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Thread: pressure problems

  1. #1

    pressure problems

    I'm new to posting on forums but have been reading your posts for some time. This may not be the best post to start with but I'm worrying myself.

    I've just started to homeload for my .243 (T3 S/S, PES mod), with a Lee kit. So far so boring. I've kept all my factory fired brass and have a good stash of mixed cases, all nicely fireformed.
    Cases are now sorted. Only neck sizing and all cases that I've checked so far under max length & trimmed if needed.

    I'm using an 87grn V-Max head and CCI primers. I've Vhit N160 (double-duty for the 6.5, in time I hope!).

    Anyway - I survived the first firing @ 42.0grn (much relief!) and wanted to get some load development going.

    Loaded some Hornady brass (stamped Frontier) with 44.0grns (others have had success with this charge I believe) and got a tidy 3 shot group. No pressure signs.
    45grn and over (0.5 increases) got hard extraction and marking on the head from the boltface - plus poorer groups. Under 44grns were not that special either.
    So...44.0 it is.
    Next batch went for 10 Federal cases, same prep. 44grns. Same seat depth (I'm finding it a struggle to get the depth really consistent - it seems to wander +/- a fraction). I have calipers.
    Anyway...first firing fine.
    Second, tiny mark on case head
    Third, bright mark.
    oh dear...forth - the flippin' primer fell out of the case as I extracted. Severe marking to case head. (I guess the primer was stuck to the boltface - not an under pressure load).
    I took this to be a bad sign and went rapidly indoors and posted this!

    Why is the pressure seemingly building shot on shot, and is some brass softer than others?
    Incidentally, in the '08 Vhit data 44grns of n160 is under the min load.
    I must be doing something seriously wrong yet had excellent results with the initial Frontier brass/load.
    I look forward to your thoughts. Thank you!

  2. #2
    Welcome to the forum,

    You said "Incidentally, in the '08 Vhit data 44grns of n160 is under the min load. " Was that a typo? Did you mean max?

    I'm just a little behind you, waiting to test my first fire formed set of brass, and using a very similar set up. 243, 87gr SPBT head, N140.

    Although I'm restricting myself to working with one make and batch of brass.

    I was getting low pressure signs with my first loads, but then Vhit increased the safe max load so I've also reloaded heaver this time.

    I can't help you much! but I'll be very interested to see what others have to say.


  3. #3
    Welcome to the forum, and welcome to reloading.

    Well, it sounds as if you did everything right on your first go with the Hornady brass, and found that 44 grains was right for you.

    In your second batch, you need to start again, you have introduced something different, the brass is different. Having said that are you sure you are being consistent, do you measure each load separately or are you using the powder measure to throw each load, if so have you checked that all the powder weights are the same? As for the variation in lengths, you need to measure to the ogive, the "shoulder" of the bullet, the bit the seating die pushes against. The tips can easily be damaged or just plain differ in the manufacturing process. Also make sure the the seating depth locking ring is snugged off.

    Start again at a lower rate, do five rounds of each load, measure all the weights separately, be as consistent as you can. Increase the load by 0.5 each time as you did before. A chronograph would be very helpful.

    Let us know how you get on.


  4. #4
    Snowstorm - I believe 44.2grns of N160 is the starting load for 87g HPBT (ok I'm using vmax) in the Vhit data.
    48.1grns is the max load.

    Were you loading up to the previous max with your N140? I agree the increases look significant.

    Having a wide selection of cases I'd like to find a load that holds a zero with a cross section of brass. Is this unrealistic? Perhaps there is more to brass than just getting it dimensionally sound (which I hoped the fire forming did) trimming and filling it with powder?
    I throw a charge with the hopper thingy and then go crossed-eyed topping it up to the desired weight. Damn those tiny grains!

    JAYB - Can brass be so inconsistent that one lot shoots better than anything I've shot before and the next tries to smack me in the head. It's such a low charge too. All is sung at the press.

