Re: .308 subsonic loads
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Witch Doctor</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: garandman</div><div class="ubbcode-body">I'd be interested in your best loads.
I'll be shooting in a DPMS LR-308 so I know they won't cycle the action.
In the little bit of playing I've done, I've noticed the bullet drops about 3-4" at 100 yards from a full pwoer load.
Normal?
Also, please tell me about this supposed secondary detonation due to not sufficiently filling the case.
Thanx! </div></div>
POI shift is dependant on the load (Velocity). It is not uncommon for POI to be about 2" to 4" low with factory ammo. FGMM 168 is consistantly 3" low at 100 yards out of my 700 5R, and BH 175gr is consistantly 2" low. As long as the POI is repeatable and consistant you are fine.
Secondary detonation is caused by the use of low density pistol powders similar to Bullseye that when in the case collect toward the bullet end and are not evenly distributed creating an air pocket between the primer and powder. The occurrance is created by slowed or delayed ignition, that causes explosive gases to build due to the smoldering, and once ignited causes a high order explosion. MAKE SURE YOU HAVE 30% CASE VOLUME.
Experimenting with several different powders by many people here have led to many threads on the subject, try the search function and you'll see. Some pistol and shotgun powders will work but are very case sensitive creating uneven burn rate and a lack of consistancy with POI. To eliminate that sensitivity you can utilize a wadding material, but that gets to be a pain. I have seen people play with Titewad, Clays, Bullseye, Trailboss, and Red Dot. I have personally tried Red Dot, Clays, and Trailboss won out. Its very bulky, 15gr fills a 308 case (Can't double charge), its easy on the hopper, and very consistant.
The next consideration should be bullets, heavier is often better depending on your twist rate and barrell length. The biggest concern is making sure they stabilize out of the barrel. Don't want any pesky baffle strikes, I particularly like this one, and besides with friends like this who needs assholes.
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I particularly like round nose bullets in the 170gr to 180gr range, they stabilize out of my 5R very nicely. ALWAYS TEST FIRE WITHOUT THE CAN ON THE GUN, and look for keyholing.
Lastly, the search function is your friend, as there is a thread posted regarding the Speed of Sound, ambient temperature is the main factor determining it. The colder the the lower the threshold. If you stick to 1000 fps to 1050 fps who will be good pretty much anywhere inside the US.
Here is my pet load for my 20" barrel with an 1/11.25 twist
Win 1X fired
CCI BR2
10.5gr Trailboss
Hornady 180gr RN
OAL = 2.643
velocity = 1001 fps @ sea level 68 degrees
Try the search fuction and have fun. </div></div>
This gentleman knows his stuff. I use this exact same load, but I have been using the 180 Sierra Round nose...I believe it is the Pro Hunter. I also use an OAL of 2.65" My 700 5r throws it at 1040 FPS and it impacts about 6" lower than my supersonic loads form the same gun. At 100 yards, I simply hold over by just shy of 1 mil in the scope. It is a solid 1.25" performer at that range, which is excellent for a round nose sub.
Another excellent powder is Unique. That .308 load uses 8.6 grains but it does not fill the case as well as Trail Boss.
If I had to pick just ONE powder for subs, it would be Trail Boss.
