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Thread: Check Those Bores!

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    Boolit Master Ricochet's Avatar
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    Check Those Bores!

    I know this has been said hundreds if not thousands of times on this board, but check your bore diameters! A chamber cast or pound cast is even better, but slugging the barrel is very valuable, and if your barrel is not badly worn, counterbored, or belled at the muzzle from rough cleaning rod use, even poking a caliper in the muzzle to measure across the grooves and across the lands is very useful. I've just reminded myself of this by checking two German Gewehr 88s, an 1891 Ludwig Loewe 88/05 that spent most of its life in Turkey, and an original model G.88 made by Spandau Arsenal in 1889 that came from Ecuador. Both have clean, sharp bores with bore diameters of .308" and groove diameters of .318". Supposedly bores with that dimension are mostly replacement barrels made in Brno. While I was at it, I checked my almost like new Persian M98/29 (which I think was an honor guard rifle, having the blue removed from all exposed metal surfaces to make it bright silver.) It has been fired very little. It has the same .308" bore and .318" groove diameters! The same Czechs made all 3 barrels, and likely around the same time. The M98/29 was made in 1938, and the Turks were engaged in a big rifle refurbishing project through most of the '30s, with the Czechs being their major parts supplier. I am surprised to find a 98 type Mauser with such a tight bore! Some of my Turkish Mausers have .326" grooves. Anyway, it's obviously safe to fire .323" jacketed bullets through these tight bores if the chamber has been reamed out to accommodate the thicker case necks of the 8mm IS cartridges. The Germans did it, marking the ones with reamed chambers with an S, the Turks did it, and I have no idea what the Ecuadorians fed them. I've sent very fat 8mm Maximum boolits (.328" bands and gas check) through these bores, as well as Turkish, Yugoslavian, and Romanian surplus ammo in the M98/29. But that surely will increase pressures somewhat, and best results may be obtained with something closer to groove diameter. Certainly it's best to know what you have so you can plan intelligently.
    "A cheerful heart is good medicine."

  2. #2
    Boolit Master Texas by God's Avatar
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    It goes to show there's no givens in MauserWorld. I wouldn't have dreamed a 98/29 would be bored tight. Good post, sir.

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    Boolit Master Ricochet's Avatar
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    Continuing this discussion, I have a warm spot in my heart for my 1944 Turkish Mauser, which I got after the days of the real bargains had passed. I had to pay $55 for it! It is one of the K. Kales with the Turkish made new receiver, the rest of the parts likely scavenged. Compared to other Turk Mausers, this one is downright homely. Its stock is larger in many exterior dimensions and roughly finished. The receiver is machined perfectly functionally, but was not originally highly polished. I suspect that at that time the Turks were under pressure to crank out usable arms in a hurry as the various WWII combatants were, because they were under heavy pressure to join both sides. The stock is noticeably thicker looking than others, the forearm crossbolt and firing pin removal tube in the butt are crudely set and recessed more deeply into the stock than normal because it's thick. The wood would be very pretty had it been finished into a fine sporter. It has a cleaning rod made of cartridge brass, which was wavy and required straightening. The receiver, barrel, sights, stock, bottom iron, and magazine floorplate all have matching numbers, but the bolt is mismatched. Roughly finished as I said, much handled, and looking "rode hard and put away wet." It came to me heavily coated in Cosmoline, of course. On the left side of the butt it had a bright red dot of paint about 2 1/2" in diameter. I wish I had photographed it before cleaning off the Cosmoline, as the gasoline I used took the paint right off without a trace. I've never heard of such markings on a Turkish rifle, but suspected it was something like the red painted band on the Romanian "Instructie" rifles, meaning one used only for training. I was disappointed to find that after thorough scrubbing with gasoline soaked patches and bronze brush, the bore was bright but only showed the gentlest of ripples for rifling grooves! I had never heard of a rifle bore so thoroughly worn out, but anything is possible, especially with an old one from over there, and there's a first time for everything. I took it to the range and fired it with 1942 surplus Turkish 8mm. I shot it over my Chrony and saw velocities near 3000 FPS with those 154 grain copper-nickel jacketed bullets, and some of the rounds showed signs of high pressure with several primers piercing. That surprised me with such a worn bore, but I'd read all the stories about high pressures and velocities with that old Turkish milsurp ammo. I couldn't get a hit on the paper at 100 yards. As inaccurate as my Mini-14! So, I got a freebie take-off barrel from another Turkish Mauser that someone was making into a sporter. I took my barreled action out and tried to remove the barrel with a barrel vise and action wrench. I couldn't budge it. So I tried the old method of using the "heat wrench" to loosen it up. (I'm doubtless making any gunsmiths reading this flinch.) I coated the action ring and breech end of the barrel heavily with SAE 30 oil, reasoning that it would smoke at around 500 degrees F and keep me from messing up the heat treatment. I applied my propane torch and heated it to the oil smoking point. To my surprise, as it stood vertically, white smoke came out of the muzzle and crumbly black particles fell out of the breech! There was no oil inside the barrel or action. I let it cool and looked inside. I could see sharp rifling at the breech end of the barrel! So I heated it similarly the full length of the barrel, with more smoke out of the muzzle and much black, crumbly, carbonaceous looking stuff falling out of the breech! I gave it a good cleaning. When finished I had sharp, good looking rifling all the way down the bright bore! After that it shot quite normally with the Turkish ammo, still no tack driver, but I could get the bullets on paper. It's much more dangerous at 200-300 yards than a Brown Bess! It's the specific one I mentioned with the .326" groove diameter, and it likes 8mm Maximum handloads much better than Turkish milsurp.

