88 TMK Loading Thread

[Nine Banger]

think of it this way.

freebore is additional case capacity. the bullet doesn't encounter meaningful resistance until it hits the lands..235" is nearly 2½x the .100 freebore in this comparison.
either you have a huge jump or you load the bullet out longer and get more useable case capacity, either way you can add powder to get to pressure.

so the +P is a modified land transition specifically to reduce the pressure spike from the freebore/bore transition. This allows more powder to be added to get back to the operating pressure which increases velocity by lengthening the pressure curve.

Weatherby is always referenced as being an early example of long freebore/high velocity.

My experience is freebore/jump/capacity will make a more dramatic difference in velocity than barrel dimensions in a comparison like this.

 

[Thegman]

think of it this way.

freebore is additional case capacity. the bullet doesn't encounter meaningful resistance until it hits the lands..235" is nearly 2½x the .100 freebore in this comparison.
either you have a huge jump or you load the bullet out longer and get more useable case capacity, either way you can add powder to get to pressure.

so the +P is a modified land transition specifically to reduce the pressure spike from the freebore/bore transition. This allows more powder to be added to get back to the operating pressure which increases velocity by lengthening the pressure curve.

Weatherby is always referenced as being an early example of long freebore/high velocity.

My experience is freebore/jump/capacity will make a more dramatic difference in velocity than barrel dimensions in a comparison like this.

True...but...his chamber is 2.50 + .100 = 2.60" with the 88 TMK and an AI to boot, which adds even more volume.

Mine is 2.340 + .235 = 2.575" with the 88 TMK and standard 5.56 chamber, so he definitely has more overall chamber volume in his chamber. I'm limited to OAL by the AR-15 platform (using a windowed magazine).

The idea of a different transition to the rifling is interesting...and who knows what else, I guess.

 

[longrangelead]

True...but...his chamber is 2.50 + .100 = 2.60" with the 88 TMK and an AI to boot, which adds even more volume.

Mine is 2.340 + .235 = 2.575" with the 88 TMK and standard 5.56 chamber, so he definitely has more overall chamber volume in his chamber. I'm limited to OAL by the AR-15 platform (using a windowed magazine).

The idea of a different transition to the rifling is interesting...and who knows what else, I guess.

it's possible other factors combined could add up to such a difference.
I know my 73ELDM/LVR load is reduced 100 fps from 40 degrees to -15.

I haven't tested temp variability above 40 because it doesn't seem to be a big enough variable to matter.

powder variation and slow/fast barrel could influence the gap, there is a lot going on there.

 

[SeanM243]

Not sure if this is the place to post this, Harvested a small (~100 lb) sow yesterday with the 22 Creedmoor/40g H4831SC/88 TMK combo and was pretty impressed. Bullet actually seemed to be slightly tougher than the 77 TMK in my opinion. 75 yard shot, total travel distance after the shot was about 3 feet. Quartered to, bullet traveled through onside shoulder and exited about 5 inches behind far shoulder. I did take some pictures and can add them if anyone is interested.

 

[Thegman]

Not sure if this is the place to post this, Harvested a small (~100 lb) sow yesterday with the 22 Creedmoor/40g H4831SC/88 TMK combo and was pretty impressed. Bullet actually seemed to be slightly tougher than the 77 TMK in my opinion. 75 yard shot, total travel distance after the shot was about 3 feet. Quartered to, bullet traveled through onside shoulder and exited about 5 inches behind far shoulder. I did take some pictures and can add them if anyone is interested.

What was the impact velocity? Thanks for the input. I've been waiting to see some examples of on-game performance from the 88s.

To add: Maybe throw a few pics in the 223 for Everything thread. I think on-game 88 pics will be the next big thing on that thread.

 

[SeanM243]

Impact velocity would be around 2625 fps, it's a very slow load.

Onside shoulder hit slightly high.


Onside shoulder removed


Exit mid ribs

I didn't open her up to see internal wounding as I was in a rush but she was very close to DRT with what wasn't a perfect shot. At my velocity, the 88 TMK seemed to be slightly tougher than a 77 TMK at similar velocities. It did seem to open very quickly and the permanent wound cavity was large with it sounding like a washing machine when I turned her over.

If I can answer any further questions about it, I'm glad to the best of my ability. I'll continue to test the 88 TMK as opportunities present themselves.