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Thread: Confused as usual; .243 AI head space gauge

  1. #1
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    Confused as usual; .243 AI head space gauge

    Here's the scenario. I had two GO head space gauges made by Pacific Tool & Gauge in .243 AI & .22-250 AI. I have stub pieces cut from the barrels chambered with the same reamers for setting up my dies to properly minimally size brass. Both rifles have been shot quite a bit and were chambered by well known and respected gunsmiths. I cannot get the bolt to close on the .243 AI GO gauge in my rifle. Yes, I removed the firing pin to try. Did I screw up by not specifying that I have 40 degree shoulders? When I check the gauge with my stub piece vs. a piece of fire formed brass the dimensions are not even close. Any ideas or info. would be greatly appreciated

  2. #2
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    OK, I've spent a metric TON of time and money on the 243AI. I haven't used one for years but still have at least 7 barrels cut from 5 different reamers kicking around and I don't own a GO gauge. Never did.....

    What are you trying to establish here? The whole "AI" scenario is wildcat and personal discretion all the way with headspaces varying wildly ......and ALL OF THEM safe and workable within established parameters.

    I personally would never want ANY AI'd chamber to close on a GO gage because I want my fireform to be much tighter than any gage could allow.

    I order my normal gages cut and marked "-.006"

    let alone AI's....... I guess I'd probably go for "-.020" on an AI gage

  3. #3
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    Cool Confused still but there is hope

    Quote Originally Posted by alinwa View Post
    OK, I've spent a metric TON of time and money on the 243AI. I haven't used one for years but still have at least 7 barrels cut from 5 different reamers kicking around and I don't own a GO gauge. Never did.....

    What are you trying to establish here? The whole "AI" scenario is wildcat and personal discretion all the way with headspaces varying wildly ......and ALL OF THEM safe and workable within established parameters.

    I personally would never want ANY AI'd chamber to close on a GO gage because I want my fireform to be much tighter than any gage could allow.

    I order my normal gages cut and marked "-.006"

    let alone AI's....... I guess I'd probably go for "-.020" on an AI gage
    Al, thanks for responding but baby steps in your explanation please. I am not officially listed as mentally challenged but it could be argued other wise. I do respect your opinion but you are way ahead of me in knowledge and experience. This might make things clearer. Bear in mind these are all switch barrel rigs.

    1) I have a switch barrel Savage single shot with several different barrels. Several of the barrels were chambered using my reamer made by Manson with a .270 neck. I want to ensure that when I screw those barrels on that I have the proper head space.
    2) I also have several other barrels chambered with the same reamer for my Borden Alpine by Borden. Needless to say I know these to be correct and I am not concerned with them. It is the Savage, with the adjustable head space, that is my concern hence my reason for wanting HS gauges.
    3) The brass that I have been shooting in my Alpine is minimally resized (.001) every time using the stub piece Jim provided that is reamed with my reamer.
    4) Could I use the re-sized brass from the Borden rig to establish head space in the Savage? This appears to be a possible acceptable method from what I have read.

    Bear in mind I ordered this gauge as a GO gauge and was expecting my bolt to close on it.

    Again, anything you can provide to lead me out of the abyss would be greatly appreciated.

  4. #4
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    I always thought that when you did a AI chamber, you simply used the Head Space Gage for the parent cartridge. After all, the first thing you have to do is fire a regular 243 in that chamber to create the AI cartridge.

  5. #5
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    Quote Originally Posted by chino69 View Post
    4) Could I use the re-sized brass from the Borden rig to establish head space in the Savage?

    Yes. Turn it in to "firm hand tight" and when you tighten the nut it'll back out to just a bit looser the headspace.

    I too have a Borden with one of them home'ade bump dies.

  6. #6
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    .243 AI head space

    Quote Originally Posted by alinwa View Post
    Yes. Turn it in to "firm hand tight" and when you tighten the nut it'll back out to just a bit looser the headspace.

    I too have a Borden with one of them home'ade bump dies.
    Thanks Al. That's the answer I was seeking.

  7. #7
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    .243 head space

    Quote Originally Posted by jackie schmidt View Post
    I always thought that when you did a AI chamber, you simply used the Head Space Gage for the parent cartridge. After all, the first thing you have to do is fire a regular 243 in that chamber to create the AI cartridge.
    Far be it for me to be an expert on this subject but I do know that a properly chambered AI will have a .004 crush fit on the parent cartridge brass before it is fireformed to the AI chamber. From what I have read the standard .243 hs gauge will actually serve as a NO GO gauge in an AI chamber. I still can't wrap my head around that one, being a slow learner and all, but that is the general consensus. You retired yet Jackie?

  8. #8
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    An AI go gauge is normally .004" shorter than the parent case go gauge at the neck/shoulder junction. This .004" is supposed to create a crush on the parent brass so it stays put when it is fire formed, so you can use normal brass. I have found that .004" isn't always right, it all depends on the brass thickness. FYI the PPC made from 220 Russian is the same way.

