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Thread: Normal Case Stretch

  1. #1
    Boolit Man
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    Normal Case Stretch

    Id like to know whats considered to be normal case stretching for the 45/70 with factory chambers using paper patched to bore bullets.

    I know there are many variables in reference to FL sized and fire formed brass and wad stacks but would like to know what to expect.

    Any input would be appreciated
    JD

  2. #2
    Boolit Buddy Distant Thunder's Avatar
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    JD,

    I don't know what is "considered to be normal" but in my .45-70 I just trimmed all my brass early last year after 5 years of shooting that rifle. I use Starline brass, which is in my experience has been excellent stuff. The rifle is a Hepburn with a tight paper patch chamber. None of my brass was more than 2.105" long, but they varied enough I felt it was time to get them all uniform again. I trimmed them to 2.095" and everything was good through last year.

    I have never annealed this brass. They were all full length sized and fireformed five years earlier. I only use two dies in my loading process, a compression die and a Lee factory crimp die that I set to close up the mouth maybe .002" to keep the bullets from coming out as I lift my cartridges out of the ammo box. The bullets can still be pulled and reseated by hand, it is a very light "crimp". I use one .060 LDPE wad over 83 grains of Swiss 1 1/2. My bullets are patched to .4505" diameter, a snug fit in the bore, and are seated .085" into the cases.

    I have never had a case failure with my brass in those 5 years. I shoot 3 to 4 Creedmoor matches a year with this rifle and a mid-range match when I can. My son usually shoots 2 Creedmoor matches with me using this same rifle. That's about 600 rounds a year figuring a few in maybe a little practice in my backyard at 200 meters.

    I bought 300 cases 6 years ago and at last count I had 297, so somewhere in my travels I misplaced 3. My brass has been fired about 10 times each. I'm careful about cycling my brass through in a way that keeps the number of times a case has been fired very uniform throughout the lot.

    Is this normal stretching? I don't know, it is what my experience has been.
    Last edited by Distant Thunder; 03-23-2020 at 09:20 AM.
    Jim Kluskens
    aka Distant Thunder

  3. #3
    Boolit Master
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    Normal stretch occurs when the case is fired however the brass gets larger in diameter.
    When you measure fired brass it will be shorter.
    When you FL size it the diametrally stretched brass will get longer.
    This stretching is affected by the diameter of the chamber and the amount of sizing done by the sizing die.
    The larger the chamber the more the case expands and stretches. The smaller the FL die the more the case elongates when sized.
    Most chambers are longer than factory brass so I just let the cases stretch as long as they are even.
    Once they are the same length of the chamber I start trimming them .002 to .005 to make the cases even.
    When I use smokeless powder loads at BP pressures I get .002 to .004 stretching per shot on an average.
    EDG

  4. #4
    Boolit Man
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    Thanks for the input.

    Just needed to know what to expect. My cases are stretching around .005” first first and second firing (second being fire formed unsized. This is a factory Pedersoli chamber .480” at the end.

    I’m not sure if I’d be better off FL sizing as it’s easier to taper crimp the mouth because the mouth is smaller. So far I can’t stop blow back and gas cutting unless I’m using a lube cookie. Poly wads appear to stretch my cases .008” sometimes so I’m just using cards and lube cookies for now.

    I would like to have a pp chamber but that’s not a possibility. This cat ain’t skint yet but it’s nailed to the wall. I’m not giving up. On the plus side it shoots pretty good.

  5. #5
    Boolit Master

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    Quote Originally Posted by Distant Thunder View Post
    JD,

    I don't know what is "considered to be normal" but in my .45-70 I just trimmed all my brass early last year after 5 years of shooting that rifle. I use Starline brass, which is in my experience has been excellent stuff. The rifle is a Hepburn with a tight paper patch chamber. None of my brass was more than 2.105" long, but they varied enough I felt it was time to get them all uniform again. I trimmed them to 2.095" and everything was good through last year.

