+ Reply to Thread
Page 2 of 2 FirstFirst 1 2
Results 11 to 16 of 16

Thread: The o-ring method of fire forming case to extend their life

Click here to increase the font size Click here to reduce the font size
  1. #11
    Really Senior Member Bruce_in_Oz's Avatar
    Join Date
    Jun 2008
    Last On
    Today @ 06:41 PM
    Location
    Brisbane
    Posts
    1,854
    Local Date
    01-23-2020
    Local Time
    06:19 PM
    Saying that 6.5 Jap chambers are "generous", is generous in itself.

    Whilst they are not even remotely "Bench-Rest" standard, they worked pretty well for "government work".

    If you are prepared to do a bit of fiddling with reloading dies and start with GOOD brass (Norma springs to mind, IF you can find it), you will get "reasonable" life from your cases.

    All of which is slightly academic. The original users were not exactly obsessive about recovering their brass on the battlefield and then studiously reloading it. The cartridge case did its job of keeping the powder dry and the components together in a handy, weather-resistant package until the moment of discharge, after which it was usually flung unceremoniously into the wild, blue, (green, or brown), yonder.

    This applies to pretty much ALL service ammo in the last century or so, with only a few countries "economizing" by reloading their cases, usually just ONCE.

    ANY ordnance system using Mercuric-based primers would be running a serious risk of a LOT of case failures on second or subsequent reloads, or even just cracking "in the packet", just as Lee Enfield "enthusiasts" have endured for decades.

  2. # ADS
    Friends and Sponsors
    Join Date
    October 2006
    Location
    Milsurps.Com
    Posts
    All Threads
     

  3. #12
    Member Mayhem's Avatar
    Join Date
    Feb 2016
    Last On
    02-18-2018 @ 09:22 AM
    Location
    Australia
    Posts
    12
    Local Date
    01-24-2020
    Local Time
    07:19 AM
    Thread Starter
    Thanks to everyone who have responded. However, I am going to have to read through these again, as I am somewhat confused. My understanding from what I had read was that this was a good idea to extend the life of the case, with subsequent neck sizing only between reloads (using the same rifle of course). I had assumed that I was just compressing the rubber and I don't have access to the necessary gauges. However, my understanding was that this was less of a consideration.

  4. Avoid Ads - Become a Contributing Member - Click HERE
  5. #13
    Member stevebc's Avatar
    Join Date
    Mar 2008
    Last On
    10-12-2019 @ 11:38 PM
    Location
    BC Canada
    Posts
    58
    Local Date
    01-23-2020
    Local Time
    04:19 PM
    Mayhem, you have it right. Use the O-rings, expect the extra resistance as you close the bolt, subsequently only neck size. It all helps, you're on the right track.

  6. The Following 2 Members Say Thank You to stevebc For This Useful Post:


  7. #14
    Really Senior Member Bruce_in_Oz's Avatar
    Join Date
    Jun 2008
    Last On
    Today @ 06:41 PM
    Location
    Brisbane
    Posts
    1,854
    Local Date
    01-23-2020
    Local Time
    06:19 PM
    Interesting experiment with the "rimless" .303.

    I saw a couple built on P-14 rifles and using M-17 bolts and some magazine components, many years ago. The sages at the time of this "fashion" reckoned the old SMLE was not up to the task of stiff loads in this modified cartridge; more likely they would simply not feed from the magazine reliably nor extract consistently because of the altered case geometry.

    History repeats.

    Back in the 1950s, here in Oz, there was an abundance of .303 ammo AND "souvenired" rifles from all sorts of interesting places.

    A moderately popular conversion was done to Jap. Type 99 7.7 rifles which, conveniently, use the same (roughly) bore dimensions as .303.

    Two approaches:

    1. Open out the bolt face for the .303 rim, sleeve the chamber and cut a new .303 shaped chamber. Crude, and feed from the mag was "marginal".

    2. Get a bit "Gucci" and turn the case heads down to "rimless" dimensions to more-or-less match the 7.7 bolt face and sleeve / recut the chamber as before.

    Had an uncle with a specimen of version 1, even fired it with a bunch of FN .303 ball ammo. Mostly functional, but a bit long in its original trim to be a handy-dandy "farm gun", which is what he used it for. I guess he reckoned that, having relieved some unfortunate Japaneseicon soldier of his burden, he may as well tuck it in his big box of military engineering equipment, along with sundry bayonets and a couple of 6.5 Jap carbines, and see if he could get his "momentos" home: he did.

    I heartily concur that the relatively tiny .303 shoulder is adequate for "headspacing". The problems arise because of "variations", (some of them "after-market" / "custom"), in the chamber dimensions.

    If you can arrange for your cases to "fire-form" ONCE to a specific chamber and to then NOT over-work them by full-length sizing back to CIP / SAAMI / "Mil" spec, you will extract greater life from the increasingly expensive brass.

    Of course, this approach may mean having distinctly separate ammo for each of several .303 rifles. Not a huge challenge for the organized person.

  8. The Following 2 Members Say Thank You to Bruce_in_Oz For This Useful Post:


  9. #15
    Advisory Panel Son's Avatar
    Join Date
    Oct 2006
    Last On
    12-31-2019 @ 11:59 AM
    Location
    On the right side of Australia, below the middle and a little bit in from the edge.
    Posts
    1,214
    Local Date
    01-24-2020
    Local Time
    10:19 AM
    Mayhem... There are other considerations to keep in mind. Yes, the o ring method will centralise your cases in the chamber so they will blow out evenly all round, and then, with the cases headspacing on the shoulder and neck sizing only, they will last longer. Well on the way to maximise brass life.
    Bear in mind the earlier comments about brass flow. If your loads are anything above mild, your cases will lengthen with firing. You must trim to length every reload. They can lengthen into the leade and crimp the projectile on chambering, causing increases in pressure when firing.
    The other thing is the cases will still stretch and eventually (i found two neck sizings on MkVII equivalent loads to be normal) the cases will have resistance when closing the bolt. Then you need to have an adjustable FLR die to set a thou or three shorter to relieve the load on the locking lugs during closing. Then you can neck size and length trim for another two or so before bumping the shoulders back a minimal amount again.

    I have cases that have done 7 or 8 reloads to MkVII spec without any signs of failure.

  10. #16
    Member Mayhem's Avatar
    Join Date
    Feb 2016
    Last On
    02-18-2018 @ 09:22 AM
    Location
    Australia
    Posts
    12
    Local Date
    01-24-2020
    Local Time
    07:19 AM
    Thread Starter
    Thanks to all that have responded. I will certainly be checking the length of the cases between loads.


+ Reply to Thread
Page 2 of 2 FirstFirst 1 2

Similar Threads

  1. Case forming 7.65 Argentine from 30-06. Which die works?
    By mrappe in forum Ammunition and Reloading for Old Milsurps
    Replies: 33
    Last Post: 07-25-2015, 01:53 AM
  2. Waterproofing method for no.32 scopes
    By vintage hunter in forum The Lee Enfield Knowledge Library Collectors Forum
    Replies: 5
    Last Post: 02-01-2011, 04:32 PM
  3. Question about case life with the #4 in 7.62 NATO?
    By ireload2 in forum The Lee Enfield Knowledge Library Collectors Forum
    Replies: 19
    Last Post: 06-28-2009, 04:12 AM
  4. Fire forming Lapua 243 to 22 CHeetah
    By Matt Anthony in forum Ammunition and Reloading for Old Milsurps
    Replies: 4
    Last Post: 06-04-2009, 07:13 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts