Is this an excessive lenght chamber?

[fguffey]

The one thing I do not want is a throat that will crimp the neck to the bullet. I do not want anything slowing my bullets dowm before the bullet gets out of the neck. I am the fan of the bullet jump, I do not like the ideal of the bullet setting at the lands wondering if it is going to be able to get past the lands. I want my bullet past the lands before the bullet knows the lands are there.

F. Guffey

 

[Uncle Ed]

Do you just make this stuff up? And you the bench rester.

F. Guffey

243winxb provided the SAAMI chamber drawing and in the lower right it has the chamber tolerances.
And the SAAMI dimensions are guidelines and not written in stone.

F. Guffey you keep telling us how smart you are but you can't even read a SAAMI chamber drawing.

You should try providing actual information instead of so much bovine scat and ignorance.

 

[Uncle Ed]

Well if you put it that way, yes, not enough to be worried about I guess.

Davey Boy

Todays chambers have to be large enough for the cartridge and also fit the company lawyer in.

Below from the SAAMI chamber drawing (Guidelines)

CHAMBER
UNLESS OTHERWISE NOTED
ALL DIA +.002
LENGTH TOL +.015

So as 243winxb stated your chamber is .005 longer than SAAMI "guidlines".

 

[243winxb]

Whats the diameter of the Sinclair chamber guage? Need to know where its* making contact.


*spelling correction.

 

[243winxb]

The one thing I do not want is a throat that will crimp the neck to the bullet. I do not want anything slowing my bullets dowm before the bullet gets out of the neck.

Vere good info, i agree.

A case trim length that is to long may crimp the bullet in the case. Pressure would go up. This is why a "safety zone" is built into chambers.

But if the reloader has taken measurements, .010" longer then maximum trim length may work well. Trim after every fl sizing, if needed.

There is another thing to consider, shoulder set back from the firing pin strike. This may allow the neck to go deeper into the chamber on firing? More testing is needed. A 223 pin strike has set my shoulder back .006" ** when i had a misfire from a bad primer. The 2nd strike pushed the shoulder back even more. Annealed brass may go even deeper? I dont anneal.

Added ** Set back confirmed by another handloader , same model rifle. Savage Axis 223.

 

[Dusty Stevens]

Whats the diameter of the Sinclair chamber guage? Need to know where its* making contact.


*spelling correction.

It is case neck diameter

 

[Davey Boy]

Whats the diameter of the Sinclair chamber guage? Need to know where its* making contact.


*spelling correction.

My micrometer is showing .332 on the Sinclair gage.

 

[Mr. Jetski]

Good day gentlemen
New poster master machinist and mechanic
Not to offend but some corrections need making
The datum is 1/2 the distance between the shoulder junctions to the bolt face
Max 308 case length is 2.020
The distance from case mouth to bullet lands is called free bore or jump and is there to transition from the case mouth to lands and grooves, Basically an “acceleration zone” and a sort of pressure buffer. Has anybody seen myth busters with the 3k FPS gunshot film?the smoke you see before the bullet exits the barrel is from this area

 

[Mr. Jetski]

There is another thing to consider, shoulder set back from the firing pin strike. This may allow the neck to go deeper into the chamber on firing? More testing is needed. A 223 pin strike has set my shoulder back .006" when i had a misfire from a bad primer. The 2nd strike pushed the shoulder back even more. Annealed brass may go even deeper? I dont anneal.

If true you have a BIG problem

 

[243winxb]

chamber length of 2.068"

.332" on the Sinclair gage.

The 2.068" measurement may be longer then the chamber , because the chamber diameter is larger then the Sinclair plug. (If using SAAMI standards)

If you trust your measurements, its possible to use a longer trim length then standard, for the 1 rifle. But SAAMI shows a "safety zone" of only .010" in a minimum chamber.

I keep my 243 win brass at maximum trim length for 1 target rifle. This required checking trim length after every fl sizing. When brass grows a few thousandth over, i trim it back. Does it make a difference? No idea. I just feel better about it, as it may help throat errosion.

