Headspace measurements

[eldon]

I have looked around the web and can't find any site that tells you the saami specs on headspace for different calibres.

Anybody know of a a site?

 

If not can somebody tell me what the measurements are for a .222 you know the x length at y diameter bit.

 

Cheers.

[Redfox]

The SAAMI case dimensions are given in nearly every reloading book, the chamber dimensions are such that the case will chamber reliably at those dimensions, each manufacturer has his own ideas on this but normally you can get a std dimension fom the use of the go/nogo gauges. Wonder why you want to know?

Redfox

[eldon]

I was just going to knock up a gauge for full sizing so I just knock the shoulder back a touch rather than the full distance.

Without these measurements I can't do it.

 

In my books the cartridges sizes are there but not the headspace dimensions.

[Andrew]

I am vague as to what a gage would tell you that would be of any practical value. There is nothing that says your rifle is exactly to SAMMI spec. The headspace could be a couple of thousandths one way or the other. If you'd like a fairly uniform method of accomplishing the same thing, I would share my method.

 

Since FL sizing is accomplished by screwing the FL die down to the shell holder, what I did was to use a flat, engineers leaf-style feeler gage between the shell holder and the FL die, choosing the amount of "back off" I wanted from Fully Resized. It worked well and was adjustable and very repeatable provided I used the same press and shell holder.

 

That's what worked for me.~Andrew

[Redfox]

Like Andrew says a go gauge would not help you and they are readily available,.

Just buy the ( stoney point) Hornady head space kit, here : https://www.hornady.com/shop/?ps_session=1d...40ac87ed0c3ee5b

Best 20 quid you will spend and you can accurately measure youre fired cases and set the FL sizing die to push back the shoulder just .002" which is perfect and the cases last as well as neck sizing. You will of course need a reasonable digital caliper as well.

You can order direct from Hornady or just get someone like SYSS ( Baldie, or WSM )to get it for you, a bob or two more but right on the doorstep as it were.

Redfox

[eldon]

Thanks andrew for your method.

 

Basically redfox youve got what I was doing and with having the facility I was going to quickly knock up what the hornady is.

 

£20 don't forget I'm a yorkshire man

 

I have already done this for the 308 and find it's a handy little device.

Without the diameter for the 222 I cant do it for this calibre.

 

I also have similar items to measure OAL to the ogive and I can do this for the 222 as the size is known.

 

Just need the diameter really, the length is not as important as its only a comparator.

[Ronin]

Paul

 

 

headspace is the measurement from the rear of the cartridge face to the front of the bolt face (in most "normal" rifles (it is a unique measurement and only found when you have the action and barrel separated, then one may measure front of bolt face to front of action face - this distance is the headspace)

 

In most cases the difference bettween a safe an unsafe chamber is about .004" (thats the difference in length bettween a Go and No Go Guage in most cartriges)

 

I think you may have asked the wrong question, do you not mean minimum SAAMI case dimensions?

[eldon]

Ronin I think your right.

 

Let me try again.

 

For my 308 I bored a piece of stainless to fit the case with a shoulder to a diameter of 0.400 ( thou) SAAMI spec whatever and used this for setting the full size die. By keeping the ends machined square and accurately measuring the length to shoulder you can also check your headspace from a fired case. I am measuring to half way ish down the taper/ shoulder.

 

What would be the diameter I should use for a .222? I would expect around 0.300''

 

Do's that make sense? I am not after a go- no go gauge.

[Andrew]

I hate to disagree but headspace for a bottle necked cartridge is, technically speaking, measured from the base of the cartridge (bolt face) to a spot about half way up the shoulder of the case. While this may (in a practical sense) show up in the area between the bolt face and the back end of the cartridge, that is not the actual measurement datum points. Only in a rimfire is that the headspace measurement.~Andrew

[Redfox]

Andrew is right, the measurement Ronin mentions is the "head clearance" subtle difference. The bushes are even cheaper for a set and you only buy one body ( or make it)they are the correct diameter for half way up the shoulder.

Yorkshiremen sometimes cut their own purse strings I would suggest this is one of them

Redfox

This explains it nicely, http://www.surplusrifle.com/shooting/headspace/index.asp

and this is the saami definition of clearance, "HEAD CLEARANCE

The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace. "

[Ronin]

My apologies

 

 

head clearance, headspace arghhhh!!

 

I was confusing myself with chambering depth, time for night off and beer

[eldon]

Now we know what I am asking is someone going to offer me a measurement?

 

I will have to cut the purse strings as I have got them in a Knot

[silentsoulsleave308holes]

about 7" give or take a few 10mm

[eldon]

Hi redfox, just followed your earlier link and the answer appears to be 0.330''.

