Fixing high ES

[TackDriv3r]

When testing @ 100 using the .308 and 168 SMK / Varget. I used 43.8 grains at 2740 fps average, used a P35 and I am seeing ES of around 25 to 30 fps and I don't like it and knew what will happen at 600 yards. @ 100 yards it shoots .1 to .2 MOA which is nice, but,,,,I won't use it beyond 600 yards.
Tested @ 600 yards, and vertical is about 4.5 inches and an inch wide and I want to fix it, so I went home and tried different primers, BR2 which I'm using, CCI200 and FGM 210 and tested again @ 100 for ES, and same variation of 25-30 fps.
I switched to Hornady 168 BTHP and I'm getting the same 25-30 fps variation.
I'm using .001" neck tension, cases are fired 2 X, annealed until it barely glows under no lights and pull out of the flame, powder is weighed by the kernel, I bumped shoulders .002" using a bushing die, seated .030" off. | I can't think of anything I can do to fix this high ES.

I could guess maybe change the neck tension to .002" or change powder to IMR 4064. But damn, Varget is a fine powder for the .308 and I want single digits.
My 6 BR ( Varget ) and 6.5 Creed ( H4350 ) has 3 to 4 ES spread that I'm happy with. But not the .308

What do you guys recommend I do to get my high ES fixed?

 

[Keith Stone]

What brass are you using and what is your brass cleaning procedure?

 

[Bill Norris]

I think you are on the right track with neck tension and ultimately a powder swap.

 

[swd]

What action and barrel are you using? Does it have a fresh main spring? Is the bolt and spring clean inside? Is the trigger clean and not gummed up? Does the pin drag anywhere in the shroud? Does it have enough firing pin protrusion? Less neck tension isn’t necessarily better. Try more .005” isn’t too much. 25-30 fps is a little high but not terrible. Low ES doesn’t guarantee a good tune.

 

[JFrank]

I’ve been spending a bit of time working on this issue and I’ve seen an improvement on paper and by chronograph.
Separate your cases by speed, high med low then confirm those sorted cases by weight. Load only those cases displaying similarities.
I would certainly test neck bushing and perhaps stop annealing until a few tests are complete.

 

[TackDriv3r]

What brass are you using and what is your brass cleaning procedure?

Lapua brass, all same lot and I don't use a tumbler. I just clean my necks with a nylon brush only. Nothing else.

 

[gme]

I'd check the rifles ignition system

 

[TackDriv3r]

I'd check the rifles ignition system

What do I look for?

 

[acloco]

Have another chrono you can borrow?

 

[Doom]

First off you don't mention the number of rounds your ES is based on so it's difficult to evaluate what it means. A 30 fps ES should only show up with about 2.5" spread at 600 yds so either something else is going on or you have a larger ES. What is you SD? I do believe you need more next tension. As for ignition system, check the firing pin and make sure protrusion is good and the pin isn't dragging. Also make sure your primers are seated and the anvil set.

 

[JFrank]

Lapua brass, all same lot and I don't use a tumbler. I just clean my necks with a nylon brush only. Nothing else.

Are you sorting cases at all ?

 

[TackDriv3r]

Are you sorting cases at all ?

No, I only have 100 pieces of Lapua brass. What variation weight do I sort? Do I just weigh only the empty weight? I could do that later and see.

 

[TackDriv3r]

First off you don't mention the number of rounds your ES is based on so it's difficult to evaluate what it means. A 30 fps ES should only show up with about 2.5" spread at 600 yds so either something else is going on or you have a larger ES. What is you SD? I do believe you need more next tension. As for ignition system, check the firing pin and make sure protrusion is good and the pin isn't dragging. Also make sure your primers are seated and the anvil set.

Just 5 rounds for two groups. As for SD I don't know, haven't bothered to turn the printer on.

 

[JFrank]

Half grain seems to work fairly well for weight sorting, load a few of the largest weight group and run them past a chrono.

 

[TackDriv3r]

Half grain seems to work fairly well for weight sorting, load a few of the largest weight group and run them past a chrono.

Will 3 X fired brass work for weight sorting or does it have to be virgin before any trimming is done?

 

[JFrank]

Will 3 X fired brass work for weight sorting or does it have to be virgin before any trimming is done?

I’ve done multiple times fired cases as well as once fired cases after neck turning and forming.
I also sort by fps.. it doesn’t cost anything just a little extra work

 

[Coyotefurharvester]

Since you tried primers, check neck tension .002 and .004. Keep it simple.

 

[CNC-Dude]

Out of a box of 100 Lapua .308 brass, I've found I can get 40 cases that are within 1/10's of a grain variation on weight. I can get 60 out of that same 100 that end up being around 3/10's of a grain variation. When I hold the brass to that close of a weight spread, I get single digit SD's and 3/8's MOA at 600 yards with a stock Savage 12FV action and barrel with only a Boyd's At-One stock added. I use Lapua 167g Scenars and VV N150. I have a bunch of Varget, but have never used any yet.

 

[22BRGUY]

What size group would you be satisfied with at 600 yds with .308?

 

[22BRGUY]

One thought is that at home you measure one thou neck tension but by the time you get
to the range, with that light of neck tension, the vehicle vibration and other factors, is it possible that the OAL could have changed a little on a few loads?
That happened to me driving over gravel roads to the range is why I asked.