I don't consider it an unknown science, what causes the difference in accuracy is actually fairly simple.A few years back I bought the TC Compass in 6.5NMB just because it was like $225 new with rebate. I did the OAL/seating depth testing with it and could see a swing from 1" to 0.5" by changing nothing but seating depth. The speed across the Chronograph was virtually unchanged. I mean like well within the margin of error. I was surprised the velocity had no change, but that was what my test showed. But accuracy was greatly affected.
I think there is some unknown science there somewhere and because of the dynamics of ammunition, I am not sure we can ever really test and verify what is actually going on, we can only observe the effects and adjust accordingly.
Rosewood
I’ve heard and read other stuff along these lines @Darkhorse - Cortina, Newberry, and all that OBT stuff that goes way down that rabbit hole you’re describing.I don't consider it an unknown science, what causes the difference in accuracy is actually fairly simple.
I am looking for the point in the node where the bore is still for a fraction of a second. I am doing this by changing the seating depth. Consider this; A bullet seated at the recommended OAL shoots 1.0" groups. To simplify things assume we are not yet at the point where the bore is still. So we seat a bullet .010" further out and get a .500" group. Why?
At 3,000 fps a bullet that is .010" closer to the node starting out will be closer to the node when the bullet strikes. Hitting farther up the slope of oscillation, possibly close enough to reduce the group to .500"
The same principle works equally well going the other direction. I cannot load a round loaded to OAL in the clip of my Browning rifle, in fact to be reliable the length will be .100" shorter than OAL. Many people swear that seating the bullet closer to or jamming the lands is the only way to increase accuracy.
Yet my rifle, a off the shelf Abolt II, That I did nothing to and left it in pure stock form shot a .188" group and many more around .250". And loaded Max. still reliably averaged .500".
I don't know about anybody else but for me a 1/2 group was and is the holy grail with a factory stock rifle. I was glad to get the accuracy I got but never really hoped for.
Realize though that just working the seating depth didn't get me here by itself. I make a attempt the get my finished round as concentric as possible to the axis of the round and true to the bore. This gives the round it's best chance to shoot those one hole groups.
You are still just observing the results, you can't observe what is going on in those micro seconds of the explosion in the chamber.I don't consider it an unknown science, what causes the difference in accuracy is actually fairly simple.
I am looking for the point in the node where the bore is still for a fraction of a second. I am doing this by changing the seating depth. Consider this; A bullet seated at the recommended OAL shoots 1.0" groups. To simplify things assume we are not yet at the point where the bore is still. So we seat a bullet .010" further out and get a .500" group. Why?
At 3,000 fps a bullet that is .010" closer to the node starting out will be closer to the node when the bullet strikes. Hitting farther up the slope of oscillation, possibly close enough to reduce the group to .500"
The same principle works equally well going the other direction. I cannot load a round loaded to OAL in the clip of my Browning rifle, in fact to be reliable the length will be .100" shorter than OAL. Many people swear that seating the bullet closer to or jamming the lands is the only way to increase accuracy.
Yet my rifle, a off the shelf Abolt II, That I did nothing to and left it in pure stock form shot a .188" group and many more around .250". And loaded Max. still reliably averaged .500".
I don't know about anybody else but for me a 1/2 group was and is the holy grail with a factory stock rifle. I was glad to get the accuracy I got but never really hoped for.
Realize though that just working the seating depth didn't get me here by itself. I make a attempt the get my finished round as concentric as possible to the axis of the round and true to the bore. This gives the round it's best chance to shoot those one hole groups.
True. But the results are what I'm after.You are still just observing the results, you can't observe what is going on in those micro seconds of the explosion in the chamber.
Rosewood
Dang, I feel like a regular ol’ Wednesday night for @Adam5 - loaded up some of the 308s discussed above in my remaining clean, sized, deprimed Lake City.
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Don’t know how I had two partial jugs of Varget but drained those and had to break into my 8# stash to finish off. Feels like a night when I got too loose with my high end whiskey.
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Time to unload on this particular round!
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Tonight we loaded some more .44 rounds.
300 .44 Spl that are a 240gr cast semi-wadcutter over 8.5gr of AA5.
300 .44 Mag that are a 240gr Xtreme plated flat point over 24gr of W296 and a CCI 350 magnum primer.
I still have 400 .44 Mag brass to play with next week. I won’t be reloading this weekend due to my girlfriend having knee replacement surgery in Chattanooga early tomorrow weekend. I’ll spend the weekend at her house playing nursemaid.
Hoping everything goes well on her surgery.
Tonight we loaded some more .44 rounds.
300 .44 Spl that are a 240gr cast semi-wadcutter over 8.5gr of AA5.
300 .44 Mag that are a 240gr Xtreme plated flat point over 24gr of W296 and a CCI 350 magnum primer.
I still have 400 .44 Mag brass to play with next week. I won’t be reloading this weekend due to my girlfriend having knee replacement surgery in Chattanooga early tomorrow weekend. I’ll spend the weekend at her house playing nursemaid.
Chattanooga is a good town to be in, hope it goes well.
You’re a beast on the reloading!
I’m not far from ‘nooga, gimme a shout if you get in a pinch or want to grab a brewski.Thank you!
I’m not sure if I reload a lot so I can shoot a lot, or if I shoot a lot to have brass to reload.
I’m not far from ‘nooga, gimme a shout if you get in a pinch or want to grab a brewski.