Measuring bore can get wacky

Discussion in 'Percussion Rifles' started by bang, May 25, 2019.

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  1. May 25, 2019 #1

    bang

    bang

    bang

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    Got a new to me unfired Zouave 58cal.
    Measured and figured numerous times and always came up with .575 and .010 patch. Got the mold today and it throws .573-.574, good deal. Untill I checked the fit. Ball scrapes the riflings by about .002 all way round. Talk about luck. New mold otw. Going to have quite a collection if this keeps happening. Three groove not as easy to measure I guess. My overall ID was only off .001 but the land was, I thought .004-.005 was really .008. So much fun.
     
  2. May 25, 2019 #2

    F.G. Ford

    F.G. Ford

    F.G. Ford

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    Ask questions here..................most likely you will get good advice.
    It would have saved you dollars and time.
    Fred
     
  3. May 25, 2019 #3

    Grenadier1758

    Grenadier1758

    Grenadier1758

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    How many lands (and grooves) are in the barrel of your Zouave? It would seem as if you had an odd number of lands and your measurement was from the top of a land to the bottom of a groove. That would explain why a ball would engrave on the lands.

    You need to know the depth of the grooves. Measure from the top of a land to the outside of the barrel. Measure from the bottom of the groove next to the land you just measured to the outside of the barrel. Subtract the measurement and you have the groove depth. Now you subtract the groove depth from the land to groove measurement and you have the bore diameter. Its difficult to measure the bore diameter when you have an odd number of lands. So you need to take a few more steps.
     
  4. May 25, 2019 #4

    towgunner11h

    towgunner11h

    towgunner11h

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    But some pin gauges. They are about $6 ea and you can get two or three in the range you need.
     
  5. May 25, 2019 #5

    45man

    45man

    45man

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    Pin gauges measure the bore and not the grooves.
     
  6. May 25, 2019 #6

    Britsmoothy

    Britsmoothy

    Britsmoothy

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    Most .58 patched ball rifles will work with .562" ball.
     
  7. May 25, 2019 #7

    bang

    bang

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    Yes I'm a bit shy on tools but have several dial calipers and never had any issues til this 3 groove. I sat with it with better lighting and by using 2 methods was able to get matching measurement sets. I included that with an impression with a lead slug and was within .001 less on the slug. I considered malability of the lead to this. Bottom line was .583 maybe .584 max bore. .566 maybe .567 min bore .575 rb rifling contact .003-.004 per rifling. Going with .562 with .010 patch possibly upto .012 patch. Think .010 will do but have to also consider the .562 rb out of mold cooled will be .560-.561. Never have produced any right at mold indicated size from any mold in my 40 plus years of BP experience. The .575 threw at .572-.574. Mostly .573-.574. Expect same tolerances with .562. Some would say get .570 Lyman. Well it's just BP shooting and for me upto $90 for a mold is out of the question especially given patch thicknesses available to accomplish proper fit. The actual fit will wind up being some less then I like but being the nature of the skinny metal ramrod the fit has to accommodate the ramrod capabilities.
     
  8. May 25, 2019 #8

    towgunner11h

    towgunner11h

    towgunner11h

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    Seems that if his ball is too big for the bore, he needs the bore measurement.
     
  9. May 25, 2019 #9

    bang

    bang

    bang

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    I do respect advice but please read my last post.
     
  10. May 25, 2019 #10

    Baxter

    Baxter

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    When I needed a RB mould for a newly built CVA .54 rifle, I took the rifle to a gunsmith who took a slug of lead, dropped a brass rod into the barrel and used a mallet to drive the slug into the barrel and then used the brass rod to drive the engraved slug out of the barrel to measure it. Still seems like a simple thing to do. ?
     
  11. May 25, 2019 #11

    bang

    bang

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    I do similar. Lead with hole in it for long bolt. Press light oiled lead in with head of bolt inside. Grab shank end of bolt with vice grips and lightly tap back out.
     
  12. May 26, 2019 #12

    bang

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    Meant 562 with ,015-.020 patch.
     
  13. May 26, 2019 #13

    bang

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    Just what I did. Plus using a better light to see what I was doing. Was able to measure as you said and accross the inside and after some minor ciphering came up with 2 identical sets of measurements. I also pressed in a lead slug and the measurements were .001 les but I contribute it to the malability of the lead. Wound up with 583 max, 567 min.
     
  14. May 26, 2019 #14

    Grenadier1758

    Grenadier1758

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    Your final measurements indicate about a 0.567" bore and a 0.573" ball would engrave about 0.003" in the bore. Your grooves appear to 0.008" deep. Based on your measurements a 0.560" ball with 0.015" to 0.010" patching would be desired. Minie balls should be sized to 0.566".

    Sounds like a Jeff Tanner mold may be on your order list.
     
  15. May 26, 2019 #15

    bang

    bang

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    Going to go with lee double .562. From my experience it should throw a .560-.561. Think .010 patch tolerable but an .015 is going to be the accurate one.
    Be real nice if a .020 would work but feel sure it would be too tight. Real shame. I have plenty of .010s and .020s. Just what I need, another component.
     
  16. May 28, 2019 #16

    Griz44Mag

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    Yes, it can be a challenge. I usually buy a box of the size I think to try or beg for samples from others that have similiar bores. Sooner or later, I find the right one then buy a mold. A measured bore does not always throw the best groups, sometimes much smaller with a thicker patch works best!
     
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  17. May 28, 2019 #17

    Rifleman1776

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    You are guessing what that .562" mould will throw. Upside is, Lee moulds are inexpensive and you can afford to experiment. Methinks you will end up with a .555" mould and ticking of .012" to .020" thick. That .560" or .562" ball might be a tight fit.
     
  18. May 28, 2019 #18

    bang

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    Never got anything that out of tolerance from any of my 8 other molds. Always -.002--.003. Majority -.002.
     

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