    Where do I get an ogive collar measuring whatnot?
    Would seating the bullet deeper from the lands reduce pressure?
    Measuring this dimension remains a mystery to me. I've read about colouring in a bullet with felt-tip sticking it up the barrel and looking for the rifling markings. What happens if it gets stuck? Any suggestions...
    Thanks for your thoughts

  5. #5
    There can be considerable differences in lots of brass from the same manufacturer let a lone from different ones.

    Try weighing your brass this will show up differences in lots.

    You can get a two main types of adaptor for measuring to the ogive they look like this 'nut' type

    or this type

    that attaches to your 'vernier' calliper try Reloading Solutions for one or the other tell them I sent you.

    Seating deeper into to the case (away from the lands) will INCREASE the pressure.

    You can get a tool like this

    for measuring the distance to the lands or depending on the type of dies you are using you can 'lightly' neck size a case and then seat a bullet so that in is only just in the case chamber the round gently and then extract measure the chambered round if you should get the bullet stuck in the rifling use a cleaning rod from the muzzle end to dislodge it.

  6. #6
    Many thanks for the information.

    What would you consider an acceptable case weight spread?
    Does the case manufacturer still matter once they are sorted by weight & is some brass ‘softer’?
    Thank you

  7. #7
    I don't tend to bother about the weights too much unless load developing.

    But I never mix Manufacturers

    For load developing I use the heaviest cases as these will have the highest pressure if the loads are ok in these then they will be ok in the rest.

  8. #8
    You have to remember that's as well as brass being different, every rifle is different, so don't get too constipated about what speeds, pressure etc you should get according to the book. Just don't exceed the maximum load.

    With regard to cartridge length 300wsm has shown you how to measure it from the ogive. However if the overall length of your initial loadings was not problematical, stick with it.

    If you want to you can colour the end of a cartridge with felt tip pen, chamber it, then extract it to see if there are any marks on it. If you get it stuck and want to remove it, then I would suggest, a long wooden dowel, a soft brass rod from the muzzle end would do the job, a plastic covered cleaning rod would do. You must remember though when doing these type of test, it is a DUMMY ROUND that you will use.

    Bullet depth can alter pressure, there is varying opinions on this, with deeper seating causing higher pressure and conversely longer rounds causing high pressure. If I was you I would not bother myself with this just yet. Just keep your rounds within the SAAMI specs and you will be fine.

    I would much rather that you started again from scratch with the different brass. If you can provide us with as much information as possible it will be easier to come to some sort of a decision, if at all Also if you have the cases with the marks on etc would it be possible to have a photo or two.

    Do the basics, do them carefully and let us know what happens.


  9. #9
    Please don't think I want to get wrapped up in this. I want a reasonably accurate & dependable round and just stick with it. Nothing fancy, hence the lee kit and double duty powder etc.
    I 'think' I'm doing it right yet get these real heavy pressure signs from a supposed low load, that happens to be a tidy grouper. It's early days for me and I'm very grateful for your help & experience.

    I hope the photo works - hopefully you can see the heads getting increasingly imprinted? It just seems a really weird coincidence that it is apparently progressive build-up. Unless I'm really consistent at messing up and at getting the charges just a little bit hotter each time.
    Fired from right to left - it's pretty evident!

  10. #10
    All I can say to the first (un-circled) case is F*&^

    The nosler manual lists 44.0gr of N160 as a max load.

    Did you trim all the cases to length?

    Do the once fired cases chamber easily?

    Do the neck sized cases chamber easily?

    have you cleaned all the cases?

    What scales are you using?

    Have you checked the scales?

    Did you load any more than you fired if so pull the heads re-weigh the powder on you calibrated scales.

    Do you have much experience of reloading?

    Where abouts in the country are you,

    because if you want help with reloading myself or another member may be able to offer assistance.

    could you de-prime all the cases in the picture, weigh them and then post the weight of each on this thread

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