 

[243winxb]

If true you have a BIG problem

Set back confirmed by another handloader , same model rifle. Savage Axis 223.

 

[243winxb]

Max 308 case length is 2.020

NO, its 2.015"

 

[fguffey]

Good day gentlemen
New poster master machinist and mechanic
Not to offend but some corrections need making
The datum is 1/2 the distance between the shoulder junctions to the bolt face

Master machinist and mechanic:

And then you say;

The datum is 1/2 the distance between the shoulder junctions to the bolt face

And then I ask: How can that be if the 8mm57m 30/06, 280, 270 and 25/06 use the same datum? The datum/round hole/circle for all of the chambers listed is .375 or 3/8". The length of the shoulder from the case body/shoulder juncture and the shoulder/neck juncture can not be located half way between both junctures for all of the chambers listed.

F. Guffey

 

[fguffey]

There is another thing to consider, shoulder set back from the firing pin strike.

I have heard that one before, I have rifles with killer firing pins, I have pulled down 'failed' to fire ammo that has been struck 8 times with 4 different rifles and I have kept up with the length of the case from the datum/shoulder to the case head and found no evidence the firing pin strike shortened the case when the primer is struck,

For those that can keep up: There is .005" clearance between the shoulder of the case and shoulder of the chamber when the firing pin is struck if the firing pin strike shortened the case .004" there would be .009" clearance between the bolt face and case head.

I understand that means absolutely nothing to anyone on this forum but .009" clearance is the difference in length between a go-gage chamber and a minimum length full length sized case. According to you the shoulder of the case starts out at the shoulder of the chamber, in my opinion that is a bad habit because the case will lock onto the chamber with the case head .009" off of the bolt face. When all of that hot, high pressure builds metal cutting gas builds the case will only have one option and that option would be to stretch between the case head and case body.

I am the fan of cutting down on all that case travel.

F. Guffey

 

[243winxb]

This works for me.

 

[Fotheringill]

How did I foretell this thread would turn to poop as soon as I saw an appearance?

 

[Davey Boy]

Well maybe I should change my mind and just trim to 2.015 which is max in the Sammi specs. Can't get into trouble using that trim length. Some on here have said that Lapua brass has been as short as 1.997 and shoots ok. I trim each firing.

 

[Davey Boy]

2.010 would be a better choice

Ok but why is that? I seem to have a long chamber, so thinking 2.015 which is max would be ok.
I'm new to reloading so why go between min and max as long as I trim to the max length each time fired.
That's why I'm here is to listen to opinions on this site. Figure most all of you have more experience than me.
Some are just harder to understand LOL.

 

[Davey Boy]

I have a Lee cartridge trim (simple) and a Lee Quick trim with separate cartridge dies, and I haven't used it just yet, waiting to do several hundred in one sitting, A Trim it Two with inserts for each cartridge I have. It trims based off the shoulder, so if you have accurate shoulders it should be accurate.

 

[fguffey]

A Trim it Two with inserts for each cartridge I have. It trims based off the shoulder, so if you have accurate shoulders it should be accurate.

Trims off of the shoulder? So, if you have accurate shoulders it should be accurate?

Davey, when a reloaders starts trimming his cases with his trimmer set up on the shoulder of the case he should have 'it' all together. I have gages that are datum based; they measure from the datum to the end of the neck and they measure from the datum to the case head.

Again, I have a rifle that is .016" longer than a minimum length/full length sized case or .011" longer that a go gage length chamber. If I set the trimmer up on the shoulder of the chamber I am not taking in consideration the chamber is long from the shoulder of the chamber to the bolt face.

I know, no one understands what that means but if I trim the neck with a trimmer based on the length of the case and then set the trimmer up on the shoulder I will be trimming the case .014" too short; so I add extra length of the case from the shoulder to the case head to the length of the case.

F. Guffey