Thread: Chamber for 223 running heavies with AICS

I have a new 1:7 18" 223 barrel that is about to be chambered in 223. I want to run both 75/ 80gn class projectiles and 55s. It will be on an AICS magazine so no limitatation there.

So if you have a barrel that happily runs both what COL and CBOL are you running?

Thanks

Out of interest, what is the max OAL that the AICS mag can take?

The plastic ones I have are 65mm max, you'd probably run them at 64mm.

I've looked into this quite a bit.
In the US a .169 free bores is very popular for running heavy projectiles, but lots of guys also just use a 223 Wilde reamer.
There are dozens of different reamers you can get and they all seem to work to some degree or another.

If you really want to maximise performance for a certain projectile weight getting them reamed with a throating reaming to a dummy cartridge dimensions is the best way.

Most 55gr bullets are pretty jump tolerant so should work just fine in a longer free bore.

It is a bit interesting.

Running 80 ELDMs with the boat tail at neck junction gives an COL of 64.0 and a CBOL of 49.70mm.

By way of comparison my old 80 Sierra load was 48.30 CBOL and a 69 in a typical factory chamber is 47.70, a 55 is 46.60. The 0.169 freebore @Beetroot mentioned is 4.30mm.

A 75 ELDM seated with the boat tail at case neck would require a CBOL of 48.22 mm, so about midway between "factory" and the 0.169 spec (which is supposedly "about normal" for FTR rifles running 80s and heavier.

I think I'll make up a dummy round using the 75gn and get Greg at Custom Guns to work with that . . . My thinking being I can still run 80s at a very sight cost to powder capacity, with 55s still being shootable? Thoughts ( including am I overthinking this haha)

Dumb question, what does CBOL stand for?

Cartridge base to bullet ogive length . . . Basically measures how soon a bullet will engage the rifling (the simple version)

A std tikka 1:8 chamber will let you seat a 80.5 gns Berger with boat tail at base of case neck and a 20 though jump. Take 25 gns of 2208 slightly compressed and shoot like stink.

If a tikka chamber dimensions are std, I’d be happy with that I reckon.


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Originally Posted by Tentman

It is a bit interesting.

Running 80 ELDMs with the boat tail at neck junction gives an COL of 64.0 and a CBOL of 49.70mm.

By way of comparison my old 80 Sierra load was 48.30 CBOL and a 69 in a typical factory chamber is 47.70, a 55 is 46.60. The 0.169 freebore @Beetroot mentioned is 4.30mm.

A 75 ELDM seated with the boat tail at case neck would require a CBOL of 48.22 mm, so about midway between "factory" and the 0.169 spec (which is supposedly "about normal" for FTR rifles running 80s and heavier.

I think I'll make up a dummy round using the 75gn and get Greg at Custom Guns to work with that . . . My thinking being I can still run 80s at a very sight cost to powder capacity, with 55s still being shootable? Thoughts ( including am I overthinking this haha)

I'd just get it throaded for the 80 ELDMs.
If that's what you plan on shooting you may as well get the best performance possible. They are the same price and seem to be less popular so should have less competition trying to source them'.
If you want an alternative bullet option the 73gr ELDM and 75 BTHP have reasonably good BCs and are less sensitive to seating depth as they have tangent ogives and are designed to run in AR length magazines.

I tried to get 75gr Amax and 75gr ELDMs to shoot in my Tikka but never had a huge amount of luck.
I developed a load for the 75 BTHP and it shoots pretty well. I then read that the 73gr ELDM is basically the same bullet so tried them out, exact same load, seating depth, etc, and they shot really well.
The 75BTHPs are pretty cheap and available in bulk if you are wanting a cheaper bullet alternative.

I had a 223AI project planned that kind fizzled out, maybe next year will take it up again.
Was planning to shoot 88 ELDMs and the 75gr BTHPs for a cheaper bullet. The 88s take up a reasonably bit of case capacity loaded to 2.550" (65mm) but the BC is amazing on them so was going to give it a go.

22ARC

Originally Posted by Beetroot

I'd just get it throaded for the 80 ELDMs.
If that's what you plan on shooting you may as well get the best performance possible. They are the same price and seem to be less popular so should have less competition trying to source them'.
If you want an alternative bullet option the 73gr ELDM and 75 BTHP have reasonably good BCs and are less sensitive to seating depth as they have tangent ogives and are designed to run in AR length magazines.

I tried to get 75gr Amax and 75gr ELDMs to shoot in my Tikka but never had a huge amount of luck.
I developed a load for the 75 BTHP and it shoots pretty well. I then read that the 73gr ELDM is basically the same bullet so tried them out, exact same load, seating depth, etc, and they shot really well.
The 75BTHPs are pretty cheap and available in bulk if you are wanting a cheaper bullet alternative.

I had a 223AI project planned that kind fizzled out, maybe next year will take it up again.
Was planning to shoot 88 ELDMs and the 75gr BTHPs for a cheaper bullet. The 88s take up a reasonably bit of case capacity loaded to 2.550" (65mm) but the BC is amazing on them so was going to give it a go.

Thanks for explaining that, I didn't know about the different ogives. I've also found the 73s to work well in two different 223s. I already have a very good 224 Valkyrie that launches the 80 plus bullets with complete authority but it is a heavy chassis type configuration and I'd like a 223 that I will shoot heaps cause it's "just right" to both hunt with and capable of gong shooting to 600M - a "cross-over"

easiest option is to do a Wylde chamber. if you wanted to maximise it you could then get the throat extended to run a 80gr around 2.5" OAL.

Originally Posted by Tentman

Thanks for explaining that, I didn't know about the different ogives. I've also found the 73s to work well in two different 223s. I already have a very good 224 Valkyrie that launches the 80 plus bullets with complete authority but it is a heavy chassis type configuration and I'd like a 223 that I will shoot heaps cause it's "just right" to both hunt with and capable of gong shooting to 600M - a "cross-over"

It's worth looking into about the ogive when thinking about seating depth, performance etc.

Long story short:
Tagent: less sensitive seating, lower BC shorter bullet length.
Secant: More sensitive, higher BC, long bullets
Hybrid: Good BC but less sensitive to seating depth

The Sierra SMK vs Berger VLD is the obvious comparison between a tangent and secant design.
SMKs being notoriously easy to get to shoot well, whereas VLDs can be a very sensitive.