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Thread: Is the Savage barrel switch really that easy?

  1. #21
    Boolit Grand Master

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    I think your'e both saying the same thing but you're looking at it two different ways. The SAMMI spec for the gauges is bigger than the SAMMI spec for the cartridges. Its comparing apples to oranges.
    The Go gauge is ground at the minimum SAMMI tolerance for the chamber, which should be only slightly above the SAMMI tolerance for the cartridge.
    Do the two standards overlap? I confess I do not know, but I do know that if you want any factory ammo to dunk right in without a hitch, then you had better go about .002 deeper than the Go guage.
    The beauty of the Savage barrel setup, is that after you bottom the barrel out on the gauge, when you torque down the locknut, it gives you that little extra gap on the gauge. The nut just pulls the barrel a couple thousandths away from the gauge, and voila! perfect headspace!
    The only worry is that if for some reason (yeah I know, chance in a million) the threads gall, or have trash in them, or anything other than the headspace gauge stops the barrel from rotating, and you torque down the lock nut, you could actually have excess headspace. That is why it is a really good idea to either drop in the Not-GO gauge, or put two layers of scotch tape over the base of the Go gauge to make for darn sure you are in spec. If you are renting the gauges, then you get both and it costs you nothing to check with the Not Go gauge. If you ponied up the $$$ for your own headspace gauge, and saved money by only getting the Go gauge, (I have done this, I hang my head in shame) you can get by with the tape trick.
    All I'm saying is that you need to check just to be sure, because on a Savage, you could have .002 over GO or .050 over go and it would feel exactly the same. So do yourself a favor and check.
    Precision in the wrong place is only a placebo.

  2. #22
    Boolit Master
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    Goodsteel, Thanks!!

    I did some checking and found the SAAMI website that has chamber and cartridge drawings, located here:

    http://www.saami.org/specifications_...wnload/206.pdf

    For the 243 Winchester (Page 43), the MINIMUM chamber headspace dimension is 1.630 inches. The MAXIMUM cartridge headspace dimension is 1.634" so it appears that there is some overlap.

    Based on this, a cartridge made to SAAMI max won't fit in a SAAMI minimum chamber.

    I sent an email off to the webmaster to see if I could get some confirmation of my interpretation, but who knows if I will receive a response.
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  3. #23
    Boolit Grand Master

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    Now that is a solid slice of good information and certainly confirms my suspicion. I am surprised that the cartridge spec overlaps the chamber spec by almost half of the allowance though. I have noticed that chambers with only .002 over Go are a bit snug sometimes, but I never understood why. Now I know.
    Thanks for the research!
    Precision in the wrong place is only a placebo.

  4. #24
    Boolit Master


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    I think you should look at the numbers again on page 43 of the SAAMI file... Minimum headspace is 1.630 where maximum is 1.640 from the datum line. This equals 10 thousandths allowable.
    When I set a new target or match type chamber I set it with a gauge at .000 to .001 headspace. If I am setting up up a hunting rifle, I set it looser at .003 -.004 maximum headspace. ( due to field conditions/ dust/ dirt/Temperature changes, etc.)
    The SAAMI Cartridge dimension shown is 1.634 MINUS .007 so minimum Cartridge datum length is 1.627...this is what commercial cartridges must stay within to be in spec. with 1.634 as a maximum. This gives .003 to .004 plus or minus to work with in reality. Most Factory Cartridges will run on the Minimum side.

    I am OLD school gunsmith and Tape is NEVER used because it compresses or tears and you cannot get a precise reading. I use a cut piece of feeler gauge the size i want and a wipe of grease to hold it on the bolt face and use a proper headspace gauge only. A tight headspace 0-1 is easier on brass for reloading where the brass will be loaded many times.

