PA-10 .308 Win load Development

[hiprimer]

I am doing load development for my 20" .308 Win and am finding it definitely likes mild loads.  In testing with Hornady 168 ELD-M, loads of 42 gr of Varget or 42 of RL-15 shot closest to POA and the tightest sub-MOA groups.   Strangely, in my Varget testing, the POI DROPPED as load weight increased.   MVs increased steadily as charge weights went up but POI dropped as much as 3 MOA from the 42 gr load to the 45.6 gr load.   Strange stuff!   MV with the 42 gr Varget is 2492 FPS.  I loaded in .4 gr (about 1%) increments ending up at 45.6 / 2693 fps.   

Brass is Win and OAL is 2.810".

43.0 of IMR4895 shot .768 MOA, 42.0 of IMR4895 shot .847 and 42.0 RL-15 shot .662.   42.0 of Varget shot .808 MOA.   Any attempt to load hotter and I'm at 2 MOA or worse.

BTW, with the buffer weight, buffer spring, gas tube and extractor issues fixed cycling is perfect.

[98Z5V]

34 minutes ago, hiprimer said:

43.0 of IMR4895 shot .768 MOA, 42.0 of IMR4895 shot .847 and 42.0 RL-15 shot .662.   42.0 of Varget shot .808 MOA.   Any attempt to load hotter and I'm at 2 MOA or worse.

What's the brass look like at those loads?  If there's zero issues, I'd push the loads up tothe next accuracy node and check brass there  - unless you see some serious brass issues along the way upwards. 

[hiprimer]

Above 43.0 RL-15 started seeing ejector marks and at the higher end of Varget some primer flattening.   Varget does not pressure spike like RL-15 does so no ejector marks, just bad precision and lower POI.   At 2.810 I still have .070" jump.   Harmonics playing hell with this rifle.    

I was not able to get a second accuracy node, just the lower end node at 42 -43 load charges and around 2500 fps.

[Sisco]

My 20” Armalite AR10 1 in 11.25” twist likes 42 gr RL15 behind 175 Sierra Match Kings. Also 43.1 gr RL15 behind the 168 gr SMK’s. Both those loads are sub MOA in that rifle and my AR10T 1 in 10” twist. For the sake of commonality I have set those loads as my standards

[98Z5V]

18 hours ago, hiprimer said:

Above 43.0 RL-15 started seeing ejector marks and at the higher end of Varget some primer flattening.   Varget does not pressure spike like RL-15 does so no ejector marks, just bad precision and lower POI.   At 2.810 I still have .070" jump.   Harmonics playing hell with this rifle.    

I was not able to get a second accuracy node, just the lower end node at 42 -43 load charges and around 2500 fps.

On Varget and 168s, you can get a max load of 44.0 grains at 2600 fps, 22" barrel.  You're pretty close, already. 

On IMR 4985, you max 2600fps at 43.3 grains. 

On RL-15, max load is 44.3 gr at 2600fps. At 42.0, you'll be under 2500fps.  There's room to grow on that one, maybe hit another accuracy node on the way up.  It's all about risk-aversion - if you're getting 0.662" with 42.0gr of RL-15 - I'd stick with that one. 

 

[hiprimer]

I think those loads will all serve for up to 600.  I can still play with seating depth some to see if I can squeeze out smaller groups.   Now, going on to 1000 I am looking at shooting either Berger 185 Juggernauts or Hornady 178 ELD-M.   BC on the Hornady is just a little lower than the Berger but both perform similar on paper.   Gotta load hot enough to stay SS and for insurance go past 1000 maybe to 1100-1150.   My Strelok Pro tells me at 2500 fps I'll be supersonic only to 900.  2600 will carry me just past 1000 so that would be the lowest velocity load I should shoot at that distance.    Next round of testing will be with the 178s , velocity => 2600 with at least one MOA precision.

[98Z5V]

14 hours ago, hiprimer said:

I think those loads will all serve for up to 600.  I can still play with seating depth some to see if I can squeeze out smaller groups.   Now, going on to 1000 I am looking at shooting either Berger 185 Juggernauts or Hornady 178 ELD-M.   BC on the Hornady is just a little lower than the Berger but both perform similar on paper.   Gotta load hot enough to stay SS and for insurance go past 1000 maybe to 1100-1150.   My Strelok Pro tells me at 2500 fps I'll be supersonic only to 900.  2600 will carry me just past 1000 so that would be the lowest velocity load I should shoot at that distance.    Next round of testing will be with the 178s , velocity => 2600 with at least one MOA precision.

You'll hit 600 yeasy with that load you have now, and he 168s will do it with ease. I'm running the Hornady 178 HPBTs in mine now, and they perform excellently.  The ELD-Ms will do a little better.  It gets to1k, but it's tricky in wind.  That load is a little higher than 2600, and I won't shoot it in my ARs, only the bolt gun.  The AR load is a little above 2400fps.  I've been slowly working with Hornady 195gr HPBTs loaded to 2.800", and they're doing damn well.  I definitely need to invest more time into them.