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Thread: Bolt Head Interchange

  1. #1
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    Bolt Head Interchange

    I apologize if this is a repeat question but I could not find any threads about it. I want to make some very accurate measurements of bullet ogive to the lands. The best way to do this is by removing the firing pin, ejector, and extractor from the bolt to allow for the best “feel” of when the bullet touches the lands. I am a bit leery of knocking out that tiny pin holding the ejector on a regular basis so I have an alternate plan. Just use a stripped bolt head in place of my normal one. My question (you knew I’d get to it eventually) is this: are Savage bolt heads dimensionally consistent enough for this to work? I realize that the spring tension of the floating bolt head my make the whole thing moot but I want to see if it will work.

  2. #2
    Basic Member Robinhood's Avatar
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    The critical dimensions of the two bol theads would need to be identical. The one being used in the firearm and the one you use to test with.

    You could remove the BAS and use the firing pin to old the cross-pin in place and then use the bolt close method. Works for me every time. There are several ways to skin this cat.
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    I learned this method watching a u-tube video. Of coarse it was on a Rem or clone style action. The PE cam caused a small audible "click" as the bullet pulled free of the lands. They kept shortening the dummy round until no "click" was present. These actions had nothing interfering with the bolt so it could actually free fall.
    In order to accomplish this on a Savage you must remove the ejector, remove the cocking pin and cocking sleeve from the bolt. Also the wave washer. Reinstall the firing pin to hold the crosspin. But the real "pita" is the removal of the detent balls & spring in the rear baffle.
    The bolt will then be in "free fall". The rear baffle will be flopping around, secure it lightly to the action with a small piece of tape. (I have a spare "stripped" rear baffle for this use).
    You do need the extractor in place for this method. I believe it is called the "Wheeler" method. It works well and you will feel the slightest "click" when the PE removes the bullet from the lands.
    Also I agree with Robin the bolt heads would have to be perfect. After you remove the ejector a few times it will become second nature and is no big deal.
    Search for the u-tube video you will be amazed.

  4. #4
    Team Savage Fuj''s Avatar
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    Using my split case method for many years, and found it was a waste of
    time to remove anything.....On extraction, I hold my hand over the port.
    Once the case head has released, I just tilt the rifle and let the dummy
    roll onto my hand. I don't over think it. My plus or minus tolerance is +.001
    -.001
    Keeping my bad Karma intact since 1952

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    If I understand your objective correctly, why not just use one of these and the comparator set?

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    "Using my split case method for many years, and found it was a waste of time to remove anything"

    Think about it. All the extractor does is snap over the case rim and hold it against the bolt head.
    When you slide the bolt into the action body, it's COCKED and the firing pin doesn't stick out beyond the bolt head surface. Wasted efforts. What it comes down to is "what ever makes you feel good".
    Out of maybe 10/12+ barrel swaps, never removed anything from the bolt head. And if the ejector has enough strength to push the case sideways in the chamber, you've got more problems than a too strong ejector spring.

    I always a Hornady tool with a modified case to set the OAL and find the lands on my ammo. Got cases for each caliber I shoot.
    Did run into a situation a while back that gave me pause. Sent a couple cases off to Hornady to have modified. Got them back and the bullet wouldn't slide in the neck??? We always do them that way??? Except for ALL the cases they had previously modified for me.
    Had a go round with the folks about that so just maybe a "split neck" case may be the better way to go, depending on availability. YMMV.
    Oz never gave nothing to the Tin Man, that he didn't already have.

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    Basic Member Robinhood's Avatar
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    For those of you that use the Hornady set up, Have you ever checked the case headspace and compared it to your sized case? When I found one at .010 shorter I started making my own.
    One Cannot Be PC And Be Intellectually Honest!

