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Thread: 45/70 case stretching problem

  1. #1
    Boolit Man
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    45/70 case stretching problem

    I hope someone can give me some guidance.

    I have a Pedersoli RB that I have shortened 45/90 Starline brass for and after firing the brass is stretching approximately 0.012”. Not all but most.

    I made a chamber cast and as best I can tell the length of the chamber is 2.129” which is the same as a Pedersoli chamber drawing I found somewhere. Also I don’t see a throat as it appears that the lands come all the way to the chamber end which has a taper (from chamber end) less than 45*. Possibly around 10+* as per Pedersoli’s drawing. I might add that what appears to be lands at the chamber very well might be the 1* or so lead angle.

    The rim thickness on the Starline brass is around 0.066”. So I assumed that allowing for the .0.004” headspace due to rim thickness I’d better use 2.125” as my max chamber length. So I trimmed to 2.122” just in case it shortened some after firing. This brass had been fire formed previously and lengthened some then also.

    My load is 82gr OE 2f with a 0.063” poly wad with around 0.100” compression with a 513 gr baco 441” patched to .449” bullet. BTW this load is shooting around 2 moa at 100 yds or better with a few fliers so I’m happy with that! I did not size the fire formed brass other than the slight taper crimp.

    After firing most of the cases measured 2.130-134”. At this point I don’t know if I need to trim to 2.129” or trim shorter or what to stop this case stretching. Or maybe it will stop now? Also I didn’t notice any mouth curl due to the cases stretch forward. I’ve read that poly wads can cause this but I don’t know. Also this brass might have been anealed but I can’t remember due to this projects been on the back burner for a few years.

    I think I’ve given all the info I have. Any help will be appreciated.

    JD

  2. #2
    Boolit Master

    Bent Ramrod's Avatar
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    They will do that. The paper (in the absence of a lube cookie) grabs the case mouth as the boolit slugs up, and drags it forward into the leade.

    A less-than-bone-dry chamber aggravates this, and longer cases stretch more, in proportion as well as frequency. I’ve had one .45-70 case separation with paper patch loads, a half-dozen (at least) with .40-90 3-1/4 Straight.

    You can counter this by making sure the chamber is dry after wiping, using a lube cookie, or dusting or rubbing the base of the PPB with graphite or mica before inserting it into the case mouth. But I still watch the shell lengths and mouths after every firing.

  3. #3
    Boolit Man
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    I think I had the case length due to the 0.004” headspace backwards in my old head. I think I should have added the 0.004” to the 2.129” giving 2.133” as max chamber length. Maybe what’s happening is upon firing the case after going rearward is stretching forward 0.004” (0.004+2.122=2.126”) and still being short it’s stretching forward to the chamber end. That makes sense to me anyway.

  4. #4
    Boolit Man
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    BR,
    Thanks I’ll try that.

    I think now the brass is stretching to the end of the chamber at 2.134” and that’s the reason I haven’t seen any indication of mouth curl on the brass. What do you think? Also if that’s true what should I trim the cases? If I trim to 2.133” do you think I’ll have a problem with the case stretching forward causing curl at the mouth?

  5. #5
    Boolit Master Lead pot's Avatar
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    JDNC,
    BR has it pretty straight.
    I would trim the fired unsized cases .005" short of the chamber end. This will allow for head space movement. Also if you full length size the case it gets longer than a unsized fired case and this will make it long enough to extend unto the throat and tightens the case neck on the bullet stretching the case some. This is amplified with freshly annealed soft cases. A case 5-6 thousands short of the chamber transition 10 degree or 45 degree is also a plus reducing verticals do to uneven bullet release pressure.
    Unchamfered case mouth will grab the paper and pull the case. Shooting a PP bullet without lube, I do this, has a tendency to grab the case if the bullet is seated deeper than needed because of the friction but it's not a problem for me because I don't anneal my brass but once when I get new cases.
    Kurt

  6. #6
    Boolit Man
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    Lead pot,

    I don’t FL size so I just think I subtracted when I should have been adding maybe.

    So, based on a chamber length of 2.129” not including 0.004”+ due to headspace what would you suggest as trim length.

    After I get this correct I’ll deal with different wads and such if this continues. I will say that my chamber was dry as I wipe the chamber thoroughly after cleaning the barrel and also the brass was sparkling clean on the inside. But I think I will try some mica on the patch that’s inside the case as BR suggested IF it continues. I don’t want to try more than one change at a time so I know what cured the problem.

