308 Winchester Chamber

[gsg5pk]

I found that based on .308 Winchester Saami drawing show case lenght 2.025"


The 2013 US-FTR reamer come with 2.045" case lenght.

Do they have any advantage to increase those number? Because I read some forum mention those gap will create carbon build up.

(New Lapua Brass case lenght around 2.005")

 

[memilanuk]

Don't know specifically why they picked those numbers.

I will say that I've never, ever, ever let a case get anywhere near either of those values... and I've never worried about carbon build up either.

YMMV.

Monte

 

[NC308]

I always trim my 308 brass to 2.005. Every time

 

[Joe Wade]

Here is the 2016 reamer I use for the 200gr. Berger hybrids. I figure the U.S. F-tr team has learned a few things about what works best. It has the same longer neck as your 2013 reamer for the 185gr. bullets. With the longer neck dimension, you never have to trim your brass. I have not seen any carbon build up using Varget in my rifle, and I periodically use a .338 bore brush to clean the neck section just to make sure.

 

[Shynloco]

I found that based on .308 Winchester Saami drawing show case lenght 2.025"


The 2013 US-FTR reamer come with 2.045" case lenght.

Do they have any advantage to increase those number? Because I read some forum mention those gap will create carbon build up.

(New Lapua Brass case lenght around 2.005")

Not sure where you got those numbers on case length. This website ".308 Info Page" drawing shows a case length of "2.015" which is still .010 longer than new Lapua Brass. And all the Reloading Manuals I use reflect the suggested trim length as 2.005. In my experiences with a .308, a case length of anything over 2.015 will surely invite a carbon ring. I too trim my brass to 2.005 as I couldn't even close my bolt in my tight dedicated match chamber with a case length of 2.025 or anything longer.

Alex

 

[clowdis]

I would think that at a 2.045 case length the case would no longer fit the description of standard .308 Winchester ammo. Therefore you could protest someone using those cases based on those dimensions.

 

[gsg5pk]

I would think that at a 2.045 case length the case would no longer fit the description of standard .308 Winchester ammo. Therefore you could protest someone using those cases based on those dimensions.

I think they check with Go Gauge and No Go Gauge.

This chamber will pass.


Just wonder in case of using New Lapua Brass (2.005") , there will be .040" between case and chamber length.

 

[Ned Ludd]

Just wonder in case of using New Lapua Brass (2.005") , there will be .040" between case and chamber length.

I suspect there will be exactly that much clearance, right up until you pull the trigger.

I also trim .308 brass to 2.005" an have never had a single issue related to this over many thousands of rounds.

 

[clowdis]

I think they check with Go Gauge and No Go Gauge.

This chamber will pass.


Just wonder in case of using New Lapua Brass (2.005") , there will be .040" between case and chamber length.

I think that F-class is still subject to ICFRA rules and they state that it should be a standard .308 case. The chamber can be long but I think the brass needs to be the correct length. Very gray area.

 

[jsn]

If you review the drawings again, you will see that the maximum case length is 2.015", the minimum chamber is 2.025". Most reamers are longer than the 2.025", but unless you asked a reamer mfg'er you probably won't get a straight/consistant answer as to why.

This topic has come up here in the past, there is a chamber plug that can get you a pretty good dimension from the bolt face to the end of the neck in chambered, barreled actions. Almost every SAAMI spec chamber I have measured with these leaded steel plugs shows a minimum of .030" longer than the case maximum dimension. Some insist that longer than max. spec length brass is the only way to keep carbon rings from forming, someone else just said the opposite.

The only thing that I know for sure is that if I am going to have a trim length longer than SAAMI maximum, I must know the distance from the bolt face to the end of the neck, the ammo will only be shot in my specific gun, and I MUST be sure of how much the headspace changes if I FL resize, so that I do not stick the neck into the throat before firing. To me, .005" or .010" clearance between the end of the neck and that portion of the chamber is acceptable as long as I do everything else in the paragraph as I stated.

 

[Zero333]

All my 308w chambers have a neck length around 2.045"
Saami factory or otherwise.

There are tools that measure existing chambers neck length.

This is normal.