At some point you just give up. Everybody is wrong but me.
Confused as usual; .243 AI head space gauge
- Thread starter chino69
- Start date
At some point you just give up. Everybody is wrong but me.
well, no..... I know plenty of people who can chamber to a classic a crush-fit AI chamber.
I useta' be a huge Ackley fan, I own a rifle built by him, with the original pamphlet. From back when he marked his barrels using a vibratory tool.
OP, I went thru my gauges and have a PTG 243ai go gauge if you need measurements.
Pidgeon? I’ll take that as a complement
We are talking about saami specs and not personal notes written on a grease covered napkin on the shop bench, correct? I’ll do the math today when I get done out in the shop. I’ve been busy trying to finish my first rifle build. The barrel is clamped in the vise for precise reaming with my dewalt 20v. Can’t be too accurate, I always say.
If I am wrong, I will call saami and let them know the typos in their manual and issue a remorseful, heartfelt apology to you gentlemen. I have really enjoyed this
Pidgeon? I’ll take that as a complement
We are talking about saami specs and not personal notes written on a grease covered napkin on the shop bench, correct? I’ll do the math today when I get done out in the shop. I’ve been busy trying to finish my first rifle build. The barrel is clamped in the vise for precise reaming with my dewalt 20v. Can’t be too accurate, I always say.
If I am wrong, I will call saami and let them know the typos in their manual and issue a remorseful, heartfelt apology to you gentlemen. I have really enjoyed this
I hope this doesn't just make things worse but I'll try ONE MORE TIME........ for the poor folks who believe that because something's been written down, it's "right."
Please note, to anyone out there who really cares to U N D E R S T A N D stuff, this again is just one version of history.
I BUILD stuff, stuff that works.
I don't read about it and try choose "who's right."
https://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/
Please note, to anyone out there who really cares to U N D E R S T A N D stuff, this again is just one version of history.
I BUILD stuff, stuff that works.
I don't read about it and try choose "who's right."
https://gunsmithtalk.wordpress.com/2010/01/13/280-ackley-improved-alert/
mwezell
Mike Ezell
I’ll bite! I just can’t help myself
Take a look at those gauges in the pic on the article. Do both noses look to end with a datum diameter of .375” ? Also, the author of that article mentions a headspace of 2.154 on the parent 280 case. No idea where he is getting that since it isn’t on the saami spec sheet.
Ahhh! Cowabunga Dude!! He's getting closer! The .375 datum of a 280 Rem gots nuttin to do wiff it, per se. The gage I used to chamber my barrel, that headspaces near perfectly with BOTH gages, was cut .004" (not .040) shorter than what a 280 rem go gage would allow the bolt to close on. That's how Ackley designed it to work. My rifle headspaces mightnear purrfect with both the 280 rem go gage protruding .004 and the bolt closes with a light feel on a SAAMI 280 AI gage. That is a fact that you can take to the bank. That 280 rem gage contacts the chamber where Ackley wanted it to...not SAAMI, near the neck shoulder junction. There weren't no SAAMI involved in how I chambered it. BUT, along comes SAAMI and a gage that fits!!! Along with a lot of confusion.
Forget SAAMI and the .280AI for a minute. How would you go about chambering the op's .243AI? It works the same way but without the confusion. Now, there are those that chamber them a little longer and a little shorter. I don't like longer as I don't think it can stop the case from being driven forward with pin strike. That's why Al and some others use a little more crush...to prevent case stretch from the web area. It works and it's RIGHT because there is no SAAMI involved to say otherwise about it, but it ain't a true Ackley, either.
mwezell
Mike Ezell
Al, scroll down a little on your link to where it says "Updated Information." Click there or here it is again.
https://gunsmithtalk.wordpress.com/2012/07/17/280-ackley-improved-emperical-headspace-test/
Easy trig could find you a new datum point that would work with both cartridges, however, saami uses .375 as the datum and that is the published, accepted chambering spec. If you want to do it differently than saami, more power to you, but don’t tell people they are wrong for doing it the saami way. Good luck in court if something happens to a customer’s rifle and you didn’t use saami specs. I prefer to use accepted saami specs. Using saami specs, the answer to the op’s question is “the headspace is farther from the base on the ackley then is is on the parent case.”
