SAMMI 280 ACKLEY IMPROVED CHAMBER LENGTH QUESTION

[Roughrice]

For those who shoot the SAMMI 280 AI chambered rifles.

How long is your fired brass measured at datum line with .375 comparator?

I have a SAMMI chamber that has a fired brass measurement of 2.135" +/- .0005.
I picked up a Remage barrel that supposedly has the SAMMI 280AI chamber and my brass comes out 2.140" +/- .0005
If I try to tighten it more to equal the other the bolt lugs contact the breech face.
Both shoot fine but just would have liked to have the same headspace to use a common load.

What are your fired brass measurements?

I know enough about the different Ackleys.... I'm only wanting to compare chamber measurements with others who shoot them and not start a long discussion about the differences.

Thanks Ahead!

 

[26Reload]

I have a 280ai...not sure on the measurement you are wanting...
But..
I have a couple 65284s..cut by same smith...same reamer...I cannot use the same brass in rifle...barely a difference..same loads will load in each rifle...but will not after firing....and one grows longer......

 

[Roughrice]

My shorter chamber fired case will fit in the longer but not vice-versa.
I was just hoping to have them a little closer to size brass the same for both for hunting rounds only.
I just didn't want to stretch cases too much.
Also wandering what the most common fired case length was as there are so many slightly different chambers out there.

 

[26Reload]

Also wandering what the most common fired case length was as there are so many slightly different chambers out there.

The Sammi chambers are a blueprint....every chamber cut is different..some may be really close to spec..but most are not exact....

 

[Roughrice]

Yes sir.
I read a post that someone had SAMMI measured brass that was much longer than mine.
If I recall correctly...SAMMI chamber is 2.140 Min -2.150 Max.

I'm curious how much variation out there with SAMMI 280 AI chambers.

My new Peterson brass is 2.131"
Nosler factory ammo is 2.30".

No wander so many case head separation stories...

.

 

[Darryle]

According to this article, there is no difference. It sounds like the Remage has excessive headspace. I would think that you could have the breech face machined to "tighten" up the headspace at the same time giving you more clearance between the breech and bolt face.

280 Ackley headspace comparison

Disclaimer: I am an armchair gunsmith, take this with a tablespoon of salt and talk with your gunsmith.

 

[Roughrice]

I agree Darryle.
I saw that exact article as well as many others.
I'm thinking the same... that's why I was questioning which may be slightly out of headspace spec on my rifles, the Remage chamber slightly long to where the lugs contact the breech face or my other chamber with shorter fired brass measurement.
Hence, the question of others SAMMI fired brass measurement to have some comparison.

Thanks

 

[kgunz11]

A lot of people out there doing work that aren't qualified to do the work. It would blow your mind how many "gunsmiths" don't know that an Ackley headspace is parent cartridge -.004". In your case, it sounds like that is what happened. The datum point measured by the person cutting the barrel was for .280 and they did not subtract the .004" for the Ackley.

 

[Roughrice]

That could very well be the situation.
The shortest I can set headspace without contacting the lugs is about 2.141"+/- according to my fired brass...which if I understand correctly is still within SAMMI spec.
I was wandering if that is excessive or in the neighborhood of other SAMMI 280 AI rifle headspace .

 

[RUFFIAN R - NY]

All depends on the Smith one is using.. I used Parker O Ackley back then for all my AI builds and never had a problem but know many others did have brass problems. Know your Smith !!!!!
It's pay me now or pay me later.

 

[kgunz11]

That could very well be the situation.
The shortest I can set headspace without contacting the lugs is about 2.141"+/- according to my fired brass...which if I understand correctly is still within SAMMI spec.
I was wandering if that is excessive or in the neighborhood of other SAMMI 280 AI rifle headspace .

There are different specs called out among calibers for "go" and "no-go" gauges. I headspace to go +.002 so when the action is torqued on the barrel you're sitting at go +.001. On an Ackley chamber, it is go -.004" and I use a sample of virgin brass to feel for contact.

 

[Roughrice]

I checked with virgin Peterson and measured 2.130-2.132 max.
I know they size virgin brass small to fit in any chamber but I'm .010 longer.
I'm just fire forming and re-sizing to my chambers.
The only problem is my 2 rifles are SAMMI and there is .005 difference in chamber length due to that lug contact issue.
It shoots very well. I'll just have to keep sizing for the two different rifles and keep them separate.

 

[Darryle]

Can you not face the breech on the Remage barrel and bring it sync with your other rifle?

 

[DUCKMAN11]

A lot of people out there doing work that aren't qualified to do the work. It would blow your mind how many "gunsmiths" don't know that an Ackley headspace is parent cartridge -.004". In your case, it sounds like that is what happened. The datum point measured by the person cutting the barrel was for .280 and they did not subtract the .004" for the Ackley.

This^^^
Have you tried to shoot standard 280rem out of that chamber? If it's not a tight bolt close on standard 280rem then the chamber is cut long/wrong.