300 Win mag crazy ballistics?

[Sir Wendigo]

I thought I had my dope down for my rifle. Its a remington 700, chambered in 300 WM. Stock 24" barrel and receiver, in an AICS chassis, with a Bushnell DMR on top. I reload for all my rifles. I use remington brass, GMM215 primers, 68 grains of reloader 22, and I top it with a berger 230 OTM hybrid. I DO NOT HAVE ACCESS TO A CHRONOGRAPH. I zeroed my rifle, then took a target to 400 yards to measure drop, played with my ballistic calc on phone, and came up with a MV of 2650. That lined up with things I read on here and other places. For an entire year this was an accurate mv and my dope has been great, until this weekend. I checked zero, it was good. Then went to 400 yards, put my dope in, and missed a steel plate high 3 times. I was scratching my head and getting frustrated with myself at this point. I then lazed my far target at 1190 yds, put my dope in of 13 something mils. Missed way high spotter said, then i shot again and was able to confirm i was multiple mils high. I ended up measuring, with my reticle, and adjusting my turret, to 9.5 mils and was right on...at 1190yds. That equated to a MV of about 3000 fps. While I would be tickled pink to have my 300 wm push this bullet this fast, I know it isnt possible, even if i had a 30" barrel. *** is going on. Someone please help me figure this out, I went and checked my 100yd zero again and it was right on.

Please send any questions you have, and I will answer them as briskly as possible, want to get this figured out ASAP.

This is my first post BTW

Thanks

Mike

 

[Trever]

What was the difference in temperature on your firing days? We're there any pressure signs? Maybe your scale was a little off. I'm pretty curious myself.

 

[Sir Wendigo]

It was only 10 degrees warmer than normal. My equipment may have been out in the sun for longer than normal, but not any amount significant. I'm very ocd when it comes to my powder charges, and there were no pressure signs. I acknowledge accidents happen, but i would have felt and seen a difference that severe.

 

[MagnumManiac]

Barrel whip.

Cheers.
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[Greyfox]

If the load is unchanged, including powder lot, I would check your scope for tightness. Other than that, it would look to your shooting parameters of cheek weld, rifle support, and degree of stock pressure on the shoulder. I would also try to ge my hands on a good chronograph and accurately test the loads.using 400 yards to check velocity gives too much variation.

 

[Sir Wendigo]

Thank for the feedback guys. I'll ask around and find a chronograph to use. And check my scope again. To be honest I'm still scratching my head about the situation.

 

[bigngreen]

For a proven trajectory to all of the sudden go high like that I'd look at my turret calibration factor or value and make sure it's right, then look at the BC and make sure something did happen like a G1 number as a G7.

 

[Deleted member 46119]

As well as the suggestions of bedding, floating and scope mounting and tracking...

Are you shooting cross canyon/valley? Canyon/valley winds can actually 'lift' the POI significantly.
How much weather change? Temperature/air density can have that much of an effect. Higher temperature of your R22 can have a big impact.

I think you may be experiencing multiple contributors but I don't think you are suddenly going 3000fps when you were going 2650.

 

[Sir Wendigo]

I am using an AI Chassis system. So I don't believe bedding or float to be a problem. Also there is no horizontal deviation, only the vertical. I assume both would come from a bad bed or inconsistnent float. Have not done a tracking test yet, but nothing has jarred my rifle or scope so I assume its fine. I store it carefully in my safe, and transport in a pelican hard case.
I was shooting over a deep valley, from ridge top to ridge top. I was unaware of a "lift" phenomenon. My cases were a bit warmer than normal, as was my barrel as I was frustratingly firing shot after shot trying to figure out what was going on. I believe air density to be similar to zero date, but may be wrong.
Obviously something is wrong here, and I assume its me, or my scope. I'm sure even with all these factors, its not adding 350 fps to my MV. I am contemplating tearing everything down and reassembling, and starting over, but then again I'm craving a new barrel. So maybe I'll just do that and forget about this headache.

 

[ShootnMathews]

Did you change the tension on the action screws? Or have they worked loose? Make sure nothing has fell in around the barrel channel. A pebble or stick. Cleaned the barrel lately? I agree hat the gun should not shoot that fast which leads me to believe its more of an equipment malfunction. Or a change in harmonics.

 

[arrow]

I too shoot a 300 win mag with 230 hybrid. I was having a problem with higher and higher impacts as my range increases to the pointy of multiple minutes at 1400 yards. I have found the bc of the 230 hybrid to be much higher than the advertised .743. Getting ahold of a good chrono is a good start than try adjusting the bc.

 

[MagnumManiac]

Did you change the tension on the action screws? Or have they worked loose? Make sure nothing has fell in around the barrel channel. A pebble or stick. Cleaned the barrel lately? I agree hat the gun should not shoot that fast which leads me to believe its more of an equipment malfunction. Or a change in harmonics.

This.
Air density plays havoc with barrel harmonics, which will change the point of bullet exit.

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