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Thread: Maximum load for 7mm Rem Mag 160 gr Nosler Accubond

  1. #1

    Maximum load for 7mm Rem Mag 160 gr Nosler Accubond

    Hi,

    I am looking for some advice.

    I have just got my 7mm Rem Mag and working up a load for it. I am using 160 gr Nosler Accubond and Viht N-165 which is easy to get hold of in the UK, so that is my definite powder of choice, although I do have plenty of N-160 but itís a bit fast for a 7mm RM.

    I have the 7td edition Nosler reloading manual. It states the starting load should be 57.0 gr and the maximum load should be 61 gr. The 61 gr load was the most accurate being sub 0.5 MOA. I have seated the bullet 20 thou off the lands.

    When I chronoed the load the average was a mere but very consistent 2633 fps. The manual says it should be more like 2900+ fps. Their test barrel was 24" whereas mine is 25.5", so in theory should have a higher velocity than the Nosler test.

    I realise all the manuals seem to over state the velocity but surely not by 300+fps!!

    Looking at other reloading info, the Vihtavouri manual says for a Speer Grand Slam 160gr bullet the start load for N-165 should be 59.1gr and the maximum is 68.1gr this should produce 2982fps. The maximum load is 7.1 gr higher than Nosler state for their similar bullet.

    The Hornady manual states for N-165 starting load of 52.7gr and maximum of 62.3gr for a similar bullet offered by Hornady.

    My question is, how safe would it be to ignore the Nosler manual and try the Viht suggestion? I am wanting to get as close to 3000fps as possible.

    I know I can make some rounds at say 1 grain increments and watch for pressure signs as I go, but I wonder if anyone else may have also done the same. I know all rifles are different so what is safe in someone elseís 7mm Rem Mag may not be safe for mine.

    I am using brand new unfired Norma brass and Federal Gold Medal Large Magnum primers.

    When I have shot 90 rounds I will neck size some brass and compare the same load vs unfired brass.

    Any other suggestions would be appreciated.

    Cheers

  2. #2

  3. #3
    Quote Originally Posted by jcampbellsmith View Post
    Try another chrono? Regards JCS
    Yes, it does sound fishy. 57.0 gr of N-160 will send a 160-gr out of my .280 Rem or 7x64 at 2,900 fps.

    Shoot the rifle at 100, 200, and 300 yards, groups of 3, and compare the drops. That will indicate the muzzle velocity, by playing with a ballistics calculator until you find something close to those groups.

  4. #4
    Quote Originally Posted by jcampbellsmith View Post
    Try another chrono? Regards JCS
    Unfortunately I do not have access to another chrono?

    Quote Originally Posted by Southern View Post
    Yes, it does sound fishy. 57.0 gr of N-160 will send a 160-gr out of my .280 Rem or 7x64 at 2,900 fps.

    Shoot the rifle at 100, 200, and 300 yards, groups of 3, and compare the drops. That will indicate the muzzle velocity, by playing with a ballistics calculator until you find something close to those groups.
    I am using N-165 for this load, although I do have N-160 that I could try. The manual states the N-160 would give a slower velocity than N-165 anyway.

    I tried the drop method yesterday for the 61 gr loads, it dropped 0.7 MRAD measured using the reticle of my S&B PM2 and also confirmed with a tape measure. The Nosler ballistics software said it would drop 0.7 MRAD at the velocity of 2633 fps.

  5. #5
    I have not shot the Nosler 160-gr in my 7x64 or .280 Rem. I shoot the Sierra GK SPBT and HPBT and the Speer Grand Slam ( for an even tougher bullet than the SGK HPBT). Maybe try one of those, or a Hornady 162-gr, to see if there is a diameter difference.

    Maybe you can borrow a few bullets.

    And maybe borrow some RL-22, RL-19, Magpro, H-4831sc, or IMR-7828.

    What primers are you using? Be sure they are magnum primers. Change those, too.
    Last edited by Southern; 18-03-2015 at 14:49.

