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January 10, 2017, 09:11 PM | #1 |
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Join Date: November 29, 2016
Location: Long island ny
Posts: 67
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Using nosler 7.62x51 data as reference.
The 7.62 data shows a volume of
49.5 gr of water My fire formed 7.62 round Trimmed to factory length 2.0075 After firing the round Reads 52.3 grains of Of water. Nosler shows a length Oacl of 2.800 with a 155 grain bullet Powder charge of 40.5 in For imr 4064. What Inn using. If I read the coal of my 7.62 round It reads 2.784 Bullet is 150 grain. 1.125/6 in long. If I take my fire formed case With neck tension on it and take the Exact bullet that factory ammo is using 150 gr BT 1.125 in lenght and put this bullet (Dummy round ) load it in my chamber And close it. I force the bullet Into the case and bullet ogive hits My lands . It reads 2.834. So I'm using 40 gr of Imr 4064 150 gr bullet Coal 2.785 These rounds should be fine Just like factory spec 7.62 Ammo I have. Then , I will increase to 2.790 Next time. Then 2.795 that's still Approx 40 thousandths from ogive To lands. See how they perform. In my rifle case and bullet Hits the lands at 2.834 I have room to move closer ? Last edited by Bytesniffer; January 11, 2017 at 08:12 AM. |
January 11, 2017, 08:55 AM | #2 |
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Join Date: February 2, 2010
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"These rounds should be fine
Just like factory spec 7.62" No reloaded round "should be just fine" unless you have followed the rule of "start low and work up". |
January 11, 2017, 10:32 AM | #3 | |
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Join Date: March 23, 2012
Location: Conway, Arkansas
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Quote:
Mobuck, if you noticed, 40gr is about .5gr under minimum. It's not like he's starting at max. Sent from my iPhone using Tapatalk |
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January 11, 2017, 11:48 AM | #4 |
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Location: Ohio
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Bytesniffer,
You have to keep the two water capacity standards separated: Case Water Overflow Capacity (CWOC) is capacity for water with the case filled to level with the mouth. This number is used with QuickLOAD. Case Water Capacity (CWC) is the amount of water space remaining after seating the bullet into the neck. This number is used together with powder bulk density to determine load density. If you have CWOC it is pretty simple to use seating depth to determine the CWC. Seating Depth = Case Length + Bullet Length - COL For a flat base bullet, where: lengths are in inches r= ½ the bullet diameter in inches 253.5 converts cubic inches to grains of water volume at 73°F (room temperature average in many places). CWC = CWOC - (Seating Depth × pi × r² × 253.5) For a boattail bullet you will additionally have to add back the difference between the volume of the boattail and a cylinder the same length. Where: l is the length of the boattail in inches r is the diameter of the bullet in inches R is the diameter of the heel of the boattail (the bottom diameter): Add back volume = 253.5 × ((l × pi × r²) - (l × pi × (r² + R² + (R × r)) / 3) Nosler's 49.5 grain number is about right for CWC with their bullet seated to their specified COL. CWOC is usually more like 55-56 grains in 7.62 cases.
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January 11, 2017, 12:50 PM | #5 |
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Join Date: February 13, 2002
Location: Canada
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You're over complicating the entire thing. You don't need to fiddle with case water capacities at all.
"...Trimmed to factory length 2.0075..." 7.62 x 51 is loaded using .308 Win data. Trim-to for .308 is 2.005". Mind you, the 2.5 thou won't make any difference. 2.800" is the Max OAL for .308 Win with any bullet. You can forget the 'off-the-lands' stuff until you have worked up a load too. Just use the 2.8" and you'll be fine. Don't know what No$ler bothers with separate data for 7.62NATO either. Or why they mention SAAMI. 7.62NATO isn't a SAMMI spec. NATO specs have nothing to do with SAAAMI anything. Nobody else provides NATO spec data either.
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January 11, 2017, 01:00 PM | #6 |
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Join Date: November 29, 2016
Location: Long island ny
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Unclenick
Very technical info on The water capacity. This explains Clearly why the volume is Larger for my case. If I subtract the space for the Boat tail bullet I'm using Its about right on. Also mobuck, I definitely start low to be safe and work Up. Previous was 39.5 grains and I had No signs of pressure issues when examining The case and primer after firing 20 rounds. I think after 40 gr I'm going to go up I'm 0.3 gr I just want To find best combination for Accuracy. Case the same , bullet the same , setting Depth same. (Cartridge overall length) same, jump the same and same powder etc I may be crazy but I seem to enjoy Reloading as much as shooting No that I'm retired. l will need to reload a lot of rounds To break even, on what it cost to Get to this point but , I'm not Doing It to save money. I'm on a quest to build reliable and Consistent ammo that should Translate into better accuracy. |
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