Help, neck sizing ruined my pet load! - Updated

[TimK]

I developed a load for my new .308 consisting of:
Virgin Lapua Brass - FL sized before loading, no other prep.
Fed Primers
43.5g Varget
168g SMK
COAL 2.810"

It's shoots very consistent 1/2" 5 shot groups at 100 yards.

Thinking I'd prolong the life of my brass and improve accuracy,I bought a neck die and a shoulder die. Using a bushing of .337", I neck sized all the brass and also bumped the shoulder back a bit. I trimmed all the cases to +-.001" in length.

Keeping everything else the same, the load with the neck sized brass shot groups in the 2" range today. The pic shows a target shot with the first loading and one shot twice with the second loading.

Where do I go from here? Do I go back to FL sizing or do I go back to load development? Did I mention that this sucks?

 

[One_Man]

Re: Help, neck sizing ruined my pet load!

trigger control? wind? neck sizing (ie using fireformed case) should only improve potential accuracy. no need to bump shoulder after only 1 firing.

 

[USMCj]

Re: Help, neck sizing ruined my pet load!

Load looks fine, shooter or wind.

 

[Fuzzball]

Re: Help, neck sizing ruined my pet load!

"...I go back to FL sizing..."

Well, I sure would. Or try a Lee Collet neck sizer and toss that bushing type die.

 

[wirehand]

Re: Help, neck sizing ruined my pet load!

The horizontal spread is indicative of lose trigger control.
To eliminate a variable have you measured the neck tension of a fullsized brass verses a neck sized case ?

My loaded Lapua cases come in at .337 for the neck diameter.
I would give a smaller collet die a try, like a .336 or .335.

Chances are the full sizing die is creating more neck tension than you are currently
running with the .337 collet.

 

[gunsnjeeps]

Re: Help, neck sizing ruined my pet load!

Measure the necks from shells sized from both dies. It is posible that the FL die is tighter than .337 the change in tension could be a cause. Try another range day and shoot both loads side by side. .337 is the most common neck I've heard for Lapua.

 

[TimK]

Re: Help, neck sizing ruined my pet load!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: wirehand</div><div class="ubbcode-body">The horizontal spread is indicative of lose trigger control.
To eliminate a variable have you measured the neck tension of a fullsized brass verses a neck sized case ?

My loaded Lapua cases come in at .337 for the neck diameter.
I would give a smaller collet die a try, like a .336 or .335.

Chances are the full sizing die is creating more neck tension than you are currently
running with the .337 collet. </div></div>

Trigger control seems unlikely. I'm pretty inexperienced with a precision rifle, but am a fair shooter. Until today, this rifle and I had never shot a group larger than 1 1/4", and that was during load development. The last 10 or so groups have been in the 1/2" range. I don't think I suddenly forgot how to pull the trigger.

The horizontal dispersion might be due to wind. All groups in the pic were fired within a 20 minute period. The wind was blowing pretty good (20 mph max maybe, I didn't check), but it was also fairly consistent, at least at my somewhat sheltered position. Ballistic FTE predicts only 1" at 100 yards at that wind speed. Maybe I was catching big gusts.

A loss of accuracy in the basic load should show as both vertical and horizontal dispersion, right? The very horizontal nature of the groups points strongly to wind, assuming I was doing my part? I guess I'll go shoot this load again on a calmer day and see what happens.

I'll also look into the neck tension. It's a long story how I arrived at 0.337", and I know it's 0.001" big at least. I'll probably order a 0.336" and 0.335" and give them a try. Still, it's hard to see how neck tension could cause only horizontal dispersion.

 

[Victor N TN]

Re: Help, neck sizing ruined my pet load!

Looks like a real good weather report. Did you ever consider looking at wind flags?

 

[jbaldwin]

Re: Help, neck sizing ruined my pet load!

I sometime get 3 loadings before bumping the shoulder back and have had 5 with lighter loads

 

[TimK]

Re: Help, neck sizing ruined my pet load!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">Looks like a real good weather report. Did you ever consider looking at wind flags? </div></div>

I love sarcasm, thanks!

No I didn't measure. Yes I had a meter with me. My bad? You bet. Unfortunately, I ran out of the original ammo before I knew I had a problem. I didn't set up flags because I was only shooting at 100 yards and was only planning to work on NPA. I expected the neck sized loads to perform the same as the originals and so wasn't expecting trouble.