    Now, what in the world fouled that bore so badly that the rifling grooves were nearly invisible, and the jacketed bullets were being squeezed down to bore diameter? I had already scrubbed and scrubbed till my arms fatigued and my hands were going numb, shot it and cleaned it afterward TWICE without loosening any of that stuff! The debris that fell out when I accidentally discovered that heating removed it didn't look like it had a trace of metal in it, just dry black coky looking stuff. It just occurred to me that if that was an instructional rifle for recruits, maybe they didn't use it only for practicing rifle assembly and disassembly, drilling, and such. They may have carried it on field exercises shooting lots of blanks, with minimal cleaning! That could account for a lot of black buildup with no bullets wiping out the grooves, and if they just pulled an oily rag through it for cleaning, that could glue the stuff together harder the next time it got hot from shooting blanks. Just an idea. Has anyone else encountered this?

    Anyway, this is another one with a very surprising bore condition! Now this thing is rough as a cob and uglier than a mud fence, but I'm quite fond of it. It's not the best shooter, but it's not the worst, either. It's definitely got character!
    "A cheerful heart is good medicine."

  4. #4
    Boolit Master 303Guy's Avatar
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    I have a Lee Enfield with a bore of almost .308 and groove close to .318. I wonder whether I can shoot 8mm bullets through it? Well maybe not. Actually, my paper patched boolits are 8.1 mm ( .319 ) and the loaded round fits the chamber just fine. Very fine actually, since these are loaded into unsized necks. A jacketed might expand the neck just enough to not release the bullet sufficiently!
    Last edited by 303Guy; 05-02-2018 at 05:30 AM.
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    Boolit Master Ricochet's Avatar
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    As I mentioned above, I have 3 8mms with .308" bore and .318" groove diameters. The Germans modified rifles like that by simply opening the neck of the chamber to accommodate rounds loaded with .323" jacketed bullets and stamping an S on the receiver ring to signify that they were OK for the spitzgeschoss or Spitzer bullets. I've been shooting 8mm boolits through those. I plan to try paper patching .30 caliber boolits to near .318" and see how those do. I know people on this board who have used .338" boolits in .329" Austro-Hungarian 8X56R carbines. Oversize boolits raise pressures, but not as much as you might think. Some believe that filling the chamber throat is more important than matching the groove diameter. Besides, many softer boolits likely obturate close to throat diameter on firing before getting squeezed down in the leade to groove size.
    "A cheerful heart is good medicine."

