Interesting discovery when loading a tight necked chamber

Discussion in 'Reloading' started by AZShooter, Feb 12, 2014.

  1. AZShooter

    AZShooter Well-Known Member

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    I chambered a 30 cal heavy varmint barrel a few years back in a 308 win variant. I had a 30 BR reamer and decided to head space it as a 308. Asked Dave Kiff if it would work. He said yes and you would have less body taper and steeper shoulder angle, an improved 308 win but you will have to turn the necks to fit the chamber.

    Why? I wanted a 308 but didn't want to buy the reamer.

    I copied the neck thickness of the 30BR I had used in another barrel. Neck would be .0105" which would allow a bullet release of .001" per side.

    The sizing was accomplished with a 30 BR RCBS FL die without the sizer ball. I thought that was pretty cool as all I had to do with the 308 is run it up into the die to wack the necks down for a .001" neck tension. If necessary the same die can be used to bump the body enough for easy bolt closure.

    Now for the interesting part. I remember reading a wonderful article called the Secrets of the Houston Warehouse.

    Secrets of the Houston Warehouse

    In this article the shooter, Virgil, didn't size his fired brass! "With about .00035" clearance on all sides between the loaded round and chamber neck, the natural spring-back of the brass, in combination with his neck preparation, correctly gripped the bullets. Some other warehouse shooters, including T.J. Jackson, followed the same practice."

    I noticed that my fired brass had a tiny bit of tension, enough that I couldn't push a 168 SMK back into the neck without some effort. I decided to deprime and load with NO case sizing. I single load so I didn't think .0005" neck tension would be an issue. The bullet also makes contact with the lands. I figure with this configuration I am soft seating and the bullet will move as bolt is closed to maintain consistent rifling engagement.

    Bottom line? It shoots tight ragged holes at 100 yds just like it did with the previously neck sized brass with .001" neck tension.

    I thought this would be an interesting find worth sharing. Imagine no case sizing! The lapua brass is on its 5th firing and the bolt still closes easily with no body bump.

    Just had to share. Hope a few of you find this interesting.

    Ross
     
  2. canderson

    canderson Well-Known Member

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    Very interesting results. Thanks for sharing. Are you getting more velocity with the improved 308?
     
    Last edited: Feb 12, 2014

  3. Erik Kiser

    Erik Kiser Well-Known Member

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    I remember that article. Pretty cool stuff
     
  4. AZShooter

    AZShooter Well-Known Member

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    The barrel is 22". Using 43 gr of IMR 8208 XBR with 168 SMK for velocity of 2765 or so. Think I could get more velocity but I don't need it.

    I don't hunt with it as it weighs 11 lbs. It is used it for all sorts of range activities. It shoots very consistent bugholes, perfect for testing suspect scopes. It has a picatinny rail so I can switch out scopes quickly.

    Also use it for practice shooting with a bi-pod. Have evaluated several approaches with rear bags and bi-pod buddy at 100 and 200 yd ranges.

    I have friends shoot it to determine if their shooting methods are working.
     
  5. Canadian Bushman

    Canadian Bushman Well-Known Member

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    Thats pretty awesome. Ive read about guys seating with the lands but doing it without sizing is really cool.
     
  6. AZShooter

    AZShooter Well-Known Member

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    Some BR shooters will use a specific sized expand iron to open up a fired case neck just enough for mild tension for the method called soft seating. They don't size anything else. The idea of soft seating is to seat the bullet out more than kissing the lands. When the bolt is closed the bullet is forced into the cartridge till it stops against the lands. A shooter can chase the lands as they wear.
     
  7. Canadian Bushman

    Canadian Bushman Well-Known Member

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    It sounds like a viable way to maintain accuracy throughout a barrels life. I dont think that im good enough at controling neck tension to pull it off though. It also seems you wouldnt want to remove a loaded cartridge from a rifle you were soft seating with.

    AZ shooter, right after you anneal, are you still able to load your rounds this way?
     
  8. AZShooter

    AZShooter Well-Known Member

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    Um er anneal? Don't do that yet...my friend Dan has a killer annealing machine. Maybe one of these days I can use his machine.

    At this point the lapua brass is doing fine. Remember I am barely working the brass. It only expands one thousandth per side and the most it was ever reduced was for one thousandth neck tension.
     
  9. Canadian Bushman

    Canadian Bushman Well-Known Member

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    Think you outta just forget annealing and see how long you can get away with it? Its been working for you so far. If it aint broke....
     
  10. AZShooter

    AZShooter Well-Known Member

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    Never annealed a case in over 30 years of handloading. Guess you are right, why start now?
     
  11. Mikecr

    Mikecr Well-Known Member

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    I've done this with 2 barrels now in 6.5WSSM. It's called 'fitted necks'.
    I run .290 loaded necks into a .291 chamber neck, which is within springback for turned 13thou thickness.

    I also did the same with the entire case, every dimension, with same results(no sizing needed), except, I only went with 35deg shoulders so bumping was needed at reload #9. Had I gone with 45deg shoulders I would not even have to bump. That's next barrel. No dies will be needed with this.

    I did this only as a test to see what kind of sizing is REALLY needed, given a PLAN other than FL sizing.
     
  12. AZShooter

    AZShooter Well-Known Member

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    MikeCR,

    I was hoping I could learn by generating this thread.
    .001" for total release is interesting. I have to keep up with an carbon buildup on the necks and clean the chamber neck carefully. Any there any special techniques you use?


    Do you end up with any brass flowing into the necks after a few firings so you have to turn them again? Bet you have designated your neck turning tool for just that cartridge!

    Is your 6.5 WSSM a target rifle? What is the measured OD after firing and then with a loaded round?

    Finally what will the next cartridge be that will have a 40 degree shoulder?

    This is very interesting!

    thanks

    Ross
     
  13. Bullet bumper

    Bullet bumper Well-Known Member

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    Nowhere in the "secrets of the Houston warehouse " does it state any neck clearance dimensions that I have read . It's quite cryptic and only talks about fitted necks and finding a secret that involved emery cloth or some such equally cryptic clue.
    However my decoding of the article would tend to agree with you that the necks were tightly fitted and did not need resizing .
    It does work as you say but it's not a new concept , for many target shooters have done the same in the past .
    However full marks to you for working it out yourself , that is what good reloading is all about , using your brains.
    My opinion of the article is that Dave Brennen needed his head read for printing it the way it was , cryptic, confusing and rather selfish .
    A good editor would have sent it back and asked for some better clarity and a few more conclusions and it would have been great . I even tried to contact Virgil King to try and get some clarity but to no avail .
    I was not surprised PS failed in the end .
     
  14. AZShooter

    AZShooter Well-Known Member

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    Thanks for the complement. This 308 improved project has been entertaining.

    Using emery cloth to sand the necks did have me wondering. It just isn't that precise.

    I didn't realize the magazine went under. I have 6 ft of old PS rags I got from a friend. I tried to read them but most of the information was old news. Always liked seeing the builds with the beautiful laminates. Never purchased a PS issue, used the net to learn stuff instead.