    Rich
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  5. #25
    Boolit Master JesterGrin_1's Avatar
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    I have to agree with Mooseman as in I also like Tight head space. Yes it does mean that the size of the brass is more critical. But to me that goes along with a Custom built Rifle. My .358 Winchester that was recently completed is a snug fit when closing the bolt but not too snug.
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  6. #26
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    The nice thing about handloading, you can adjust for any minor head space problems on most chamberings. Remove the spring from your bolt, and close it on an empty case. You should feel just slight drag as you lock down the bolt. It doesn't take a lot of trying to figure out just how much to size your brass.
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  7. #27
    Boolit Master
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    I understand tolerance, but the fact remains that a SAAMI minimum chamber will not accept a SAAMI maximum cartridge. It ends up being an interference fit. Don't know why, but that is what the numbers say.
    My luck is so bad that if I bought a cemetery, people would stop dying.- Rodney Dangerfield

  8. #28
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    Quote Originally Posted by rtracy2001 View Post
    I understand tolerance, but the fact remains that a SAAMI minimum chamber will not accept a SAAMI maximum cartridge. It ends up being an interference fit. Don't know why, but that is what the numbers say.
    I see that also, so I guess it is possible to get a rifle that just closes on a Go gauge that would not accept factory ammo. But I have never encountered such a rifle, infact just the opposite, I have a 308 that I set HS with a factory loaded Remington round, it will not close on a Go gauge, which is what I prefer. I also had a Remington sendaro 300 wim mag that would not close on my Go gauge, but it would accept ammo from all three of the major US manufacturers. As far as I know the ammunition manufacturers in US make ammo very close to SAAMI minimum dimension, which is not the same as minimum chamber dimension, it is actually less by 3-.004" dependant on cartridge. Another thing I notice in the SAAMI drawings is maximum chamber dimension is not NO GO headspace dimemsion, at least not according to any of my headspace gauges, but infact look to be field reject dimension.
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  9. #29
    Boolit Master


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    The problem with headspacing to a brass cartridge is it is soft and will compress with the camming action of the bolt. This is the reason that Gauges are Hardened steel, they wont compress like springy brass. so you get a true reading when headspacing.
    If a rifle is set to .003 to .004 Headspace it will close on a Saami Maximum length cartridge with a .000 to .001 interference fit but as stated, it would be unusual to find Factory ammo already at maximum spec. Notice Saami also includes a -.020 in the case diameter measurement.
    I have never had an issue with new brass or ammo not fitting my close tolerance guns, it always fit.
    If you have ever picked up range brass and you try to chamber it more often than not it will not chamber without resizing due to most commercial rifles not being close headspaced or worn rifles that let the brass fireform over maximum. You must FL resize them to fit because neck sizing will only work from brass out of the same rifle.
    On a close fit rifle, one slight disadvantage is that cases will grow longer at the case neck faster so they will need to be trimmed sooner to keep them in proper length, which is not a problem for most benchrest/target loaders who keep cases trimmed to a uniform length. The brass cannot expand rearward so it grows forward, however the advantage is less chance of case head separation from multiple firings, so you get longer reloading life from your brass.
    You Know You Might Be Facing your DOOM , if all you get is a click, Instead of a BOOM !

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  10. #30
    Boolit Master


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    Thanks to all on this thread on headspace and the use of go/no-go gauges. I have been in this shooting game a very long time but have never done any of this work. It is very interesting and makes me want to give some of it a try. However the expense of the tooling, vices, wrenches, etc makes it impractical for me. However I did enjoy the differing takes on the subject. Thanks again.
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  11. #31
    Boolit Master
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    I got a reply from the folks at SAAMI. While they did not answer the "why" question, they did confirm that the 243 "like most modern bottleneck cartidges" has a small interference fit in arms chambered to minimum dimensions.
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  12. #32
    Boolit Grand Master


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    Does anyone know for sure, is the SAAMI maximum chamber dimension shown in the drawings the field reject gauge dimension? I do not know as I don't own any field gauges.
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  13. #33
    Boolit Grand Master

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    Set the headspace to work with the ammo you will be using. All else is irrelevant.

