300 Blackout reloading data

[Julian D]

Afternoon all,

Does anyone on here reload for the 300 B/O ?
Need a bit of info, will be using 200 - 220 pills subsonic.

Can you tell me if IMR 4198 is the same as AR 2207 or AR 2215 ?

I have found a fair bit of info on the net, but it is all from the states, and they all seem to be using gas guns (AR's), so I wonder if their reloading data would be similar out of a bolt type gun.

And I only have a 14" barrel.

Any help greatly appreciated.

[UL1700]

I thought that the next big cartridge in Fopen is still a secret

Can't help with load data but but according to adi ( www.adi-powders.com.au/powder-equivalents/ ) 2207 is the closest to IMR 4198

[ajvanwyk]

I thought that the next big cartridge in Fopen is still a secret

You know its called the Low Boy...... although we have likely changed this to the 7mm SSS (I know you know what that stands for) while we wait for patent approvals

[RDavies]

I have Quickload so send me vital statistics and I will see what I can work out for you. I used to use 250gn Barnes in my 300 whisper but never the little, light 220s

[Seddo]

9.8-10gr 2205 with a 208 amax was subsonic in my 300 Whisper (30-221).

[BATattack]

I thought that the next big cartridge in Fopen is still a secret

You know its called the Low Boy...... although we have likely changed this to the 7mm SSS (I know you know what that stands for) while we wait for patent approvals

$h!+loads of super senters? Haha

[BATattack]

I think trail boss is probably the go to for sub loads. Still fast burning but super fluffy to fill the case, prevent double charged and apparently you can load it up or down to get everything from 95 to 250gr bullets sub sonic.

[Seddo]

Trail boss is too bulky for heavy projies in a small case, it’s good in a 308 case with 11gr TB and a 208 amax at 2.905" for 1040fps (16" 8tist)

If you batch cases and projies you can get good accuracy, I’ve had half moa groups at 100m with my whisper. I haven’t fired it for 7-8 years though.

My 300 Whisper load is 9.8gr AR2205, 208gr AMax, Fed GM, OAL 2.415". Its around 1050 in a 16" 8T barrel, I cant find the chrono data. I used 221 brass expanded. The data is interchangeable with 300 Blackout but the blackout has thicker necks so the cases aren't interchangeable both ways. The whisper chambers in the blackout.

[BATattack]

Trail boss is too bulky for heavy projies in a small case, it’s good in a 308 case with 11gr TB and a 208 amax at 2.905" for 1040fps (16" 8tist)

If you batch cases and projies you can get good accuracy, I’ve had half moa groups at 100m with my whisper. I haven’t fired it for 7-8 years though.

My 300 Whisper load is 9.8gr AR2205, 208gr AMax, Fed GM, OAL 2.415". Its around 1050 in a 16" 8T barrel, I cant find the chrono data. I used 221 brass expanded. The data is interchangeable with 300 Blackout but the blackout has thicker necks so the cases aren't interchangeable both ways. The whisper chambers in the blackout.

Do you find that the heavies are seated too deep to leave enough capacity for trail boss?

How do you go with case fill and pressures with 2205?

Did you find any good sub loads that expanded well?

[mike H]

The ADI Handloaders’ Guide has loads with pressure details for 208 and 220 grain projectiles.

[Seddo]

I know people who have used Lehigh Defence projectiles and they expand reliably and will drop deer as well as the old 220gr RN but I think that one tumbles on impact and doesn't open. There is a new Hornady 190gr projie that claims to open at 900fps.

Quickload suggest about 70% fill with 2205 and its seems to work well, it also suggested that with a 5gr charge of Traillbos (99% fill) a velocity of 885 which is too low. I was running 5.5gr Traillbos in a 223AI with 80gr amax running subsonic so the bigger projie and smaller case has no chance.

Trail boss is too bulky for heavy projies in a small case, it’s good in a 308 case with 11gr TB and a 208 amax at 2.905" for 1040fps (16" 8tist)

If you batch cases and projies you can get good accuracy, I’ve had half moa groups at 100m with my whisper. I haven’t fired it for 7-8 years though.

My 300 Whisper load is 9.8gr AR2205, 208gr AMax, Fed GM, OAL 2.415". Its around 1050 in a 16" 8T barrel, I cant find the chrono data. I used 221 brass expanded. The data is interchangeable with 300 Blackout but the blackout has thicker necks so the cases aren't interchangeable both ways. The whisper chambers in the blackout.

Do you find that the heavies are seated too deep to leave enough capacity for trail boss?

How do you go with case fill and pressures with 2205?

Did you find any good sub loads that expanded well?