  6. #6
    Boolit Master Ricochet's Avatar
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    I am of the opinion that with boolits that fit snugly into unsized necks and the loaded rounds fit snugly into the chamber there is no reason to be concerned about pressures rising as they can with jacketed bullets. Lubricated lead boolits won't bond to brass necks and can slide straight out without obturating the neck. I wouldn't crimp them, though. Lube and debris could get between the crimp and chamber wall, making uncrimping harder. That may not be significant either, though.
    "A cheerful heart is good medicine."

  7. #7
    Boolit Master Ricochet's Avatar
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    Julian Hatcher investigated some kabooms with target shooters using Springfields. He discovered the spontaneous "welding" of jacketed bullets to brass case necks. No big problem when there was room for the case neck to expand, breaking the bond with the bullet. But it was popular in those days for match shooters to dip each bullet in Mobilgrease before loading. He said the common attitude was that if a film was good, great greasy blobs were even better. The grease, he reasoned, squished back on loading between the neck and chamber wall. Being incompressible and highly viscous, the grease prevented neck expansion. He found bullets downrange with the ripped off case necks still bonded to them, squeezed down through the rifling. Hatcher also reported a 6.5mm ArisKa that someone remembered to .30-06, neglecting to bore out the .6.5 mm bore to .30 caliber. He fired a number of rounds before discovering the error, without damage. The original 1889 Swiss rifle has a nominal bore of .296" and groove diameter of .307", but with 3 groove rifling. The actual land to groove distance is .303" all around. The GP90 cartridge they fired had a lead shank of .315" and a heel of .308" laper patched to .321". I think Col. Rubin did that to get a similar shot start pressure to the metal jacketed bullets he pioneered but the Swiss were too cheap to pay for. The early smokeless powder probably needed that resistance to burn properly. I've been copying that for my 89, but mine come closer to .323" patched.
    "A cheerful heart is good medicine."

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    Quote Originally Posted by Ricochet View Post
    As I mentioned above, I have 3 8mms with .308" bore and .318" groove diameters. The Germans modified rifles like that by simply opening the neck of the chamber to accommodate rounds loaded with .323" jacketed bullets and stamping an S on the receiver ring to signify that they were OK for the spitzgeschoss or Spitzer bullets. I've been shooting 8mm boolits through those. I plan to try paper patching .30 caliber boolits to near .318" and see how those do. I know people on this board who have used .338" boolits in .329" Austro-Hungarian 8X56R carbines. Oversize boolits raise pressures, but not as much as you might think. Some believe that filling the chamber throat is more important than matching the groove diameter. Besides, many softer boolits likely obturate close to throat diameter on firing before getting squeezed down in the leade to groove size.
    I forget what famous authority wrote it, but I read where he said the initial high pressure is pushing the oversized bullet into the bore/groove and after that it's normal.

    I'm a follower of fit the throat. Reason is when the bullet is getting kicked by the gas pressure the base doesn't have much room of getting misaligned to starting straight into the bore. I've had more success with that then any other method.

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    Quote Originally Posted by 303Guy View Post
    I have a Lee Enfield with a bore of almost .308 and groove close to .318. I wonder whether I can shoot 8mm bullets through it? Well maybe not. Actually, my paper patched boolits are 8.1 mm ( .319 ) and the loaded round fits the chamber just fine. Very fine actually, since these are loaded into unsized necks. A jacketed might expand the neck just enough to not release the bullet sufficiently!
    If the neck portion of the chamber is large enough to accept a 8mm bullet then yes. Or at least a bigger bullet that is at bore/groove size that will still let the round chamber. You have find the neck area diameter and then you can determine what you can fit to it.

