Subsonic .308 and Trailboss

[79M1a-texas]

Just got back from the range. Used the following

1. Took LC Match brass and enlarged flashhole to 9/64"
2. LR Mag primers,
3. Trailboss @ 10.8g
4. 220g RN Sierra #2180
5. 2.810" COAL
6. Remington 700 PSS
7. Velocity as measured from Labrader - 2146 f/s

Was expecting to see velocity around 1150 f/s. Wanting subsonic. will start backing down. Do you see any problems with the Trailboss load?

 

[Mullhead]

My loads for 308 and trailboss
11.1gr TB 200 SMK
13.3 gr TB 220 round nose hunter
No need to drill the flash hole or magnum primers. Both loads around 1040-1060

 

[Gunfighter14e2]

Just got back from the range. Used the following

1. Took LC Match brass and enlarged flashhole to 9/64"
2. LR Mag primers,
3. Trailboss @ 10.8g
4. 220g RN Sierra #2180
5. 2.810" COAL
6. Remington 700 PSS
7. Velocity as measured from Labrader - 2146 f/s

Was expecting to see velocity around 1150 f/s. Wanting subsonic. will start backing down. Do you see any problems with the Trailboss load?

I doubt your velocity was anywhere near 2146fps
That load with a jacketed bullet, weighing 220 grs, I expect to see, between 1040-1100fps with the average barrel, custom tube maybe 1120fps.
No need for brass prep an std primers work just fine with trailboss.
If you had the can on, did you hear a crack?

 

[b6graham]

Velocity reading seems way off. I was around 10-10.5gr trailboss and was hitting subsonic with 175SMK.

 

[79M1a-texas]

Thanks for the reply. Will re-test next weekend.

 

[Greg Langelius *]

Velocities may misread as faster if the chrono is set up too close to the muzzle. The problem arises from muzzle blast, where the gas cloud passes the bullet in close and can sometimes trigger velocities like you're seeing. Chrono distance should be 20ft, with a 15ft absolute minimum.

Greg

 

[NELAshooter]

My subs are with 208 Amaxes, cci 250 primers, Winchester Nickel plated brass and Trailboss. They are shot from a 16.5”, 1-8 twist Mullerworks barrel on a R700 Action. I get 1011 fps on average with a 17 fps SD.

 

[xdeano]

Velocity reading seems way off. I was around 10-10.5gr trailboss and was hitting subsonic with 175SMK.

This is exactly what I saw with my 22" gap. I drilled my flash holes, standard fed primers, 10.3grns trailboss, with 175 smk. Its fun for back yard rabbit work. Ive also flipped the bullet around so the boattail came out first and that also works. I always worked up sub loads without a can on. Just to avoid baffle strikes and to make sure the bullet wasn't tumbling. Then id throw the can on.

Xdeano

 

[deltawiskey]

This is exactly what I saw with my 22" gap. I drilled my flash holes, standard fed primers, 10.3grns trailboss, with 175 smk. Its fun for back yard rabbit work. Ive also flipped the bullet around so the boattail came out first and that also works. I always worked up sub loads without a can on. Just to avoid baffle strikes and to make sure the bullet wasn't tumbling. Then id throw the can on.

Xdeano

Excellent point to work without a can first, I'm glad I did when I tested these rounds! As you can see they were hitting sideways at 100 yards...

 

[300ATT]

I have found that you need a 1:10" twist barrel to reliably stabilize a 220gr RN bullet out of a .308. 190gr matchkings work well with about (10.7gr of TB) and a muzzle velocity of 1,050 fps in 1:11.

12-13gr TB for the 220RN bullets. 220gr matchings are longer and did not stabilize reliably with a 1:10 twist barrel.

 

[ah1356]

12.5gr Trailboss works great for me in an 18-in 10-twist .308 with 220gr rn bullets. The barrel is a Criterion prefit. It’s averaging 1050FPS, stable, accurate, and very quiet.

