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Thread: Micro Grove and fire lapping

  1. #21
    Boolit Master MGySgt's Avatar
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    Quote Originally Posted by dubber123 View Post
    You'll die of old age before you "accidentally over lap" one.
    dubber123 - that statement can be misleading. If you usee too aggressive of a grit you can make matters worse in as little as 10 or 15 shots. I use the LBT lapping compound because it has been throughly tested. Yes some individuals have use valve lapping compound and got wonderfull results from useing it. I am just not going to take a chance.

    With a revolver I use 6 shots between each cleaning and inspecting (one for each chamber). Once I get done cleaning this Marlin I will use 5 rounds per inspection.

    I have got most of the trash out of the barrel, but I am still getting what I think is a mix of carbon and bullet lube each time I use the bore bursh. Wet the barrel with bore cleaner (I use Montana Extreme) then run a bore brush down the barrel 10 times and follow with a wet patch - Black, normally 2 or 3 patches till no more black, repeat process. I did slug the barrel - it is .430 with 2 tight spots in the bore, I could push the slug past them with just a little force, so I am hoping that 15 to 20 shots will smooth them out - but we will see.

    One of the tight spots is about 2 inches in front of the rear sight dove tail and you can see something on the right side of the barrel as you are looking at it from the muzzel. The wet patches use to bump against this spot so there was some build up of lead/carbon/bullet lube there. I don't feel it as much now as I did, but I can still see it witth a bore light.
    Big Bore = 45+

  2. #22
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    All I use is 320 grit. Many consider this too aggressive, but once you see the finish it puts on a bore, you may think otherwise. The grit begins breaking down finer immediately on it's trip up the bore. One of the best tips I was given is to pick out a tooling mark close to the muzzle. (easy on most Marlins) When you just begin to see this tooling mark being worked on, stop.

    The way this works so well, is that the abrasive action becomes less and less as it heads towards the muzzle, and it puts a proper taper in the bore, meaning subsequent boolits or bullets get an ever tightening grip when they are fired. Reverse tapered barrels aren't unheard of, and good luck getting one to shoot. I agree that it's better to be careful, but my 1895 Cowboy took nearly 100 firelapping boolits, all 320 grit to cure that barrel of it's multitude of issues. Other than looking like a mirror inside, the rifling still looks sharp as new to me.

    I'm sure you will have success with yours.

  3. #23
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    I have 18 rounds down the barrel and the bore size has not grown (as farr as I can tell that is). I shoot 6 and clean. Using BullEye powder and 155 SWC Keith Style. Yes It does lead that is why I clean every 6 rounds. (I know I said I was going to do 5 at a time but I had 6 I use for 44 mag fire lapping so......)

    There are 3 tight spots in the barrel. They are getting easier to push a bore slug past.

    Yes I have stuck some in the barrel (3 to be exact) settled on 2.5 grains with the boolit seated with the front griving band even wth the case mouth. Push the boolit in with my thumb except for one case I have to use the press.

    I have the next 6 ready to go and the rifle has been cleaned.
    Big Bore = 45+

  4. #24
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    Quote Originally Posted by MGySgt View Post
    I have 18 rounds down the barrel and the bore size has not grown (as farr as I can tell that is). I shoot 6 and clean. Using BullEye powder and 155 SWC Keith Style. Yes It does lead that is why I clean every 6 rounds. (I know I said I was going to do 5 at a time but I had 6 I use for 44 mag fire lapping so......)

    There are 3 tight spots in the barrel. They are getting easier to push a bore slug past.

    Yes I have stuck some in the barrel (3 to be exact) settled on 2.5 grains with the boolit seated with the front griving band even wth the case mouth. Push the boolit in with my thumb except for one case I have to use the press.

    I have the next 6 ready to go and the rifle has been cleaned.
    Good deal I believe the last I did took about 30-35 to do with 320 grit. I did 5 and clean. Glad you are making progress.

  5. #25
    Boolit Master MGySgt's Avatar
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    Finished up today - 36 rounds total - final bore size is just under .431. Now I have to breakin the 'New' barrel. Shot 10 rounds of a plain base 250 Keith Style (wonders upon Wonders, they functioned through my Marlin - suprised me).

    Cleaned it after shooting with dry patches and a bore brush - some leading but came out easy enough. I will load up some more rounds probably 250 Keiths with about 17.5 grains of 2400. Just need to shoot some and then clean it and shoot it some more before I shoot it with my hunting load for velocity and accuracy.

