Bolt Head Interchange

[mnbogboy2]

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.

[Ted_Feasel]

Are you referring to this part of the shoulder or head space being .01 off?https://uploads.tapatalk-cdn.com/20200523/54977316a9cb8195533e1a863c9a91a5.jpg

Sent from my SM-N975U using TapatalkBecause 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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[mnbogboy2]

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.

[Ted_Feasel]

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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[Robinhood]

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.

[Ted_Feasel]

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. 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 bullt 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 land are moving. That oddball BTO bulet comes in handy here.

Good banter and thank for humoring me.I definitely start far and work closer, I recon thats why it never played a hand in my load dev and jump dev. BTW, I cleaned the garage and took a nap also:)

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[Fuj']

I drank a Molsen XXX and watched a retro world series between
the Twinns And Atlanta. Some where in between the third and
eighth innings I caught my nap.

Last couple of years has found me to start at .015 off the lands.
Seems to have saved me in resources overall.

Good thread !!

[Robinhood]

I'm glad I'm not the only one.
Gunracr, sorry for hijacking. Did you get the info you wanted?

[strut64]

nobody has mentioned the wheeler method as of yet. also very effective. check out their website Wheeler engineering

[Robinhood]

If this is the video, that is what I was talking about by setting it on bolt close. I find that to be exact as in within .001"


https://www.youtube.com/watch?v=TWmIwPwLyyg

[mnbogboy2]

nobody has mentioned the wheeler method as of yet. also very effective. check out their website Wheeler engineering

I mentioned this in post #3 with all the modifications to the savage bolt.
Thanks Robin, that's the video I mentioned too. Yes, super accirate. The "human" feel of the bullet seating gets a realistic assist from the PE.

[GaCop]

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. :tea:

[GaCop]

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 :thumb: Been doing it that way for years when I don't happen to have the modified case.

[Bill2905]

If this is the video, that is what I was talking about by setting it on bolt close. I find that to be exact as in within .001"

Thanks for posting this. I have been using the Hornady tool and it works ok but is not always repeatable. I learned a lot reading this thread.

[Ted_Feasel]

I watched that video and I remember my dad and uncle doing something real similar to that when I was a kid just learning

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[Fuj']

Thanks for posting this. I have been using the Hornady tool and it works ok but is not always repeatable.

A lot of methods and tools available to get it done. As most have found on here,
"repeat ability" is not absolute. Some of these new fangled slender pencils we have
been enjoying for longer ranges, can be a pain in the ass. There are times that you
have to do multiple pushes and settle on the best dispersion. My latest headache
was with the 6.5 150gr Sierras. Those things are real slender and wanted to stick
more then most, which brings up another piece of the puzzle. There are some
machined angles at the start of the lands that are more abrupt then others. These
are easier to feel, whereas an angle that is close to perfect, can be troublesome
If tension is too great in your test case.

[Ted_Feasel]

Just throw this out there.. sometime when you have a box of pills.. measure from the base of the pill to the ogive..sierra, hornady and bergers I have always found as much as .003 variation .. belive it or not the best I've found is the new hornady Atips.. i guess my point is the inconsistency in where the ogive is can add to the difference in readings... not saying it is the only factor but definitely plays a part.

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[Fuj']

Just throw this out there.. sometime when you have a box of pills.. measure from the base of the pill to the ogive..sierra, hornady and bergers I have always found as much as .003 variation .. belive it or not the best I've found is the new hornady Atips.. i guess my point is the inconsistency in where the ogive is can add to the difference in readings... not saying it is the only factor but definitely plays a part.

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Right you are, and why I use a Holland comparator for my anal stuff. I've also
read that the A-tips have been consistent and probably from the fact that the
lot batches are directly packaged as they come off the press. Buddy tells me
that they ship a cloth to wipe the oil off as you receive them !!

Holland comparator.....Not real cheap, but a good tool.

[Ted_Feasel]

Right you are, and why I use a Holland comparator for my anal stuff. I've also
read that the A-tips have been consistent and probably from the fact that the
lot batches are directly packaged as they come off the press. Buddy tells me
that they ship a cloth to wipe the oil off as you receive them !!

Holland comparator.....Not real cheap, but a good tool.Yes sir, I dont have the Holland, ive found what the chambers are on my rifles, at least within the variation you may get but because I start with the deepest or default and work my way out until I find what I'm looking for.. i guess it would be neat to know the precise distance.
I have 2 boxes of the atips but have not had the time to do load dev with them. They are very nice, you can tell a great deal of pride and craftsmanship went into the atip.. i love that they are sequinchely packaged into their own slot. I picked out 10 just to see how consistent they are and the 10 i measured were all identical as far as my 49 year old eyes could see on dial cals.. they are mitutoyo my daddy passed down. Very accurate.

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[Dave Hoback]

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.

I would think that would make it all Moot. But I guess anything’s possible in the new Covid-pandemic world of death! LOL! I promise I am simply joking Robin. :becky:


Boy oh boy...You guys are WAY more “precisionalistical-icious” than I with your technique. I do use a Hornady Lock n Load Comparator, but I measured OAL with an Frankford Arsenal OAL kit. The brain fluid aroma is palpable in here!

Thank you for sharing guys. Quite an interesting discussion.