    Thanks for your input,
    JD

  7. #7
    Boolit Man
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    I purchased this rifle several years ago. It’s a Pedersoli John Bodine 45/70 34” barrel. I shot some greasers in it and put it in the safe. I’ve retired now and have time to mess with it so I got it out with the intention s of shooting pp. I have a lot of experience with pp in smokeless but I’m just plum ignorant when it comes to BPCR. I don’t even know what to expect in ref to case stretching with these.

    I don’t shoot competition but love to target shoot. I’ve got a buddy in Va that has a 3’x22’ steel target at 830 yds and I would love to ring that bad boy this summer!

  8. #8
    Boolit Master
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    I have never fired a round of BP in a 45-70. However never had significant case stretching.
    and I have been loading and shooting the 45-70 with light smokeless loads since 1972. I have one box of brass that has been fired in 7 or 8 different rifles and reloaded about 30 times. They have not been trimmed much even though the primer pockets are now loose from having so many primers seated in them.

    I suspect your compressed BP charge with its sharp grains is grabbing your case walls when fired.
    I have read many accounts on this site, as well as the BPCR sites and single shot sites, of case stretching and tube pull offs. The tube pull offs seem to also be associated with cannelured brass.
    Those accounts always involve black powder. I have never heard of a tube pull off or a case stretching problem in the 45-70 when using smokeless. I have personal experience shooting 11 different 45-70s. One was a bolt rifle the rest were single shots. One is a Pedersoli 1874 Sharps replica.
    EDG

  9. #9
    Boolit Man
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    EDG,
    My experience with smokeless is somewhat the same. I also agree with you in ref to the powder and patch grabbing the case wall. I guess what I’d like to know is if I trim near the chamber length will this stop some of it. 0.013” every firing the brass isn’t going to last long.

    Thanks for your input,
    JD

  10. #10
    Boolit Master
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    I do not have an exact answer for you.
    You might try FL sizing the cases so they can expand a little when fired. You may still get a little stretching.
    Were it my ammo I would polish the cases after firing so they are smooth and clean on the interior to reduce friction with the powder and wad.

    My experience with chamber length brass was with a 6.5 Mannlicher. I trimmed formed .303 Brit brass to the exact length of the chamber in a 6.5 Dutch Mannlicher rifle. Those cases actually jammed against the front edge of the chamber. This is not accepted conventional practice so proceed with caution. With this combination the cases actually got shorter by .004 to .007 on the fire forming shot.
    EDG

  11. #11
    Boolit Master Lead pot's Avatar
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    You have a good chamber cast just trim the case .005" short of the chamber end.
    I don't think I would use a Mica lube. That stuff has an abrasive in it like alumia and silica about 45% especially with a PP bullet. But it might brighten the bore using it

  12. #12
    Boolit Buddy
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    The poly wad is the problem. It expands radially and grips the case wall tight enough to stretch the case on the way out. Try a Walters wad or one cut from a milk carton or cereal box and you will solve your problem. These wads do not expand radially upon firing.

  13. #13
    Boolit Bub
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    Quote Originally Posted by sharpsguy View Post
    The poly wad is the problem. It expands radially and grips the case wall tight enough to stretch the case on the way out. Try a Walters wad or one cut from a milk carton or cereal box and you will solve your problem. These wads do not expand radially upon firing.
    My experience with a 40 2.5 Sharps is the same a sharpsguy. With 0.060 poly wads in BA stretched 30-40 Krage brass, and gg bullets I had many case separations. Fiber wads or cork wads solved the issue.

    How deep is your PP bullet set into the case? Normally I set my PP bullets about 1/10th of an inch into the case. Even with a poly wad under the bullet, I can not imagine the wad having a lot to grab onto.

    Keep on hav'n fun!
    MikeT

  14. #14
    Boolit Master

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    my current BPCR/TR gun is another pedersoli sharps that started its life as a .40-65 and has been fully relined (bbl and custom PPB chamber) for a custom reformed .45-70 PPB cartridge (to fit the new PPB chamber). i have reloaded brass in that gun that started out four u/s cleanings ago, no stretching - yet! my PPBs (BACO JIM443530E) are set almost loose into their .45-70 case mouth a scant 1/10", over a .060" LDPE wad, over 80 grains of drop tube compacted swiss 1-1/2f, under light 1/16" compression. i check the brass with analog calipers and a wilson micrometer trim gauge. maybe stretching will happen, dunno. all brass is left fire formed, ultra-sonic cleaned with much added attention to the case insides, then loaded back up.
    "Owning a handgun doesn't make you armed any more than owning a guitar makes you a musician." - Jeff Cooper

  15. #15
    Boolit Man
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    Well, back inside after a beautiful afternoon shooting and I can’t think of one word to describe my felling other than disgusted. Lol

    In all my 50+ years of handloading I’ve never seen anything like it.
    Again my load is 82 gr OE 2f drop tubed with a 0.060” poly wad compressed about 0.080” or so leaving me 0.100” for seating of a BACO 441520M patched to 0.449” with 16:1 alloy. Using Starline 45/90 brass shortened.

