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Thread: EDM rifling and cast bullets

  1. #1
    Boolit Bub
    Join Date
    Jan 2012
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    EDM rifling and cast bullets

    Iím thinking of getting a new Smith 686 and understand that these are manufactured with EDM rifling. What are guys doing to get good results with plain base cast bullets in these revolvers? Will JB bore paste be enough to smooth the micro burrs or is fire lapping necessary? Iíd really like to use my MP 358429 clone but if the boreís going to lead like crazy I donít want any part of that.

  2. #2
    Moderator

    ShooterAZ's Avatar
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    I'd run a couple of hundred jacketed bullets through it, that should smooth it out. You should be fine with cast after that.

  3. #3
    Boolit Master tazman's Avatar
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    I purchased a new S&W 686+(the seven shot version) about 3 weeks ago. It has been to the range 3 times now. I have fired over 400 rounds through it, all of it cast boolits.
    I changed the grips because they just didn't work for me. I put a set of Pachmyr presentations grips on it and now it feels great.
    It shoots about 1 inch groups at 10 yards for me. I practice at 10 yards because that is the distance from my bedroom door to the middle of my living room. It is my second best shooter. The best one is a 686-3 with an 8-3/8 inch barrel. It will do under an inch.
    I have yet to need to clean the barrel on the new 686. It shows no trace of leading after 400 rounds.

  4. #4
    Boolit Man
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    I read online where some had leading issues with the S&W EDM rifling so planned to use some JB bore paste or shoot J words to smooth up my M69 when I got it. Although the rifling looked rough I've not had any leading with 600+, lubed or powder coated boolits in it. I haven't shot anything but cast in it and it's very accurate if I do my part. I actually killed a groundhog off hand, right at 70 yards a few weeks ago. Probably more luck than skill but it's as accurate as any handgun I've owned.
    I don't see the EDM as a problem at all.

  5. #5
    Boolit Master
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    I have had no leading issues shooting plain base boolits in my Mdl 69 Smith with a 4-1/4" bbl
    It's all chicken, even the beak!

  6. #6
    Boolit Man
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    Jun 2014
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    North Salt Lake, UT
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    My S&W 329PD definitely leads with .44 SPC loads that have never leaded in my S&W 624-3 or my Rossi Model 92. Not very bad leading, just a few minutes with a brass brush to get it out, but more than my other 44's.

  7. #7
    Boolit Master
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    I'm not 100% sure to blame the rifling yet, but my new model 57-6 seems to be leading considerably more than the old 80's built 57. So far I'm looking at the throats more than anything, which are .410". I can't seem to get an accurate measure of the bore, but the slug will not fall freely through the throats, so I assume it too is about .410". I had absolutely no idea about EDM (or does Smith call it ECM?) rifling until last week. Everybody is worrying over nothing with MIM parts and an easily deleted lock. This EDM rifling seems like it could be a much bigger deal. Fingers crossed throat lapping helps. A handgun that can't shoot cast is completely useless.

  8. #8
    Boolit Master

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    MY S&W 69 does not lead !
    I have two Nowlin EDM cut barrels for the 1911 a 38 super & 45 acp no leading in them either

  9. #9
    Boolit Master



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    I have shot THOUSANDS of my home cast bullets through various modern Smith revolvers with EDM rifling with NO issues. None, whatsoever. That includes my rather exotic Model 520:

    This is a titanium cylinder with composite barrel. It is a SHOOTER!



    I have a 625-8 JM Special that has had thousands of rounds through it without issue (it is my current favorite of all of my revolvers and that is saying something).



    I have friends that have shot a good bit with similar Smith's without issue, also.

    As far as I am concerned, it is a non-issue.

    Most leading issues with revolvers are a result of cast bullets not properly fitted to the revolver or of the wrong alloy. That's my opinion and I am stickin' to it...(:>))

    YMMV
    Dale53

  10. #10
    Boolit Master
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    S&W uses ECM (electrochemical machining) to rifle barrels.

    From another firearms forum:
    "....Since 1993, Smith & Wesson has been using ECM to manufacture most of their revolver barrels. They use machines manufactured by Surftran to do their work. The barrels are hardened and annealed before the rifling process. The hardened barrels are then placed in the ECM machine and held stationary. The electrode is a plastic cylinder with metal strips circling around the exterior. The metal strips are a reverse image of the desired rifling and are inset into the plastic cylinder. This way, only the plastic part of the cylinder touches the barrel and not the metal strips. The electrode is placed inside the barrel and the whole is immersed into an electrolytic solution of sodium nitrate which is constantly circulating under pressure. The electrode is moved down the barrel and rotated at the desired rate of rifling twist. As current flows from the cathode (the electrode) to the anode (the barrel), the material is removed from the anode to duplicate the grooves in the shape of the electrode. Because the metal parts of the electrode never actually touch the barrel (only the plastic core does) and because the flowing electrolyte removes any material from the barrel before it has a chance to accumulate on the metal strips, the electrode usually lasts a very long time and needs no cleaning or maintenance. In fact, the electrode is replaced only when the plastic core which contacts the barrel to provide proper centering and spacing of the metal strips, wears out.

    The advantages of this are that the process is extremely precise and can be used to machine hard materials like hard steel alloys, titanium alloys etc. Similar to the EDM process, it also produces no heat or stress on the barrel during the rifling process and also produces an excellent finish. Unlike the EDM process though, it is much faster to machine parts using this technique. A typical rifling job for a 357 magnum revolver barrel can be done in about one minute using this process, making it ideal for mass production. The tool can also be repeatedly used as there is very little tool wear......"
    Last edited by Petrol & Powder; 05-22-2018 at 04:26 PM.

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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