Finding your lands (video)

Discussion in 'Reloading Forum (All Calibers)' started by Alex Wheeler, Jan 9, 2016.

  1. spitfire_er

    spitfire_er Silver $$ Contributor

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    I must admit, just watched the video and makes perfect sense.
     
  2. RenoMD

    RenoMD Silver $$ Contributor

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    So I gave it a go; but, unfortunately I think the case may have given me false feelings of extractor camming. I got to the point where the bolt would finally close all the way with an coal of 2.3485, and I felt what I thought was the extractor cam. But kept feeling the hangup despite holding the bolt handle to the rear. Ended up seating the oal ( I was ensuring ogive too) to 2.224 with a Berger 105 hybrid in virgin 6br lapua brass in a dasher 272 neck 104 fb and kept feeling the hangup. I knew something was wrong. I looked at the case and there were circumferential rub marks and longitudinal rub marks too. I pulled the berger 105 hybrid, and the same hangup feeling was there...aargh...so goes 20 min of my time... The chamber and bore were cleaned how I clean every rifle before I use it. This rifle is unfired though. I might end up just using the number I get when I can close the bolt via gravity on a dummy round and call it good. Was kind of surprised the case itself was causing that hangup feeling since its brand new.... I wonder if the chamber is just a bit tight.
     

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    Last edited: Jan 8, 2017
  3. rardoin

    rardoin Silver $$ Contributor

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    Reno..is this 'new' brass sized? If you can't freely close the bolt on an empty case I would size it down until you can. then repeat your test to find the lands.
     
  4. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    One thing I should have mentioned in the video, the longer the freebore the more important it is to have a straight case. If there is runout in the case or at the bullet it will bind up in the freebore. A dead give away is a half ring mark on the ogive then 180 degrees across another half ring mark down by the case mouth on the bullet.
     
  5. RenoMD

    RenoMD Silver $$ Contributor

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    Hey fellas brand spanking new 6mmbr lapua case in a dasher chamber,just expanded with a mandrel, concentricity at the neck of the case and ogive of bullet is .001-0.002 using a Forster tool and dial indicator. It's a bit weird... I'm just going to fireform with the appx lands depth I get with the close to bolt technique and do it again once I get fire formed brass and bump the should back a bit. I have a feeling I'm getting those markings and continued hangup feeling upon opening the bolt Bc I'm using a 6mmbr case in a dasher chamber....
     
  6. Kyle Schultz

    Kyle Schultz Gold $$ Contributor

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    I've been following your progress but I am very confused about what you are trying to accomplish. Are you trying to find the lands in your 6 Dasher chamber using a 6br case or are you trying to fireform 6br brass into 6 Dasher brass?

    First, if your chamber neck is 0.272" greater and your chamber length is at least 1.555", a stripped bolt WILL close on a stick of Lapua 6br brass by gravity alone. If it won't, stop right there and figure out why not. If your chamber has a tight neck, you may need to first turn the 6br neck so that the loaded neck will fit. If the chamber is short, you will need to trim the brass.

    If the brass fits, then I really don't understand why you need to form a false shoulder just to locate the lands. Just long seat a bullet into the 6br case and follow Alex's tutorial. There's no reason that the case needs to headspace. All you care about is the bullet touching the lands.

    Now, if your objective is to fire form brass, I would suggest you consider the jam method as an easy alternative. Find your lands using a 6br case, add 0.020", and seat your bullet with .002" or .003" of tension and fire away. Use a soft cup primer like a Fed 205. I used 30.6 Varget in my gun and achieved a pretty consistent OAL of 1.542" after fire forming. Zero cases lost. Trimmed the cases to a consistent 1.540" and I'm ready to rock and roll.

    Not sure if any of this will be of help to you but I hope so. Good luck!
     
    Last edited: Jan 8, 2017
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  7. bobinpa

    bobinpa Gold $$ Contributor

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    OK, I hate to sound dumb but, How do you accomplish this with a Savage bolt? I have done this countless times with a Remington, but never with a Savage. My brother wants to learn more about reloading and he has a Savage 110 (I think). I know the bolt is different. It seems like there is resistance even when the firing pin is released. I would like to educate myself before I have to educate him.
    Thanks in advance!
     
