7.5" 300BLK questions

HALL,AUSTIN · April 11, 2018, 08:04 AM

I've recently built a 7.5" 300 blackout. Mainly as a range toy and home defense rifle. Are there any other options for expanding bullets at the lower velocities I'll be getting besides the tac-tx? I was wondering if the nosler 125gr or v-max 110gr would expand. Any firsthand info would be greatly appreciated.

bedlamite · April 11, 2018, 08:37 AM

http://www.cavitybackbullets.com/category-s/126.htm

Bartholomew Roberts · April 11, 2018, 08:53 AM

Hornady claims 110gr VMAX starts failing to expand at 1600fps. However, in this test (https://www.thehighroad.org/index.ph...r-vmax.811923/) it didn’t do much at 1,783fps either; but that is such a wonky number for a 16” barrel, I’d suspect that there is something wrong with the chrony or ammo.

Hornady also claims their new Sub-X line expands down to 900fps.

No idea on the Nosler but pay attention to manufacturers who note that the bullet is designed specifically for .300 BLK as that usually (but not always) means “expands at lower velocities than our normal .308 round and probably flatbase too.”

Sharkbite · April 11, 2018, 11:51 AM

7.5” is getting pretty short.

That short i would look into the offerings from Lehigh defense. Thay make a line of expanding bullets specifically designed for low velocity performance.

Maybe one of their subsonic bullets loaded as hot as you can get it out of that short tube would work. You could try some of their factory loaded ammo, but i thinkntailoring the ammo to that gun will get you much better results.

The caliber does good from short barrels. I have a 9” SBR and a 16” boltgun. Velocity loss from the shorter barrel is surprisingly light. Generally a cpl hundred FPS. in subsonic loads its even less. I load my sub ammo to be ~1050 in the boltgun and it runs right at 975fps aout ot the 9”.

The first thing you should do is actually CHRONO the ammo you are considering out of your gun. Id be curious what the velocity of the 110 Amax ACTUALLY is out of the 7.5” barrel. You might be surprised. 300blk does not lose velocity nearly as bad out of short barrels as say 556

Bartholomew Roberts · April 11, 2018, 12:18 PM

5-shot average in 9” barrel measured with MagnetoSpeed v2 Chrony:

Barnes TAC-TX 110gr: 2170fps (about 300yds to 1400fps)
Hornady 110gr VMAX (.300 Whisper marked): 2199fps (about 225yds to 1600fps)

Sharkbite · April 11, 2018, 01:33 PM

Quote:

Barnes TAC-TX 110gr: 2170fps (about 300yds to 1400fps)
Hornady 110gr VMAX (.300 Whisper marked): 2199fps (about 225yds to 1600fps)

That matches almost exactly with my 9” gun. Avg of 2205 with Hornady 110gn Amax. That is the load i use as my SD/HD ammo.

HALL,AUSTIN · April 11, 2018, 04:00 PM

I'll do my best to borrow or buy a chrono soon. After years of consideration I'm finally starting to roll my own, i guess a chronograph is something I do need to buy.

Sharkbite · April 11, 2018, 04:08 PM

If you plan on loading SUBSONIC ammo, a Chronograph of some type is mandatory. Otherwise you are just guessing at the speed of that load. The published velocity for a given charge weight is not going to be from your barrel length or your barrel/chamber.

Gotta know exactly WHAT your gun is doing.

raimius · April 11, 2018, 06:01 PM

The cartridge is optimised for a 9in barrel, so most of your supersonic loads should still be ok for expansion at defensive ranges.

April 11, 2018, 08:04 AM	#1
HALL,AUSTIN Senior Member Join Date: June 23, 2011 Location: asheville north carolina Posts: 556	7.5" 300BLK questions I've recently built a 7.5" 300 blackout. Mainly as a range toy and home defense rifle. Are there any other options for expanding bullets at the lower velocities I'll be getting besides the tac-tx? I was wondering if the nosler 125gr or v-max 110gr would expand. Any firsthand info would be greatly appreciated.

April 11, 2018, 08:37 AM	#2
bedlamite Senior Member Join Date: August 10, 2000 Location: WI Posts: 1,395	http://www.cavitybackbullets.com/category-s/126.htm __________________ A plan is just a list of things that doesn't happen.

April 11, 2018, 08:53 AM	#3
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	Hornady claims 110gr VMAX starts failing to expand at 1600fps. However, in this test (https://www.thehighroad.org/index.ph...r-vmax.811923/) it didn’t do much at 1,783fps either; but that is such a wonky number for a 16” barrel, I’d suspect that there is something wrong with the chrony or ammo. Hornady also claims their new Sub-X line expands down to 900fps. No idea on the Nosler but pay attention to manufacturers who note that the bullet is designed specifically for .300 BLK as that usually (but not always) means “expands at lower velocities than our normal .308 round and probably flatbase too.”

April 11, 2018, 11:51 AM	#4
Sharkbite Senior Member Join Date: November 4, 2013 Location: Western slope of Colorado Posts: 3,679	7.5” is getting pretty short. That short i would look into the offerings from Lehigh defense. Thay make a line of expanding bullets specifically designed for low velocity performance. Maybe one of their subsonic bullets loaded as hot as you can get it out of that short tube would work. You could try some of their factory loaded ammo, but i thinkntailoring the ammo to that gun will get you much better results. The caliber does good from short barrels. I have a 9” SBR and a 16” boltgun. Velocity loss from the shorter barrel is surprisingly light. Generally a cpl hundred FPS. in subsonic loads its even less. I load my sub ammo to be ~1050 in the boltgun and it runs right at 975fps aout ot the 9”. The first thing you should do is actually CHRONO the ammo you are considering out of your gun. Id be curious what the velocity of the 110 Amax ACTUALLY is out of the 7.5” barrel. You might be surprised. 300blk does not lose velocity nearly as bad out of short barrels as say 556

April 11, 2018, 12:18 PM	#5
Bartholomew Roberts member Join Date: June 12, 2000 Location: Texas and Oklahoma area Posts: 8,462	5-shot average in 9” barrel measured with MagnetoSpeed v2 Chrony: Barnes TAC-TX 110gr: 2170fps (about 300yds to 1400fps) Hornady 110gr VMAX (.300 Whisper marked): 2199fps (about 225yds to 1600fps)

April 11, 2018, 04:00 PM	#7
HALL,AUSTIN Senior Member Join Date: June 23, 2011 Location: asheville north carolina Posts: 556	I'll do my best to borrow or buy a chrono soon. After years of consideration I'm finally starting to roll my own, i guess a chronograph is something I do need to buy.

April 11, 2018, 04:08 PM	#8
Sharkbite Senior Member Join Date: November 4, 2013 Location: Western slope of Colorado Posts: 3,679	If you plan on loading SUBSONIC ammo, a Chronograph of some type is mandatory. Otherwise you are just guessing at the speed of that load. The published velocity for a given charge weight is not going to be from your barrel length or your barrel/chamber. Gotta know exactly WHAT your gun is doing.

April 11, 2018, 06:01 PM	#9
raimius Senior Member Join Date: January 27, 2008 Posts: 2,199	The cartridge is optimised for a 9in barrel, so most of your supersonic loads should still be ok for expansion at defensive ranges.