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Thread: Firelapping?

  1. #1
    Boolit Master
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    Question Firelapping?

    I have been told that All revolvers need firelapping, especially new Rugers, to remove the constriction caused by threading the barrel to the frame, and it makes them more accurate.

    So, My revolver cylinder throats are all very close to .358 A .358 ZZ minus pin gauge will just fit with some oil and gentle persuasion. About equal resistance is met in each chamber throat. However, a .356 ZZ minus gauge will not enter the muzzle. O.K., the cylinder throat is supposed to be the critical measurement, right?

    Slugging the bore won't work, because it has 5 lands, and I don't have or don't know anyone with the proper(and expen$ive) tool to do that.

    I have some Hornady swaged 158 gr. semi-wadcutters, which are said to be very soft, and measure ~.358. So, If I do decide to firelap, could I seat them backwards over a light load of Trailboss, using JB Bore compound, and do a reasonable job, at the same time, not changing the diameter of my cylinder throats?

  2. #2
    Boolit Master contender1's Avatar
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    A fine gentleman named Fermin Garza wrote an article on Firelapping. I have a copy somewhere in my stuff,,, but do a search, read what he has to say about it. He's one of those folks who has been there, done that, and knows what he's talking about.

    You are correct in that firelapping is about cleaning up bore constriction at the threaded portion (usually.)

    I'm curious as to your gun only having 5 lands/grooves. I may be the ignorant one here,,, but I'm not familiar with a brand that uses an odd number of lands & grooves. But,,, If your concern is thread constriction and you wish to firelap,,, I suggest you do the proper test to see if it's actually needed. Slugging the barrel isn't the way to do that.

  3. #3
    Boolit Master
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    Quote Originally Posted by contender1 View Post
    If your concern is thread constriction and you wish to firelap,,, I suggest you do the proper test to see if it's actually needed. Slugging the barrel isn't the way to do that.
    Yep. I suppose someone meant well when they told Sniper his revolver needed lapping (just because "they all do") but how does it shoot? It may not need any work at all.
    Warning: I know Judo. If you force me to prove it I'll shoot you.

  4. #4
    Boolit Mold
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    S&W's

  5. #5
    Boolit Master

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    Do the slug. Not just for measurment, but if you start at the muzzle and once started the pressure required to push the slug through stays consistent, you don't have significant constriction. You will probably feel a couple tight spots where the barrel is roll marked, and at the barrel threads but if the slug slides on by with a bit more force, no big deal. If you have to break out the bigger hammer to get it past the thread, you have significant constriction and may need to firelap. Otherwise, Load a few soft bullets and see if you get leading just past the forcing cone, a tell tale sign of thread constriction.

    Also, if the slug you push through the barrel will fit through the cylinder throats, you have a favorable bore-throat relationship, regardless of number of lands or actual measurment.
    "In God we trust, in all others, check the manual!"

  6. #6
    Boolit Master
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    What jcren said x2...

    Slug the barrel first if you are worried about it. Or just to shoot it and see what happens. Anyone that says all Rugers have constrictions doesn't know what they are talking about. There is no way you can firelap the barrel without having some effect on the throats unless your using a different cylinder.

  7. #7
    Boolit Master dkf's Avatar
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    You could also push in a very tight patch from the muzzle and pay attention to the resistance throughout the length of the bore. If it tightens up quite a bit at one spot you probably have some constriction.

  8. #8
    Boolit Mold 6string's Avatar
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    Try slugging the barrel and then drop fitting it to the cylinder throats. You'll be able to tell if there's a discrepancy.
    jim

  9. #9
    Boolit Master
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    Slugging odd groove is no problem, just need a few simple things. A micrometer is much better than a vernier for these task but the latter is close. Cut a strip of soda can, a .001"-.003" feeler gauge, shim stock, something like that. Push slug and then stand slug, wrap shim and pinch with thumb and index of one hand and mic with the other. Double thickness of stock then subtracted from total equals odd grooved slug.

  10. #10
    Boolit Master
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    Quote Originally Posted by contender1 View Post
    A fine gentleman named Fermin Garza wrote an article on Firelapping. I have a copy somewhere in my stuff,,, but do a search, read what he has to say about it. He's one of those folks who has been there, done that, and knows what he's talking about.
    You are correct in that firelapping is about cleaning up bore constriction at the threaded portion (usually.)
    I'm curious as to your gun only having 5 lands/grooves. I may be the ignorant one here,,, but I'm not familiar with a brand that uses an odd number of lands & grooves. But,,, If your concern is thread constriction and you wish to firelap, I suggest you do the proper test to see if it's actually needed. Slugging the barrel isn't the way to do that.

