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7mm reload problems (ballistics)

 
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  #15  
Old 06-14-2010, 10:54 AM
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Join Date: Feb 2008
Location: Memphis Tn
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Re: 7mm reload problems (ballistics)

I have loaded my Ruger 77 Mark II in 7mm Rem mag for a number of years. I have used many different powder and have been able to get both accuracy and good speed shooting 160 grain Nosler Accubond bullets. My gun has a long throat so it take a little more powder that many manuals list to achieve the stated velocity. My current favorite load with the 160 Accubond uses RP case, WLRM primers, and 67.0 grains of RL-22. I know this is over most published data.It is safe and very effective in my gun. It may not be in your gun!

However, if I were you I would increase my powder charge. Work up slowly and watch for signs of pressure. I just looked at the Alliant data and they show 65.0 grains of RL-22, and a 160 Grain Speer SP bullet for 2900+ ft/sec.. My 67 grains with the 160 Accubonds give 2950 ft/sec.. I have also used H1000 with the 160 Accubonds and with 70-72 grains I have gotten 2950+ ft/sec. This is also a very good load in my gun.

If I were loading 61.0 grains of RL-22 in my gun I would be getting close to the same velocity as you are getting.

Last edited by Shortmagman; 06-14-2010 at 09:52 PM.
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  #16  
Old 06-14-2010, 11:56 AM
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Join Date: Jul 2009
Location: Idaho
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Re: 7mm reload problems (ballistics)

shortmagman
I am considering increasing the charge but I am worried about pressure.
I had a incident with pressure using a berger load everything was shooting great no signs or anything. then one day (about 20 degrees hotter and sunny)
had a major pressure problem. The increase in temp is the only thing we could come up with for a cause. other than I guess its possible I messed up that one round loading it but i am carefull but I guess its possible.
so I dont know what to do really
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  #17  
Old 06-14-2010, 09:50 PM
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Location: Memphis Tn
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Re: 7mm reload problems (ballistics)

retiredcpo,

I do understand fear of too much pressure. I also have experienced it.One day while shooting a load in a 270 Winchester that was very safe and effective in mild weather I started noticing hard bolt lift etc and even blown primers.
The temperature in Memphis was 95+ and I had left the loaded rounds out in the sun on the shooting bench.

Now when I shoot on a hot day, I make sure that my loaded rounds are out of the sun, and also not in the cab of the truck where the sun can heat them up. If they are left out in the sun they can get as hot as 140+ degrees or more and this is sure to raise the pressure sometime to a dangerous level.

When I work up a load and I am getting near the max I work up at .5 grains at a time. If you do this carefully and make sure your rounds are kept cool you can gain more velocity and still be safe. Your velocity will also tell you when you are approaching a max load. If you are below the stated velocity in a good manual you can work up and approach that velocity.

Example: We know that it is safe to get 2900 ft/sec out of a 160 grain bullet in a 7mm Rem Mag rifle in good condition. If you are getting 2700 ft/sec you can be reasonably sure that you are below the max and therefore you can work up the powder charge.
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  #18  
Old 06-14-2010, 10:08 PM
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Join Date: Jul 2009
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Re: 7mm reload problems (ballistics)

shortmag
thats what I was thinking and will probably increase the load
but I really dont understand why im 400 fos below where the load data says i should be 100 fps or less I could see but 400 is alot.
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  #19  
Old 06-14-2010, 11:34 PM
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Re: 7mm reload problems (ballistics)

One thing you could try is shooting/chrono some Federal premium in 160 gr Accubond. I got 2921 FPS, out of my 24" barrel, which seemed about right vs. the reported 2950 (26" barrel) with those rounds. If you can get around 2900+ FPS with those factory loads, then you should be able to work up to it with your components.
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  #20  
Old 06-15-2010, 04:39 AM
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Location: Carlisle, PA
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Re: 7mm reload problems (ballistics)

Quote:
Originally Posted by visigoth View Post
One thing you could try is shooting/chrono some Federal premium in 160 gr Accubond. I got 2921 FPS, out of my 24" barrel, which seemed about right vs. the reported 2950 (26" barrel) with those rounds. If you can get around 2900+ FPS with those factory loads, then you should be able to work up to it with your components.
That is a brilliant suggestion. Shoot the factory ammo - it's a known quantity. The perfect way to break out of "paralysis by anlaysis". To that I can only add, get a chronograph.

Fitch

Last edited by Fitch; 06-15-2010 at 04:51 AM.
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  #21  
Old 06-16-2010, 10:25 PM
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Location: La Plata NM
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Re: 7mm reload problems (ballistics)

I have learned over the years that powder and pressures DO NOT mirror each other but velocity and pressures do. In other words if the load shows a certain velocity and pressure that is what I load to. Powder lots vary and some lots can be slow but as long as you are using a chrono load to the velocity and the pressure will be right there. That is why I like Hodgdons load data because it shows pressure and velocity and that is what I load to and I have never had a problem. If you don't feel comfortable with this just load one each and work up in small increments in the .2 to .3 range and watch everything closely.
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