    One test I have to do before I shoot it over my chronagragh is check to see if I loose any gas checks when the boolit leaves the barrel. The gas check is loose on the heal of the boolit after sizing at .432, but shooting it down the .430 barrel they stayed on - no holes in my chronograph. I really want to keep it that way. Don't know if I can replace it with another Ohler 35.

    Now how do you check that - easy enough - take your target stand 15 feet from the bench and put newspaper across it and shoot thrugh the paper. If the gas check is going to come off you will have 2 holes in the paper for every round you fire. I will test with 10 rounds to see what happens
    Big Bore = 45+

  6. #26
    Boolit Master MGySgt's Avatar
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    Well I have shot it for accuracy and velocity.
    Very dissapointed.

    Velocity dropped 30 FPS

    Accuracy has gone to poop.

    I really do not believe the barrel is gone. I really think it is the boolit I am useing. The loss of velocity may hve brought the boolit down past that magical speed to stay stable. If you look at my boolit real close you can see it is almost the profile of a wad cutter and to get good accuracy past 60 yards with them you have to drive them fast.
    25 yards while chronographing the load was one ragged hole in the target.

    I am going to re-work the load with Alliant Prower Pro 300-MP and H-110. I can get another 75-100 FPS out of them.

    Drew
    Big Bore = 45+

  7. #27
    Boolit Master
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    I've not once seen accuracy decrease, but you may have to re work loads. I doubt VERY highly you did anyhing to harm your barrel.

  8. #28
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    I am surprised your bore is that tight. Marlins are known for "fat" bores though I can't say for sure they go over the SAAMI spec of 0.431" much or often, though my .44 mag. Marlin bore slugged at 0.4315"... but tenths of a thou are a bit elusive.

    As a side note, I started out using the famed Lyman 429421 SWC Keith style because everyone said it was simply the best boolit for .44 mag... more towards revolvers I suspect but what did I know?

    Not only didn't it feed well but accuracy was very mediocre and I got a lot of leading. Turns out that it cast exactly to 0.429" with WW. No, I didn't go the Lyman #2 alloy route. So the boolit was 0.0025" undersize. That explained leading and poor accuracy or at least partially.

    Fatter boolits helped with accuracy and reduced leading but it wasn't until I slugged the whole bore looking for tight spots that I solved the leading issue. Once I hand lapped those tight spots out things improved a bunch with better accuracy and no leading.

    I actually haven't shot the gun much since but I have it feeding the H&G #503 well and it likes the Mihec 434640 which is an RNFP design. Both have given quite acceptable accuracy out to 50 yards anyway. I have to sit down and do some serious shooting at 50 and 100 yards to see how it does.

    I've mostly shot my lightweight 165 gr. plinkers in it since I did all that work!

    Longbow

  9. #29
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    Dubber123 - I really don't think I hurt the barrel - like stated earlier the 'new' size is just under .431 and I size my boolits to .432. I have a few other molds for the 44 but they are clones of the 429421 Keith, they are both over .432 so the size will be good.

    My Mountain Mold 265 gr GC just feeds so darn smooth and hits so hard with that big flat point I just want it to work. But if it doesn't I will change to one of my 429421 clones, they just don't feed as smooth, they will feed though.

    Looking at QuickLoad today I found that LilGun might be the powder to try as it showed the highest velocity of any other powder I plugged in, Yes that included H-110/296. Going to a LGS tomorrow maybe I will pick up a pound. Wonder if LilGun needs Mag primers - I have some, just need to find out if it needs them or not, have to look up some loads that use it.

    Drew
    Big Bore = 45+

  10. #30
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    Longbow - I quit using the Lyman 429421 30 years ago because it leaded so bad due to it being under size. I have had a number of Mountain Molds that worked great, but like an idiot I sold them off for one reason or another. My current one (the 265 gr GC shown earlier in this thread) shoots great out of my Stainless SBH with a 4 1/4 in barrel - yes it has been firelapped. I was 'Trying' to make it work in the Marlin, it was designed with the Marlin in mind.

    May have to sell it off too (still a great boolit for 50 yards and under) and find another one that has a wide meplate and is in the 260 - 280 grain range that would be a WFN or LFN boolit.

    Drew
    Big Bore = 45+

  11. #31
    Boolit Master
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    I only ever had one that didn't show a marked improvement, a Marlin CB in 45-70. It shot a little better, but not a ton. It did reduce the leading by a bunch. I could shoot 2 full grains higher powder charge before leading started to creep in, so a substantial improvement there.

    That gun was a problem child since day one, I'm glad I paid a lot for it

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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