    Contender;

    Like jcren mentioned, I was shooting a mixture of my own cast~15 BHN boolits, and Hornady Swaged SWCs, with Hornady's suggested load of .38 Spl level loads, and I did get some leading in the first 1-1 1/2" of the barrel, so, I figure I must have some constriction.

    I'd be interested in reading Mr. Garza's article...so far, I've read a couple, and bought Beartooth Bullets' lapping manual. I'll see if I can find it, somewhere.

    AFAIK, it may not be exactly 5, but Smith & Wesson also uses an odd number of lands/grooves. Leastways, my ancient 586 did.

    BTW; What is the "proper test", for barrel constriction, and how is it accomplished?

    Thanx for the suggestions, all! C.
    Last edited by sniper; 06-02-2018 at 11:38 PM.

  11. #11
    Boolit Master

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    Push a oiled soft lead slug through the barrel completely ... measure it.

    Push a oiled soft lead slug in about half way, or before the threaded area starts ... push/pull it back out*, measure it.

    If they both measure the same, you don't have a thread constriction problem. Some of the older Ruger's also had a very heavy roll mark, which caused problem ... the newer ones if seen use laser etching ...


    *I use a brass rod to drive the slug in, and through ... I then took a 1/4" wooden dowel and cut it in length to fit in the cylinder frame window, I put the first one up the forcing cone, and push it in, then add a second one ... continue until the barrel is cleared.
    Shawn


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  12. #12
    Boolit Master
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    Given the presence of rifling in the barrel, and given the bore diameter is around .350” or so (do not confuse the correct meaning of the word with groove diameter) I am unsure of why a .356” pin gauge was introduced to the muzzle.

    A pin approaching the mentioned .350” or near that will go in. There is no reason to believe one significantly larger in diameter will do so. The rifling will get in the way.

  13. #13
    Boolit Master contender1's Avatar
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    sniper,,, Fermin Garza is a frequent visitor over on the singleactions dot com forum. He goes by the handle; "2 dogs." His article is over there,,, or at least a link to it can be had. If not,, PM him over there & he'll send it to you. It may also be over on the gunblast website, in the archives.

    A proper way to check the bore constriction is listed above. I prefer the tight patch method myself. I use a cleaning rod, a jag tip, and different thicknesses of patches to get the snug fit I need. Then,, I start my push. if I get it to "stop" or feel resistance, I stop, mark the rod, and continue. Once I have the patches out,, I look at my rod, re-insert it and stop it at the mark. It will let me know where it MAY be constricted. I often repeat the test with fresh patches, no markings etc, to make sure of my original findings.

    And as noted,, pin gauges only show the lands dimensions,,, not the groove dimensions in the rifling. Pin gauges work great for chamber measurements, and if they can fit the window, a start in the bore of a revolver. But again, that's only part of the overall information you need.

  14. #14
    Boolit Master contender1's Avatar
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    A quick search,, Over on the gunblast website, Fermin's article, from 2011.

    "A Contemporary Look At Barrel Leading and Related Sixgun Issues"

    This is an excellent read.

  15. #15
    Boolit Master
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    Lots of good information here. I highly recommend Fermin's article. While not every handgun needs to be fire lapped, you're unlikely to hurt one by fire lapping, assuming you are following directions as Beartooth or Fermin describe. It is important the cylinder mouths not be undersize of the groove diameter while fire lapping. You'll essentially size your lapping slug to be under groove diameter and not accomplish much in the way of throat lapping. If your cylinder mouths are undersized have them opened before you fire lap the barrel.

    Ross Seyfried also wrote an excellent article about the fire lapping process on his GunsAmerica blog.
    Only left handed guns are interesting!

  16. #16
    Boolit Master

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  17. #17
    Boolit Master
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    Firelapping always seemed like a good way to take the edge of the lands to me. I have a few revolvers and all shoot quite well and none have been firelapped, but the throats have been uniformed.

  18. #18
    Boolit Master
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    Quote Originally Posted by str8wal View Post
    Firelapping always seemed like a good way to take the edge of the lands to me. I have a few revolvers and all shoot quite well and none have been firelapped, but the throats have been uniformed.
    I have lapped quite a few, some extensively, and all still looked sharp to me, just a lot shinier, and with much improved accuracy.

