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Old January 13, 2013, 12:59 PM   #1
wrightme43
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First run .308 win. work up. Please check my work.

Ok, I have a Lee breech lock kit. RCBS dies. Central Mach. Micrometer.

I have 7.62x51 CBC brass 2012 manufactured, I fired in my Ruger Gunsite Scout.

Lubed cases, full length resized, deprimed, swagged the primer crimps, resized to 2.008. (that is where my lee resizer stops and will cut no further) Hand polished cases, and beveled inner and outer neck.

Primed 2 sacrificial cases, measured grains of water. 54.4 grains of water. pretty dog gone close to the others I have read on here. Still starting low of course. I disposed of these cases.

Primed all cases with remington large rifle primers untill the primer was flush.

Using IMR 3031 and Hornady 150 grain BTSP I found loads using EDIT hornady load data book. EDIT I did not find 3031 in the hornady book for 150 grain btsp. I found that data at the IMR/Hogdon website.
Start load, 40.2, max load 43.5 Compressed

Bullet 150 grain BTSP

I wieghed all loads light after zeroing the scale and trickled up to the load.
I made
1 round @ 39.2 and labled it with a sharpie.
1 round @ 39.7 and labled it with a sharpie
3 rounds @ 40.2 and labled them with a sharpie
3 rounds @ 40.7 " "
3 rounds @ 41.2 " "
3 rounds @ 41.7 " "
3 rounds @ 42.2 " "
3 rounds @ 42.5 " "

I then seated all the bullets, COL is 2.770-2.775 based on deformation of the soft point.

My reasoning is this. I will start with the lightest loads, and work my way up, checking for any problems after every firing.
The max loads/never excede loads are all compressed loads, with this bullet, in a longer overal cartridge length. 2.800 max.
Since none of my loads are compressed, and I have a slightly (very slightly) smaller case capacity than lapua, or norma brass, I should not excede any pressure levels that can cause harm. Is this thinking correct?
I worked up to a 42.5 grain load because it is a Chuck Hawks pet load, with that powder and tha wieght and style of bullet.

I am not exactly following the Optimal Charge Wieght load plan. I will follow this as soon as I can, but I wanted to test these first.

Here is the Optimal Charge Weight link http://optimalchargeweight.embarqspace.com/

The basic concept (you guys most likely all know this but just in case) is that, if the bullet exits the barrel while the shock wave that travels up and down the barrel is at the crown it will make fliers, and if it exits as it at the breech the barrel will be more stable and produce more accuracy.

Its a neat idea. Maybe its all bunk. I dont know. I am really really really new to this. I keep good records and like to experiment so I am just going to see what happens.

Now if I have done something stupid please tell me. If you have a idea I would love to hear it.
Thank you
Steve
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Last edited by wrightme43; January 13, 2013 at 02:03 PM.
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Old January 13, 2013, 01:42 PM   #2
rduckwor
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Looks fine. Your charge weight differences may be too small to see much variance. The longer distance you shoot at the more value you will get (with respect to a ladder text, OCW is typically done at 100 yds). I typically jump in 0.5 Gr increments for the initial series and then fine tune at 0.3 Gr increments to try to nail the node down. If a ballistic calculator shows my muzzle velocity to be too low for the distance I plan to shoot, I clearly have to change something and start anew.

Chrono the session if you can and double the output of data you get from the session.
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Old January 13, 2013, 01:56 PM   #3
wrightme43
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Thank you!

I dont have a chrono or know anyone that does.

I am going to try these, and then try to work on the OCW load like you said at the .3 grain changes.
Once I have a good solid load. I will sit and make a bunch of them.

This is actually a hell of a lot of fun!
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Old January 13, 2013, 02:21 PM   #4
Bart B.
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I don't think anybody's proved that where that shock wave's at in a barrel as it travels back and forth at about 16,000 fps has any effect on accuracy when the bullet leaves.

First off, nobody's identified where that wave starts at. Depending on the lenght of a cartridge, that place could be anywhere over a distance equalling the cartridge length. Depending on the barrel's length and where the wave starts, it could be anywhere in the barrel when the bullet exits. Nobody's done any tests with proper instruments to find out.

Second, if that shock ave starts anyplace except at the case head, there'll be two of them; one starting forward and the other backwards in the barrel; they do go both way. They're sound waves.

Third, if one does the math, they'll see that there will be several back and forth round trips that shock wave (or both, it there's 2 of them) make in the barrel before the bullet exits.

Fourth, I've worn out four 7.62 NATO barrels in Garands in competition. When each was new, there was copper wash from bullet jackets all the way to the muzzle's crown. After 4000 rounds fired and cleaning the barrel from the muzzle with a bare solid steel cleaning rod every 50 to 60 shots, the lands and grooves had been worn away such that there was no copper wash for the last 5/8th to 3/4ths inch of the lands and grooves. Yet accuracy was still 2/3rds MOA at 600 yards with the best commercial match ammo when properly tested for the life of the barrel. So, the bore and groove diameters had opened up a tiny bit in that area; bullets no longer touched the barrel at that point. The claim is that that shock wave enlarges the muzzle when there and that hurts accuracy. I don't believe that OCW theory is anything close to reality; just an unscientific wild ass guess. Bullets shot with equal accuracy whether or not they touched that last fraction of an inch at the muzzle. Same for all four barrels.
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Last edited by Bart B.; January 13, 2013 at 02:56 PM.
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Old January 13, 2013, 02:48 PM   #5
wrightme43
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Now I do have a question.

Ok IMR site says 2.800 max C.O.L for 150 gr Nosler BT
Hornady says 2.735 C.O.L for thier BTSP but it doesnt say max.

Am I ok at 2.770-2.775 ?(the variation is in the soft lead point on the end of the bullet. All cases measured 2.008, all bullets are seated with the same amount of cannelure showing. Which is also identical to the remington 150 grain soft point interlock my gun likes so much.
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Old January 13, 2013, 02:50 PM   #6
wrightme43
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Thank you Bart. I am trying to understand, and when you are new it is easy to overthink things.
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Old January 13, 2013, 03:36 PM   #7
Bart B.
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Wrightme43, all bullets have different tip positions relative to their overall shape. A few thousandths inch spread is very normal and will not effect accuracy unless your worst many-shot test groups are no bigger than 1/100th of an inch at 100 yards. That's about the most that tiny difference will make.

Biggest accuracy robber of all bullets is how much they're unbalanced. The density of the lead core and copper jacket isn't all perfect. Neither are their dimensions and weight. So, they all are unbalanced a tiny, tiny bit. But the best of them will shoot no worse than 1/2 inch at 200 yards. So says Sierra Bullets about their best match bullets that all have tiny, minor imperfections in weight, shape and balance.
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