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Thread: Normal Case Stretch

  1. #21
    Boolit Master
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    That sounds better than my rifle . Do your primers back out at all? My first clue on my rifle was that all of the primers backed out a little bit. As far as I could tell they were backed out by exactly the amount of excess headspace.

    Chris.

  2. #22
    Boolit Man
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    Quote Originally Posted by Gunlaker View Post
    That sounds better than my rifle . Do your primers back out at all? My first clue on my rifle was that all of the primers backed out a little bit. As far as I could tell they were backed out by exactly the amount of excess headspace.

    Chris.
    No my primers are not backing out.

    I remembered that I had a device with dial indicator that was for determining headspace for contenders and that it would work perfectly for determining how much the case was below the barrel face. I also had a indicator for indicating protrusion that would work for measuring primer back out.

    First as I have posted previously my breach block locks forward touching the barrel face. If you place .001” feeler guage between the block and barrel you can’t get it out. So I removed the breach and hammer to give me room to use the indicator and placed a FL sized case with known rim thickness in the chamber. With the indicator block flat across the barrel face I found the case to be 0.004” below the barrel face. This was using a case with a rim thickness of 0.065”.

    My Starline and Win brass rim thickness varies between 0.065”-0.066”(most at .066”). So this gives me a total headspace of 0.003”-0.004” unless there is some underlying problem with breach lock up that I can’t see. So just to check, I decided to fire an empty case just with a primer and measure the primer back out. The results of that were exactly 0.004”!

    So I’m satisfied that my total headspace is 0.004” which is not excessive. Just to satisfy my curiosity, I loaded a case with 80 grs 1.5f with no compression and just a card wad and fired it. I found no case stretch. I then loaded a 80 gr Load with grease cookie with a little crimp and removed the bullet. Fired this and found no stretch.

    I then annealed 5 cases and loaded 2 with the pp bullet and both stretched 0.008”+.

    It’s pretty clear (to me anyway) that the powder column is ironing out and stretching my brass forward. But why in my chamber when others are not experiencing the same? Is it due to the load not producing enough pressure to blow the case out to the chamber? If so why? Is the bullet not bumping up enough to cause enough resistance for the case to blow out to the chamber? Is my chamber super slick polished?

    Anyway I’ve determined it’s not headspace, and now I’m going to try a 84gr Load without compression. Then a softer alloy and full groove diameter pp and gg. It’s just puzzling to say the least as it appears no one else has experienced this except with excessive headspace or wet chambers.

  3. #23
    Boolit Master Lead pot's Avatar
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    Well that clears the head space thought.
    Quit annealing your cases.

  4. #24
    Boolit Man
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    Quote Originally Posted by Lead pot View Post
    Well that clears the head space thought.
    Quit annealing your cases.
    Actually I hadn’t been annealing them. I just thought since everything seemed to be working backwards I’d try that too! Lol

    I appreciate all the input I’ve received from you guys. I’m just going to have to try everything even if I don’t think it’d make a difference.

    JD

  5. #25
    Boolit Man
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    I’m thinking now that I’m not building enough chamber pressure to get the case to grip the chamber walls in this factory chamber. Maybe due to the patched to bore bullet and the 16:1 alloy. Maybe this alloy is just not bumping up tight enough to give enough restriction to allow the case to grip the chamber. I may sound nuts, but I’m just grasping for some solution at this point!

    Based on this theory, maybe a patched to groove bullet might give more restriction, or a gg bullet for that matter.

    I’m really tempted to dust a case with pine rosin to see if that would stop the stretching. If it did it would indicate to me it was a chamber pressure issue.

    I’m just riding around. You guys can jump in if you want. Lol

  6. #26
    Boolit Master
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    One more thought. I have no experience with this, but have heard that if you lightly lubricate your patches it can help case stretching. I would ask Don McDowell as he's played with lubed patches.

    The case not grabbing the chamber is definitely something that contributes to case stretch. It's a reasonably common problem with breech seated black powder loads, depending on the chamber design. I can say that with breech seating black powder, case stretching is reduced a lot by going to a coarser powder. Swiss Fg will actually work quite well in the .45-70 for paper patching too. You'd loose a little velocity though.