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    Quote Originally Posted by Ricochet View Post
    Continuing this discussion, I have a warm spot in my heart for my 1944 Turkish Mauser, which I got after the days of the real bargains had passed. I had to pay $55 for it! It is one of the K. Kales with the Turkish made new receiver, the rest of the parts likely scavenged. Compared to other Turk Mausers, this one is downright homely. Its stock is larger in many exterior dimensions and roughly finished. The receiver is machined perfectly functionally, but was not originally highly polished. I suspect that at that time the Turks were under pressure to crank out usable arms in a hurry as the various WWII combatants were, because they were under heavy pressure to join both sides. The stock is noticeably thicker looking than others, the forearm crossbolt and firing pin removal tube in the butt are crudely set and recessed more deeply into the stock than normal because it's thick. The wood would be very pretty had it been finished into a fine sporter. It has a cleaning rod made of cartridge brass, which was wavy and required straightening. The receiver, barrel, sights, stock, bottom iron, and magazine floorplate all have matching numbers, but the bolt is mismatched. Roughly finished as I said, much handled, and looking "rode hard and put away wet." It came to me heavily coated in Cosmoline, of course. On the left side of the butt it had a bright red dot of paint about 2 1/2" in diameter. I wish I had photographed it before cleaning off the Cosmoline, as the gasoline I used took the paint right off without a trace. I've never heard of such markings on a Turkish rifle, but suspected it was something like the red painted band on the Romanian "Instructie" rifles, meaning one used only for training. I was disappointed to find that after thorough scrubbing with gasoline soaked patches and bronze brush, the bore was bright but only showed the gentlest of ripples for rifling grooves! I had never heard of a rifle bore so thoroughly worn out, but anything is possible, especially with an old one from over there, and there's a first time for everything. I took it to the range and fired it with 1942 surplus Turkish 8mm. I shot it over my Chrony and saw velocities near 3000 FPS with those 154 grain copper-nickel jacketed bullets, and some of the rounds showed signs of high pressure with several primers piercing. That surprised me with such a worn bore, but I'd read all the stories about high pressures and velocities with that old Turkish milsurp ammo. I couldn't get a hit on the paper at 100 yards. As inaccurate as my Mini-14! So, I got a freebie take-off barrel from another Turkish Mauser that someone was making into a sporter. I took my barreled action out and tried to remove the barrel with a barrel vise and action wrench. I couldn't budge it. So I tried the old method of using the "heat wrench" to loosen it up. (I'm doubtless making any gunsmiths reading this flinch.) I coated the action ring and breech end of the barrel heavily with SAE 30 oil, reasoning that it would smoke at around 500 degrees F and keep me from messing up the heat treatment. I applied my propane torch and heated it to the oil smoking point. To my surprise, as it stood vertically, white smoke came out of the muzzle and crumbly black particles fell out of the breech! There was no oil inside the barrel or action. I let it cool and looked inside. I could see sharp rifling at the breech end of the barrel! So I heated it similarly the full length of the barrel, with more smoke out of the muzzle and much black, crumbly, carbonaceous looking stuff falling out of the breech! I gave it a good cleaning. When finished I had sharp, good looking rifling all the way down the bright bore! After that it shot quite normally with the Turkish ammo, still no tack driver, but I could get the bullets on paper. It's much more dangerous at 200-300 yards than a Brown Bess! It's the specific one I mentioned with the .326" groove diameter, and it likes 8mm Maximum handloads much better than Turkish milsurp.

    Now, what in the world fouled that bore so badly that the rifling grooves were nearly invisible, and the jacketed bullets were being squeezed down to bore diameter? I had already scrubbed and scrubbed till my arms fatigued and my hands were going numb, shot it and cleaned it afterward TWICE without loosening any of that stuff! The debris that fell out when I accidentally discovered that heating removed it didn't look like it had a trace of metal in it, just dry black coky looking stuff. It just occurred to me that if that was an instructional rifle for recruits, maybe they didn't use it only for practicing rifle assembly and disassembly, drilling, and such. They may have carried it on field exercises shooting lots of blanks, with minimal cleaning! That could account for a lot of black buildup with no bullets wiping out the grooves, and if they just pulled an oily rag through it for cleaning, that could glue the stuff together harder the next time it got hot from shooting blanks. Just an idea. Has anyone else encountered this?

