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Thread: Reloading pressure signs

  1. #1

    Reloading pressure signs

    Bit of advice required, I have been home loading .270 WSM (Barnes 130gr TTSX, RL 19, Norma once fired brass, Federal 215M primers), I have worked the book loads up slowly from the Barnes manual, no pressure signs until 64.0gr (max book load is 65.0gr). The two on the left are the once fired Norma factory ammo cases, the two on the right show the load in question. You can see the ejector slot marking on the bolt face at 12 o'clock. The primers look fine (they're cratered whatever you shoot in this rifle), bolt operation was normal after firing and no other pressure signs were evident. On the chronograph the load measured 3119fps average (60 fps below book value). The factory Norma measures 3199fps. Some of the factory ammo Norma cases have a similar (although fainter) mark after firing. Is Norma brass known to be quite soft? Should I be reducing the loads now based on the above or do I have some scope left to go higher considering there are no other pressure signs apart from the ejector slot marks?

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  2. #2
    How are they grouping? They look OK to me,

  3. #3
    Sako,

    You look to be getting very close to the max there. Ejector marks and cratering as you say are a sign of high pressure.

    I have always found monolithic bullets to give pressure signs often way before "book max".

    How far are you off the lands ? This will influence the load in two ways....if you are jamming them in then you will have a high initial pressure.....if you are "deep seating" you are decreasing case capacity and that will also increase pressure.

    Like everything.....speed isn't all! What is the accuracy like?

    Check those cases before the next reload...check for early case head separation and check the primer pocket...if you can feel any slackness in seating the primer and any ridge inside the case......ditch the brass and throttle back on the powder!

    DT

  4. #4
    Why do you need to go higher?
    Find your best group and just try altering the seating depth,but be aware that this can also alter the pressure.
    Good luck
    dave
    Ps just looked at the pictures and if it was mine it would be the last round I would fire at that load!!
    Last edited by plonker; 15-10-2016 at 19:25.

  5. #5
    I'll scale back the loads, best groups so far at 62.0gr (approx 3000fps) anyway, seem to be opening up a bit the faster they go. My Winchester 70 seems to have a very short throat (compared to my Sako where I can't get shorter bullets anywhere near the lands), I'm seating these the same overall length as the Norma factory rounds as a guide. I measured the distance to the lands out of interest and it is approx 0.050" off the lands, fortunate as that's what Barnes recommends.
    Last edited by Sako308; 15-10-2016 at 19:38.

  6. #6
    Quote Originally Posted by Sako308 View Post
    I'll scale back the loads, best groups so far at 62.0gr (approx 3000fps) anyway, seem to be opening up a bit the faster they go. My Winchester 70 seems to have a very short throat (compared to my Sako where I can't get shorter bullets anywhere near the lands), I'm seating these the same overall length as the Norma factory rounds as a guide. I measured the distance to the lands out of interest and it is approx 0.050" off the lands, fortunate as that's what Barnes recommends.
    But is it the same length to ogive?
    I wouldn't say the marks are of concern as the primers aren't remotely flat.

    In terms of book values, they are a guide and unlikely to ever be precise.

  7. #7
    Chronographing by reloaders is never going to really match lab testing where test barrels are used under controlled conditions.
    For the reloader readings are a clear guide for your loads using your own barrel/rifle and data will be slightly affected by different conditions .. i.e. temp. Altitude etc than on the day of testing.

    Ejector marks and cratered primers are an indication that pressures are too high. Personally I'd back off.
    Blaser K95 Luxus Kipplaufbüchse .25-06Rem. Zeiss 8x56, 110gn Nosler Accubond = Game Over!

  8. #8
    Ejector marks without a heavy bolt lift are not necessarily an indication of high pressure same as cratering not being a particularly useful indication either (more often than not indicates a loose fit of firing pin, which in itself is not generally a problem).
    Chronographing the load will give you a quantitative idea of what is going on - velocity is a function of pressure - i.e. you cannot achieve velocity without pressure.

    Don't worry about the 'lab testing' crock, the reason there are variations is simply there are no two alike test barrels and chamber dimensions. Tests are not all done in the same atmospheric conditions - hence not being able to duplicate the 'factory' velocities
    A young man who isn't a socialist hasn't got a heart; an old man who is a socialist hasn't got a head.
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  9. #9
    I purely chronograph just to check things are roughly where they are suppose to be during the loading process, not obsessed with achieving book velocities. There are a few good articles around about pressure signs and it seems no one indication is necessarily a sign of over pressure, more like a combination of symptoms is a better guide, i.e. ejector marks in combination with flattened primers and a sticky bolt. My only indication is the ejector marks so maybe I have room to manoeuvre, I will experiment (carefully) further.

  10. #10
    While you are right to be vigilant, from the safety of my keyboard, I don't think you are seeing dangerous over-pressure signs (so long as the ejector mark isn't coupled with stiff bolt, loose pockets, etc.)

    The WSM series are fat cases, based on the 404Jeffrey. The large internal diameter will have an influence on bolt-thrust, so you might expect to see ejector marks at lower pressure than more conventional designs. I know my 7WSM does compared to some of my other cartridges. This is a complex area (lots of factors) and I'm speculating! I'm not suggesting you should ignore ejector mark/swipe. Probably worth checking your chamber is oil-free and cases have no residual lube on the sides.

    Federal primers are quite "soft" and flow more than others. Your cratering isn't accompanied by flattening (look at the junction between edge of primer and head.) If you change primers, drop your load and work up again.

    As others have said (and I think you have done), check your jam/jump using the ogive, not over all length. If you are close to the rifling, be careful your next loading is the same, or you may raise pressure by jamming (or reducing available case volume, if shorter.)

    No need to chase velocity unless you have a specific application that requires it (e.g. bullet must stay above transonic zone at a given range). Also, being below book velocity is not an indication your pressures are ok.

    While it is important to check cases for incipient case-head separation, this is a late sign (unless you have a headspace problem and/or are working your brass too hard with respect to shoulder bump...) The "bright line" can be very subtle and sometimes witness-marks from the FL resizing die can worry you if you haven't seen it before. Probing the inside of the case for the dip/dimple, is also something of a "feel". I have kept some cases that exhibit these features, to show novice reloaders what they are looking for.

    If you think you will get better (useable) accuracy at a faster node, or you are chasing a specific minimum velocity, you are probably ok to increase in appropriately small increments. Beware changes in climatic conditions and components between range sessions and reloading respectively.

    Not sure what barrel-life a 270WSM delivers at max loads... Don't mess around too much on load dev!
    Last edited by xavierdoc; 16-10-2016 at 08:57.

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