OT, 300Blk out.

[kenbro]

In need of help here.
Is it possible to calculate what pressure would be needed to drive a 30 caliber x 110 grain bullet fast enought to produce 1750 ft lbs using a 300 Blackout case. (Fireball?)
Any help appreciated, Ken.

[squirrel_slayer]

any barrel length in particular? i'll try and crunch a few #'s

ETA: ok so my calculations show it will take 2677 ft/sec to get a 110gr bullet up to 1750 ft/lbs

i'm showing with quickload about 60,600 psi from a 22" barrel and over 73.5k from a 16" barrel.

thats with lil gun and a vmax bullet. the pressures were even higher with a barnes bullet.

so in short I think you need more case capacity to safely get those #'s. doing a straight 30-223 or the 7.62x40wt will help lower pressures. i'll try those next.

[squirrel_slayer]

ok with a 22" barrel in 7.62x40wt you can get your goal with pressures just under 55k psi
going to a 16" barrel your still outside safe pressures 67k.

going to a straight 30-223 only saves you about 2" of barrel to get your goal at 55k psi but then your outside of the AR platform cartridge length if that matters (2.45")

going to something like the 30 grendel (aka 30 arx) will hit your goal with a 16" barrel and still AR friendly

now if your going with a bolt gun something like the 30br would get your goal easily with room to spare. or you could go with a .308 and down load it with H4895?

i'm doing a simple setback for a friend using a .308 barrel and just machining off .255" from it. I already shortened the die and so far it forms cases without issue. looking like it will reduce case capacity to ~46gr

by doing the .308x1.75 it will push a 110gr barnes tsx (standard not blacktip due to velocity design) to your goal with 34gr of H4198 @ 50k psi from a 16" barrel 2.4" coal

[kenbro]

Originally Posted by squirrel_slayer

any barrel length in particular? i'll try and crunch a few #'s

ETA: ok so my calculations show it will take 2677 ft/sec to get a 110gr bullet up to 1750 ft/lbs

i'm showing with quickload about 60,600 psi from a 22" barrel and over 73.5k from a 16" barrel.

thats with lil gun and a vmax bullet. the pressures were even higher with a barnes bullet.

so in short I think you need more case capacity to safely get those #'s. doing a straight 30-223 or the 7.62x40wt will help lower pressures. i'll try those next.

Hi squirrel_slayer,
Couple guys here in UK reckon they’re LEGALLY shooting red deer with 300 Blackout using 110 grain bullets.
I think one guy is shooting sub sonic with 220 grain bullets and Lil’gun?
Other doing fast bullets is loading 110 gr bullets and, i think Trail Boss, or so he says.
To be red deer legal in all UK would require min. 100 grain bullets and 1750 ft lbs at muzzle.
As these will definitely be bolt guns, would you base the calcs. on 24” barrel.
Sorry I didn’t state that sooner.
I’m doubting they can safely reach those figures, but, it would be nice if they can.
I’ve been playing with my 25-45 for several months now,and i’ve exceeded those figures, using 100 grain bullets and RL7.
Thanks for helping, it’s much appreciated. Ken.
Ps. Some chap on an American forum reckons he can get 1800 ft lbs! With the 30” Blk out.
We really are only concerned with 300 blk out just now. Not interested in other case sizes. Thanks again.

[JohnHenry]

Originally Posted by squirrel_slayer

any barrel length in particular? i'll try and crunch a few #'s

ETA: ok so my calculations show it will take 2677 ft/sec to get a 110gr bullet up to 1750 ft/lbs

i'm showing with quickload about 60,600 psi from a 22" barrel and over 73.5k from a 16" barrel.

thats with lil gun and a vmax bullet. the pressures were even higher with a barnes bullet.

so in short I think you need more case capacity to safely get those #'s. doing a straight 30-223 or the 7.62x40wt will help lower pressures. i'll try those next.

With the small 300 blackout case may be able to increase energy by using a heavier(125 grain) bullet and lil gun. Would need 2512 fps to achieve 1750 ft-lbs. Hodgdon data shows 2402 fps with a compressed load of 21.0 gr. lil gun and a 16" barrel. The pressure is 48800 psi. Will an additional 8 inches of barrel increase velocity by 110 fps?

[squirrel_slayer]

Originally Posted by JohnHenry

With the small 300 blackout case may be able to increase energy by using a heavier(125 grain) bullet and lil gun. Would need 2512 fps to achieve 1750 ft-lbs. Hodgdon data shows 2402 fps with a compressed load of 21.0 gr. lil gun and a 16" barrel. The pressure is 48800 psi. Will an additional 8 inches of barrel increase velocity by 110 fps?

well I have in my experiences seen that pressures don't exactly track with quickload with lil gun and reloader 17 for some reason. using the above QL predicts a velocity of 2396 ft/sec (only 6 fps off) but pressures show 61,985 psi

so I feel it safe to say QL's pressures are high in this example but the velocities seem to be within reason. so given that with a 125gr bullet from the 300 blk and 21gr of lil gun your goal should be possible. it shows 2535 ft/sec and 1784 ft/lbs.

[georgeld]

I have no exp with this bo toy.
Only read so far it's supposedly used with heavy bullets
at a very slow velocity.
This is the first Iv'e seen of such a light slug in it.

Sure hope you're not getting into this one Ken!

[Oso Polaris]

As far as barrel length there is a nice ballistics comparison of 5.56 vs 300BO. The 300 BO is effectively a suped-up pistol round using a fast burning powders and requires a big jump. Otherwise, you will build a nice pressure spike. If you want a tighter fit (less jump) then consider using a 300 Whisper reamer.



As far as powder there are a handful. Off top of my head these include H110 (Winchester 296 is same), CFEBlack, VihtaVuori N110 (based on price this must be made out of powdered Unicorn Horn), Trail Boss and Lil'gun...i'm forgetting the IMR and AA powder numbers. H110 is the favorite (my loads are 18.5 gr for 110gr bullet and 17.5gr for 125 gr Speers). Lil'gun is perhaps the least favorite because it builds a pressure spike and has the weird temperature inversion (at higher temps it shoots slower, at cooler temps it shoots faster).



There is a good selection of 300 BO specific bullets with ogee that feeds well in AR15. I have found the Speers 125gr to be a great all around bullet (accurate and cost effective $0.20/bullet). The best bullet for hunting is the Barnes 110gr Tac-TX. It dumps all its energy within first 8-10 inches. We use it on wild hogs.



Using a 16" barrel on AR15 I am getting 2,250 fps on the 110gr bullets and 2,100 fps on the 125gr bullets. Using same loads out of 8.5" barrel the velocities are approximately 250 fps slower for both. 300BO is only round that can reliably operate AR15 while shooting subsonics (requires bullets +195gr). If you aren't concerned with running subsonic through a AR15, and you want an AR platform with barrel no longer than 18" then you'll need to consider an alternate caliber, such as 6.5 Grendel or 7.62x39.

The ballistic chart above indicates 2,500 fps capability with barrel lengths that you wouldn't typically see used on AR15 platform. The other limiting factor with AR15 is mag length limits COAL. A bolt gun is better for longer barrel and magazine will allow some extra case fill as you set bullet longer. Last summer I converted a CZ527, and it shoots under 1/2" using my AR loads. Unfortunately, I haven't started a load development program for this gun, yet, so no chrony data for the longer barrel.

Good Luck

[georgeld]

There's NO SUCH thing as AR types in the UK

[Spook]

Originally Posted by georgeld

There's NO SUCH thing as AR types in the UK

well, kinda, kinda not ...still pretty cool rifles.

https://www.youtube.com/watch?v=LwZbVM7KGhU