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Thread: Hmm.. help me make sense of this.

  1. #1

    Hmm.. help me make sense of this.

    Have a look at this photo of some shell cases I fired yesterday.

    The loads are increasing from 39gr to 39.5 gr left to right, there are 6 rows 0.1 gr increments, running diagonally bottom left to top right.

    Row 6 - 39.5 is getting close to the maximum 0f 40.3 gr (VV data) and I'm not going any higher.

    Look at the powder marks on the shoulders increasing as the load increases.

    I had low pressure signs down at 35 grains and they gradually decreased as I passed 38.5. I thought they would go completely as I passed 39 not come back.

    So, is this also a high pressure sign? There are no pressure signs/marks on the heads. Bear in mind the rifle at this point is probably getting quite dirty inside.

    Your thoughts appreciated.

    243, 87 grain head, winchester brass and primers. VV N140.

    Cases are all fired once and neck resized.

  2. #2
    I assume you haven't had this problem before.

    If you haven't cleaned the rifle try some other known loads including factory loads both in same and different brass which normally do not exhibt this problem to see if same effect. If so you get the same problem then fault probably lies with the rifle/cleaning.

    Clean rifle or start with a clean rifle and try loads again. By a process of elimination you should be able to narrow the field and identify the problem.

    If you have to load more to test weigh each load and carefully check all components for contamination. If you have some left pull a few and check all is ok.

    If you have access to a chronograph use this when testing loads as it will give valuable information as to how your loads are performing in comparison to each other and to factory loads.

    Don't attempt the following if you are clumsy, hamfisted don't pay attention to detail or are unlucky, if you are give up reloading now!

    Primers from different batches can be roughly assessed by loading a few of each batch into empty cases, going to a safe location loading them one at a time and firing preferably in a dark location so you can compare the bang and the flash. Probably not a reccomended proceedure and you do it at your own risk and responsibility. Its interesting and gives a subjective comparison but not an accurate one. For purposes of elimination only.

    Different Heath Robinson tests can be tried for powder again at your own risk. Use an A4 size piece of plywood or hardboard -outside, not in the house!- and make some lines of powders you wish to compare about a pencil length and thickness. Set a match to them and compare burning speeds! Be careful and be very careful if trying out black powder as it goes very quickly. Make sure all powder containers are closed and well away from the test area before lighting the powder trails. It has'nt altered my ability to type but then I only use two fingers anyway. Really not too dangerous and if you think about it The Customs officers used to test for proof in distilled alchol by mixing black powder and the distillate and setting a spark to it. if it flashed then it was proof alcohol, if not it wans't. The proof testers were hand held I believe as were flint lock pistols where the priming powder was held outside the barrel in the flash pan.

    Have fun and I'm sure you will sort out your problem quickly!


  3. #3
    What are you using to neck size and what is the neck tension like?

    I have to say that obturation looks poor on most of the cases regardless of powder charge.

    I would look at either getting at factory crimp die or a die that you can increase the neck tension on.

  4. #4
    Thanks both,

    I know, it's a lot and wasn't expected. The residue is very evident at 34 then minimises at 38-39, then increases again.

    I'm not sure how to quantitatively measure neck tension, but it takes a fair bit of pulling to get the heads out. I need leverage from the press to do it.

    I'm using the Lee neck resizing die, I also have a Lee crimp die but most things I read say not to use it. I'm worried this might be a high pressure sign and I don't want to do anything to increase the pressure any more.

    One thing that did catch my attention - the instructions for the neck resizing die said a lot of effort is needed at the end of the stroke to resize - I did not have to exert a lot of effort to use it, and I'm sure I had it set correctly.

  5. #5
    You'll want to be carefull as the bullets you are using are not meant to be crimped, they don't have a cannelure.
    Was it difficult to open the bolt?

  6. #6
    No Rene, the bolt was as normal.

    Can what you see in the photo also be due to excessive pressure?

  7. #7
    No, not to my knowledge/experience. Excessive pressure forms the case to the chamber/headspace and will always seal well by expansion, what doesn't seem to have happened in your case. Even if the rifle was still dirty from earlier low pressure rounds the progressive loads would have sealed and cleaned it out eventually, but it seems that de higher loaded ones created stronger low pressure signes. In that case it would almost be as if the bullet was loose in the brass and was rambling through the bore, preventing proper pressure build-up.
    Sorry, no straight forward answer here.


  8. #8
    Yes, it's the same rifle. That's why this is unexpected, I tried to control all the variables except the powder load.

    The brass was all new from the same batch, and the primers from the same batch of 1000. The heads were from the same box.

    The only thing suggested to me is that my scales are out, I will test them tonight with a selection of heads to see how accurate they are.

    Another confusing thing is that within each load there is such a variation in how much residue there is.

    Edit : tested scales, they are spot on.

    Also : depending on where I read the powder charge for this head starts at 29.6 gr and goes up to a max 40.1 gr. You can see why I'm struggling to see a 39.5 gr load as producing low pressure?

  9. #9
    Crimp (a Lee Factory Crimp Die does not require a cannelure) and if not, switch to a faster powder like 4895. ~Muir

  10. #10
    Quote Originally Posted by Muir
    Crimp (a Lee Factory Crimp Die does not require a cannelure) and if not, switch to a faster powder like 4895. ~Muir
    Thaks Muir, it sounds like a plan. I have a Lee Crimping Die, but didn't use it because the Lee site says not to crimp hunting loads.

    Do you hny idea why they say that?


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