Thanks for the helpful response. (See, I can use sarcasm,too)

 

[Victor N TN]

Re: Help, neck sizing ruined my pet load!

I realize it doesn't look right. But I really didn't intend it be scarcastic. But when I'm working on a new load or different components in a load, I put up at least 3 flags for 100 yards. 20, 50 and 75 yards mainly. Our range has a couple of hollows that lead into the right side. I move one of the flags to monitor the wind action from that. I've been shooting benchrest since 1990. I still haven't mastered the wind. But I'm a lot better than I was.

 

[leathel]

Re: Help, neck sizing ruined my pet load!

did you adjust the scope in between loads...is it a good tracking scope.....just another option as I have had cheaper ones move with each shot until it settles

yip and try neck tension....measure the neck size pre seating a projectile in a FL sized one and a neck sized one that should show any difference

 

[One-Eyed Jack]

Re: Help, neck sizing ruined my pet load!

It's only 100 yards, I don't think wind is to blame. The three groups all have excellent an spread in elevation, it's only the windage that has gone wild. I would look for something loose: rifle, scope, front rest,... I really doubt it's the ammo.

 

[TimK]

Re: Help, neck sizing ruined my pet load!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">I realize it doesn't look right. But I really didn't intend it be scarcastic. But when I'm working on a new load or different components in a load, I put up at least 3 flags for 100 yards. 20, 50 and 75 yards mainly. Our range has a couple of hollows that lead into the right side. I move one of the flags to monitor the wind action from that. I've been shooting benchrest since 1990. I still haven't mastered the wind. But I'm a lot better than I was. </div></div>

Thanks for that, I clearly missed your intent. Damn internet doesn't allow us to read body language.

The more I think on it, the more I'm inclined to believe it was the wind. It was a very windy day, and we selected our shooting position so it would be sheltered. The wind could easily have been gusting to 30 or 40 mph 20 yards past us. Flags are an excellent idea, and I'll take them when I go try again this weekend.

As for something being loose, I had the same idea. No luck. All was tight. No adjustment were made to the scope except paralax, and it's a high end Leupy so I don't think it's the problem.

I'll order a smaller bushing and try that, but I guess my plan as of this moment is to just go shoot it again and take some more data. Thanks for all the help.

 

[Victor N TN]

Re: Help, neck sizing ruined my pet load!

Good luck on the next trip. Keep us posted. I would like to hear how it turns out.

 

[MALLARD]

Re: Help, neck sizing ruined my pet load!

i dont think wind is the factor. Looks like a bedding issue or ammo issue, even a blown out throat. Maybe you dont have proper torque setting on your rifle, could be a scope mounting issue , i wouldnt blame shooter, looks like gun issues.

 

[MitchAlsup]

Re: Help, neck sizing ruined my pet load!

If I remember correctly, the 338 bushing is for Lapua brass in tactical situations.

In any event. measure the neck outside diameter before and after seating a bullet. You want the difference to be 0.0015-0.0025. I suspect you have closer to 0.003-0.0035 maybe even 0.004.

So, take ONE sized case unprimed unpowdered and measure the before seating a bullet and after seating a bullet. Then based on this buy the correct sized bushing.

There may be a different aspect, and to know you need a case micrometer (RCBS, stoney-point--n.e. hornady) and measure the case sholder position.

 

[TimK]

Re: Help, neck sizing ruined my pet load! - Updated

It was wind. I got out this morning in dead calm and shot a typical group. Quite a coincidence the other day that the wind picked up at the exact moment I changed from one load to the other. All that panic for nothing.

One interesting note, POI did change one full MOA with the new load.

Thanks for all the input.

 

[Victor N TN]

Re: Help, neck sizing ruined my pet load! - Updated

I'm glad it wasn't anything too bad.

Among benchrest shooters, a wide straight horizontal group like that is most often credited to wind.

 

[808Huntress]

Re: Help, neck sizing ruined my pet load! - Updated

Yep after seeing your pics I would have guessed wind as well. Glad you double checked that load in calm shooting conditions before going and doing something with your dies etc smart move.

Where I shoot is like that as well really windy so I must sometimes double check loads to make sure. I know 100 yds dont seem like alot but when the winds blowing 20 MPH+ it can and does sometimes make alot of difference. Also the shooting positions are in the open and not sheltered. This causes all kinds of issues when it gets real gusty. Hard to remain stable and still in these conditions. I try my best to time my shots when the wind dies down or the gust stops.

Congrats on figuring it out and Good Shooting!