that the 1.3gr free space over a normal charge weight means a case fill of 90%-95%. This seemed much worse during the Shake Test because of the the length of the gap/running room in the neck amplifies the sound/feeling of the empty space.

[myrifle]

I topically go the opposite direction. I seat as long as possible, then after I find my powder charge, I start reducing the coal length by 5 thousands at a time and shoot a 5 round group at each shorter coal length.

[Oso Polaris]

I topically go the opposite direction. I seat as long as possible, then after I find my powder charge, I start reducing the coal length by 5 thousands at a time and shoot a 5 round group at each shorter coal length.

Agree - this is normally how I do load development and I starting with bullet set .002" of the lands until I establish a powder charge. Once my chare weight is locked in I then play with seating depth from slightly jammed to seating deeper in .005" increments.

As with factory barrels, my rifle's chamber is long by a couple of hundredths. I went with the standard load length recommendation because of short bullet profile of the TNT and my rifle's long chamber. If I were to touch the lands then the bullet would only be seated 1/2 into the neck. It's a field rifle so I trying to be more practical with my reloading so things don't get shifted while getting bouncing around.

[myrifle]

Agree - this is normally how I do load development and I starting with bullet set .002" of the lands until I establish a powder charge. Once my chare weight is locked in I then play with seating depth from slightly jammed to seating deeper in .005" increments.

As with factory barrels, my rifle's chamber is long by a couple of hundredths. I went with the standard load length recommendation because of short bullet profile of the TNT and my rifle's long chamber. If I were to touch the lands then the bullet would only be seated 1/2 into the neck. It's a field rifle so I trying to be more practical with my reloading so things don't get shifted while getting bouncing around.

Proper neck tention from the resizing die and the bullet wont move.

You should see how lil of the bullet is in the neck on my 85 grain maker trex handloads.

[Harpoon1]

[Oso Polaris]

Everything just seems a little bit faster than 8208XBR...

I have a good amount (#16) of XBR that I had planned to use for shooting precision long range 223 Rem. Its hard to ignore that LVR generates greater velocity so better powder for my long range. I am trying to find a good use for the XBR in other 223-based cartridges as well as for lighter bullets in the Grendel. I will just have to live with going a little slower with a temp stable powder with the 90gr TNT... paper targets out to 300 yards aren't going to notice.