    I have never annealed this brass. They were all full length sized and fireformed five years earlier. I only use two dies in my loading process, a compression die and a Lee factory crimp die that I set to close up the mouth maybe .002" to keep the bullets from coming out as I lift my cartridges out of the ammo box. The bullets can still be pulled and reseated by hand, it is a very light "crimp". I use one .060 LDPE wad over 83 grains of Swiss 1 1/2. My bullets are patched to .4505" diameter, a snug fit in the bore, and are seated .085" into the cases.

    I have never had a case failure with my brass in those 5 years. I shoot 3 to 4 Creedmoor matches a year with this rifle and a mid-range match when I can. My son usually shoots 2 Creedmoor matches with me using this same rifle. That's about 600 rounds a year figuring a few in maybe a little practice in my backyard at 200 meters.

    I bought 300 cases 6 years ago and at last count I had 297, so somewhere in my travels I misplaced 3. My brass has been fired about 10 times each. I'm careful about cycling my brass through in a way that keeps the number of times a case has been fired very uniform throughout the lot.

    Is this normal stretching? I don't know, it is what my experience has been.
    i fully agree. with my sharps .45-70 that also has a PPB chamber (we might even have the exact same DT reamer used, too), i don't get case stretching, i don't anneal, i don't resize the starline brass. the only time the brass goes in a press is to compress the LDPE wad/powder column, or to lightly squeeze the case mouth (though that should end with the new, larger diameter BACO slick that'll allow a tighter bore ride). new starline brass gets reformed, to fit the PPB chamber, and never gets sized or reformed again.
    "Owning a handgun doesn't make you armed any more than owning a guitar makes you a musician." - Jeff Cooper

  6. #6
    Boolit Buddy Distant Thunder's Avatar
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    JD,

    On your other two concerns, blow back and gas cutting.

    I'm not sure how much blow back you're getting, but with BP you will very likely get some fouling show up on the outside of the case mouth that shows up as black decolorization. That is pretty normal and isn't really blow back, just fouling that colors the case after it springs back some from the chamber wall.

    Gas cutting is bad, always. If you're getting gas cutting you are probably not getting a good seal as your bullet moves from the case, through the lead angle and into the bore. When you use the grease cookie you are getting a better seal, but that shouldn't be necessary in a .45-70 because your wad should do that job.

    I use poly wads (LDPE) exclusively in several rifles and I don't get case stretching at all and never have in any of my rifles.

    If your FL sizing each time that will cause your cases to grow as EDG explained. You would most likely be better off not sizing. I never size my cases after they are fireformed. Never!

    With a bore diameter PPB in a grease groove chamber you probably should reduce the case mouth in some manner to help hold the undersize bullet in place. This can be done with a taper crimp die, or a neck size die and sizing only down the neck as far as the bullet is seated. I use a Lee Factory Crimp die to just close up the mouth a little. It is easy to adjust and you can see it in action.

    The other thing that might be worth looking into is the 2-diameter style of paper patch bullet. These will fit your case/chamber better and should give a better seal as the bullet starts moving forward. 2-D PPB are the design for grease groove chambers and they work very well.

    What bullet are you using? How deep are you seating your PPB in the case? What size are your bullets patched to? They should be a snug fit into the bore and require a light push to get them through the barrel. Are you making or buying your poly wads? What diameter are they? What type of paper are you using? I'm just looking to see where else I might be able to offer suggestions. Any details you can give on your loads would be useful.
    Jim Kluskens
    aka Distant Thunder

