Bizarre 300 Win Mag behavior

[markm]

Pappabear has a weird tactical bolt gun in 300 Win Mag that has messed with us for quite some time. We seem to have fixed its zero at least 4 times, and yet when we bring out, it’ll throw us some odd ball flyer rounds.

Specs on gun/ammo:
Rem 700, 300 WM, Thunderbeast suppressor, 225 gr ELD bullets in Norma Brass.

Sunday the gun was out again, and right out of the gate, the first shot wasn’t even on paper at 100… here we go!!

I could see the bullet strike was high behind the target, so Pappabear took aim at one of the bottom row round targets and go the two errant rounds you see in the top left quadrant of the green target sheet. WTF? 12” high and 5” left of his point of aim.



After this I took the can off and shot the exact same ammo at dead center of the entire target and got the half inch cluster you see in the middle of the target. Near perfect POI and great group.

We don’t see any obvious baffle or end cap strikes.
We then shot 208s and 190s with the can in place, and had no issues.
I think the 225s are lightly kissing the end cap.

Any ideas???

[Pappabear]

Also, if you closely at the first two holes you could see they look ragged and not a perfect circle. Like the bullet destabilized and was wobbling.

Big D was surprised we could stabilize these 225’s in my 300’s, suggesting we where on the brink of destabilizing. ???

FYI, the gun is a laser. It has shot .25 groups many a time.

[lsllc]

I would call Thunderbeast and have the suppressor evaluated. That seems to be the first place to look in my experience.


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[Pappabear]

Not if it shoots 190 FGGM and Marks 208 AMAX load just fine. I was going to send it back into to Tbeast until it shot the other bullets lights out.

This gun has tormented me so many times, having no idea it’s just the heavy bullets. I’m pretty sure I sent my Nightforce back to get evaluated for floating reticle. I took off all my mounts and loctited the screws. I have re zeroed the gun 5 times. Also, sometimes it would shoot the 225’s. I think we had just the right atmospheric conditions to trash the process.

But I don’t understand the why’s?????

PB

[lsllc]

Also, what is the twist? Is it on the ragged edge of stability with the 225s?


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[Pappabear]

Also, what is the twist? Is it on the ragged edge of stability with the 225s?


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1/10 yes 225’s. Another member suggested I clean my brake and crown. Which is a good idea because they are crusty as can be.

PB

[TomMcC]

Those flyer holes look like the bullets are on the verge of keyholing. I vote for not enough twist, with a wobbly bullet base kissing the can.

[markm]

Those flyer holes look like the bullets are on the verge of keyholing. I vote for not enough twist, with a wobbly bullet base kissing the can.

They spray with the can on, and STACK with the can off. I tend to agree that there's a C-hair tickle of the end cap.

Eyeballing the alignment through the chamber doesn't show anything alarming.

[lsllc]

1/10 yes 225’s. Another member suggested I clean my brake and crown. Which is a good idea because they are crusty as can be.

PB

I think that they may be in the verge of instability. How do they shoot at extended range with the can off? Say 800-1200?

Turbulence is a thing and dirty muzzles and muzzle devices can be a problem.


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[TomMcC]

They spray with the can on, and STACK with the can off. I tend to agree that there's a C-hair tickle of the end cap.

Eyeballing the alignment through the chamber doesn't show anything alarming.

How bad is the vertical stringing? Maybe an ignition prob. Are you using magnum primers?