  6. #6
    Quote Originally Posted by Southern View Post
    I have not shot the Nosler 160-gr in my 7x64 or .280 Rem. I shoot the Sierra GK SPBT and HPBT and the Speer Grand Slam ( for an even tougher bullet than the SGK HPBT). Maybe try one of those, or a Hornady 162-gr, to see if there is a diameter difference.

    Maybe you can borrow a few bullets.

    And maybe borrow some RL-22, RL-19, Magpro, H-4831sc, or IMR-7828.

    What primers are you using? Be sure they are magnum primers. Change those, too.
    I have a few other bullets to try, but I want a bonded bullet, something on the heavier side hence me using Accubonds. I am going to South Africa in 2 weeks time and I want a heavy hitting flat trajectory round.

    I am using Federal Gold Medal Large Magnum primers.

    The Reloader and Hodgdons powders are not so readily available as what they are on your side of the water.

    When I took up reloading I made a vow to myself that I would only use European powders due to the ease of procurement Vs American powders.

  7. #7
    The Speer Grand Slam is a tough bullet. So is the SGK HPBT, and the SPBT is softer. The Sierras have very high BC, but if you are not shooting at 300 or 400 yards, who needs it? The Sierra HP 160 is probably as tough as the Accubond, if not more so.

    The Federal GM250s are giving great accuracy. But try a CCI 250 for kicks. And try a Barnes bullet.

  8. #8
    270Buck,
    How do your reloads compare in OAL to factory offerings & to the OAL values published in your manuals & online?
    If you are loading them long, your pressure will be low & that will obviously result in low velocity.

    According to the Vihtavuori data (& drawing a charge weight /velocity graph to interpolate), your 61grain powder load should give about 2730ft/sec, so you are definitely getting a slow result.

    You are loading at 20 thou off the lands which is an arbitrary measurement relating to your rifle & not necessarily comparable to the published data. You may not make up all the desirable velocity difference by seating deeper, but it should help.

    You have some bullets, powder & primers which should do the job, you have got a trajectory that matches the chrono results so you can believe your measured velocity.

    Are you getting sooty cases after firing (an indication of poor ignition/low pressure)?

    Assuming that you are not getting any high pressure signs, your best way forward is to trust the Vihtavuori data & work up your load. You may not get to the magical 3000ft/sec as you seem to have a "slow" barrel with the components / load mix you have tried, but you should get a lot closer.

    Are you crimping the bullets? That can improve initial burn rate & pressure rise characteristics, particularly useful in big capacity cases.

    You could try a different make or batch of primers, but that means starting again & you haven't got much time before you travel. You have a baseline so work up from that.

    In my experience I have had more accurate velocity results by following powder makers' data than by using bullet makers' manuals, but that isn't with your calibre.

    One final reminder - be aware of the different temperatures here compared to Africa & bear that in mind - don't take high pressure loads developed in chilly GB to scorching hot Africa or you could get excessive pressures.

    Ian

  9. #9
    I would take the manafacturers BC measurement with a pinch of salt. They can be way off which will make your velocity estimate from trajectory innacurate.

  10. #10
    not the same but I found a significant difference between data and MV's in the 300WM

    How close to book data are your Muzzle velocities?


    Products - Lapua

    10,4 160 Naturalis Lapua 81,8 3.220 N160 3,15 48.6 753 2470 3,76 58.0 859 2818
    N165 3,65 56.3 786 2579 4,08 63.0 868 2848
    N560 3,67 56.6 843 2766 4,03 62.2 943 3094
    10,4 160 Grand Slam Speer 82,0 3.228 N160 3,31 51.1 784 2572 3,99 61.6 880 2887
    N165 3,83 59.1 812 2664 4,41 68.1 909 2982
    N560 3,91 60.3 823 2700 4,45 68.7 925 3035


    your results don't look to be a million miles away from Lapua data though

    56gr 2579fps
    63gr 2848fps

    7gr increase 270fps increase
    roughly assuming 40fps per grain within that range
    a 61gr load would be 2779fps
    100fps off your results


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