Any experience in subsonic 30BR

[londonhunter]

Hi I have a BAT 30 BR near completion.

Has any member actually successfully loaded and shot a true subsonic load in 30BR?

Would you like to share your experience ?

Accuracy ?

All I want is to punch paper and steel plates between 100 - 200 yards on a range with the use of a silencer which is legal in England. My barrel is a 1 in 15 twist Lilja

Thanks in advance

 

[280man]

I have not done it. But I think for you to do it and have any accuracy you will need a faster twist barrel to shoot the heavy bullets in the 210-240gr range those are the ones that work well in 300 whisper

 

[people]

Have not tried it but you will be truly limited with the bullet weight as you will need a 1:8 twist for the 220gr bullets.

 

[Forum Boss]

There's no reason you must shoot very heavy bullets. IMR 4198 is one powder commonly used to replicate black powder loads in the 1100-1300 fps range.

I would just take a good accuracy bullet and see how it works at 1100 fps or so. Ideally choose one with a softer jacket so you get good engraving even at the lower velocities.

Remember you'll need a FASTER twist as the velocities slow down.

With that 1:15 Lilja you may be limited to pretty short bullets in order to have enough stabilization at 1100 fps. It may even work best with lead pistol bullets,of the right dimensions). Sierra has a good selection of short .308 caliber bullets in the 100-135gr weight range.

I would try the 125gr Sierra ProHunter, item 2120. It's 0.882" long and should stabilize in a 15-twist at slow speeds.

As 280 man explains however, if you want to shoot the longer bullets you'll need a faster twist.

There is a MILLER TWIST RATE formula that can help you calculate if a bullet will stabilize.

Formula in Excel: http://accurateshooter.net/Blog/millerformula.xls

Using this formula, assuming 1100 fps MV, and 1:15" twist, it suggests you can stabilize a 150gr bullet 0.95" long at 60deg F. Play with the formula and you'll get some ideas as to what might be stable. Per the formula, the 125gr Sierra should work even at 1000 fps.

There's no voodoo to stabilizing 100-150gr bullets in a slow-twist barrel at subsonic speeds ... pistols do that as a matter of course.

I'd try to find a round nose flat-base such as the "government round nose" design. These are suprisingly accurate at 100-200m.

 

[londonhunter]

Thank you

I was going to cast my whole as I am not looking for absolute bench rest accuracy. As stated on the 30BR advice page dowloading it to subsonic speed with a silencer would be quite a fun gun to shoot at steel plates......

 

[Forum Boss]

I just added some stuff to my prior post, including a recommended bullet and a stabilization formula.

I agree, shooting slow bullets with a suppressor would be great. Just remember the huge amount of drop from 100 to 200 meters.

 

[ADRIANB]

Hi

Dont know jack shit about 30br but, I have loaded after some time, 3 years an "accurate" 308 subsonic round. 220gr hornady round nose soft point, 13.5gr of vectan sp3 for a 20 inch barrel. It shoots sub 1 inch at 100. but the bullet drop out to 200 takes some compensating for! mildot's required. This round was sorted after using many powders and heads. If you want more info send me a message.

Regards

Adrian

 

[LRCampos]

On the next weeks I will start some test on a new 30BR 1-12 twist rifle. My plan is to have a 180gr. cast bullets around 1.800fps.

I already did this load on a .308win 1-10 twist and had very good accuracy,around 0,8 to 1,2 inches at 100 meters). By the way, the bullet shots great from velocity as low as 1.400 fps to 1.950 fps,I did not test over this velocity).

Once I have some results I will post here.

 

[ADRIANB]

Oh forgot to mention did all the casting bit with virgin metals lead,antomany and tin mix. I have tried 115gr/150gr and 210 gr molds. The 210 grain lead head was OK 3 inch groups at 100m regular,not as good as others so I am here, Please Mr Campos tell me more. But the 220 gr hornady is far better for accuracy sub 1 inch but costs more!

The rifle I have has a 1 in 11 twist. 20" barrel

the mix I cast with is 17lbs soft lead, 2lbs tin and one lb antomany.

I do use a moderator for vermin with this round and this will obviuously change the harmonics.

Regards

Adrian

 

[lmorrison17]

Ok lets say I got 17 twist barrel 118 Bibs could this combo be loaded subsonic and still stabilize the bullet? If so what powder and what weight range?
Larry

 

[farshooter]

I played with one for about 2 years- found out that any change is magnified at the target- I had a 1-9 twist 30 cal barrel and go SR 4759to give groups of sub 1 inch. I can't find the load, but it was extremely sensitive. ie . if you changed primers or seating depth the point of impact moved a bunch.