SAAMI and Cartridge Length Question

[1J04]

Would appreciate input on the following. Picked up a Remington 700 BDL in 25-06. Have brand new Winchester Brass and have shot, and twice reloaded the same brass. Out of the box every piece of brass is under the SAAMI max length of 2.494 and every piece of "fire formed" brass is still under 2.494. Being fairly new to this I would think after 3 times fired I should have "some" brass atleast around the max SAAMI length, right? I understand all guns aren't created equal, but really? I'm in the mid 2.475 to 2.484 range on brass length and want all things to be of equal length like other guns I load for but I've never come across the problem of already having "short" cases and then have to trim more for consistency.

On SAAMI's website they have the drawings/specs of cases and for the 25-06 regarding case length it shows 2.494 - .020 what's the - .020 stand for? Does that mean you should be safe down to 2.474? If ya know, fire away, but please just let me know

Thanks Folks

 

[BobinNC]

Re: SAAMI and Cartridge Length Question

2.494" is the not the SAMMI MIN length, but the MAX length, as are all dimensions on the SAMMI site. The site lists MAX cartridge and MIN chamber dimensions. You are OK with 2.474" as a MIN. that's what the minus 0.20" is for.

 

[Fuzzball]

Re: SAAMI and Cartridge Length Question

The spec you reference is for factory cases and it is 20 thou. That has nothing to do with safety, as such, it's simply a practical minimum case limit for ammo makers to strive for. Normal case "trim-to" length is 10 thou under max length but that's just a suggestion, it's not a specification.

SAAMI specs both chambers and cartridges, not "OAL" (cartridge length), as such.

 

[1J04]

Re: SAAMI and Cartridge Length Question

Thanks BobinNC. Stand corrected, I meant Max 2.494, anyhow I thought that tic (-) or minus was for .020 min under but was not for sure. Nice to know.

Appreciate the input also FuzzBall. I understand what you're saying. Safety first, hence the question.

Great response time, really appreciated. Gotta love this sight.

 

[Clark]

Re: SAAMI and Cartridge Length Question

The true max length is the chamber length [from the bolt face to the end of the chamber neck] minus how far the firing pin will push the case forward.

That means that full length resizing of brass can not only make the brass longer, it can make the max allowable length of the case shorter, by pushing the shoulder back. The further the shoulder is pushed back, the further the firing pin can push the case forward, before it is stopped by the chamber shoulder.

If your load is so hot that you expect to get between 5 to 10 firings of good brass before the primer pocket is loose, AND if a case is so long that the firing pin can jam that case neck into the chamber throat [thus pinching the bullet, delaying bullet movement, and spiking pressure], THEN you just got you last firing on that case. The primer pocket will be loose, and the case goes to the bone pile. The velocity of that shot will be higher and that might make a flyer on your target.

 

[1J04]

Re: SAAMI and Cartridge Length Question

Clark, agreed. Isn't that why when you set your FL resizing die you have the ram to the top and then screw down the die to just touch, then back off a turn so you don't over work the shoulder?

 

[Clark]

Re: SAAMI and Cartridge Length Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1J04</div><div class="ubbcode-body">Clark, agreed. Isn't that why when you set your FL resizing die you have the ram to the top and then screw down the die to just touch, then back off a turn so you don't over work the shoulder? </div></div>

Qualitatively yes.
Quantitatively, maybe sometimes, but I doubt it.

The die and press have 7/8-14 threads.
That is a pitch of .071"
That is 5 degrees rotation for every .001" change in depth
The major diameter of 7/8-14 male thread is .875"
The circumference is 2.749"
0.039" on the surface of the thread rotates passed for every .001" change in adjustment.

The headspace for 25-06 chamber is 2.0487" to 2.0587"
The headspace for 25-06 cartridge is 2.0526 - .0070"

If you have a factory rifle, they probably chambered it at ~2.050".
Your fired brass may be 2.051"
You may want to get your brass to 2.049"
The brass may spring back from the sizer by .001".
So you may want the die set in the press at 2.048" top dead center.

To get .001" resolution on your die adjustment is not going to be easy. 1) Tightening up the die after adjusting can change the adjustment by more than that. 2) Turning a die in 0.039" increments are tiny steps. Pencil marks can be that wide.

To get the die adjusted, I take a population of brass that has grown too long. I mark the die and press with Sharpie marks to keep track of where I am. I try to creep up on re-sizing a case [of course no expander ball] until it chambers easily. Then I back off the die a little and size another case in smaller steps. Once I find the threshold, then I screw in the die .039" along the surface of the die threads, and lock the die. That adjustment only works with that rifle and that press.

What does it all mean?
If you backed off your die a whole turn from the shell holder, you have most likely been partial neck sizing, and not pushing the shoulder back at all. That works great most of the time with just one rifle, but when the bolt gets hard to close, it is time to push the shoulder back.

 

[1J04]

Re: SAAMI and Cartridge Length Question

Outstanding !!! Now there's an answer to take to the bank. Thank you so much for taking the time to help me gain more understanding of how and why this, and other steps are needed and what they mean.

 

[500grains]

Re: SAAMI and Cartridge Length Question

Just so you guys know, Clark has some excellent pit bull recipes. Email him and get the specifics!

However, he has taken a very scientific approach to reloading which is seldom seen. He skips the myth and folklore and gets down to real world data.

 

[1J04]

Re: SAAMI and Cartridge Length Question

I'm impressed and thankful. This is just outstanding as an information base. Thank you all.