Book Trim length vrs actual Chamber Casting measurment,,7-08 Handi

[necchi]

Well i went down to Track and picked up some cerrosafe today. Followed the directions, even used a blow drier to preheat the chamber ( boy is that easy!) and got a nice chamber cast of my 7-08. Kinda neat, looks just like a cartridge. I went about 1" into the bore also.

 Most manuals list trim-to length at 2.025 with a max length of 2.035. My casting quite plainly shows the chamber neck ending with a case over-all length of 2.071 average, ya gotta tip that caliper to reach from the head to the neck so let's call it 2.070. That's alot of differance! I know cases stretch a bit when fired but .035?

Here's the question, do I still need to trim to 2.025, or can I leave my cases at max 2.035 for a better grip on the bullets?
I don't want to go longer than max because the possible space left in the cartridge could change the pressures on me.
 I'll still seat bullets at or below the 2.800 recomended COL(COAL). I dummy round with a 140 in it showed I have 2.082 at rifleing contact. This is the only 7-08 I have and my brass will be dedicated to this rifle..

[Tom W.]

COL is for Cartridge overall length. It's always best to follow what the loading manual says, or before you know it when you fire that Handi it will pop open at the shot....Believe me, it's a scary thing when it happens, too.

Now, you should be able to seat your bullet out quite a ways with your Handi, I know that I can really stretch out my 30/30 Handi bullets. It takes a little tinkering, but really, for the most part, follow the load manual.

[blpenn66502]

Necci, 

The whole concept behind a trim to length is so you don't have to trim after every firing.  If you are going to keep the case at SAAMI specified max length and not allow it to be exceeded, then you should expect to have to trim more frequently.

The 0.010" of extra neck length isn't going to give you any advantage in gripping the bullets so don't worry about.  You seem to be confused about how case length changes pressure.  Max case length is only going to be a factor in pressure once you exceed the cut chamber dimensions and jam the case mouth into the throat/rifling in effect creating an unreleasable crimp.  The seating depth of the bullet is what changes internal volume of the case not the case neck length.  In a Handi, not restricted by a magazine's dimensions, you can seat the bullet further out than the max but you don't have to and from reading your post don't want to/aren't comfortable with doing that.

Bottom line:  Do you have to trim to 2.025" every time because that is the trim length? No, not unless you want to.  Can you exceed the max brass length? Yes, based on your chamber cast.  Will max brass length give you any advantage?  No.  Should you read/reread and follow the instructions in your reloading manual(s) to include starting low and working up?  Yes.

Best,
Brian

[necchi]

With all respect and to clarify;  

The whole concept behind a trim to length is so you don't have to trim after every firing.  If you are going to keep the case at SAAMI specified max length and not allow it to be exceeded, then you should expect to have to trim more frequently.
I'm gonna trim, that's something i don't get, why some guy's don't want to trim. It's too simple a task.

The 0.010" of extra neck length isn't going to give you any advantage in gripping the bullets so don't worry about.  You seem to be confused about how case length changes pressure.  Max case length is only going to be a factor in pressure once you exceed the cut chamber dimensions and jam the case mouth into the throat/rifling in effect creating an unreleasable crimp.  The seating depth of the bullet is what changes internal volume of the case not the case neck length.  In a Handi, not restricted by a magazine's dimensions, you can seat the bullet further out than the max but you don't have to and from reading your post don't want to/aren't comfortable with doing that.
Your right, I've read so much and asked so much the info is becoming a bit overwhelming, I don't want to just "copy" factory loads, I do want to stay away from throat crimps. I'm comming from a ML background and know max loads are never accuracy loads, besides the 22" handi isn't going to need heavy loads, just quick loads, notice I didn't say fast?

Bottom line:   Can you exceed the max brass length? Yes, based on your chamber cast.  Will max brass length give you any advantage?  No.
 OK, but it just seems like a terrible waste of space. The .045 is alot between 2.025-2.070.
 None of this post is meant to re-butt your advise at all, I'm just trying to sort this all out. I included a photo of the cast

p.s. the angle of the camra makes the micro look like it's not at the head of the case,,it is

[wncchester]

What you have learned is that manufactors sometimes actually do make things safer than required.  SAAMI chamber measuremnts are toleranced from a dimension to something larger, in thousants.  Fact is the manufactors can/do make things quite a bit larger than the loading book drawing minimums indicated, expecially so for chamber (throat) length.  (Cartridge max is chamber miniimum.)

KNOWING our actual chamber length can allow us to use longer than specified cases but we had better KNOW what the max case length really is if we do that.  Few people ever know what their chamber length is so book max is the logical limit for them.

We can easily find the forward edge of any throat by using brass plugs loaded in case mouths that will stop at the end of the throat  when the case is chambered.  Sinclair International sells the plugs for cheap enough, or they can be quickly made on a metal lathe.