  19. #19
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    Here is a VERY SIMPLE test you can do that will tell you if there is any choke or not. It won't give you a measurement in numbers, but this is also not necessary.

    Tightly patch a plastic cleaning jag into the clean dry bore with paper towel. Push the jag through the bore towards the breech. You want to observe how much force is required to keep the jag moving. ANY change in resistance, accurately reflects a change in the bore at that particular spot. If you can push the jag through and resistance is constant and does not increase when the jag gets to the spot where the barrel joins the frame, there is NO CHOKE. If it gets tight, a little harder to push, there is minimal choke. If it stops and you have to beat it through the rest of the way, there is severe choke..

    This is good enough to detect less than a .001" change in bore diameter.

    You can also remove the cylinder or swing the cylinder open, place a piece of white paper on the breech face, hold the revolver up to a bright light and look down the bore. If there is even a slight choke, you will see a hazy ring inside the barrel, a bit of a distortion in the light reflected, by the choked portion of the bore.

    Personally, I think OP has been reading a little more into the situation than is necessary because S&W 357 barrels are RARELY choked, and the 357 barrel is rather thick, which again would prevent distortion in the bore from torquing the barrel into the frame.


    Thread choke happens more in 44 and 45 caliber revolvers because the barrel walls are much thinner and not nearly as strong, so they choke rather easily by comparison to smaller bore revolvers.

    Quote Originally Posted by sniper View Post
    So, My revolver cylinder throats are all very close to .358 A .358 ZZ minus pin gauge will just fit with some oil and gentle persuasion. About equal resistance is met in each chamber throat. However, a .356 ZZ minus gauge will not enter the muzzle. O.K., the cylinder throat is supposed to be the critical measurement, right?
    Yes. Not so much the diameter, as long as they are larger than groove diameter, but the critical part is how even they are in diameter. Uneven throats cause variations in pressure which in turn causes the gun to recoil differently in the shooter's hands, causing point of impact to change from shot to shot. Having the throats all even with each other is the MOST IMPORTANT part of the cylinder. You can always size to fit the throats, or with a soft enough alloy and a stout enough load, boolits will gladly bump up to throat diameter upon firing, but you cannot size to uneven throats.


    Quote Originally Posted by sniper View Post
    I have some Hornady swaged 158 gr. semi-wadcutters, which are said to be very soft, and measure ~.358. So, If I do decide to firelap, could I seat them backwards over a light load of Trailboss, using JB Bore compound, and do a reasonable job, at the same time, not changing the diameter of my cylinder throats?
    You could use a soft wadcutter, but using one with a lube groove clean of lube but filled in with J&B bore cleaner would work. I did this, used a bottle of J&B that was broken and sat on a shelf for years, poured all the oil off and used the paste, packed into the lube grooves and loaded over a decent charge of Unique. This was many years before the internet and not much about firelapping was available, I just took my best guess as to how to do it and it worked a charm. Groups shrunk by half and the tool marks in the Ruger Blackhawk barrel were MUCH smoother.

    You won't do much to the throats being the boolit is sized to push through with finger pressure. Lapping with a larger than throat diameter lapping boolit will definitely change the throats.
    Last edited by DougGuy; 06-09-2018 at 07:06 AM.
    Got a .22 .30 .32 .357 .38 .40 .41 .44 .45 .480 or .500 S&W cylinder that needs throat reaming? 9mm, 10mm/40S&W, 45 ACP pistol barrel that won't "plunk" your handloads? Shoot me a PM! Also on Facebook: https://www.facebook.com/Cylinderhone-756429174391912/

  20. #20
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    I sure wouldn't do it unless the gun told me it needed it. I do shoot a box or two of jacketed bullet through a new handgun and then clean the barrel before shooting lead. I have fire lapped rifle barrels (not to shoot cast) mostly they were problem childs. Ive never seen one shoot worse after it and have seen a slight improvement in a couple but your not going to get sweet lemonade out of a lemon. I think if I had a ruger that had a bad constriction id be boxing it up and sending it back to ruger. Once you put the lapping compound to it there not going to warrantee it anymore.
    Soldier of God, sixgun junky, Retired electrical lineman. My office was a 100 feet in the air, closer to God the better

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BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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