Headspace for 300 ultra with 35deg?

[J E Custom]

The simple way to set the head space is to use the go gauge that fits the chamber.
Even the chamber can be a little off so use the tool designed for the chamber and set the head space off it to .001 to .003 and after fire forming you will know where the actual datum line is if you want to "Bump the shoulder". Shoulder angle may move the datum line but head space needs to be set off the proper go gauge. As mentioned for AI chambers they are normally set with .004 to .006 crush to hold the case in place and minimize case stretch.

Just My opinion

J E CUSTOM

 

[Mram10us]

The simple way to set the head space is to use the go gauge that fits the chamber.
Even the chamber can be a little off so use the tool designed for the chamber and set the head space off it to .001 to .003 and after fire forming you will know where the actual datum line is if you want to "Bump the shoulder". Shoulder angle may move the datum line but head space needs to be set off the proper go gauge. As mentioned for AI chambers they are normally set with .004 to .006 crush to hold the case in place and minimize case stretch.

Just My opinion

J E CUSTOM

If I would have used the 300 rum go gauge, the chamber would have been about .014" short since it has the 30deg shoulder and I wanted the neck/shoulder junctions to be the same for virgin 300 rum brass.

 

[J E Custom]

If I would have used the 300 rum go gauge, the chamber would have been about .014" short since it has the 30deg shoulder and I wanted the neck/shoulder junctions to be the same for virgin 300 rum brass.

I always recommend buying a go gauge when you have a reamer cut buy the same reamer maker because it is ground to match his reamer. They are only $30.00 to $40.00 dollars and well worth the money to be precise. I normally don't buy a no go gauge unless it is for a used rifle that needs to be checked and even then with shims on the back of the go gauge it is easy to find the exact head space that that chamber has.

In this case where you added a 35o shoulder to a 30o cartridge/chamber and you retained the same neck to shoulder junction length the 300 RUM go gauge would work because it would seat at the neck shoulder junction being a smaller angle.

Some cartridges use the same go gauge, but the need to check the loaded ammo is still there in case the different reamers cut a slightly different chamber.

When I design a wildcat, I insist of buying a matching go gauge. (Even if I have to pay for it).

Just a recommendation

J E CUSTOM

 

[Mram10us]

I always recommend buying a go gauge when you have a reamer cut buy the same reamer maker because it is ground to match his reamer. They are only $30.00 to $40.00 dollars and well worth the money to be precise. I normally don't buy a no go gauge unless it is for a used rifle that needs to be checked and even then with shims on the back of the go gauge it is easy to find the exact head space that that chamber has.

In this case where you added a 35o shoulder to a 30o cartridge/chamber and you retained the same neck to shoulder junction length the 300 RUM go gauge would work because it would seat at the neck shoulder junction being a smaller angle.

Some cartridges use the same go gauge, but the need to check the loaded ammo is still there in case the different reamers cut a slightly different chamber.

When I design a wildcat, I insist of buying a matching go gauge. (Even if I have to pay for it).

Just a recommendation

J E CUSTOM

I have a clymer go gauge for 300 rum. I assumed the gauge is built for the headspace at datum point (.420"). I'll call and ask because if they are using the neck/shoulder junction for their gauge it would work.
If I don't have gauges for a specific cartridge, I just make them. Super easy and I don't have to wait

 

[J E Custom]

I have a clymer go gauge for 300 rum. I assumed the gauge is built for the headspace at datum point (.420"). I'll call and ask because if they are using the neck/shoulder junction for their gauge it would work.
If I don't have gauges for a specific cartridge, I just make them. Super easy and I don't have to wait

Yes it is but just like the Ackley's, they use the neck shoulder junction instead of the datum line. the datum line is used because it is the center of compression of the shoulder and has very little give but as I said the neck shoulder junction will become the new temporary datum line until it is fire formed because you increased the shoulder angle.

I would be interested in what they say.

J E CUSTOM

 

[Mram10us]

Yes it is but just like the Ackley's, they use the neck shoulder junction instead of the datum line. the datum line is used because it is the center of compression of the shoulder and has very little give but as I said the neck shoulder junction will become the new temporary datum line until it is fire formed because you increased the shoulder angle.

I would be interested in what they say.

J E CUSTOM

Ackleys use it except the 280ai since it has a saami spec. Screwed everything up. That's for another thread.
The 300rum go gauge measures 2.598" long with a ~.292" tip. I'm curious if they are using the n/s junction or the datum. I'll let ya know

 

[J E Custom]

Ackleys use it except the 280ai since it has a saami spec. Screwed everything up. That's for another thread.
The 300rum go gauge measures 2.598" long with a ~.292" tip. I'm curious if they are using the n/s junction or the datum. I'll let ya know

The original Ackley used the parent case go gauge even though the finished chamber had the 40o shoulder and less body taper it still head spaced at the neck shoulder junction.


J E CUSTOM

 

[Mram10us]

The original Ackley used the parent case go gauge even though the finished chamber had the 40o shoulder and less body taper it still head spaced at the neck shoulder junction.


J E CUSTOM

True, but saami screwed it all up by putting a datum on the 280ai. Thus, the confusion began about JS junction v datum.

 

[J E Custom]

True, but saami screwed it all up by putting a datum on the 280ai. Thus, the confusion began about JS junction v datum.

Yes they did !!!

J E CUSTOM