    Bill
    If it was easy, anybody could do it.

  14. #34
    Boolit Master
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    Quote Originally Posted by swheeler View Post
    Does anyone know for sure, is the SAAMI maximum chamber dimension shown in the drawings the field reject gauge dimension? I do not know as I don't own any field gauges.

    One of the links DCM provided says this about the field gauge:


    FIELD: Corresponds to the longest safe headspace. If a rifle closes on a FIELD gage, its chamber is dangerously close to, or longer than, SAAMI’s specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. FIELD gages are slightly shorter than the SAAMI maximum in order to give a small safety margin.
    My luck is so bad that if I bought a cemetery, people would stop dying.- Rodney Dangerfield

  15. #35
    Boolit Master


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    Maybe this link will explain it better...http://www.forsterproducts.com/store.asp?pid=24834
    You Know You Might Be Facing your DOOM , if all you get is a click, Instead of a BOOM !

    If God had wanted us to have Plastic gun stocks he would have planted plastic Trees !

  16. #36
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    I just did my first one, without proper headspace gauges. I don't shoot commercial ammunition, and it's for me only, so I only care that it's headspaced to the specific sizing die that I wll be using. Two things I found on this particular gun, a small-shank 110 with 20 TPI: The slack taken up in the threads for 40 lbs of torque was .003", checked using a combination of .001" and .002" brass shim stock, and you can make your own headspace gauge out of a resized case filled with wheel weight alloy. I resized the case again after filling to make sure it didn't change, and it definitely made the case rock-solid. I could feel the difference when "bottoming" the barrel by hand against the filled case vs. empty.

    I feel it worth mentioning to double-check the case head for flatness before using it for a gauge, sometimes the rims get peeled back a few thousandths by extractors or shellholders, or have burrs on them.

    BTW, Goodsteel's 7mm-08 and .223 barrels are no longer for sale

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  17. #37
    Boolit Master

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    Quote Originally Posted by rtracy2001 View Post
    Goodsteel, Thanks!!

    I did some checking and found the SAAMI website that has chamber and cartridge drawings, located here:

    http://www.saami.org/specifications_...wnload/206.pdf

    For the 243 Winchester (Page 43), the MINIMUM chamber headspace dimension is 1.630 inches. The MAXIMUM cartridge headspace dimension is 1.634" so it appears that there is some overlap.

    Based on this, a cartridge made to SAAMI max won't fit in a SAAMI minimum chamber.

    I sent an email off to the webmaster to see if I could get some confirmation of my interpretation, but who knows if I will receive a response.


    I do believe the numbers are smaller on factory ammo that the min and max for chambers. A new factory round is likely to be smaller than chamber min 1.630 by 0.000-0.004 thousandths. A headspace guage setup like Hornady's and a box of factory fresh ammo will bear that out. I use my Clymer headspace gages for reference when analyzing such things.

  18. #38
    Boolit Master
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    Quote Originally Posted by Lance Boyle View Post
    I do believe the numbers are smaller on factory ammo that the min and max for chambers. A new factory round is likely to be smaller than chamber min 1.630 by 0.000-0.004 thousandths. A headspace guage setup like Hornady's and a box of factory fresh ammo will bear that out. I use my Clymer headspace gages for reference when analyzing such things.
    I would fully expect most factory ammo to be less than max. It is fundamentally impossible to mass produce anything with exactly the same dimensions every time. There will always be variation. To reduce rejects, you set your nominal dimensions in the center of the tolerance band (in most cases anyway). That way if you overshoot or undershoot, you will still be within the acceptable range. There is a whole science dedicated to maximizing production and minimizing rejects by studying tolerance and adjusting the machinery as appropriate.
    My luck is so bad that if I bought a cemetery, people would stop dying.- Rodney Dangerfield

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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