• .308 subsonic loads IMR SR-4759

Posted: **Fri Aug 22, 2008 10:26 pm**

Trying to help Glockandroll with some handloads using these components:

Winchester Brass w/flash hole drilled 9/64
Federal GM215M Primer
IMR SR-4759 powder
Sierra 220GR round nose

COAL 2.80

18.5" 1/10 twist bbl

G&R is on Jack Daniels single barrel....I"m staying sober so he doesn't F--k himself up.....

Posted: **Fri Aug 22, 2008 10:58 pm**

Don't use SR-4759 myself

Googling up SR-4759 didn't find much

http://www.handloads.org/loaddata/defau ... type=Rifle
173gr LFP 19.5 gr SR-4759 1,800 fps CCI LR guest
Lyman cast gas check .6" at 100 meters! from Savage tactical.

Posted: **Sat Aug 23, 2008 4:41 pm**

Thanks bsp212, learned allot last night about reloading.
I did forget to get the long string to put on the trigger for the 1st shot.

Posted: **Sat Aug 23, 2008 4:45 pm**

Artful wrote:Don't use SR-4759 myself

Googling up SR-4759 didn't find much

http://www.handloads.org/loaddata/defau ... type=Rifle
173gr LFP 19.5 gr SR-4759 1,800 fps CCI LR guest
Lyman cast gas check .6" at 100 meters! from Savage tactical.

Thanks for the tip Artfull.
We worked up to 12.2grns of SR-4759 from 10grns in 5 shot incriments using the sierra 220 round nose.

We bored out the primer flash holes and used federa 215 magnum primers.

I had no idea that hand-loading would be so time consuming... but see's what BSP's rifle can do with good loads I'm a firm believer.

Dave - can you post some pics of your rifle and the groups?

Posted: **Sun Aug 31, 2008 3:22 am**

Found this also..
http://www.quarterbore.net/forums/archi ... t-280.html

Posted: **Mon Sep 01, 2008 10:20 am**

at 10" it takes 15 grains to get a 240 to 1060

Posted: **Mon Sep 01, 2008 11:03 am**

rumlover wrote:at 10" it takes 15 grains to get a 240 to 1060

Thanks RL - now can anyone tell me what to expect from a 220grn with 10-12.2 grains at 18.5"?

Also, I'm sure you had the magnum primers and drilled out the primer flash-hole as well?

Posted: **Wed Sep 03, 2008 8:44 am**

Nope, in 13 years of loading sub rounds, I've never drilled anything and never had any problems. I do always use mag primers for a little extra heat. It can't hurt, but I've never seen evidence that it was necessary.

With a lighter pill and the few extra inches, you should still be in the sub range. I highly suggest using a chrony to develop sub loads. Without it, it may sound sweet, but you may be well below the 1050 mark and therefor creating unnecessary drop and energy loss. If punching paper, it's not a big deal, but if you want to chase hogs or other critters, it matters.

Posted: **Wed Sep 03, 2008 10:16 pm**

1050 is the mark I guess?
I'm going to start with the 12.2 grains, and see if it makes a crack.

I'll probably get a chrono soon.

Also, what is the twist rate for your 10"?

Posted: **Wed Sep 03, 2008 11:43 pm**

G&R,

The speed of sound depends on temperature and less so altitude, mainly.

Sea Level, mach 1
0F 1116.4 fps
100F 1219.3 fps

5000 ft (in Colorado), mach 1
0F 1097.1 fps
100F 1201.64 fps

So... 1050 fps is safely subsonic for all temperatures and all altitudes at which you could shoot. unless... you were on top of a 20,000 foot mountain in the winter time, and testing your subsonic rounds.

Posted: **Thu Sep 04, 2008 1:57 am**

Yup... and you are absolutely correct. I'm actually a licensed pilot and remember studing density altitude and how it affects take off performance, etc.

I'm really only worried about two things.
1. secondary explosive effect.
2. Bullet stuck in BBL.

Do any of you guys think that 10grains of this powder, with a 220grn LRN in reamed Winchester brass with magnum primers is a risk for either.

Honestly, I'm tempted to tie a string to the trigger for the 1st round or so.