Thanks.

 

I owe you a pint .............................................. to share.

 

As always good forum full of info. Thanks

[Redfox]

No problem mate glad to help. Silent your looking down at the wrong cartridge and making me jealous.

Redfox

[eldon]

For the benefit of others

The short answer to what I was asking is here, cheers redfox

 

 

http://www.hornady.com/shop/shop_image/pro...auge_chart1.jpg

[JR__]

For the benefit of others

The short answer to what I was asking is here, cheers redfox

http://www.hornady.com/shop/shop_image/pro...auge_chart1.jpg

 

222 Remington--1.294” go--1.297” no go--1.300” field

222 Remington Magnum--1.493” go--1.496” no go--1.499” field

 

JR

[eldon]

Cheers JR, added bonus.

[Andrew]

My apologies

head clearance, headspace arghhhh!!

 

I was confusing myself with chambering depth, time for night off and beer

 

I knew what you were saying. If you chamber a rifle with too much distance between the bolt face and the rear of the cartridge you get excessive headspace. That's the practical aspect of it.

 

In reality, once the chamber is cut (provided it is within safe tolerances) and your brass has all been fired, the SAAMI dimensions are moot. Your headspace measurement is what it is from then on. I have a very accurate Pattern 1914 Enfield .303 that which will stretch brass to ruination if I don't snug the bullet into the rifling on the first loading. By doing so I support the brass on both ends and safely move the shoulder forward, compensating for the screwed headspace. UI neck size from then on, of course.

 

Likewise, I never, ever, fire factory ammo in an Ackley Improved chamber unless I did the chambering myself. I always start with virgin brass and the bullet nudging the rifling.~Andrew

[eldon]

Likewise, I never, ever, fire factory ammo in an Ackley Improved chamber unless I did the chambering myself. I always start with virgin brass and the bullet nudging the rifling.~Andrew

 

Interesting point Andrew so would you fire form on a new calibre using the bottom book figures to avoid over pressure.

Thought about a 243 ackley in the past but not sure I can be bothered messing with the brass.

 

Wonder why nobody, or have or is there made factory ackley brass in the common calibres (243 etc).

[Ronin]

Paul

 

.243 AI bras is readily available, just place standard 243 cartridge in a 243 AI chamber and pull the trigger so long as your bullet is out to the land (pushing the case back to the bolt face) you should have well formed brass every time (it works for me in my own 22-250 AI)

 

I also have a 243 AI reamer throated for 105 bullets.........

[Andrew]

I would fire a sane load. Not max, as I never load such, but healthy. Remember, the pressure drops as the shoulder blows forward. It takes very little pressure to pop out the shoulder, really.

 

I don't care for the Improved chambers. I have built many for others, and currently own one just because the rifle it's in is rather neat. I have owned Ack IMP chamberings that wouldn't generate any appreciable extra velocity without spiking pressures beyond a reasonable level. I have a 30-06 IMP now that caps off at standard 30-06 velocities unless it is used with the slowest powders and then I can improve on the top end velocities for that particular powder. My first Ackley Imp gun was a 220 AI Swift I bought about 25 year ago. I have owned, and chambered for, a few others in the years since but I don't seek them out. Other than the 25 Ackley Imp Krag, I have never chambered one for myself, either.

 

The Ackley Improved chamberings have never been standardized because frankly, there is little use for them. What an Ackley chambering does can be done by other calibers. Adding to the problem of marketing is that there are/were a lot of different chambers professing to be Ackley Improved but who knows what the actual chamber dimensions are? If a company markets a "XXX Ackley Improved" round and it blows up in a rifle so marked... well, too much like a legal headache.

 

When I was a young man in New Mexico, I used to correspond with PO Ackley quite a bit. He was right up the road from me a couple hundred miles and when he was the reloading editor for Shooting Times Magazine we got into a discussion about case forming in one issue: He said X, I said Y. We ended up writing back and forth on that and other subjects for a little better than a year. During that time, he mentioned that the "Improved" chamberings were mostly devised as a way to make use of the slow, surplus powder that was flooding the markets in the 50's and 60's. The shoulder was blown out to add powder capacity and thereby increase pressures with these slow powders; powders which otherwise wouldn't generate enough useful pressures in the standard case. There was also the theory that this shoulder caused a more complete burn in the chamber, adding to the pressure.

 

I don't think Ackley would bother with the Improved chamberings today, either. With the vast array of powders and chamberings available today there would be little use. JMHO~Andrew

[Ronin]

Andrew

 

I think there are some limited benefits with the increased shoulder angle in some, but not all AI cases.