    Last week I was getting about 1’ groups at 50 yds due to gas cutting with a 0.060 veg wad. I then cut me some 0.063” wads from a food grade bucket lid and placed it on top of the veg wad and that stopped the gas cutting and all was well and it began giving 2 moa and less groups. So I continued to fire form the brass noticing that it was stretching pretty bad (.008” .012”).

    Today I’ve tried every combination of poly, cork, and veg wads and I’m getting a consistent 0.012” stretching. I also tried a max case length and trimmed one to 2.1” and still the same consistent 0.012” stretch. Also I noticed that every case fired (second firing) had a bright ring at the web indicating separating at the head. So this brass is gone! This brass was sparkling clean inside and I also brushed it inside to see if that would work.

    I have some Win 45/70 brass that measures 2.098” that I will try next to see if it’s a soft lot of brass or something. I might try veggie fiber wads again but I don’t think they’ll seal enough to stop gas cutting. The cork stock I have is 0.125” and pretty soft. I have to admit I haven’t tried any combination using just card wads yet. Also I made double sure the chamber was dry.

    Beats me, but brass is pretty expensive! Lol
    Just can’t get my head wrapped around this one.

    JD

  16. #16
    Boolit Man
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    One other thing which I don’t think was a cause but I’ll mention it is that I was using ballistol just a squirt in a container with water that I wet my patches in. Probably 500:1. But it was patched out until the patches squeaked and grabbed in the bore and the chamber separately patched with a clean dry patch.

  17. #17
    Boolit Master Lead pot's Avatar
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    If your getting a bright ring around the web at the base that is a good sign of head space problems or a bad lot of brass. Eventually you will get this.
    In my case it was the brass when it was drawn.

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  18. #18
    Boolit Master
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    Quote Originally Posted by sharpsguy View Post
    The poly wad is the problem. It expands radially and grips the case wall tight enough to stretch the case on the way out. Try a Walters wad or one cut from a milk carton or cereal box and you will solve your problem. These wads do not expand radially upon firing.
    I am shooting High DensityPE wads (cant locate the Low density stuff downunder) would you expect the same - similar - less - nil - effect?

    Grease boolits though

  19. #19
    Boolit Man
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    Lead pot,

    That’s exactly what I’ve got with two firings! I’ve got some Win 45/70 brass that I’m going to experiment with before I buy more brass.

    indian joe,
    I’ve tried both and had same results. I thought the HD would be better but I couldn’t tell any difference.

    It’s remarkable to me how consistent the stretch is. I mean 8 out of 10 will stretch dead nuts 0.012” some a little more. Doesn’t matter if they’re trimmed a max length or 2.1”.

    If I have this with the Win brass I’m going to try combinations of card wads and see what happens. At this point I don’t think it’s headspace in the gun. I sure don’t think pressures are high enough to spring the bolt back either. But I’ve been wrong before.

  20. #20
    Boolit Man
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    Well boys and girls I think I found the problem with the help of all of you.

    After Lead pots pictures I got to thinking that the location of the separation ring is where most brass separates due to headspace. So I decided to try and check the headspace with what little I have to do so.

    A rolling block as most know pivots from the bottom and the last part of the block to get to the barrel is the top of the block. So I decided I’d use some plastic guage to check that closure but I could find it in my shop so I just used some folded aluminum foil instead.

    I placed it at the top of the barrel and closed the block pushing hard and continued folding the aluminum foil until I just felt drag while lowering the hammer. I repeated this several times while measuring with my digital calipers which by no means is the best but good enough for a start.

    After several measurements I got 0.012” ....exactly the length of my case stretching! Once I measured 0.013”. I’m now convinced that I have a headspace problem.

    I purchased this gun new several years ago and remember shimming the left side of the sight base to get the sight staff plum. I also remember that if i looked very closely that it appeared that the barrel had not been completely turned enough to align the top of the barrel flats perpendicular to the sides of the action. Not a lot but maybe enough to close most of this headspace.

    I really think that maybe this might be all that’s needed to correct this problem provided there is enough room in the extractor slot to allow the barrel to be turned enough.

    I don’t know who to contact with Pedersoli as I think they should repair it under warranty but my gut tells me to source out a reputable gunsmith.

    I would appreciate any gunsmith recommendations.

    Thanks,
    JD

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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