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    Something else I've consistently found, even in bergers, smk, eld, every pill I've bought, when you measure the base of the pill to the ogive, i have had as much as .003 variation in the same lot of pills so I started measuring and sorting the pills themselves to get my loads as close as possible. I only do this on ammo I'm loading for competition

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    Quote Originally Posted by Robinhood View Post
    For those of you that use the Hornady set up, Have you ever checked the case headspace and compared it to your sized case? When I found one at .010 shorter I started making my own.
    Not sure i follow ya.. would that matter if your just getting the jump space measurement?

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  10. #10
    Basic Member Robinhood's Avatar
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    Quote Originally Posted by Ted_Feasel View Post
    Not sure i follow ya.. would that matter if your just getting the jump space measurement?

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    When you measure your loaded ammo length you measure from the base of the case to the ogive...at least I did. ( I guess if you measured from the shoulder to the ogive you would be ok, I have not seen a tool for that) If the modified case is .010" shorter than you case, your jump will be .010" different. You are not using a case that is within a few thousands of your bolt face you could be using a case that is .010" off of your bolt face or longer. This is the reason I don't use this method anymore.
    One Cannot Be PC And Be Intellectually Honest!

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    Quote Originally Posted by Robinhood View Post
    When you measure your loaded ammo length you measure from the base of the case to the ogive...at least I did. ( I guess if you measured from the shoulder to the ogive you would be ok, I have not seen a tool for that) If the modified case is .010" shorter than you case, your jump will be .010" different. You are not using a case that is within a few thousands of your bolt face you could be using a case that is .010" off of your bolt face or longer. This is the reason I don't use this method anymore.
    Isn't base to ogive what your after? Its just a relative measurement to get the distance, for example on one of my match 308s , using hornady 178gr ELD I can push it out to 2.886 OAL for ogive to touch. That distance from the base to ogive touching is a constant isnt it or am I still not understanding you?

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    Basic Member Robinhood's Avatar
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    It would be nice to know what dimension you measure once you used your method for finding the lands. This way I could explain things more clearly.
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    Basic Member Robinhood's Avatar
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    I'll try this, Do you push the modified case to the shoulder then push the bullet to the the ogive to get your measurement? Do you then measure your base of the case to the ogive for your BTO length?
    One Cannot Be PC And Be Intellectually Honest!

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    Quote Originally Posted by Robinhood View Post
    It would be nice to know what dimension you measure once you used your method for finding the lands. This way I could explain things more clearly.
    What I do is place the modified case with a bullet in it, making sure I'm keeping the modified case seated in the chamber i push the bullet out until it stops, tighten the thumb screw to lock it in place then with bullet comparator bushing and calipers I measure from base to ogive and get my baseline. Then when I load my resized case I usually start lets say since my 308 shilen gives me a oal of 2.886 max, I start with seating at 2.866 and work out until I see pressure issues and groups doing what I want, once I find the magic spot for a particular type of pill, I take the bullet comparator bushing and measure that load from base to ogive and seat my pills to that depth.

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    Basic Member Robinhood's Avatar
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    Have you measured the Base to Shoulder of your modified case and compared that length to a fired case?
    One Cannot Be PC And Be Intellectually Honest!

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    Quote Originally Posted by Robinhood View Post
    Have you measured the Base to Shoulder of your modified case and compared that length to a fired case?
    No because the base of the modified or resized case stop the case shoulders from touching. When I resize for my bolt, I neck size and shoulder bump only to .002 headspace relief

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  17. #17
    Basic Member Robinhood's Avatar
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    If you don't recognize that the length of the case base to shoulder dimension on your modified case is critical in your measurements, then it is all mute.
    One Cannot Be PC And Be Intellectually Honest!