 

The 22-250 and 243 for example seem to resond better than the larger cases (or so I have read)

 

I have the 22-250 AI and used to own a standard 22-250, I opted for the larger volume case to enable me to use heavy for calibre bullets (75g) and in my application the case design works very well indeed. I could have gone for a 223, but didnt want to mess with a specific bolt faced rifle and small primers (at the time anyway)

 

I have no desire to send them to the target as fast as possible, I want consistant accuracy, this is delivered in bucket loads. AI, have their problems, such as poor feeding - I could alter the ranmp angle on my rifles action but as this would be a once only never reverse fix I think I will decline.....

 

The other problem is actually one of the "benefits" - that being percieved reduced pressure, when in reality the more powder one fits into a case the higher the pressure, so long as you are aware of this and respect the fact that pressures may be higher again it is something to always have in the back of your mind when loading.

 

What I have found is the fact that my own rifle despite having several thousand rounds through it is showing no firecracking at the throat, there must be something in the fact that the gases "meet" within the case neck rather than at the throat by the design of the shoulder angle. Again this is my rifle, I dont know about others who have AI chamberings - every one is unique I guess

 

Interesting subject though - even if I am twenty / maybe thirty years behind you

[JR__]

I would fire a sane load. Not max, as I never load such, but healthy. Remember, the pressure drops as the shoulder blows forward. It takes very little pressure to pop out the shoulder, really.

 

I don't care for the Improved chambers. I have built many for others, and currently own one just because the rifle it's in is rather neat. I have owned Ack IMP chamberings that wouldn't generate any appreciable extra velocity without spiking pressures beyond a reasonable level. I have a 30-06 IMP now that caps off at standard 30-06 velocities unless it is used with the slowest powders and then I can improve on the top end velocities for that particular powder. My first Ackley Imp gun was a 220 AI Swift I bought about 25 year ago. I have owned, and chambered for, a few others in the years since but I don't seek them out. Other than the 25 Ackley Imp Krag, I have never chambered one for myself, either.

 

The Ackley Improved chamberings have never been standardized because frankly, there is little use for them. What an Ackley chambering does can be done by other calibers. Adding to the problem of marketing is that there are/were a lot of different chambers professing to be Ackley Improved but who knows what the actual chamber dimensions are? If a company markets a "XXX Ackley Improved" round and it blows up in a rifle so marked... well, too much like a legal headache.

 

When I was a young man in New Mexico, I used to correspond with PO Ackley quite a bit. He was right up the road from me a couple hundred miles and when he was the reloading editor for Shooting Times Magazine we got into a discussion about case forming in one issue: He said X, I said Y. We ended up writing back and forth on that and other subjects for a little better than a year. During that time, he mentioned that the "Improved" chamberings were mostly devised as a way to make use of the slow, surplus powder that was flooding the markets in the 50's and 60's. The shoulder was blown out to add powder capacity and thereby increase pressures with these slow powders; powders which otherwise wouldn't generate enough useful pressures in the standard case. There was also the theory that this shoulder caused a more complete burn in the chamber, adding to the pressure.

 

I don't think Ackley would bother with the Improved chamberings today, either. With the vast array of powders and chamberings available today there would be little use. JMHO~Andrew

 

Oh I think he would. PO was the type of guy that would do it just to do it. The improved shoulder not only bumps up powder capacity, but that design often leads to less case stretch at the nether regions, beneficial to the handloader. I'd have to disagree it was purely to generate pressures, though that is a good thing with today's variety and choice.. There are of course, many AI 'improvements' that do nowt...But there are some which show significant plus, one is the 30-06 ai..Much better cartridge than the original..

 

JR

[Andrew]

Oh I think he would. PO was the type of guy that would do it just to do it. The improved shoulder not only bumps up powder capacity, but that design often leads to less case stretch at the nether regions, beneficial to the handloader. I'd have to disagree it was purely to generate pressures, though that is a good thing with today's variety and choice.. There are of course, many AI 'improvements' that do nowt...But there are some which show significant plus, one is the 30-06 ai..Much better cartridge than the original..

 

JR

 

JR:

I'm just telling you what he wrote to me. If you know otherwise, I'm happy for you. I have a 30-06 IMP and it will not get generate extra velocity with any but the slower varieties of powder. With quicker powders you get no added velocity without increasing powder and pressures appreciably.

 

Additionally, I my experiences with various Improved cartridges show (with a few exceptions: 220 Swift and 25 Krag notably) no particular resistance to case stretching that simple neck-sizing of the standard round couldn't accomplish.

 

To each his own, but to me, they aren't worth the grief. ~Andrew