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Thread: Question about 7mm Remington magnum:

  1. #1
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    Default Question about 7mm Remington magnum:

    Hi all. I have little problem. I have Tikka M65 Deluxe varmint rifle, barrel is 620mm long, caliber is 7mm Rem Mag. Now, i use Sako/Norma Cases, Sierra Match-King 168gr bullet and Vihtavuori N165 powder, load is 64.5 gr. Now, if i load more than 64.5 gr, cases will "blow" i mean that primer is falling off if i try reload it. Couple of my fellow hunters uses bigger loads, such as 70,7 gr, and case is all right after shooting.

    Whats wrong with my rifle?

    Thanks for any reply, Jimmy.

  2. #2
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    May not be anything wrong with your rifle! How do your velocities compare with your friends?

    til later

  3. #3

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    64.5 grains has to be a fairly stiff load for that bullet. My Speer manual is the only manual that I have that even shows using V165 for the larger 7mm bullets.

    Your buddies rifles could be longer throated than yours giving them a tad more case capacity by seating the bullet further out. However the numbers that your talking means they are some how getting 9% more powder to work in their guns than yours for the same projectile. That is significant. Something is missing here. Are they also using Norma brass? Even then I can't see a 9% difference being possible regardless of brass manufacture.

    The only thing that I can think of si...is it possible that somebodies scales are wrong? Pull the bullet on the buddies round shooting over 71 grains and weigh it on your scale.

    I guess if it were me I'd probably start over with a more suitable powder like reloader 19,22 or even 25. IMR 4831 is my brothers powder of choice for the 7MM Mag and he has been shooting it for years!

    Let us know how this turns out. I'm curious!

  4. #4

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    Quote Originally Posted by elmerkeithclone View Post
    I guess if it were me I'd probably start over with a more suitable powder like reloader 19,22 or even 25. IMR 4831 is my brothers powder of choice for the 7MM Mag and he has been shooting it for years!
    I dont know much about Vihtavuori N165 but IMR 4831 was also my powder of choice in my 7mm rem mag. Been a long time since I reloaded for it but my go to bullet was the 160 partiton and I believe I was using about 60 gr or so of IMR4831. I think I was getting close to 3000 fps.

    Are your buddies using the same bullet? If they are using a lighter bullet they would tend to use more powder. Could be any of a number of variables. You should chrony your loads and theirs and see what kind of velocities your getting. With your 168 gr bullet you should probably be getting about 2800-2900 fps.

    Also you might try H4350... It' a temperature stable powder and will give more consistant results than non temp stable powders.

  5. #5
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    Somebodys scale is not right is my guess.

    It is not uncommon to have different rifles have different different maxes for a given powder. I have not had them be 64.5-70.7.

    I always use loads that are more than a few tenths under max. I say most times I am a half grain or more under max.

    If I had a primer fall out, which would be way over max, I would back off at least 2 grains. Max is way before primers start falling out.

    If you have access to a chronograph you should use it. The velocities will tell you what is max. Just because your powder charge is way different your pressures and velocities may not be that different.

    Your buddies may be using 150 matchkings.
    "You have given out too much reputation in the last 24 hours, try again later".

  6. #6

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    Just checked the Hodgdon site and it showed Retumbo being used for the 7mm Rem Mag and getting better velocites than most other powders. Interesting... I may have a new powder for my 7mm... Retumbo is also temp stable.

  7. #7

    Default Tighter chamber?

    Granted, the powder capacity difference before hitting max does seem a little weird. My Sierra manual lists 64.6 grains as the max load for a 168 match bullet in 7mm. It sounds like you're reaching max about there in your rifle too. I would guess that someone else's scale is wrong, and it's also possible that your rifle is showing signs of pressure either because of a little bit tighter chamber than someone else's rifle or the difference in brass wall thickness. Just my $.02.
    NRA Life Member, Prior F-16 crew chief.

  8. #8
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    I donīt know how many fps my 7mm shoots. Anyway that makes sense, that thereīs something wrong in scales (goes to check it out)
    Thanks, ill let you know...

  9. #9
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    Default Your problem is not serious. Just don't use more than 64.5 grains.

    I think it's most likely that you have too high pressure, (with that load combination in your rifle) Loose primer pockets is a sign of very high pressure. It sure doesn't take much to send your pressure sky high.

    Chonograph your 64.5 grain load and see if your velocity is in the ball park for what your loading data suggests. (5 shots and average them)

    If it is close to max velocity, for that powder, you don't need any more grains. You may even decide to use less.

    Your rifle is different from every other rifle, and perhaps a lot different than the rifles of your buddies use.

    Just because they use more powder than you do, doesn't mean you should, or even that they should, for that matter, so don't worry about matching their powder charge. It may not be relevant.

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  10. #10

    Default Temp

    The temperature of the ammunition can be a big variable. As temperatures go up so does pressure. Some powders are less temperature sensitive than others, some are a lot more picky about temperature. Even different lots of the same brand and kind of powder can vary pressures. That's why you start 10% below the max load and work your way towards max, 1/2 grn at a time until you see pressure signs, like cratered or flattened primers. AT THAT POINT, you have the max load for that lot of brass, powder, bullet brand/weight and temp.
    Loose primer pockets or blown out primers are a sign of excessive chamber pressure as is a hard to open bolt.
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  11. #11
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    Well, my rifle shoots very well with my standard load, i mean Vihtavuori N165 powder, 64.5 grains, Sierra Match-King 168gr bullet, Federal M215 Primer and Sako & Norma Case. 5 shot group from 100 meters away is about 1cm. Best is 7.9mm, so far. 300 meters away 3 shot group is usually about 30mm.

    Then, if i load same powder 69.5 gr, it shoots exactly same group, but all cases are shoot & forget them. It is quite easy to open bolt, but there is very serious over-pressure marks all over the case. Primer is dead-flat, and it will drop easily off.

    It was really good point to think that perhaps scales are wrong, but iīm still quite curious about this..

    And for some ridiculous point of view, i suggest that all of you who feels that this thing is intresting, i suggest that read new Vihtavuori - manual again and carefully. It can be downloaded from Lapua.com - site. I mean, thereīs 168 gr Sierra MK - bullet with Vihtavuori N165 etc. but top amount of N165 is 70.7gr!!!!!!!! For godīs sake, i called into Lapua and i told that load is quite bomb, but they were like: No no no, It is ok. Although they check it out again, but they still thinked that 70.7 is proper maximum load. Thereīs a several other powder manufacturers, who say that 70.7 VVN165 is quite hard load. I must admit, that im very proud about being from Finland. We have very beautiful country, several thousand islands and lakes (and i mean lot of them), one huge forest (whole country) free medical services for anyone, we have one of the best rifle manufacturer in the world (old Tikkakoski and Valmet rifles were and are much better ones) and Lapua for all shooters of the world. But i dont understand this f***ing reason why this 70.7 gr load has to be proper one? Because it aint! Even recoil is massive.

  12. #12

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    Jimmy, Have you checked your bullet seating depth? Sometimes if your bullet is seat too high it might engage the lands which could cause higher pressures.

    But anyway, it sounds like you have a real good load with 64.5 gr of powder. Why do you want more?

    *wonders why Jimmy can get Fed 215 primers and I can't???*

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