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Thread: chambering thru headstock

  1. #1
    Join Date
    Aug 2007
    Location
    Kansas
    Posts
    278

    chambering thru headstock

    I did a lot of checking of the last three barrels, 1 Hart 5groove 6ppc, 1 Krieger 6Dasher, 1 Proof Research 6x47.

    First setup was indicating throat then very breech end of each barrel. Then checked the indicator runout at Ĺ inch or so in front of the indicated throat.
    Second setup was indicating throat then muzzle of each barrel. Then checked the indicator runout at Ĺ inch or so in front of the indicated throat.

    The Hart and Krieger where chambered with the Throat and muzzle setup. The Proof Research Throat and breech set up.

    Each time I checked in front of the throat I could not see any differences in the indicator reading between the two setups.
    After chambering each of the above three barrels I checked the runout on the free bore, shoulder and at the end of the chamber.
    All three barrels indicated zero using Interapid 312-15 indicator (same amount of needle movement if any)

    I used the Grizzly rod to first indicate the throat on each setup than double checked the throat with the 312-15 also at the Ĺ mark. I have found for myself that using the Grizzly rod first REALLY speeds up my time indicating the throat and ¬Ĺ inch or so in front.

    Chet

  2. #2
    Join Date
    Feb 2003
    Location
    Texas Panhandle
    Posts
    1,953
    Chet, the more barrels you do the quicker you get indicating barrels. I havenít timed how long it takes me to indicate a barrel in, but I figure 5 minutes or less. That last little bit of tweaking to get the indicator to repeat to the same mark seems to take the longest. I really think when it comes to barrel work most of us tend to over think things. Not that itís bad to do that, but some things matter some donít. It seems that Iím always learning when it comes to barreling. I have an easy one to do today chambering a 6 BRX. Then after that itís going to be a hard one or at least a time consuming one. Iíll have to make some tooling to do it. I wish Iíd have talked with Tom Martin more when he was alive as this one was right up his alley as he did these routinely. Itís a .50 BMG on a big McMillan action. My long point Interapid would only reach up about midway of the body of the case. So will build an indicator rod that will let me reach in to the throat area. This barrel is 1.75 in diameter at the breech. Fortunately it tapers down to about 1.35 quickly like a Douglas taper so Iíll be able to get it through my headstock.

  3. #3
    Join Date
    Feb 2003
    Location
    Fbks,Alaska
    Posts
    339
    Mike,
    DO NOT run breech clearance closer than .015"or barrel heat expansion will bind up the coned bolt nose into the 120 degree included angle of the barrel breech.

    Been there...once on one of my McM 50BMG DBM Repeaters.

  4. #4
    Join Date
    Aug 2007
    Location
    Kansas
    Posts
    278

    50 tms

    Hello Mike
    Like you it only takes me 5 minutes or less to indicate the barrel in at any point. When using the Grizzly rod even less time and still using the 312-15 to double check the runout. Yes Tom was a 50 BMG man to know. Below is a picture of the 50 cal. Tom Martin Spleical. (6PPC--Tom Martin Speical--50 BMG)
    Chet




    Click image for larger version. 

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  5. #5
    Join Date
    Feb 2003
    Location
    Texas Panhandle
    Posts
    1,953
    Quote Originally Posted by Dans40X View Post
    Mike,
    DO NOT run breech clearance closer than .015"or barrel heat expansion will bind up the coned bolt nose into the 120 degree included angle of the barrel breech.

    Been there...once on one of my McM 50BMG DBM Repeaters.
    Thanks, Dan. I appreciate that.

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