Do seat depth affect like my test?

[gsg5pk]

I have a chance for test load for my new rifle in .308 win.

Rifle Spec;
Stiller Viper SS
Bartlein 5R 300/308 32"
.342"nk, .150" fb with 1-30
Chamber by Whidden Gunwork.

Lapua Brass
Berger 185 Juggernaut
CCI BR-2
42.5 - 44.0 of Varget
COAL 2.950" (CBTO 2.300")
COAL 2.900" (CBTO 2.250")


Seem like when seat with shorter coal, the mv increse a bit and both sd/es lower than longer coal.

 

[gsg5pk]

Group size @ 100 yards.
COAL 2.950" (CBTO 2.300")

 

[gsg5pk]

Group size @ 100 yards.
COAL 2.900" (CBTO 2.900")

 

[gsg5pk]

Do any one have an experienced with this 185 juggernaut target?


Just wonder when both es/sd lower why group size was bigger.

 

[dkhunt14]

I never let ES determine my load. Sometimes the best ES is the worst groups. I prefer to test farther then 100 and let the target determine the load. If the velocity was faster with the shorter COAL, it could be because you are using up capacity and increasing pressure. Matt

 

[Keith Glasscock]

Yes, a lot of us do. Great bullet, easy to tune.

I haven't run them in a 32" barrel, but in a 30" they run pretty well just short of max (for my rifle, not book max). Theoretically, they would like to be around 2750 fps per the OBT in a 32" barrel.

ES/SD and tune are independent of one another. Sometimes, adjusting seating depth can bring the two together. I'd suggest working the seating depth in much smaller increments .005 or less per step Don't be afraid to run right up to touching the lands. They shoot well for me with a very short jump.

 

[Catfish]

I have found that more times than not I get better accuracy with the bullets seated out farther than samm`s recommends. I never check the load velocity until I have settled on the load I wan t shoot and never gave it a thought about batting more velocity with the bullets seated deeper into the case, but it does make sense since you would have less case capacity creating higher pressures.

 

[3081FTR]

Do any one have an experienced with this 185 juggernaut target?


Just wonder when both es/sd lower why group size was bigger.

At 100 yards ES/Sd is unlikely to play a part but a barrel will show a strong and tangible like for a particular seating depth via group size at 100 yards.

 

[Dos XX]

Other than 42.5, your velocities are basically identical. I would try 43.5 to 44 in .1 increments. You will likely find something in there. The 185 Juggernauts have shot best for me around .020 off in numerous barrels. Don't be afraid to jump them.

 

[barefooter56]

Do any one have an experienced with this 185 juggernaut target?


Just wonder when both es/sd lower why group size was bigger.

gsg5pk,
Larger groups can occur at short ranges (100 yd or so) just due to the long nose bullets like the Juggernaut sometimes needing more distance to completely " go to sleep". In short , the nose is still rotating in a little wider arc called " epicylic swerve" that can give a larger group size. Once the bullet has fully stabilized this event goes away. Think of a top just starting out and the tip is running in a small arc until it fully stabilizes and the tip in running true. Test your load that has the flattest "waterline" out at 2-300 yards. That load that gave you an SD of 2.6 could be really hard to beat. The horizontal spread you see is mother nature. Probably not the load. You may think there's no wind but unless you have an indicator like surveyors tape or something . You don't know. Test that 44 grain load on out and see what happens.

 

[gsg5pk]

gsg5pk,
Larger groups can occur at short ranges (100 yd or so) just due to the long nose bullets like the Juggernaut sometimes needing more distance to completely " go to sleep". In short , the nose is still rotating in a little wider arc called " epicylic swerve" that can give a larger group size. Once the bullet has fully stabilized this event goes away. Think of a top just starting out and the tip is running in a small arc until it fully stabilizes and the tip in running true. Test your load that has the flattest "waterline" out at 2-300 yards. That load that gave you an SD of 2.6 could be really hard to beat. The horizontal spread you see is mother nature. Probably not the load. You may think there's no wind but unless you have an indicator like surveyors tape or something . You don't know. Test that 44 grain load on out and see what happens.

Thx for sharing.

I just wonder both target were shoot @ 100 yards with same projectile. But why first target which seat out to 2.950 was tight group and second target which seat 2.900" was open up.


I had seat a new projectile and close bolt in my rifle. As you can see the rifting mark on bullet. All were jam.

Why my chamber with .150 fb was too short coal.

Left : 185 LRBT @ 2.850"
(2.200" by Hornady Tool)
Middle : 185 LRBT @ 2.900"
(2.250" by Hornady Tool)
Right : 185 LRBT @ 2.950"
(2.300" by Hornady Tool)

 

[LR Hunter]

You might try a seating depth test with 43 grains from just touching lands to .040" jump in .003" increments. I think you will be surprised how much the groups will open up and close up during this test. Re test the best groups. Then using your best length with the seating depth test, do a test from 42.5 - 43.5 in .1 grain increments. This is the best method I have used to find the best load the easiest. There is a long discussion on here that was started by Erik Cortina describing it.

 

[Zero333]

Sometimes answers to these questions are irrelevant. If longer coal means smaller groups then you have your answer.

That being said... I found that less air space in the case produces lower ES/SD, most of the time.
Hence why ES/SD was lower when bullet was seated deeper in the case.

If 20fps ES shoots better scores at 1000yards than 10fps ES, that's all that matters.

This is because "Optimal Barrel Time" is independent from ES/ED numbers and can sometimes make up for them.

 

[gsg5pk]

Sometimes answers to these questions are irrelevant. If longer coal means smaller groups then you have your answer.

That being said... I found that less air space in the case produces lower ES/SD, most of the time.
Hence why ES/SD was lower when bullet was seated deeper in the case.

If 20fps ES shoots better scores at 1000yards than 10fps ES, that's all that matters.

This is because "Optimal Barrel Time" is independent from ES/ED numbers and can sometimes make up for them.

2.950" was hard jam.

Hard to open bolt without shoot.

 

[Zero333]

2.950" was hard jam.

Hard to open bolt without shoot.

At least you know it shoots better Jammed. Now find a seating depth where it's still jammed and not hard to open the bolt. That's what I would do, then re-test.

 

[Shynloco]

Might I suggest you be careful of something, other than es/sd. Yes seating depth will make a difference in a .308....BUT, I have experienced some .308's HATE the jam and love the jump and visa versa, depending on the rifle. In other words, the rifle's chamber ending up dictating to me how far I could go (either way) before accuracy completely went out the window. So now I start out with the COL with what the manual calls for with the bullet I'm using and work from there for better grouping. Food for thought.

Alex

 

[jsthntn247]

Seat the bullet .005 deeper and chamber it each time until the land marks on the bullet go away. Seat the bullet .012 deeper than that (.012 off the lands) and go shoot the test again.