 

[BigUn]

why are so many guys trying to subsonic a 308?
I use the 300 blk with 8” 1:7 twist and I could not be happier. I understand you have to run what ya bring sometimes, but are there other reasons to do that to a 308?

 

[Gunfighter14e2]

why are so many guys trying to subsonic a 308?
I use the 300 blk with 8” 1:7 twist and I could not be happier. I understand you have to run what ya bring sometimes, but are there other reasons to do that to a 308?

Many.

 

[atomic41]

why are so many guys trying to subsonic a 308?
I use the 300 blk with 8” 1:7 twist and I could not be happier. I understand you have to run what ya bring sometimes, but are there other reasons to do that to a 308?

I'm curious too. Is this for 100 yard paper punching and more pleasant (quieter) shooting? Or SBR home defense?

 

[Gunfighter14e2]

The old saying, "Be-where of the man who owns but one gun an knows how to use it" holds more weight than "most now here" know. Ponder on that for awhile.

 

[BigUn]

Ya, I’ve heard that, but I also wouldnt hire a mechanic that owns one tool, no matter how good he was with it, LOL

 

[mrbig]

after shooting 308 with Trailboss I wondered why anybody would buy a 300BO,,with the 308 you can make Subsonic ammo with Trailboss and load a number of bullets and powders to reach 1,000 yards if needed,,not so much with the 300BO,,

223 loaded with Bluedot and the 69 SMK makes for some very good subsonic ammo also,,,,

 

[magnum_99]

My load:
. 308 Win
20" Krieger 1/10
185 Berger Target Match
9.7 grains Trail Boss
Federal 210M Primer
~1,050fps

This load groups .5"@100 yards for me. It stays subsonic even in cold temps.

 

[nfoley]

Twice I played with trailboss and 308s with cans and both times I would get significant drop off in velocity with rounds fired. Made me fear shooting too many rounds in a row would eventually land me with one stuck in the barrel. I would clean the 20" barrel every 8-10 rounds or so. I believe I was using around 11g trailboss and 200smks.
Wondering if anyone else has noticed that.

 

[Gunfighter14e2]

Twice I played with trailboss and 308s with cans and both times I would get significant drop off in velocity with rounds fired. Made me fear shooting too many rounds in a row would eventually land me with one stuck in the barrel. I would clean the 20" barrel every 8-10 rounds or so. I believe I was using around 11g trailboss and 200smks.
Wondering if anyone else has noticed that.

What your seeing is the lack of trace lube that Trail Boss is not leavening behind because it's lacking in that powder. Then add a jacketed bullet an the problem compounds. If the powder charge is correct each time, the speed will drop a little each shot but will level off at about 100- 150fps slower than the first shot in a barrel that had reg powder residue left behind. I quit using jacketed projo's an TB long ago, an now only use those I cast pushed by Red Dot or 700X. With the charge weights an 193 gr projo's I use, you'll get over 1K loads from a single 1 lb bottle of powder.

I suggest those who reload that are just getting into subsonic shooting, start looking at casting or just buying cast bullets. The market is flush with cast projo's for most every caliber the look at a fast pistol powder rather than TB. The draw back is it is very easy to double charge with a fast pistol powder, so heed all the reloading safety warnings I shot over 12K of subs I loaded just this last year an have been casting an reloading from the time my Grandfather taught me when I was 10yo that was over 60 yrs ago. I still have all body parts an eyes but there have been a few extra heart beats along the way. LOL. Done safely it's fun, cheap, an very enjoying. Done wrong an it can be a life changing event!!!!

 

[GARFIO]

My .308 Subsonic loads

Lapua case 2.005"
Hornady 220 GN Round Nose Interlock
Hodgdon Trail Boss 14.1 GN
CCI LARGE PRIMERS
OAL 2.735"

TIKKA T3 TACTICAL 24"1:11 TWIST
SEA LEVEL
83 FARENHEIT
SPEED CHRONO 10FT

1.1082 FT/S
2.1102
3.1098

1/4 MOA AT 100Y

HORNADYS 178 GN ELD-X
LAPUA CASE 2.005"
TRAIL BOSS 10.1 GN
OAL 2.800"

1.1070 FT/S
2.1062
3.1059

 

[panakamana]

Hello Garfio,

You seem like a knowledgeable guy. Can you help me?