    Anyway, this is another one with a very surprising bore condition! Now this thing is rough as a cob and uglier than a mud fence, but I'm quite fond of it. It's not the best shooter, but it's not the worst, either. It's definitely got character!
    Do you think that maybe carburetor cleaner or brake cleaner (the spray stuff) may have cleaned that black gunk out of the barrel?

  11. #11
    Boolit Master 303Guy's Avatar
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    I still have a boolit wearing it's neck that it took with it down the bore. I had the bright idea of embedding grit on the whole boolit shank before seating for fire-lapping. I stopped doing that since it was going to cost me a case per shot plus the seated shank area of the boolit wasn't going to lapp anything that way.

    I have considered sizing down 8mm bullets, thinking that even if the jacket springs back a little, the lead core will obturate on firing, thus negating the loose core issue. But, paper patching is more fun.
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  12. #12
    Boolit Master Ricochet's Avatar
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    I don't think carburetor or brake cleaner would have gotten this stuff out. Not sure what it was, but it had to be as hard as epoxy.
    "A cheerful heart is good medicine."

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    You know it's too bad you don't have access to "steam" I bet a hot jet of high, but not real high, pressure steam would have cleaned it out, especially since you mentioned that heat helped.

  14. #14
    Boolit Master Ricochet's Avatar
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    High pressure steam would have done it, I'm sure. I doubt that atmospheric pressure saturated steam would have. Heat in the 500 degree F range is what got the stuff out. I have a vague memory that I may have sprayed brake cleaner through the bore as part of my effort to get cosmoline out. I had no idea that something was clogging the rifling grooves. I thought they were completely worn away. I was changing out the barrel when I heated it, the stuff fell out, and to my great surprise there were grooves there!
    "A cheerful heart is good medicine."

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    I'm glad you posted this! I have a 98/29 Brno Mauser that I've never fired. Guess I'd best determine what the proper size boolit/bullet is before I do!
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    Be careful, chlorinated carb cleaner when heated becomes highly toxic.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
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    Boolit Master madsenshooter's Avatar
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    That's interesting Ricochet. I have a Krag sporter barrel that has the worst carbon fouling I've ever seen. The guy I got it from replaced the barrel without attempting any cleaning. I got some of it out, and I can see there's nice sharp rifling, but I can't get to the bottom of the grooves! Lot of brushing, lots of patches with different chemicals and I'm still getting carbon! It's short enough I could put it in the oven for a short time!
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    Hey Ricochet back before the EPA days when you could take your engine block and heads to the shop and have them acid tank. It sure cleaned them down to bare cast iron and didn't hurt anything that I know of. I just wonder if that would have cleaned that barrel out?

  19. #19
    Boolit Master Ricochet's Avatar
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    Acid tank would take off every bit of finish and "patina." It would be worth consideration of you wanted to start with a fresh, shiny, bare steel barrel, but I like the "used" look. I have a Persian M98/29 that had all of the exposed blueing taken down to bright metal. The blue is all there in the concealed areas, with a couple of smudges left in hard to reach areas. I've heard theories about how that happened in cleaning at the importer but I don't believe it. I think it was done for show in an honor guard. The only sign that this rifle has been used is a water stain on the butt where it likely has been held in "parade rest" with water standing. What did happen in cleaning is that someone tried to degrease it with a solvent that turned the varnish stock finish into a gummy mess. I finished stripping it and refinished it with spray clear nitrocellulose lacquer. Where a spot of oxidation appeared on the barrel from my handling, I rubbed it with vinegar and immediately got shiny silver metal like the rest of it. As for the carbon fouled bore, all I can tell you is that heating mine to oil smoking temperature, around 500 degrees F, got this awful stuff out that lots of scrubbing with solvent hadn't touched. Good luck with it!
    Last edited by Ricochet; 05-13-2018 at 06:34 PM. Reason: Autocorrect
    "A cheerful heart is good medicine."

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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