Same EXACT load as last years load shoots like crap

[Korhil78]

All I know is, I can't get ANY of my rifles to shoot a 5" group during load testing even when I'm out of the nodes.

 

[Hunterjones]

 

[LVJ76]

Maybe a mix up if some sort. A few years ago I had developed a killer load for my wife's rifle, and for a couple month I went crazy trying to duplicate the load. I verified powder load, primer, brass, bullet, COAL, etc. And according to me everything was the same, I just could not believe I could not duplicate that cloverleaf load.

Then out if the blue I found a note in my reloading notebook, genius me somehow confused RL17 with RL16. I loaded up with the other powder and yup, found the load again.

So, can it somehow be a different powder, primer, brass, COAL, etc?

Go back and check it again, and again, patiently, don't assume, check all your notes.

Hope this helps and you don't go insane trying to figure it out.

 

[Calvin45]

Guys. READ THE WHOLE ORIGINAL POST.
The guy has some old ammo loaded that shoots well. He loaded some new ammo EXACTLY the same and the groups are 5 times bigger.
The gun shoots the old ammo FINE and the new ammo POORLY.
It is not a RIFLE ISSUE

My bad…not a scope issue either then

 

[Calvin45]

Is there any way the neck tension has changed in a significant manner? That'll do it.

 

[Hunterjones]

I have a Kimber Mountain Ascent that consistently shoots under 1/2 MOA out to 800 yards WITH the Muzzlebrake attached .
300 yards is as far as I've shot it without the brake and it is 4-4.5 MOA with the brake removed. TOTALLY CHANGES barrel harmonics….

 

[wardog5]

I am frustrated beyond expression. My 30-06 was a tack driver. Then it quit shooting well. Had it glass bedded, changed the load a bit, played with seating depth. Settled on an OK load which gets 1moa (it used to get 1/2 Moa). So I decided to load up all my empty cases and then test the load. First, I shot some of last September's load (this is now April). It shot well. So I loaded up several EXACTLY the same. Shooting 168 gr. Hornady BTHP over 59.3 grains of IMR 4350. (My old load was 59grains). This is a compressed load. The bullet seating depth, measuring cartridge base to ogive is exactly the same to .001. My cases are matched to within .004 of the same head stamp. This exact same load shoot 5" groups, all over the place. So, I shot 3 of my old loads. It shot a 1" group. So I went home, and very carefully loaded up more of the same EXACT load. It shot a crappy group. This does not follow the laws of physics and I cannot take this kind of weirdness lightly. BTW, each shot was put in the rifle individually and not in the mag, lest any chance of the seating depth being affected. Why is this happening?

Check the length of the cases they might be a hair to long and causing extra tension on the bullet when you close the bolt

 

[wardog5]

Have you chronographed both loads? Old and new? Temps will make a difference in velocity, but with last year's ammo shooting better than this year's, you need to verify speeds between the two.

There has to be something different.
One thing different, could be that ammo built last year had a bit more neck hold due to a very slight bullet weld to the case neck. But, if last year, you shot your ammo fairly soon after loading, that should not be it.

Verify primers are the same
Verify primer seating is the same
Pull apart a loaded round from last year and reweigh the powder charge. Scale might have drifted, so this year's loads are a bit different.
Try a new bottle of powder and see if that changes anything
Neck tension
Check headspace from last years loaded ammo to this new batch
Verify seating depth (CBTO) is the same between last year's and this year's ammo. Maybe your die got adjusted or bumped inadvertently

I agree with all the above and would like to add check your case length make certain they don't need to be trimmed …

 

[MagnumManiac]

Who did the bedding?
Rugers are different, the front 60° recoil lug has to be bedded tight with no clearance and a pillar has to be used.
I did these as a specialty for years and if not done correctly the rifle will shoot like crap.
As soon as you remove the pressure point in the stock, the entire action drops in the bedding between .040"-.050". This has to be filled to get the action back where it should be….the best way is to use tape under the barrel to get the action square while the front and rear pillars set up.
Then the action gets bedded, not just the front and rear, but the entire action as Rugers have a tendency to bend when the middle screw is tightened.
I would say this has a lot to do with what you are seeing.

Cheers.

 

[greenejc]

I am frustrated beyond expression. My 30-06 was a tack driver. Then it quit shooting well. Had it glass bedded, changed the load a bit, played with seating depth. Settled on an OK load which gets 1moa (it used to get 1/2 Moa). So I decided to load up all my empty cases and then test the load. First, I shot some of last September's load (this is now April). It shot well. So I loaded up several EXACTLY the same. Shooting 168 gr. Hornady BTHP over 59.3 grains of IMR 4350. (My old load was 59grains). This is a compressed load. The bullet seating depth, measuring cartridge base to ogive is exactly the same to .001. My cases are matched to within .004 of the same head stamp. This exact same load shoot 5" groups, all over the place. So, I shot 3 of my old loads. It shot a 1" group. So I went home, and very carefully loaded up more of the same EXACT load. It shot a crappy group. This does not follow the laws of physics and I cannot take this kind of weirdness lightly. BTW, each shot was put in the rifle individually and not in the mag, lest any chance of the seating depth being affected. Why is this happening?

Check your lot number on the powder. Different lot numbers burn differently. If you have a different lot number, start all over again and work up loads beginning at around 56 grains. You're using the same primers and projectiles, it gets the same accuracy from the original loading and seating depth is the same, so that leaves the powder lot number. You might also note that with wear, you may need to seat slightly farther out with the projectile, depending on how many rounds you've put through the barrel.

 

[ShtrRdy]

This is a thought without any proof. If you have ever taken a pan or bucket of mixed sand, pea gravel and stones that are mixed well and start to shake or vibrate the pan/bucket, the larger sizes will migrate to the top due to more space between the larger pieces, and the smaller pieces migrate down by sifting between the gaps of the larger pieces. Is it possible that powder in a canister can fracture into smaller pieces and migrate to the bottom of the canister? The shape is a major player in speed of progressive ignition.

That's not at all what I was suggesting.

 

[greenejc]

Ruger MK 2 (M77) 30-06.

I have that exact rifle. Its picky about screw torque and powders, but will shoot Speer, Hornaday and Sierra 180's into .7 in to about 1.2 inch at 100 yards with 55 grains of IMR 4350. It really likes the 178 grain Hornaday match bullets, and the 168 grain Amax works pretty good in it. I find that Winchester and Remington brass are the most accurate, with Lake City being about as good, and I use Remington 9 1/2 primers. I've got about 4,000 rounds through it now, and I set the bullet out a little to compensate for wear. These are 5 shot groups at 100 yards. I do about 56.5 grains with the 168 grain projectiles. My experience with compressed loads is that they can be erratic, and so can a 100% load density. I seem to get best accuracy in all my -06's with loads that are in the 90% to 95% range for case fill.

 

[26Reload]

Start with the easiest switch.....
Pull 5 bullets from old load and put in new loads...
Put 5 new bullets in old loads....
If still shooting odd........
Make sure powder used in new was used in old loads....
Lastly try switching the primers....
Other than oal and brass problem...only logical test.....
Especially since.....'old loads still shoot'

 

[Dirtrax]

I'm of the opinion that cold weld/neck tension is a factor. Outside of that the OP mentioned that this is a "compacted" or compressed load as it it more commonly referred to as. It is not unheard of for such loads to push the bullet out creating a longer (greater?) CBTO. So…measure the CBTO between old and new loads again. If it's the same pull bullets in one of each. It may be as simple as adding tension via the neck sizing or even adding a crimp.