 

[BuildItYourSelf]

It's very important to add barrel length in sub load recipes. It throws alot of people off when pipe leangth isn't considered.

My go to 308 in a 20" bolt gun loads are.

Lc brass
11gr trail boss warm air, 10.8 coldAir
190smk
Cci 200
Zero crimp, two thousands tension.
Coal 2.625
1050 +/- 30

Lc brass
10.5gr trail boss
180gr Rainer plated bullets.
Cci 200
Coal 2.625
1050 +/- 20

If no one tried the Rainer 180gr 300blk platted bullets I highly recommend them. They fuy just as good as any at ¢12ea

 

[MaxVasc]

I spent weeks trying to get an idea of where to start for subsonic .308. After having developed a consistent load, I want to post it to make it a little easier on the next guy.

My subsonic load below:

Case: Lake City 7.62x51 once fired in my rifle. Full length size.
Bullet: 220gr Sierra Pro Hunter RN (MFG Part #2180)
Powder: Trail Boss
Charge Weight: 13.7 grains
Primer: Federal 210
COAL: 2.775" In my investigation, this is just about touching the powder without actually compressing it at all. This is about .096" jump in my chamber.
Medium Crimp (through initial load development, my SDs were lower with a crimp as opposed to without)
Rifle: Bolt action, 20" barrel, 1:10 twist

In my rifle, this produces a MV of 1,074 fps (magnetospeed) with a SD in the single digits and about 1 MOA accuracy.

 

[jamebeck]

What your seeing is the lack of trace lube that Trail Boss is not leavening behind because it's lacking in that powder. Then add a jacketed bullet an the problem compounds. If the powder charge is correct each time, the speed will drop a little each shot but will level off at about 100- 150fps slower than the first shot in a barrel that had reg powder residue left behind. I quit using jacketed projo's an TB long ago, an now only use those I cast pushed by Red Dot or 700X. With the charge weights an 193 gr projo's I use, you'll get over 1K loads from a single 1 lb bottle of powder.

I suggest those who reload that are just getting into subsonic shooting, start looking at casting or just buying cast bullets. The market is flush with cast projo's for most every caliber the look at a fast pistol powder rather than TB. The draw back is it is very easy to double charge with a fast pistol powder, so heed all the reloading safety warnings I shot over 12K of subs I loaded just this last year an have been casting an reloading from the time my Grandfather taught me when I was 10yo that was over 60 yrs ago. I still have all body parts an eyes but there have been a few extra heart beats along the way. LOL. Done safely it's fun, cheap, an very enjoying. Done wrong an it can be a life changing event!!!!

I've noticed a velocity drop after first shot also with Trail Boss.

 

[FuhQ]

after shooting 308 with Trailboss I wondered why anybody would buy a 300BO,,with the 308 you can make Subsonic ammo with Trailboss and load a number of bullets and powders to reach 1,000 yards if needed,,not so much with the 300BO,,

223 loaded with Bluedot and the 69 SMK makes for some very good subsonic ammo also,,,,

This is an old thread, but you do realize that the same bullet moving at the same speed from either a .300 BLK or .308 Win will still have the exact same effective range, regardless of the cartridge that it's seated into. Because it's the exact same ballistically.

 

[CMP70306]

This is an old thread, but you do realize that the same bullet moving at the same speed from either a .300 BLK or .308 Win will still have the exact same effective range, regardless of the cartridge that it's seated into. Because it's the exact same ballistically.

Pretty sure he is referring to the fact that if you step outside of the subsonic realm then the .308 handily beats the .300 Blackout due to its versatility. You can load a .308 down but you can’t load a .300 Blackout up to anywhere near the same level so if you aren’t trying to cycle in an AR the .308 is probably the better option.