View Full Version : Bizarre 300 Win Mag behavior
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.
https://i.imgur.com/ROjj5JO.jpg
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???
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.
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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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
Also, what is the twist? Is it on the ragged edge of stability with the 225s?
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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
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.
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.
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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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?
How bad is the vertical stringing? Maybe an ignition prob. Are you using magnum primers?
Not if they shoot great without the can. huh? I buffed the brake and barrel out. Cleaned end cap of can, hardly anything there but what the hell....
PB
Eyeballing the alignment through the chamber doesn't show anything alarming.
Did you do the pencil test?
... a sharpened #2 pencil is a perfect fit in a .308 barrel. Push one through the can, down the barrel, to check your clearance. (I learned this trick on TFL.)
Or maybe it's just a barrel harmonics problem? The combination of heavy bullets and the weight of the can is screwing things up?
Not if they shoot great without the can. huh? I buffed the brake and barrel out. Cleaned end cap of can, hardly anything there but what the hell....
PB
Then I misunderstood what markm meant by "stacking". Looking back I guess it means stacking one shot on the other, not vertical stringing.
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?
Good. I shot 3 rounds at 1300 yards. No fanning out or anything.
Yes, stacking holes inside one another. Not walking up the paper.
So always good with no can...
Sometimes ok with can, sometimes not ok with the can.
How’s the bedding and action torque? Perhaps the weight of the can could also be causing some form of changes in barrel harmonics.
The key change seems to be suppressor related.
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Did you do the pencil test?
... a sharpened #2 pencil is a perfect fit in a .308 barrel. Push one through the can, down the barrel, to check your clearance. (I learned this trick on TFL.)
Or maybe it's just a barrel harmonics problem? The combination of heavy bullets and the weight of the can is screwing things up?
Yes, it dropped through like it (#2 Pencil) had eyes. And I checked the screws, they were tight.
PB
So always good with no can...
Sometimes ok with can, sometimes not ok with the can.
How’s the bedding and action torque? Perhaps the weight of the can could also be causing some form of changes in barrel harmonics.
The key change seems to be suppressor related.
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Yes yes and yes it could be harmonics, good idea. I thought the same.
PB
eightmillimeter
04-03-19, 02:31
Find a way to get another 50 FPS on that load by upping the charge or switching powder. You’ve got more recoil force and a slower bullet with that heavy and the gun may have started moving a c-hair before the pill is out of the can. That’s my official guess.
Find a way to get another 50 FPS on that load by upping the charge or switching powder. You’ve got more recoil force and a slower bullet with that heavy and the gun may have started moving a c-hair before the pill is out of the can. That’s my official guess.
We loaded some hunting bullets at 75grains but went back to 74.5 H1K because it was so hot on the brass, we can take some of those loads.
PB
So always good with no can...
Sometimes ok with can, sometimes not ok with the can.
How’s the bedding and action torque? Perhaps the weight of the can could also be causing some form of changes in barrel harmonics.
The key change seems to be suppressor related.
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Bedded like a dream and torqued nice and tight, just checked the torque. Good idea though.
PB
Any signs of the barrel making contact during recoil?
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eightmillimeter
04-04-19, 01:53
We loaded some hunting bullets at 75grains but went back to 74.5 H1K because it was so hot on the brass, we can take some of those loads.
PB
Just for giggles go down a node and see what happens.
Any signs of the barrel making contact during recoil?
Not on this gun. Plenty of room between the stock and scope.
Just for giggles go down a node and see what happens.
yea, where are probably just going to test the two loads we have, and can-no can and check velocities. And some other lighter bullets. If it hates the 220/225's, then Ill shoot our old faithful 208 AMAX load. Served us well for years.
PB
Not on this gun. Plenty of room between the stock and scope.
Then I’m going to say you’re on the verge of instability with the heavier bullet. Rework the load or use a different bullet.
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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.
I'm not a reloader by any means and the bold part above stuck out to me after reading all of this thread. Is it possible to mark the end cap exit hole so that after firing a rew rounds you would see some sort of marking that the bullet was tickling the end cap as it exits? If so that could help diagnose or eliminate a possible cause.
I'm not a reloader by any means and the bold part above stuck out to me after reading all of this thread. Is it possible to mark the end cap exit hole so that after firing a rew rounds you would see some sort of marking that the bullet was tickling the end cap as it exits? If so that could help diagnose or eliminate a possible cause.
I buffed the exit hole out so we will know, Im worried about blowing the cap off quite frankly.
PB
I'm not a reloader by any means and the bold part above stuck out to me after reading all of this thread. Is it possible to mark the end cap exit hole so that after firing a rew rounds you would see some sort of marking that the bullet was tickling the end cap as it exits? If so that could help diagnose or eliminate a possible cause.
There was some signs of disruption of the crust on the inside of the endcap. I know from getting cap kisses in 308 that the bullet can be like 4 feet off at 100 yards and still not totally wreck the end cap. So a very subtle tick would yield the results we're seeing.
So so so, I buffed out the brake. It was Crusteeee, and buffed end cap , I also took a round file lightly bore out baffles. Just to knock off any such crust.
Gun shot everything lights out. Mark May have some pics. I shot two bullets through one hole. I mean I didn’t open it up in the slightest. Then placed one right beside it. We are more about slapping steel, but damn we enjoyed some good groups. Only 3 round groups because I can’t make myself 5 precious rounds into paper.
Wind kicked our but. It was stopping starting and changing directions all day. That being said, it was good times.
PB
Coal Dragger
04-08-19, 11:28
Throw a .338” brake on it and a .338” can.
Plenty of clearance, problem solved.
Throw a .338” brake on it and a .338” can.
Plenty of clearance, problem solved.
I run a 338 can on a LMT MWS and sometimes a 300WM, I’m a big fan.
PB
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