Hello, I have a new rifle sako trg 22 .308.
I use ammunition Norma Diamond lines 168gr
I also reload sierra hpbt 168, with case Norma

I am looking the measure of Factory Headspace Dimensions (CHAMBER HEADSPACE)

Can some owner of you give me their data?

Thanks a lot from SPAIN

I would suggest that you read your manual a few more times, as you are having some difficulty with terms.
Headspace is the distance from a datum line on the shoulder of the case to the bolt face. The chamber has a tolerance of (IIRC) 0.000 to +0.006 while the ammo has a tolerance of -0.001 to -.007.
You seem to be asking about the bullets OGIVE to the lands, or OGIVE to the bolt face, dimention, which is something else entirly.

Thank you Tailgunner.

I look for to know the headspace of my rifle camera.

I measure with my rcbs precision mic but http://glarp.atk.com/2004_IRL/RCBS/pages/Precision%20Mic.htm I am not sure that the data that im obtaing. In the manual of my rifle doesn't explain anything about this.

THE HEADSPACE

I'm trying to determinate the headspace with rcbs mic and i'm finding some difficulties.

1.- I choose some cases getting from NORMA DIAMOND LINE HPBT 168 grains after shooting with my sako trg22 .308 rifle and I measure the level (or the value) with the headspace nut.The result that I obtain is -0,002.Because of the "dimension A" is 1,6300 / 1,6400, I think then that the obtain result means that my headspace is 1,6280. But this data is lower than the ANSI / SAAMI measure. How it is possible?

2.- I choose some cartridges of NORMA DIAMOND LINE HPBT 168 grains and I measure its headspace , I obtain the level (or the value) -0,002. Is that possible? From the two previous facts I can deduce that my headspace is exctly the same as the ammunition measure before I shoot. I can not understand this.

FINDING
THE BEST BULLET SEATING DEPTH
====================================
I insert the freebore tool in the chamber and the value that I obtain is 0,32. But, What kind of unity is this? I suposse to understand that it is 0,32 + 1,6300 connecting to "dimension A" or not? If I measure with a caliper is 2,18 inch. Do you think that it is right? The OAL that I obtain is 2,850 inch, do you think is also correct or not?





thanks a lot

hello! (abajo en castellano)

i have a TRG42 in 338 lapua. i really don't understand what you are trying to do or what you are looking for? Are you only trying to find when the bullet is touching the lands?

Hola!

yo tengo un TRG42 en 338 lapua. De verdad no tengo muy claro lo que estas buscando? ¿tienes problema alguna? o ¿solamente quieres saber cuando la bala esta tocando las estrias?

cheers from Costa, Spain
saludos de la Costa Brava, España

Most likely is that your chamber is at "zero" (1.630), and the reason your seeing -002 on the fired brass is simply brass spring back.

For the bullet, use the "iron bullet" to establish where the .300 diameter is relative to the bolt face. When you measure the "iron bullet" that number is "Zero" for the land dimention, now measure a live round, the difference is the distance to the lands for that bullet . Your simply measuring the gap between the .300 diameter of the bullet and the .300 diameter of the lands. What ever you measure the OAL to be is, simply, what the OAL is when that bullet is that distance off the lands.
As the throat erodes, this distance will change (lenghten).
I'm working off memory, because it's been a number of years since I've played with my RCBS Precision Mic.

quote:

Most likely is that your chamber is at "zero" (1.630), and the reason your seeing -002 on the fired brass is simply brass spring back.

Tailgunner, what you said about springback is true.

But I wouldn't trust the RCBS case gage to give an accurate 'dimensional measurement' of headspace. Headspace gages should be used for that purpose.

I'm not knocking the RCBS case gage. It is an excellent tool to set your sizing dies properly. But I wouldn't use it to try to determine actual chamber dimensions.

Madrid, As soon as I have a chance I'll Mic some of my TRG-22 cases to see how close mine are to yours. I don't remember every one but I have several of the case Mics and a couple of them do have -.00x chambers, so I wouldn't worry too much if your TRG is sub .001. Try sizing your brass to 0.000 and see if it's a little snug or not......................DJ