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    Team Savage Fuj''s Avatar
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    Another thing nice about the split case method is actually seeing where the
    boat tail starts in relation to the donut region after the push is made. Gives
    a good idea for ya' if you decide to try deeper and jump em'. I picked up
    some .264 144gr Bergers to test in a 7.5 twister. For the hell of it, I pushed
    them to touch the lands in my 8 twister. The beginning of the boat tail was
    only half way down the neck !! Super Extra Slender !! LOL

    No matter the method, and what's been mentioned in several posts, it all
    really boils down to your bullet sort. I sorted some of the new Berger .264
    144 grainers. Just a box of 100 gave me 5 piles sorted with my Harrrels.
    I really expected better ??
    Keeping my bad Karma intact since 1952

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    Quote Originally Posted by Robinhood View Post
    If you don't recognize that the length of the case base to shoulder dimension on your modified case is critical in your measurements, then it is all mute.
    How is what I'm asking? In the context of finding base to ogive, shoulders play no part unless the were pushed out to far to where the were affecting how far out the base of your case is out

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    Quote Originally Posted by Robinhood View Post
    If you don't recognize that the length of the case base to shoulder dimension on your modified case is critical in your measurements, then it is all mute.
    Are you referring to this part of the shoulder or head space being .01 off?

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    Agreeing with Fuj, the split case method works great I used a variation of that for years. I drilled and tapped the case head of standard primer cases to 1/4-20 and small rifle cases to 12-24. Then set the neck tension to just under a thousandth. The tapped holes were used to push the bullet back out after forcing them in. A Sharpie mark was added when seating depth was close to touching.
    Once first contact is made CBTO can be measured for that rifles baseline.

    My current method uses a brass rod measurement from muzzle to bolt face and then from bullet tip to muzzle. The bullet can then be set in a dummy to verify the difference with a Sharpie mark. CBTO measurement off that dummy is also almost a "perfect" baseline.

    Many ways to skin this cat. And all are only related to the action/barrel they were taken from.

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    Quote Originally Posted by Ted_Feasel View Post
    Are you referring to this part of the shoulder or head space being .01 off?

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    Because that may be wear im not getting what your saying. If your saying that edge of the shoulder then I can understand that make a difference but if your referring to head space of the modified case then I can't see it making a difference

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    Thinking outloud, the modified case should have the same headspace as the bump you set in your handloads or the CBTO will be different between the two.
    The baseline however is what we all work with and should be consistent. The baseline is where we work from incrementally. It doesn't make a difference where we physically end up because best results will be unique to that rifle only.

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    Quote Originally Posted by mnbogboy2 View Post
    Thinking outloud, the modified case should have the same headspace as the bump you set in your handloads or the CBTO will be different between the two.
    The baseline however is what we all work with and should be consistent. The baseline is where we work from incrementally. It doesn't make a difference where we physically end up because best results will be unique to that rifle only.
    I agree. The comparator is not dealing in absolutes as much as it is giving a reference point or baseline that is worked up from.

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  25. #25
    Basic Member Robinhood's Avatar
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    Ted, Sorry for the gap in time, I had to take an old man nap. My point hinges on a gauge that is significantly longer or shorter than the length gauged of ones rifle chamber. That is why I asked if anyone had ever measured the case headspace on there modified cases. Some may be close to your headspace. Many of mine were off.

    When you have found your lands with the hornady tool, you take you measurement from the base of the of the modified case to the ogive(CBTO). Then you you will load based on that information. If you cases that you are loading are a different dimension from the base to the shoulder then the point where the bullet touches the lands will be an unknown. Granted, that may not matter if you start with a .030 jump.

    Some people start with the bullets touching the lands and work away once they have found the load. If you notice that some guys are worried about any little interference that may impact their measuring. I'm not quite that anal. If you push something into the lands it will scar the bullet. Possibly even stick the bullet when you extract.



    I believe the split neck gauge is an improvement over the hornady setup for the reason that if you are using a case that fits that chamber, you are getting a very precise measurement. I use a dummy round and us the bolt close method. I retain the dummy round for reference I can re run the test after x number of rounds and see if my lands are moving. That oddball BTO bulet comes in handy here.

    Good banter and thanks for humoring me.
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