    Chris.

  7. #27
    Boolit Grand Master Don McDowell's Avatar
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    I have not had the case stretching problems except for cases that have been shot a dozens of times.
    I do use jojoba oil on the exposed patch in some rifles/loads it makes a positive difference in accuracy, other rifles it either has no affect or one it has a detremental affect.
    I suspect from reading thru this thread, the problem, if it really is a problem is coming from 1 or 2 things, quite possibly a combination of both.
    1 the cases are likely to short to begin with, that's not an uncommon problem with the Italian chambers and the early Shiloh and C Sharps chambers with the long throat. A good chamber cast may reveal that the case length needs to be something closer to 2.2 inches.
    2. The bullet diameter being used is a bit small, and given the generosity of the diameter in that chamber should probably be somewhere north of .445 before patching. A dual diameter bullet with the base section measuring .450 and the bullet wrapped in 7 or 8 lb paper may prove quite beneficial.
    Long range rules, the rest drool.

  8. #28
    Boolit Man
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    Quote Originally Posted by Don McDowell View Post
    I have not had the case stretching problems except for cases that have been shot a dozens of times.
    I do use jojoba oil on the exposed patch in some rifles/loads it makes a positive difference in accuracy, other rifles it either has no affect or one it has a detremental affect.
    I suspect from reading thru this thread, the problem, if it really is a problem is coming from 1 or 2 things, quite possibly a combination of both.
    1 the cases are likely to short to begin with, that's not an uncommon problem with the Italian chambers and the early Shiloh and C Sharps chambers with the long throat. A good chamber cast may reveal that the case length needs to be something closer to 2.2 inches.
    2. The bullet diameter being used is a bit small, and given the generosity of the diameter in that chamber should probably be somewhere north of .445 before patching. A dual diameter bullet with the base section measuring .450 and the bullet wrapped in 7 or 8 lb paper may prove quite beneficial.
    I have made a chamber cast and the length of the chamber is 2.129”. As for the throat there is no freebore as the rifling starts at the end of the chamber. That’s not to say that there’s not a tapered throat. Also at the end of the chamber there is possibly 10-20 degree angle not 45. Chamber diameter at end is .480”. You are correct that the brass is short at 2.1. I originally used shortened Starline 45/90 brass until it separated and now I’m using WW brass I had on hand. The 45/90 was shortened to 2.125” and it stretched to 2.135”

    I patched a .451” slick to .458” today (RCBS 57926) and loaded it with 70gr OE 2f. Results the same. It stretched .005”.

    I’m going to try 25:1 alloy next and also I’m going to try some powdered rosin dusted on the brass to see if that might stop the stretching. If so it would indicate to me that the brass is just not gripping the chamber wall. I don’t know if cross hatching the chamber with sand paper would help or not but I’m considering that if the rosin stops the stretching.

  9. #29
    Boolit Grand Master Don McDowell's Avatar
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    What happens if you leave the brass length alone and keep firing it?
    Long range rules, the rest drool.

  10. #30
    Boolit Man
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    Quote Originally Posted by Don McDowell View Post
    What happens if you leave the brass length alone and keep firing it?
    It separates on the third or forth firing after stretching .004-.008” per firing. What’s also puzzling is occasionally a case will only stretch .001-.002”!

    I was using a squirt of Ballistol in my water at the beginning but stopped due to thinking maybe it was the culprit. I now use just water but haven’t seen any change.

    I’m considering purchasing more Starline 45/90 brass and trying again because the first Starline brass was separating at the head (like a headspace problem). Lead pot posted he had a bad lot of brass that done that. I don’t really think chamber length brass will help as it stretched past the chamber last time but it’s worth trying again.

    JD

  11. #31
    Boolit Man
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    Quote Originally Posted by Gunlaker View Post
    One more thought. I have no experience with this, but have heard that if you lightly lubricate your patches it can help case stretching. I would ask Don McDowell as he's played with lubed patches.