  7. #7
    Boolit Master Lead pot's Avatar
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    Getting gas cutting with a PP bullet will show up when you clean your rifle. You will see it on your patch.
    The patch will have specks of lead and also when you get all the fouling out, pushing a clean dry cotton patch through and you still see gray streaks on that white patch chances are you got some gas cuts or your patch was not far enough up past the shank.
    You will also see evidence of it looking at the patch remnants.
    Chances getting gas cuts is a little greater with using a harder alloy than necessary in a standard chamber shooting a PP bullet at or slightly below bore diameter even with a good wad and lube cookie because in a standard chamber gas will get past the wads while the bullet is just getting pushed out of the expanding case mouth before the bullet and wads are past the chamber end and well into the throat when obturation starts sealing the throat and bore. A lot of gas cutting can be stopped if you keep the paper slightly thicker then the grooves are deep. I have spent a lot of time studding bullets running tests to see what keeps the gas cuts to a minimum.
    Gas cuts or even none gas cut bullets that do not obdurate fast or fully will show up as a lot of vertical on the target.
    Below in the photo the left bullet has sever gas cuts and it was one that was patched using .0015" paper and the alloy was 1/16 tin/lead that is a good alloy for the PP bullets but with just a single .06" polly wad over the powder did not hold the gas back. One 1/8" lube wad between two .023" card wads I very seldom see gas cuts in my test loads and if I do it will be using a hard alloy like 1/14 T/L and at the most it will look like mouse nibbles at the sharp base edge.
    My rifles I use for the matches have a very tight chamber with a long 4 or 5 degree funnel type throat. A groove diameter will not fit a unsized case and I don't have stretching problems. You have something going on that is not proper the way your barrel was fitted to the action to have that much stretching.
    When I get new brass I will anneal it once and fire it several times then I will trim the cases to uniform them and very seldom will I have to trim them again. I trim my cases .005" short of the chamber end transition to allow for the cases to have room to move when fried. You don't want them to get pulled past the chamber end. This will cause the cases to grow and you will see a bunch of verticals down range.


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    Last edited by Lead pot; 03-24-2020 at 10:12 PM.

  8. #8
    Boolit Man
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    In a nut shell, at this point I’m trying different things to see what may be causing the case stretching. As for FL sizing I just tried it to see what would happen and found little difference.

    I too, know that fire forming the brass and not FL sizing should be best but the brass just stretches. I don’t know if it’s the powder compression, wad stack or what.

    I have a Pedersoli RB just like rfd. Except mine is FACTORY chambered 45/70. I’ve made a chamber cast and the best I can measure it appears the chamber length is 2.129”. At the chamber end the diameter is approx .480”. It DOESN’T have a 45 degree angle in front of the chamber but something like maybe 10-20*. It also DOES NOT have a freebore but has rifling starting at the front of the chamber that appears to be a throat that has a diameter of around .460”

    As for gas cutting I know without a doubt. As Lead pot pointed out I can tell by leading and torn and black patch material not to mention it patterns like a shot gun. But this is remedied by a lube cookie.

    The bullet I’m using is a baco#442530E ( I think that’s correct) patched to .450-.451 using #9 25% cotton. 16:1 alloy seated .100”. 80 gr OE 1.5 is compressed about .150” in WW brass.
    Last edited by JDNC; 03-25-2020 at 05:46 PM.

  9. #9
    Boolit Master
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    JDNC, with respect to stretching, and problems I've had stretching cases with pp bullets has either come down to thinking the chamber was dry enough but it wasn't, or excessive headspace.

    A while ago I was shooting one of my .45-70's and I'd forgotten to bring dry patches with me. I just had the wet ones. I decided to use some blue shop towel instead of my usual dry patch after the wet ones. I thought that the paper towel would be more absorbent than the cotton patches. Everything looked dry to me, but stretched a few cases and even ripped one in half. I have made sure to pack my dry cotton patches since then. I guess my point is that sometimes tiny things can make a big difference.

    With respect to gas cutting and lube cookies, I used to own a C. Sharps 1885 in .45-70. I could never get it to shoot paper patch well at all. If I didn't use a lube cookie it shot terribly. That's the only rifle I've tried PP in without good results. I did find that if you are not getting a consistent seal it will show up very quickly on a chronograph as erratic muzzle velocity. If I still owned that rifle I'd probably try again with a two diameter patched bullet which will have less trouble sealing.

    Chris.

  10. #10
    Boolit Master Lead pot's Avatar
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    It's frustrating but I'm sure you will get to the bottom of this.

