.223 load help

[DanSavage]

Hi guys, I've been shooting the 69gr matchking for a while now in a 7 twist barrel. The load was something I just stumbled upon when I first put the barrel on. l

The problem is lately I've been getting some mild vertical stringing, up to 1/2" at 100 yards. It seems to be a pretty weak load also.

69 SMK bullet
20.9 Accurate 2495 powder
cci 400 primer
Lapua brass
2680 fps
McGowen 26" 7 twist bull barrel

What should I mess with first? Seating depth? or Charge weight?

Thanks

Dan

 

[jr600yd]

How many rounds have been fired?

 

[mac86951]

Hi guys, I've been shooting the 69gr matchking for a while now in a 7 twist barrel. The load was something I just stumbled upon when I first put the barrel on. l

The problem is lately I've been getting some mild vertical stringing, up to 1/2" at 100 yards. It seems to be a pretty weak load also.

69 SMK bullet
20.9 Accurate 2495 powder
cci 400 primer
Lapua brass
2680 fps
McGowen 26" 7 twist bull barrel

What should I mess with first? Seating depth? or Charge weight?

Thanks

Dan

If you haven't done pressure testing, I'd start there (charge weight). A good increment is 0.2gr for 223, watch for pressure signs. See OCW or ladder testing. Alternate would be a cbrono to assist.

 

[jimcasey01]

Has your shooting rest changed in any way?

 

[DanSavage]

I've shot about 800 rounds give or take,, used to shoot some clean scores at short range but it doesn't seem like it's old self.

My rest,,well prone bi bod and protector rear bag.

It could be me I guess I haven't shot it that much this year since the 6 BR has been shooting really well.

I'll try 3 five shot groups,, 20.7 20.9 21.1 from the bench and report back.

Dan

 

[GrocMax]

Might maybe recheck the torque on the action screws.

 

[DanSavage]

Might maybe recheck the torque on the action screws.

Will do.

 

[DanSavage]

I shot the first 5 shot group on left to warm up the barrel, then the 3 shot groups where fired round robin.

 

[strut64]

My 6 BR did the same thing. Might be heavy carbon deposit at the front of the chamber between the brass and the start of the rifling. Called a carbon ring. Once built up and hardened it is hard to remove. I cleaned and soaked it using a bronze brush loaded with Bore Tech Eliminator. Then scrubbed with a patch and JB Bore paste (blue label/ non embedding concentrating on the throat area. I don't have access to a bore scope so I can't say for sure but when I scoured it with JB the patch did pick up black carbon residue. Since I had to any way , I gave the whole bore a thorough going over with JB and finished up with bore Tech eliminator to make sure all copper was out of the bore. It helped a lot. Good luck.

 

[rmist]

Also check for throat erosion. My 223 moved .003" in under500 rounds.

 

[jsthntn247]

I'd be willing to bet it was throat erosion and your not seating the same distance away from the lands as you were to start. My 223 has moved .030 in 1600 rounds. From the test above 21.3 is where I'd adjust seating depth.

 

[DanSavage]

Thanks for the help folks.

Checked throat and found it has moved about .015".

Looking bag in my log book I't looks like I have more like 1200 rounds through it.
It still has a short throat though, .110 from case neck to rifle engrave mark's on the bullet.

I'll try moving bullet out and shoot 5 shot groups of 21.3, 21.4, and 21.5.

Wind was not very nice for testing,, but wanted to get it done.