    The case not grabbing the chamber is definitely something that contributes to case stretch. It's a reasonably common problem with breech seated black powder loads, depending on the chamber design. I can say that with breech seating black powder, case stretching is reduced a lot by going to a coarser powder. Swiss Fg will actually work quite well in the .45-70 for paper patching too. You'd loose a little velocity though.

    Chris.

    You know, I was actually wondering about that. I wondered since most I assume are using Swiss powder maybe I should try that.

    JD

  12. #32
    Boolit Grand Master Don McDowell's Avatar
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    I really think you're putting way more worry than necessary into the case length thing. But rocket on..
    Long range rules, the rest drool.

  13. #33
    Boolit Man
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    Quote Originally Posted by Don McDowell View Post
    I really think you're putting way more worry than necessary into the case length thing. But rocket on..
    Well maybe you can afford to replace brass after it separates in the center after 2-4 firings but I can’t. So it is a worry to me. But on the other hand if this is the norm for everyone shooting bpc I think I’ll move to smokeless powder. I was under the impression that was not the case based on what several have posted though(you being one BTW).
    Last edited by JDNC; 04-01-2020 at 01:08 PM.

  14. #34
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    Quote Originally Posted by JDNC View Post
    Well maybe you can afford to replace brass after it separates in the center after 2-4 firings but I can’t. So it is a worry to me. But on the other hand if this is the norm for everyone shooting bpc I think I’ll move to smokeless powder. I was under the impression that was not the case based on what several have posted though(you being one BTW).
    from my experiences with BPCR guns and both greaser and PPB cartridges, the case issues you are experiencing are not at all "normal" or "common". there is a problem to be sorted out. i'm beginning to suspect perhaps a chamber issue.
    "Owning a handgun doesn't make you armed any more than owning a guitar makes you a musician." - Jeff Cooper

  15. #35
    Boolit Man
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    Rdf,
    I agree. What’s puzzling to me is occasionally after firing 5 rnds 2 cases will only stretch .001-002”. As Don mentioned, the chamber is long. If there is a chance it would stop after reaching the length of the chamber the win brass has began to separate before that point. That’s why I’m considering purchasing Starline 45/90 and shorten to chamber length (again) to see if maybe last time I had a soft lot of brass.

    I really think the case is not gripping the chamber wall enough mimicking a wet chamber sort of. I tried a patched to groove bullet hoping that more resistance might help the case grip the chamber better, but no deal!

    Only thing left is softer alloy but before that I’m goung to dust the case with pine rosin to see if maybe my theory is correct. If I don’t set stretch using rosin I think that taht will prove it’s a case to chamber grip thing. But I don’t know what to do to correct it other than scuff up the chamber.

    Beats me but it gives me something to do in these scary days.

    Thank all you guys for your input and be safe.

    JD

  16. #36
    Boolit Man
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    Well for those interested, today I loaded the same load 80 gr OE 1.5f with lube cookie and .442” dia. patched to .450”

    Only change was after cleaning the chamber with alcohol and drying I dusted the case with pine rosin. As I suspected after firing I didn’t have any case stretching. Also the primer backed out a little, so the rosin didn’t allow the case to move rearward at all either.

    So, apparently the problem is the case is just not adhering to the chamber wall upon firing. I don’t think I have a choice other than to cross hatch the chamber wall.

    I might add that I need to fire a few more rnds to make sure I can duplicate the same results.

  17. #37
    Boolit Grand Master Don McDowell's Avatar
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    If that's a new gun, ie. you are the first owner I'ld contact Pedersoli to see about having it checked out, cases pulling into for no apparent reason after a couple of firings is a sure indication something is wrong. If it's a used gun, well now you now why. Might be time to find a gunsmith to rebarrel it.
    Long range rules, the rest drool.

  18. #38
    Boolit Master

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    just get it rechambered by a good gunsmith and have it test fired, too. i'd heartily recommend lee shaver in MO.
    "Owning a handgun doesn't make you armed any more than owning a guitar makes you a musician." - Jeff Cooper

  19. #39
    Boolit Man
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    It’s actually a gun I bought new several years ago. I’ve just recently pulled it out of the safe to try it out.

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