  8. bobinpa

    bobinpa Gold $$ Contributor

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    ?????
     
  9. RenoMD

    RenoMD Silver $$ Contributor

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    I am finding the lands with a 6br case in a dasher chamber. What you said is exactly the problem. After talking to my smith I found my chamber is 1.555 which is why I kept feeling the hangup. Good call on trimming back a bit.
     
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  10. Patch700

    Patch700

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    Hi Bob.. You must completely strip the bolt , that means no firing pin assy , no ejector , and remove the rear baffle (extraction ramp) you can leave the extractor hook on the bolt face but you must hook the case into it before sliding case into chamber.
    You will need to reinstall the bolt handle itself and the large screw that holds the bolt on. Doing it this way there will be absolutely no resistance to closing if there is no contact being made by case or bullet. The only resistance you will feel is if the case is not sized enough or the bullet is touching.


    IMG_2704.JPG

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  11. 1shot

    1shot Site $$ Sponsor

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    I have been using Alex's method for years with very good success, but recently started working with a bullet, barrel combination that is giving me fits, so I'm asking what others are looking at for their "touch" measurement.
    I paint my bullet on the set-up round with Dykem lay-out dye which really help in the definition of seeing the engraving from the lands. I strip the bolt, place the cartridge under the Sako extractor and insert the assembly into the receiver raising and lowering the bolt handle several times. I then extract the cartridge and measure the length of the marks created by the bullet scuffing on the lands with a digital caliper while viewing through a large lighted magnifier. I measure all of the marks length, ie. a 4 groove barrel would give you 4 marks. For the sake of conversation if those marks were .040 long, should I assume that my touch measurement would be B2O -.040?
    To put another way, if my set up cartridge measured 2.680" B2O and the engraving marks were .040 long, then my touch measurement would be 2.640"? This would be my base measurement that I would reference for seating depth changes, throat erosion etc..
    Any thoughts would be appreciated.
    Thanks,

    Lloyd
     
  12. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    No, the length of the marks do not correlate to the depth your in the lands. The closer the lead angle matches the ogive shape the longer the marks will be for any given amount of jam. Two different shaped bullets both .010" in the lands will have different length marks.
     
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  13. rwj

    rwj Silver $$ Contributor

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    Many thanks to Alex Wheeler for enlightening users to an excellent methodology! Having just used it, the repeatability is unbelievable! I vote he be awarded the next user “tip award”!
     
  14. Alex Wheeler

    Alex Wheeler Gold $$ Contributor

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    Then I would have to give the award the one who showed me this method. I learned it at Deep Creek. Tom Mousel suggested the video. Its not the Alex Wheeler method. Deep Creek method would be more honest, but maybe it came from PA.?? Who knows.
     
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  15. Jeff A

    Jeff A Formerly known as BikeEffects Gold $$ Contributor

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    BUT, you are the one that is successfully getting the word out to an audience of at least 40,000 people! You have some credit due, Sir.
     
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  16. 1shot

    1shot Site $$ Sponsor

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    That makes sense, thanks Alex.
    Thanks Alex,
    Your reply just reminded me of something. When the barrel was chambered, I had my "smith" go back in with a throating reamer to give me the most use of the capacity of the case, as well as keeping the BT bearing surface in front of the neck/shoulder junction. It is very possible that the angle of the throater and/or the profile of the bullet is contributing to the situation I have. Thanks again for the clarification.

    Lloyd
     
  17. ChocDog

    ChocDog

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    I was wondering how this would work with a Tikka. With my Remington style bolts it is not an issue. The bolt handle is attached to the bolt body. With the Tikka, the firing pin holds the bolt handle in place. Remove the firing pin and the handle can slide in the dovetail. Would this not interfere with the sensitivity required to feel the touch?
     
  18. paulT

    paulT

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    Great Video Thanks Alex.
     

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