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Posted: 2/17/2010 3:32:23 PM EDT
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I recently got a good deal on a Winchester Model 70 in 7mm Rem Mag. Also included was a set of dies.
I have been reloading .308, .223 & .25-.06 for about a year or more. So I am not a complete Rookie 
I haven't looked up any loads yet for the 7mm but today I found some WLR Magnum Primers and got excited & bought 300. Then I found out that I'm not supposed to use Magnum Primers. Is this accurate? |
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I use WLR Magnum primers in all my 7mm Rem Mag. loads and they shoot great. It's a big case and the mag. primers are just what you need.
I use H4350 and IMR4831 in my reloads to shoot 140's, 150's and 160's. I load to near maximum pressure and have never had a bit of problem. Most modern 7mm Mag's are built strong, I don't think you'll hurt anything. IMR4831 is especially good for 7mm Mag. by the way. 
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Quoted:
I recently got a good deal on a Winchester Model 70 in 7mm Rem Mag. Also included was a set of dies. I have been reloading .308, .223 & .25-.06 for about a year or more. So I am not a complete Rookie
I haven't looked up any loads yet for the 7mm but today I found some WLR Magnum Primers and got excited & bought 300. Then I found out that I'm not supposed to use Magnum Primers. Is this accurate? It's a magnum cartridge, which is what magnum primers are designed for. I've loaded a lot for my M-700 7 rm and I only use magnum primers. Chris |
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In 7mm Mag, I use magnum primers for anything slower than and including IMR4350 and any ball powders. So the only powders you shouldn't use mag primers for in 7mmRM would be something like a light bullet/Varget/IMR4064 combo. JMO. Thanks, I'm glad to here that. I bought some IMR4350, Any good loads reccomended? |
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Dryflash3 mentions something that you should be very aware of when loading for the belted case 7mm Remington Mag and something that should be fully understood to make the most out of your case life.
Because this round is intended to headspace on the belt, rather than the shoulder (like an '06 for example) rifle makers tend to let the chamber be a bit generous in shoulder-to-belt dimensions. To a degree this is not unusual or even bad. A slight amount of headspace "slop" is common with typical factory rifles and brass. Factories tend to ream chambers at the long end of accepted headspace, because the typical bolt-action .30-06 has to chamber dozens of brands of ammo, both American and foreign. Unfortunately for the reloader, rifles chambered for belted cases often show even more slop. The belt theoretically controls headspace, so chambers are often cut more tolerantly, and ammo varies more widely. Sadly it has been my experience that the 7mm Rem Mag is one of the worst offenders in this, with chambers varying all over the place, from tight to loose. The result is that the brass is stretched along its length from the belt to the shoulder upon firing (pressure forces the case to conform to the chamber dimensions at that time). Slop in this dimension stretches the brass and thins it just above the belt because that is where the case walls go from thick to thin. After a certain amount of reloadings, the brass is so thin here that the case head separates from the case body. You want to catch that before it happens, obviously! If you feel that you might not be able to feel or tell if you have the proper crush fit to headspace the round on the shoulder then get a RCBS Precision Mic Cartridge Headspace Tool for the 7mm Remington Magnum. This micrometer cartridge headspace tool will enable you to set up full length sizing dies for the precise amount of shoulder bump you wish. Precision Mic gages are initially calibrated on a once-fired case, and the micrometer will read shoulder set back variation from initial set-up. If you can't find it locally, then try Sinclair International or other internet reloading tool suppliers. As to IMR 4350, It will work best for 140-150 grain bullets, but I usually prefer slower burning powders for 150-175 grainers like RL-22, H-4831sc, H-1000, Ramshot Magnum, and others of similar burning rates. You should also be aware that published data for the 7mm Rem Mag has some of the widest variations of any caliber because of the chamber dimension issues above. So get a lot of various data sources and work up carefully. A chronograph really helps you get a handle on what is going on in work ups. |
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Quoted:
I recently got a good deal on a Winchester Model 70 in 7mm Rem Mag. Also included was a set of dies. I have been reloading .308, .223 & .25-.06 for about a year or more. So I am not a complete Rookie
I haven't looked up any loads yet for the 7mm but today I found some WLR Magnum Primers and got excited & bought 300. Then I found out that I'm not supposed to use Magnum Primers. Is this accurate? Some load data recommends mag primers, other doesn't. Depends on several factors. I use magnum primers because I load with IMR 4831, which is a very slow powder. |
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I have had really good luck with my Rem 700 in 7mmRemMag with all of these:
100gr Hornady HP 100gr Sierra HP 120gr Hornady HP and SP 120gr Nosler Ballistic tips 140gr Sierra ProHunter and GameKing, All of the above using IMR 4350 and Rem 9 1/2M magnum primers. I am now working on loads for the 162 BTSP from Hornady with Retumbo and 9 1/2M magnum primers. Just start with the starting loads and work up. What works for me may or may not work for you. My dad's pet loads in his Sako 7mmRemMag won't work in mine and mine won't work in his. I use this site for suggested powder loads, when I am working up new combinations. I also use the latest versions of the Hornady and Sierra manuals. Good luck to you. |
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When you adjust your sizing die, you want the case to headspace on the shoulder not the belt. Or cases will stretch and separate quickly. You want to be able to just barely feel some pressure when you chamber a empty case. Same for any belted magnum case. I never resize my 7mm brass, only neck size. If all the brass is going in and out of the same rifle I think that is the way to go, longer life from the brass and in my opinion more accuracy. |
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When you adjust your sizing die, you want the case to headspace on the shoulder not the belt. Or cases will stretch and separate quickly. You want to be able to just barely feel some pressure when you chamber a empty case. Same for any belted magnum case. I never resize my 7mm brass, only neck size. If all the brass is going in and out of the same rifle I think that is the way to go, longer life from the brass and in my opinion more accuracy. Eventually your brass will work harden, lose its springback and need to have the shoulders bumped back so you can close your bolt. Modern belted magnums, like the 300 WM and 7 RM, headspace off of the shoulders and not the belt, as is the case with the ancient 375 H&H, which has a very shallow shoulder angle, necessitating the belt to keep the case from jamming into a well worn chamber and getting stuck. I have the Hornady headspace gages and I also have an adjustable Wilson drop in gage for my 7 RM and that works quiet well, but I agree with you, I bushing size my necks most of the time and I have no issues. Chris |
| I also have a Win 70 7mm Rem Mag 26' barrell. With 150gr or higher mine likes Retumbo, lighter bullets like 120 like H4831. I have used both regular and mag primers and can't say that I have noticed a difference. In real cold weather I could see the absolute need for mag primers. |
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I get better accuracy from LR primers than LRM primers. I've used Rem, CCI, Win, and Federal primers for my Parker Hale 1200.
I use R22, R19, IMR 4350, Varget, IMR 4064 for powders. R22 mostly, but IMR 4064 is great for reduced loads. Winchester/Remington brass mostly. Starting to use FC. But I got great accuracy with 150gr Win PP factory, so I had a lot of that brass. Rules of thumb as I've seen them is, ball powder or very cold temperatures use magnum primers. Until you get a lot of time in the reload bench and field or range, go straight off the load data. At 35 below F, we used magnum primers and R19 and IMR 4350 powder. We did not test with LR primers. |
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