The SAKO ANSWER
Dear Sir,

The measures of your TRG 22 are within the specifications of C.I,P.There is no possibility ,that the head space would be something else.
The priciple of firearms and cartridge measures is: The Largest possible factory cartridge must fit into the chamber of the smallest rifle chamber.Therefore both the cartridge manufacturer and the rifle manufacturer must be able to follow
the given measures and the industrial tolerances.
Thus, when you chamber a new factory cartridge, it MUST BE A LITTLE LOOSE in the chamber.The tolerances are so small,
that a well manufactured rifle and a well made cartridge will produce a reasonably good accuracy.
However, when the cartridge is fired in the chamber, the pressure inside the case will cause the case to swell into
the actual dimensions of the chamber of YOUR RIFLE.
If you want to reload the case, and want to get still better accuracy, DO NOT USE A FULL LENGTH RESIZING TOOL!
Use a rezizing die that only resizes the neck of the case. This way, you have a Custom fitted tight cartridge that
shows no head space at all! Naturally, this may not fit into a chamber of another rifle. Do not mix these cases with
any other.
To get a really well made reload, you might get an advantage, if you purchase a set of Redding type S bushing match Neck Die Set , item number 38155(catagog tells the cost is USD 207,-- See their Website .http://www.redding-reloading.com
When you reload, the other things like: high quality cases, good resizing tools, trimmer, quality primers(I use RWS 5341)
and powder:Vihtavuori N 140 or 150, Good match bullets: Sierra 168 grs Matchking or Lapua 167grs Scenar.
A very important thing in reloading is to find the OAL(overall legth) of the realoaded cartridge, that the rifle "likes".
There are differences here, depending of the primer,powder,powder load and the bullet. For example there are 2 different
Lapua Scenars available: the normal GB422, HPBT, and the molycoated GB422 CHPBT. These require a different powder load
due to the lower barrel friction of the coated one.
Have also a look at: www.vihtavuori.fi and www.lapua.com

Best regards
SAKO
Product Manager
--------------------------------
--------------------------------------------------------------------------------

NEW QUESTION

Dear Sir,

Thank you very much for your answer and your kindness for the
explanations you have sent to me.

It is true everything you say. However I get confused when the useful RCBS PRECISION MIC gives me ?3 below measurements. Never before an useful RCBS has provided me with so bad information. I can?t understand this point.

Could it be possible for you to provide me with the CIP measures of my chamber? I can?t find it on any website. It would be very useful to reconstruct and identify the real image of my chamber with its contour heights and measures (perhaps in an autocad file?)

Would it be posible to know the maximum size of the OAL, according to the manufacturing measures, to calculate the freebore? I know that it can be calculated with a wire put in through the gun or with a cartridge, and that the freebore changes depending on the
characteristics of the headspace.

Now again many thanks and should you need anything from me please
feel free to contact me.

Best regards


===========================

CAN HELP ME????

Thanks from lat 40,4 long-3,68333

Hey madrid

I have heard that the barrel manufacturers get new chamber reamers that are at the largest SAAMI measurements for a caliber. The chamber reamer is used and gets smaller until it no longer can ream a chamber out to the smallest SAAMI dimensions.

If this is true, then you could have 2 rifles in the same model and caliber from the same manufacturer that have different chambers, although both would be within SAAMI specs. Therefore your request for a headspace measurement for your particular gun is something only you can measure on your particular gun.

Hey woods, It is true everything you say

.... but like I can have a camera -0.002?


Thanks

____________________________________
The last SAKO reply

Dear Mr. ,
I do not understand ,why you try to compare some measurements with SAAMI or ANSI measures, as our rifle is not made according to these. Your rifle has been proof shot with 2 overpressure proof cartridges and after this, the head space has been verified to be right.It is measured with 2 gauges; go and no-go. The bolt does not close on the no-go.The head space of a 308Win is measured from a surface in the chamber "shoulder" to the surface of the bolt, when the bolt handle has been turned down.
TRG is a precision weapon. The measures of the barrel are tighter than in a hunting weapon. You do not have to be worried.
Do not , by any means try to change anything in the bolt locking lugs!
What comes to the freebore or lead, the CIP does not define that. You can pretty easily find out the max OAL of the cartridge.
Just make one "cartridge" without primer and powder,Seat the bullet very far out(too long), hold the bullet inside a candle flame to get it sooted with fine black color. Then try to chamber this trial cartridge.Close the bolt on it. When you open the bolt, you can see the marks of rifling on the frontal part of the bullet. Now you can measure the length of these marks.
Shorten the try cartridge by the same measure , and you will get a cartridge, that is maximum OAL . Noto, that when different bullets have different ogives, this must be done for each bullet type separately.
Notice also, that the maximum nominal OAL of a .308Win. cartridge is defined to be 71,12 mm, but this is not long enoug to let the bullet to reach the beginning of the rifling.If you want to make a catridge, that has the bullet seated more out, thus giving a longer OAL, you will have to shoot these one at a time, because the probably will not feed from the magazine.

Best regards
Sako
Product Manager
___________________________________________