I read your link a couple times and see how the nose on the parent gauge would hit since the shoulder/neck junction is shorter for the ackley. In the instance of a 243 ackley, the accepted method is measuring from base to .400” and it should be about .035” longer than a parent 243.
Been fun gentlemen. I need to hit the chamber with some 80grit ao paper to get the scratches out. Not sure why the reamer leaves scratches ..... I’m holding the drill true....
I read your link a couple times and see how the nose on the parent gauge would hit since the shoulder/neck junction is shorter for the ackley. In the instance of a 243 ackley, the accepted method is measuring from base to .400” and it should be about .035” longer than a parent 243.
Been fun gentlemen. I need to hit the chamber with some 80grit ao paper to get the scratches out. Not sure why the reamer leaves scratches ..... I’m holding the drill true....
mwezell
Mike Ezell
One more comment and I'm outta this one. I found the new Norma 280 Rem brass and the new, still loaded Nosler 280 AI factory loaded round. I tried several times to get a pic that would show what I can see in my hand to no avail. That being a faint line in the dykem near the neck shoulder junction after chambering both. They have both been chambered multiple times for the same reason as this discussion, when showing others.
I also chambered my saami 280 ai go gage in the gun with very light feel, so I put a single piece of cellophane tape on the back of the gage and it will not close. This barrel was chamered for a .004 protrusion of the std 280 rem go gage...before there was any such thing as a saami 280 ai.
I then measured the new nosler saami round with a 375 comparator and did the same with a fired piece of brass from my chamber. At this point, the new nosler and the old brass were within .002", the new case being the shorter of the two. I no longer have a go gage for a std 280 rem or I'd have checked with it too. I also made a comparator insert with a .3175 id and the fired case at this location measured .006" shorter than the new norma 280 rem case at the same spot. Remember the .004" crush.
All that needs to be done to see that the two are in fact not different, is to cut a barrel stub and measure over it with both gages, which is pretty much what the link and video I posted earlier is doing.
I've done all I can do and more than I should have to help clarify this. If ya can't believe what I've said, and ya can't believe the video, and the word of those that made it...I guess ya should get both gages and a reamer, and try it for yourself. I hope you will and will report your findings after doing just that.
I also chambered my saami 280 ai go gage in the gun with very light feel, so I put a single piece of cellophane tape on the back of the gage and it will not close. This barrel was chamered for a .004 protrusion of the std 280 rem go gage...before there was any such thing as a saami 280 ai.
I then measured the new nosler saami round with a 375 comparator and did the same with a fired piece of brass from my chamber. At this point, the new nosler and the old brass were within .002", the new case being the shorter of the two. I no longer have a go gage for a std 280 rem or I'd have checked with it too. I also made a comparator insert with a .3175 id and the fired case at this location measured .006" shorter than the new norma 280 rem case at the same spot. Remember the .004" crush.
All that needs to be done to see that the two are in fact not different, is to cut a barrel stub and measure over it with both gages, which is pretty much what the link and video I posted earlier is doing.
I've done all I can do and more than I should have to help clarify this. If ya can't believe what I've said, and ya can't believe the video, and the word of those that made it...I guess ya should get both gages and a reamer, and try it for yourself. I hope you will and will report your findings after doing just that.
Wilbur, normally I would agree, but this is important to understand the basics of headspace to keep people safe.
As luck would have it, I am chambering a 7-08AI today. I will use my 7-08ai gauges but will also throw in some 308 gauges to verify the differences between the two. Brass and loaded ammo is NO WAY to verify headspace.
Again ....
1. HEADSPACE has ZERO to do with neck/shoulder junction! Very important! (Unless talking about traditional ackley NOT saami)
2. You CANNOT use headspace gauges that have different shoulder angles than the cartridge you are chambering. (Unless using traditional ackley methods)
3. 280ai is the only saami spec AI chamber. That is why the 280 to 280ai comparison is the best to use for understanding
I’ll post honest pics today when I’m done. Trying Jackie’s crown style on this one.
