Headspacing a 243 ai

[bushwackr]

Hello. Does a person need a 243 ai go no go to set it up?

[bsekf]

If the chamber was cut right, you can use a standard 243.

[bushwackr]

Well im seriously considering a criterion with the match throat and 8 twist for the heavy 6's from NSS. I talked to jim about them and im just trying to educate myself a little more.

[BillPa]

Well im seriously considering a criterion with the match throat and 8 twist for the heavy 6's from NSS. I talked to jim about them and im just trying to educate myself a little more.

Let allow me to educate you a bit more.

Go gauges are unique for rimless bottleneck improved cartridges. The parent cartridge's head clearance ( or the lack of it in this instance) in an improved chamber is established on the neck-shoulder junction with a .004"-.006" crush fit. Why the parent Go becomes the No GO for the improved, its .004" longer at the junction.

For example.....


The first gauge is the Go for 22-250 Improved, the second the GO for the 250 Improved and finally the GO and NO Go gauges I made for both the 22-250 and 250 Improved with a 40 degree shoulder. The first two are unique lengths and are not interchangeable.

A more graphic example ...


The first set is the 22-250 parent and it's improved counterpart. The second, the 250 Savage and it's improved sibling. The third are both wildcats, the 270-08 and it's improved version. We call it the 270-08 improved but in fact its not, its another wildcat.

Notice the ring on the neck shoulder junction of all three parent cartridges, where they contacted the chamber for firing-forming. If you look closely you'll see the difference in the placement of the junction of the parent and their improved versions. When the parent is fired the body diameter is increased from the web to the top of the shoulder, the shoulder angle increased to 40 degrees and the junction "pulled" back the .004"-.006" .


Clear as mud?.....

Bill

[Sixpointfivex55]

So you need AI Go gauge for the AI version but can use parent GO gauge as a No Go for the AI version?

[scope eye]

Correctamundo


Dean

[bushwackr]

does anyone have this in a criterion barrel, im getting confused I see there is a 243 ai with a 40deg shoulder and one with a 30deg shoulder

[bootsmcguire]

Criterion uses the 40* I am pretty sure. The 30* is a bit odd. Most AI chambers will be 40* for most cartridges.

Call Jim Briggs at Northland to confirm.

[bushwackr]

ok I will have to decide if I should jump on the 243ai or wait out the 6xc barrel decisions decisions

[Westcliffe01]

Mansonreamers.com typically make Ackley gauges and every time I called them, they had one in stock.

I personally would rather get the trur ackley gauge which makes full contact on the shoulder as opposed to using a regular gauge with a shim that makes a line contact and there is increased risk of damaging the chamber due to the high load concentration with the line contact. The Ackley gauge costs the same $30, so why not just buy the right gauge ? I have never needed to buy a no-go gauge, I just add a piece of thin paper behind the gauge and it is a no-go gauge and the bolt has never come close to closing on the paper after setting headspace with the go gauge without the paper.

[bootsmcguire]

I personally would rather get the trur ackley gauge which makes full contact on the shoulder as opposed to using a regular gauge with a shim that makes a line contact and there is increased risk of damaging the chamber due to the high load concentration with the line contact.

Not quite sure I understand what you are saying here. How can you shim a Regular Gauge and make it .004" shorter to even attempt to use it on a AI as a Go-Gauge?

[Westcliffe01]

A regular go-nogo gauge set has a nogo that is longer than the go gauge (go gauge = minimum head space whereas the nogo is the maximum allowable headspace. Field is even longer)

So when you use a "proper" ackley go gauge, it is used to set minimum head space and the addition of the paper lengthens the gauge to see if the bolt will still close. Its just a sanity check to be sure that you didn't make a mistake in setting the head space to the go gauge.

[243LPR]

The 30° version is usually called the 6mm SLR,it's still a 243 case. I don't see the point and would rather have a 40° Ackley and the benefits of it.

[bushwackr]

Ok perfect thats answered. OK that just from quick glancing the 6xc is just a shorter 243 ai

[scope eye]

Probably not as sexy as they others, but I would still go with they 243AI anyway.

