Subsonic loads for .223 rem, 75 gr HPBT match

[DannyLandrum]

Have some 75 HPBT Hornady match bullets, and a pound of Titegroup. Want to get 1050-1075 fps with acceptable accuracy, from a 1 in 8 AR15. What's my starting point to work up from?

 

[GooseGestapo]

Sounds to me like a stuck bullet in the bore.
I shoot 75’s in my match AR, at 2,700fps. Practically no recoil, from 13lb Rifle.

I’d sell the 75’s and get a mold for a cast bullet. The Lee mold I have for the 55gr FNGC cost me $25. Less than cost of 75’s for 200, which in bulk run about $15/100.

My cast bullet load for a .223 is either a Lyman 50gr semi-pointed gaschecks or said Lee over 7.2gr of Unique. This delivers approximately 1,850fps and sub-1” groups at 50yds to point of aim from my Rem Mod-7, sighted for a 60gr Hornady PtSpt.

A subsonic 75gr likely won’t exit the barrel on a gas operated rifle.
But who knows? Sounds like an interesting experiment. Have a 0.20” x 26” brass rod handy.

 

[pdsmith505]

Hodgdon provides some data for subsonic .223 with 55 grain bullets:

Manufacturer    Powder      Bullet Diam.   C.O.L.        Grs.  Vel. (ft/s) Pressure      
Hodgdon         Trail Boss   .224"         2.200"        4.0    1,074  
Hodgdon         Titegroup    .224"         2.200"        3.1    1,064    4,000 CUP
Hodgdon         Clays        .224"         2.200"        3.2    1,060    3,700 CUP

Keep in mind that an AR is not going to be able to cycle on subsonic .223.

 

[25-20 WCF]

Will that long bullet even stabilize under 1150 fps? Even a 1:8” twist may not do it, a lighter/shorter jacketed or a shorter cast bullet should.


.

 

[berettaprofessor]

Yeah, I've tried something similar to that Trail Boss load even slightly hotter with 6.0 grains behind a 68 grain bullet. It exits 7.5" and 16.5" barrels, and is actually slightly supersonic (1350 fps), but it won't cycle either rifle. I wonder if it could be done with IMR4227; My 300BO rifles will cycle a 208 grain bullet with that and stay subsonic. Maybe with 223, but Hodgdon doesn't list any 4227 load for 223, sonic or subsonic.

 

[GarrettJ]

A subsonic 75gr likely won’t exit the barrel on a gas operated rifle.
But who knows? Sounds like an interesting experiment. Have a 0.20” x 26” brass rod handy.

Not sure why you don’t think a subsonic 75 would not exit. I’ve done it with Trailboss in a 16” 1:7 barrel.

But the advice to keep a squib rod handy is sound. When developing subsonic rifle cartridges, it’s best to start high and work down to the desired velocity. And ensure the bullet clears the barrel between every shot.

I get the allure, but I’ve never gotten great accuracy from subsonic rifle cartridges, unless they have a really small case. The .221 Fireball does ok. But still shoots better with supers.

At then end of the day, I’ve gone back to .22LR for suppressed small bore shooting.

But it is fun to work up different loads.

 

[Grumulkin]

1. I hightly doubt a subsonic 75 gr. HPBT will stabilize in a 1:8 twist barrel and maybe not even in a 1:7 twist barrel. A Speer 70 grain Semi Spitzer might.

2. I doubt any powder will cycle an AR-15 with that weight of bullet with the usual buffer spring.

 

[Toprudder]

My first thought was that it would not stabilize. With a 1:8 twist, a 75gn bullet is generally considered about the max that will stabilize at normal velocity. However, I ran the JBM stability calculator for that bullet, and it appears it may work.

 

[farmerboy78]

so, you are wanting to make really expensive 22lr ammo. makes no sense for a 223. you can run the aguila sss 60gr. and accomplish just as much for way less

 

[Toprudder]

so, you are wanting to make really expensive 22lr ammo. makes no sense for a 223. you can run the aguila sss 60gr. and accomplish just as much for way less

That is what I would lean towards myself, especially since I have a CMMG 22 conversion that works extremely well for me. I believe that Aguila 60gn is supposed to work very well in the typical twist rates of an AR.

 

[Legionnaire]

Somebody who knows QuickLOAD better than I might run some numbers for you. I don't trust my facility with the program yet. That said, at first glance it does not appear that Titegroup will work. It looks to me like the minimum safe pressure to drive that bullet through the barrel will do so faster than your desired subsonic velocity. Again, don't trust me on this; I'm still learning the program.

 

[Toprudder]

I remember reading about someone that used Titegroup in 223, for dispatching pigs, but stuck a bullet in the barrel when he had to shoot with the barrel pointed down (powder forward). It is not supposed to be position sensitive, but the small charge in a 223 is an extreme case.

Trailboss powder might be a better choice, as it has better case fill. They have a published load for it in 223.