7MM-08 Ackley Go Gauge
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Edd
Gold $$ Contributor
The short answer is no.
A std go gauge will contact the improved chamber at the neck shoulder junction. The neck diameter and the radius of the junction will determine the diameter of the contact point. That diameter will determine what the gauge needs to be the correct length.
If you are loading your ammo, you can size it to fit your chamber so headspace isn't as critical.
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shortgrass
Silver $$ Contributor
I am always more concerned with the No-Go side of chambering a AI. If the chamber is too long, the brass will stretch at the head to fill the chamber when fired. When chamber is of the proper length, the cartridge will have an 'interference fit', being 'trapped' between the bolt face and the neck/shoulder junction in the chamber, forcing the case stretch to AI to occur at the shoulder end of the brass. Stretch at the head weakens the cartridge case in the wrong area! There's a good write-up on Manson reamers we site concerning AI chambering. No need to make a simple task complicated.
Chamber the barrel until the bolt closes about halfway on a standard 7mm-08 go guage, Works like a "Chimp"
You should feel a slight resistance when you close the bolt on virgin brass.
Understood, and grinding .004" off a gauge is not complicated.
The question is " Can the accepted point of contact using a gauge with a 20 deg shoulder for no go be used for go"?
I may just break down and buy a .308 AI Go Gauge, but I'm in a time constraint and can't wrap my head around why it wont work. But befor I scrap a Go Gauge I thought Id ask.
If you are NOT rechambering a barrel, And you are starting with a blank, Then using the standard go-gauge as a no-go is an accepted way of doing it and will work fine.
If rechambering, You should get the proper gauge.
If rechambering, You should get the proper gauge.
shortgrass
Silver $$ Contributor
I don't know! I've been chambering AIs for over 30yrs, never needed a Go gauge. The only AI I have gauges for is the SAAMI .280AI
I think Ackley should have termed it differently. It's wrong to call anything made for a different shoulder angle a "gauge". The AI concept is to change the shoulder angle of the chamber. A proper "gauge" for this new chamber would have that new angle. What Ackley was going for was a way to judge the chamber depth necessary for a new case to set firmly enough that it would fire and form to the new chamber. If the parent case go gauge is just tight enough, the case should also be tight enough for the fire forming.
AckleymanII
Gold $$ Contributor
For my own rifles, I really detest brass stretching, and work to avoid it at all costs.
Here is what I do for my own purposes. I buy 100 new pieces of brass of the brand that I want to use. I will use a 33 or 35 caliber ogive gauge and using this gauge, will measure the "headspace" length of 25 or so cases, write the length on the outside of the cases with a sharpie.
Within 25 cases, you will be able to determine what is the shortest headspace length of the batch, but if you are killing time, measure and record all 100.
I like to use the shortest case of the bunch as a headspace gauge or close to it. I like to feel slight resistance on the bolt closing. With the longer cases, I will run them through a full length sizer, just barely bumping the shoulder back. I re lube the bolt lugs every 25 rounds during fire forming. Using this method, you will never loose a case from head seperations due to case stretching.
From past experience, I can tell you that cases may vary as much as .010 over a lot number depending on the brand of brass, etc. I reduced the headspace on one 22/250 AI by .025 as that lot of Rem brass was all over the map on new brass. I bumped back the shoulder to accommodate the short headspace, and never had a problem later on.
OP's question on shaving .004 off a go gauge is a good thinking.
Question: What has the longer headspace length, a go gauge or a No go gauge? Enough said.
Here is what I do for my own purposes. I buy 100 new pieces of brass of the brand that I want to use. I will use a 33 or 35 caliber ogive gauge and using this gauge, will measure the "headspace" length of 25 or so cases, write the length on the outside of the cases with a sharpie.
Within 25 cases, you will be able to determine what is the shortest headspace length of the batch, but if you are killing time, measure and record all 100.
I like to use the shortest case of the bunch as a headspace gauge or close to it. I like to feel slight resistance on the bolt closing. With the longer cases, I will run them through a full length sizer, just barely bumping the shoulder back. I re lube the bolt lugs every 25 rounds during fire forming. Using this method, you will never loose a case from head seperations due to case stretching.
From past experience, I can tell you that cases may vary as much as .010 over a lot number depending on the brand of brass, etc. I reduced the headspace on one 22/250 AI by .025 as that lot of Rem brass was all over the map on new brass. I bumped back the shoulder to accommodate the short headspace, and never had a problem later on.
OP's question on shaving .004 off a go gauge is a good thinking.
Question: What has the longer headspace length, a go gauge or a No go gauge? Enough said.
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Understood about the go gauge being no go, but the chamber will be no go until its .0005" to long then its to late. Unless you want to do that and re face the shoulder and breech face .004"
I have never had a problem, Sneak up on it, 5 tenths is probably not going to make or break it.
Thanks for the illustration and post, that is what I was thinking driving in this morning, it seemed that simple (to simple) and I had never seen it in print or discussed. I pushed the easy button and called Manson, they said yes, but I ordered a gauge anyway.
I see no reason why you can't, as long as you take it from the bottom of the gauge. For Ackleys, your std go becomes your no-go. But I also don't see why you'd need to. Just let the go protrude by .004". Being a wildcat, there's no absolute right or wrong. You just want a light crush fit on parent case when you chamber a round.
Yes. The gauges for the parent case would both contact the chamber at the same place, so that woun't change as long as you remove the .004 from the flat end of the hs gauge. Since there is no standard, you could use a case as a gauge, too. The biggest concern then is not having the chamber so short that you have to modify the die or shell holder in order to bump the shoulder back
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