    I still feel your problem is head space. Here is one way to check this out.

    Take a empty case and put a slight flair on the case mouth.
    Chamber the empty case and use a wood dowel and tap it in till the rim makes firm contact seated in the chamber.
    Cut a 3/8" wood dowel that will fit down the muzzle and inside the case with an inch sticking above the muzzle being careful that you don't push the case back out and take a depth gauge and measure what is above the muzzle.
    Check and make sure the case is fully against the case rim recess and close the breach.
    Now push the dowel till you'r sure that the case head is against the breach block face and measure the dowel to see how much it moved. Make sure that the firing pin is back and the hammer is off the pin holding it forward.

    Good luck with your problem.......Kurt

  11. #11
    Boolit Man
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    Kurt,
    I’ll try that but it’s going to be difficult as to the firing pin and holding the breac closed without having the hammer down. Wouldn’t a case without a spent primer work with the hammer down?

  12. #12
    Boolit Master Lead pot's Avatar
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    try it

  13. #13
    Boolit Man
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    Another question is what’s considered excessive headspace in a rolling block.

    If the rim recess is cut 0.070” it’s going to have 0.004” right off the bat because the rim thickness on the brass I’ve checked is 0.066”.

  14. #14
    Boolit Master
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    Quote Originally Posted by JDNC View Post
    Another question is what’s considered excessive headspace in a rolling block.

    If the rim recess is cut 0.070” it’s going to have 0.004” right off the bat because the rim thickness on the brass I’ve checked is 0.066”.
    I don't know if it's useful info for you but maybe:

    I have a C. Sharps 1885 with excess headspace. Basically they cut the rim recess of the chamber to the full rim thickness and then left a 0.010" gap between the breech block and the end of the barrel. I can close the action on a case with a 0.010" shim between the breech block and a chambered round and the shim an easily be pulled out. This rifle often stretches cases that full 0.010". I have thickened the rims of some Starline .45-90 brass and those cases do not stretch upon firing.

    Chris.

  15. #15
    Boolit Man
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    Chris,
    That’s interesting. I’m looking into how to measure the headspace now.

    Thanks
    JD

  16. #16
    Boolit Master
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    JD, you'll find some people recommend using strips of scotch tape on the cartridge head. I'd avoid that and just use a set of automotive feeler guages. Of course that won't help a lot if the rim recess is cut too deeply.

    Chris.

  17. #17
    Boolit Mold
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    the way i was shown, is use scotch tape on the case head, keep adding layers until block wont close. then measure total thickness
    Gerald C

  18. #18
    Boolit Master Lead pot's Avatar
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    For a roller and Stevens actions thin lead sheets or tape works well and there is no expansion when the pressure is released.
    I used it when I had rollers in the past as well as bolt actions.
    This does not work well with the Sharps or other falling actions because they don't lock in


    https://www.bing.com/search?q=THIN+LEAD+SHEETS

  19. #19
    Boolit Man
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    The breach block closes against the the barrel. I have tried aluminum discs on the case but it’s difficult to handle and measure. I’ll try tape and see if I can get consistent measurements. As for the aluminum foil discs I can’t get consistent measurements. My assumption is that I’ll have 4 or 5 thousandths due to case rim thickness but that wouldn’t be considered excessive. It’s a pita to measure.

    I tried cleaning my chamber and cases with alcohol and also polishing the inside of the cases to a mirror finish today but I still get stretching with cases starting to separate half way down the case.

    If it is headspace I’d expect it to stretch with smokeless too. I might try some smokeless loads to see what happens. I’m also wondering about the chamber finish. Was it polished after chambering to a mirror finish. I’m tempted to sprinkle some rosin on the cases to see what happens.

    I’ve never seen anything like it. Hell im getting less than 2 moa and today 4 inside moa. Would be great to get more than 3 firings on brass though.

  20. #20
    Boolit Man
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    BTW, if I have excessive headspace it going to be due to the rim recess being cut too deep as the breach is touching the barrel extension when closed.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check