Dean

[bootsmcguire]

A regular go-nogo gauge set has a nogo that is longer than the go gauge (go gauge = minimum head space whereas the nogo is the maximum allowable headspace. Field is even longer)

So when you use a "proper" ackley go gauge, it is used to set minimum head space and the addition of the paper lengthens the gauge to see if the bolt will still close. Its just a sanity check to be sure that you didn't make a mistake in setting the head space to the go gauge.

Ok, that I totally get. A go is minimum and no-go maximum. That is standard headspacing 101 so long as those gauges are for the chamber you are headspacing.

I personally would rather get the trur ackley gauge which makes full contact on the shoulder as opposed to using a regular gauge with a shim that makes a line contact and there is increased risk of damaging the chamber due to the high load concentration with the line contact.

What I don't get is how you could use a "regular" (non-AI) go gauge with a shim to headspace for an AI chamber. You said you wouldn't want to to use a "Regular Go gauge with a shim" for fear of damaging the chamber because of the smaller single point contact area that the standard gauge would have when inserted in a AI chamber.

If a Go-Gauge for the standard/parent chamber is the No-Go gauge for the Ackley Chamber, then in what combination would a person ever insert a Gauge for the regular/standard chamber with a shim when headspacing an Ackley chamber? The Parent/Standard/Regular Go-Gauge is already .004" longer than the Go-Gauge for the Ackley Chamber.

Not trying to be a jerk or anything, just not sure why a person would ever put a Standard Go-Gauge with a shim into a Ackley Chamber.

[bootsmcguire]

Probably not as sexy as they others, but I would still go with they 243AI anyway.

Dean

Yup, more room for more powder. But then if a person is thinking like that then better step up to a 6-06-AI or a 6-WSM or 6- Mach IV.

[bushwackr]

It should toss the 105, and 107 grainers faster

[sharpshooter]

I would NOT go with the 40 degree A.I. after I bore scoped a barrel the other day. The short neck concentrates the blast of erosion on the first .100" of throat and it is quite severe.
This must just be a phenomenon with the .243 because of the short neck. This barrel only had 80 rds through it, and it had washout erosion that extended down to the neck diameter. It only took .100 more depth to clean it up, but the depth of the erosion was something I'd never seen before. If you look at the turbulance point, it crosses at .060" below the case neck, but the point of blast impact is .090" ahead of the neck. I would suggest something with a longer neck and less harder on throats, such as the 6x47 Lapua or the 6 XC.

[Westcliffe01]

Plenty of people use the 243 AI in tractical competition and they should go about 1000 rounds. For the cost of a barrel per year, they offer nearly unbeatable ballistics with the 105gr VLD's. I only use mine for hunting and do my training with a 223 or 308 but I expect my 243 AI will still give me years of service.

bootsmcguire it looks like I miss spoke. Sounds like the "regular" 243 Win "go" gauge can be used as a "no go" gauge for the 243 AI. Seems someone a long time back gave me the advice if using a 243 Win gauge and using a shim, but that was totally off since the AI gauge needs to be shorter than the regular gauge. Possibly one could grind material (if equipped) off a 243 Win gauge to make a 243 AI gauge, but I figure that the #30 spent on the correct gauge is the right way to go.

[bootsmcguire]

bootsmcguire it looks like I miss spoke. Sounds like the "regular" 243 Win "go" gauge can be used as a "no go" gauge for the 243 AI. Seems someone a long time back gave me the advice if using a 243 Win gauge and using a shim, but that was totally off since the AI gauge needs to be shorter than the regular gauge. Possibly one could grind material (if equipped) off a 243 Win gauge to make a 243 AI gauge, but I figure that the #30 spent on the correct gauge is the right way to go.

Ok, gotcha. It happens. I just wanted to check it out and make sure my math was still good, and hate to see anyone take it like I did and not know and end up with excessive headspace and cause themselves potential trouble.

[chukarmandoo]

The 243 with the 30* shoulder is called 243 improved 30* and you can read about over on 6mm AR. com. Redding makes the dies for it. The 243 SLR is not fire formed. It is still a 30* shoulder but is formed with a die that only pushes the shoulder back thus making the neck longer. I have the 260 improved 30*. I would like to try the 260 SLR through. Seems like it would save barrel life by not having to fire form not to mention the savings on components for loading.