As luck would have it, I am chambering a 7-08AI today. I will use my 7-08ai gauges but will also throw in some 308 gauges to verify the differences between the two. Brass and loaded ammo is NO WAY to verify headspace.
Again ....
1. HEADSPACE has ZERO to do with neck/shoulder junction! Very important! (Unless talking about traditional ackley NOT saami)
2. You CANNOT use headspace gauges that have different shoulder angles than the cartridge you are chambering. (Unless using traditional ackley methods)
3. 280ai is the only saami spec AI chamber. That is why the 280 to 280ai comparison is the best to use for understanding
I’ll post honest pics today when I’m done. Trying Jackie’s crown style on this one.
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mwezell
Mike Ezell
Results?
Most AI cases also remove most of the taper from the case body.
There is just enough to allow for chamber entry and extraction.
That gets a decent share of the increased case volume.
7-08 ai turned out fine. Haven’t shot it yet though to see if I did my part.
I decided to drop the whole ackley thing. I don’t like when threads get that heated. Takes the fun away from the forum. Traditional ackley supporters will always use the neck/shoulder junction to headspace the 280ai rather than using the parameters of the saami specified cartridge. Other cartridges, without saami specs, I get. Either way, rifle turned out fine, thank you.
I decided to drop the whole ackley thing. I don’t like when threads get that heated. Takes the fun away from the forum. Traditional ackley supporters will always use the neck/shoulder junction to headspace the 280ai rather than using the parameters of the saami specified cartridge. Other cartridges, without saami specs, I get. Either way, rifle turned out fine, thank you.
L-O-frickin'-ELL!!!!
Well, that and "my argument wasn't making any sense" .........
"I can explain it to you"
"But I cain't understand it for you!"
"But I cain't understand it for you!"
L-O-frickin'-ELL!!!!
Well, that and "my argument wasn't making any sense" .........
"I can explain it to you"
"But I cain't understand it for you!"
My argument : use the datum and headspace length on the saami specs, cause it is approved.
Does that make sense to you now???
I was walking away peacefully and you hit my in the back with a proverbial snowball
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My argument : use the datum and headspace length on the saami specs, cause it is approved.
Does that make sense to you now???
I was walking away peacefully and you hit my in the back with a proverbial snowball
You are probably on the wrong forum if you want to argue saami specs. I don't think that is the most important thing accuracy people worry about. Although I am sorry to find out JGS doesn't know what they are doing. I'm pretty sure on a 6.5x08AI reamer, they send a 308 -.004 go gage.
.................
I was walking away peacefully and you hit my in the back with a proverbial snowball
LUVvittt......
wimp
OK, and MY argument is, an irrelevant number regarding FIRED datum is completely useless in the real world.
Generally speaking, "headspace gages" are used as chambering tools and chambering to a SAAMI spec by "comparing numbers" as in this case just makes it confusing. The gage will probably never be used to "check headspace" on a fired case.
In the real world, we use stuff that makes good product
LUVvittt......
wimp
OK, and MY argument is, an irrelevant number regarding FIRED datum is completely useless in the real world.
Generally speaking, "headspace gages" are used as chambering tools and chambering to a SAAMI spec by "comparing numbers" as in this case just makes it confusing. The gage will probably never be used to "check headspace" on a fired case.
In the real world, we use stuff that makes good product
Wimp??? Ha! Now this is getting good. If we were face to face, ma’am, I guarantee you wouldn’t call me a wimp. That aside, you can argue saami all day, but it is the accepted spec. No confusion on the 280 ai saami. Just with traditional ackley methods. If you want to hold to the tradition, fine. But you can’t discount saami specs.
I’ll stay, but thanks. Had some good info I got from jgs last week on ai, but I won’t waste my time.
ooohhh you don't react so well to flippin' thee chit eh..... well, sorry I stepped into your bowl Big Guy
(((BTW that's a "sticks tongue out" emoji..... didn't mean to ruffle you)))
..........Crawls back under rock, tongue firmly IN.........