Any.input ?

[swampthang]

Question?
Saami says my brass is 1.910-1.920.
I have always uniform.trimmed them after fireforming to 1.910
Just got a chamber length guage and my is 1.940. I.guess I've been over trimming, do I throw the book out and let them go to 1.940 because that's MY CHAMBER measurement.?

 

[dedogs]

I think you can go to 1.930- 1.935 without any worries. Certainly not to 1.940. dedogs

 

[mikecr]

You should see now that there was never a reason to trim to any book value.
IMO you should choose -5 to -10thou of chamber end(always measured) after fire formed.

 

[Shynloco]

Swamp,
IMHO, SAAMI is a STANDARD and not an absolute. Just because you have a rifle chamber that doesn't match up to SAAMI standards doesn't really mean much, other than you have to load to your chamber specs for best accuracy. But what I'd do if I were faced with your situation, I do some comparison firing using the same loads, then trim some new brass and again use the same loads, and then see if there is a measureable change on the downrange. Many custom chamber differs from what a Reloading Manual (their test rifle) reads and blows away SAAMI specs. But remember, SAMMI is used primarily by manufacturers for "general production" rifles and "general production" ammunition so they're on the same page and their products will shoot universally.

Alex

 

[Webster]

Question?
Saami says my brass is 1.910-1.920.
I have always uniform.trimmed them after fireforming to 1.910
Just got a chamber length guage and my is 1.940. I.guess I've been over trimming, do I throw the book out and let them go to 1.940 because that's MY CHAMBER measurement.?

Somewhere I read that the chamber has about 0.060" clearance in front of the case neck for safety reasons. Your gauge probably indicated the trim length plus additional clearance for safety? The SAAMI chamber drawing should show a neck longer than the trim length? I'll let someone else more expert comment.

 

[swampthang]

Thanks men.

 

[fguffey]

do I throw the book out and let them go to 1.940 because that's MY CHAMBER measurement.?

No, I would suggest you learn to measure the length of the chamber from the beginning of the throat to the bolt face.

F. Guffey

 

[swampthang]

No, I would suggest you learn to measure the length of the chamber from the beginning of the throat to the bolt face.

F. Guffey

Freebore ??
I own the reamer so if that's what your saying I know my freebore,.if not kindly enlighten me.

 

[NorCalMikie]

Get gauges, (Sinclair has them) measure your chamber, write it down and refer to that measurement "before" you even think about trimming. Screw the reamer. Measure the chamber length yourself so there's no questions!!
Got a couple of BR chambers that are .020 over max trim length. I don't trim!! Bushing bump dies keep the brass from growing.

 

[swampthang]

Get gauges, (Sinclair has them) measure your chamber, write it down and refer to that measurement "before" you even think about trimming. Screw the reamer. Measure the chamber length yourself so there's no questions!!
Got a couple of BR chambers that are .020 over max trim length. I don't trim!! Bushing bump dies keep the brass from growing.

I use small base die to bump.my shoulder back 0.001 , so I'm familiar with them.

 

[rardoin]

I did a similar overtrim on some cases I converted for 6.5 Creed- 1.910 in a 1.960" chamber. The difference I found between overtrimmed and 1.935 trimmed was the carbon ring that built in the gap was heavier and harder to clean out on the 1.910" cases. I did not record any change in precision.

 

[fguffey]

I own the reamer so if that's what your saying I know my freebore,.if not kindly enlighten me.

Determining the length of the chamber from the end f the neck to the bolt face is a matter of using a case with a long neck and short case body meaning a case that is short from the shoulder to the case head. I form cases with short case bodies and long necks. When deterring the length of the chamber from the end of the neck/beginning of the throat I chamber a formed case with a long neck. I know, it seems complicated, my chambers have more than one length, there is maximum case length from the end of the case neck to the case head and there is the length of the case from the shoulder to the case head. When checking the length of the chamber from the end of the neck to the bolt face I get the shoulder on the case out of the way. And I understand there are reloaders that believe they can move it back; when forming my shoulders do not move.

F. Guffey

 

[swampthang]

Determining the length of the chamber from the end f the neck to the bolt face is a matter of using a case with a long neck and short case body meaning a case that is short from the shoulder to the case head. I form cases with short case bodies and long necks. When deterring the length of the chamber from the end of the neck/beginning of the throat I chamber a formed case with a long neck. I know, it seems complicated, my chambers have more than one length, there is maximum case length from the end of the case neck to the case head and there is the length of the case from the shoulder to the case head. When checking the length of the chamber from the end of the neck to the bolt face I get the shoulder on the case out of the way. And I understand there are reloaders that believe they can move it back; when forming my shoulders do not move.

F. Guffey

,makes sense. Thank you for your reply. I'm just tinkering with a wild idea I had. They say benchrest shooters are innovators lol
Testing a theory regarding accuracy and case neck length.

 

[XBBR Shooter]

Question?
Saami says my brass is 1.910-1.920.
I have always uniform.trimmed them after fireforming to 1.910
Just got a chamber length guage and my is 1.940. I.guess I've been over trimming, do I throw the book out and let them go to 1.940 because that's MY CHAMBER measurement.?

You should not let necks get closer than 0.020" to the end of the chamber.

Also, if they are stretching that much, ask yourself where is that metal coming from and why is it stretching that much.

 

[swampthang]

They don't stretch more than 0.02
After fireforming new nosler brass.
Then they stretch VERY LITTLE if any.
My chamber just seems little long.

 

[swd]

You should not let necks get closer than 0.020" to the end of the chamber.

As long as they're not into a carbon ring what's wrong with .005"-.010" under?

 

[XBBR Shooter]

As long as they're not into a carbon ring what's wrong with .005"-.010" under?

Because it is impossible to remove all of the carbon ring. Right up to the edge of the chamber edge, it builds up and makes a little slope that the brush cannot get to. At 20 thou, even when there is a teeny bit of carbon there, the case doesn't come close to it.

 

[mikecr]

XBBR Yours is a notion of cure that's cause.
Problem carbon rings form due to gas blow-back around necks, causing slower neck sealing, and neck & chamber neck sooting. My standard method of mitigating this is tighter neck and chamber end clearances. The closer case mouths are to chamber end the higher angle gas must blow back to get under necks. At -5thou end clearance, normal pressure load, reasonable neck clearance(~2thou), there is little to no sooting of necks, and with this you know there is little to no carbon piling up at case mouths.

It's wise to confirm this now & then with a borescope. And it's wise to watch your case OAL/trim length to counter growth toward chamber end. If you don't have a borescope, you can usually see signs of reaching an end at the case mouths by looking at each ejected (a quick glance) for shiny spotting/flattening. Of course any crimping found at case mouths means it's time to stop and look at this more carefully.

With some cartridges & chambers it's easy to achieve and maintain tighter end clearance. These are modern and/or improved combinations that require little FL sizing(so little growth). Old cartridges(any 30-06 taper & low shoulder angle) will require a lot of sizing leading to a lot of trimming. I don't know that they're worth the disciplined attention for a relatively small gain that tight end clearance provides.
But, you're trimming them constantly anyway,, might as well keep em in the ~10thou end clearance range.
If you don't pay mind to it, then you should probably live with bigger clearances across the board.

Where shooting something like a 6Dasher, you can stop sweating and really tighten things up. It's among many little benefits in a modern cartridge like this.

 

[Zero333]

I let them grow 0.015" short of the chamber end. So in your case, I would let them go to 1.925"

Some of my rifles have chambers that are 0.035" longer than the max case length, and others like your rifle are only 0.020" longer than the max recommended case length.

Glad you measured your chamber. I hate not knowing as much as I hate trimming.