    Some people have a conniption fit if you were to run a AI reamer in up to that neck/shoulder junction, cause you don't have the crush fit on the bolt close. "What if you ever sold it......."? Simple fire forming 101. Usually, a long seated bullet with a lot of neck tension does fine holding the brass in place. Or, sizing up the neck then carefully sizing down the neck to get a shoulder which is relatively same crush on bolt close.

    Some won't agree with this.

    People were typing the same time as me. Disregard.

  9. #9
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    AI chamber

    Quote Originally Posted by Wayne Shaw View Post
    An AI go gauge is normally .004" shorter than the parent case go gauge at the neck/shoulder junction. This .004" is supposed to create a crush on the parent brass so it stays put when it is fire formed, so you can use normal brass. I have found that .004" isn't always right, it all depends on the brass thickness. FYI the PPC made from 220 Russian is the same way.

    Some people have a conniption fit if you were to run a AI reamer in up to that neck/shoulder junction, cause you don't have the crush fit on the bolt close. "What if you ever sold it......."? Simple fire forming 101. Usually, a long seated bullet with a lot of neck tension does fine holding the brass in place. Or, sizing up the neck then carefully sizing down the neck to get a shoulder which is relatively same crush on bolt close.

    Some won't agree with this.

    People were typing the same time as me. Disregard.
    Wayne, all of my brand new .243 brass has a crush fit until it is fireformed. I seat the bullets into the lands and use a max. load for the parent cartridge which provides nice sharp shoulders.

  10. #10
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    I fire formed a bunch of 257 AI brass. Most were OK, but there was thin brass where the bolt closed easy, and then some thick brass where I had a lot of effort to close the bolt. Don't recall the brand of brass now.

  11. #11
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    Quote Originally Posted by jackie schmidt View Post
    I always thought that when you did a AI chamber, you simply used the Head Space Gage for the parent cartridge. After all, the first thing you have to do is fire a regular 243 in that chamber to create the AI cartridge.

    That is essentially true.... the plan at least...... "MINUS .004 of course.

    But in the real world brass varies. Gages vary. N/S radii vary

    If I were chambering an AI today I'd do it the same way I do everything else, buy a hundred or two cases from the same lot and chamber to a tight crush on those cases. And if the cases ran too wild, I'd plan on re-setting the shoulders on every case to make them consistent.

    Doing it this way I have trouble finding much use for gages at all anymore. For instance thru the years I've 6MM BR cases that vary by .004, 220R cases aren't much better. THEN, you start mixing in Win/PMC/RWS/Peterson/Hornady/Norma/Starline/Quality etc etc........ stuff is all over the map.

  12. #12
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    One thing a lot of people don't realize is that the AI setup allows for A LOT of latitude and still call it "crush fit"

    Lay a .243 case on the table and trace around it.

    Now lay a fireformed 243AI case, trace around it.

    See what I mean??? I'm dead serious about the "20 thousandths"

  13. #13
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    crush fit on new brass

    Quote Originally Posted by alinwa View Post
    That is essentially true.... the plan at least...... "MINUS .004 of course.

    But in the real world brass varies. Gages vary. N/S radii vary

    If I were chambering an AI today I'd do it the same way I do everything else, buy a hundred or two cases from the same lot and chamber to a tight crush on those cases. And if the cases ran too wild, I'd plan on re-setting the shoulders on every case to make them consistent.

    Doing it this way I have trouble finding much use for gages at all anymore. For instance thru the years I've 6MM BR cases that vary by .004, 220R cases aren't much better. THEN, you start mixing in Win/PMC/RWS/Peterson/Hornady/Norma/Starline/Quality etc etc........ stuff is all over the map.
    Actually Al I followed your recommendation(s) several years ago in setting up a .308 barrel on my single shot Savage. I bought 100 rds. of Lapua brass and screwed the barrel in until there was a snug fit on the brass. When I tightened the barrel nut it gave me minimal headspace. I like that method because once the brass is fireformed it is a matched set with that chamber.

  14. #14
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    Quote Originally Posted by chino69 View Post
    Actually Al I followed your recommendation(s) several years ago in setting up a .308 barrel on my single shot Savage. I bought 100 rds. of Lapua brass and screwed the barrel in until there was a snug fit on the brass. When I tightened the barrel nut it gave me minimal headspace. I like that method because once the brass is fireformed it is a matched set with that chamber.
    Well, yeahh, "matched set" is part of it BUT,

    it's even cooler than that. It's not only "matched".... it's STRAIGHT which absolutimally cannot be accomplished any other way (altho this statement will promote arguments in any room, anywhere LOL! Always by guys who have no clue how to tell the difference)

  15. #15
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    Like Al I have more 243AI reamers than I need. Different neck diameters and throats. I started with a 243 AI go gage or so I thought. That didn't last long as customers started complaining about varying chamber lengths. I said REALLY WTF. Then it slowly seeped into my hard head. I was using a shortened 243 Win gage. Varying neck diameters were causing different length chambers. I had 40 degree gages made for all my AI chambers. Lesson learned.

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