Quick question on Sinclair chamber length gauge

[bm11]

Just got one yesterday. In reading the instructions, it says "it is still not recommended to exceed SAAMI max measurements for your chamber. If you still choose to trim your brass to longer specifications, make sure it is at least .024" less than the measurement you attained"
^^^ This is me paraphrasing, because I don't have the instructions.

Now, I know that the first part about not exceeding SAAMI specs is just for liability. I am pretty sure the second part about .024" is as well, but I wanted to ask to be sure.

Using this tool, I can safely attain maximum case length measurements, and not have to subtract .024" from it, yes?

 

[427Cobra]

Re: Quick question on Sinclair chamber length gauge

I don't trim until I get to .010, if you have a butt loads of rounds down range in the chamber it may be pretty long.

 

[bm11]

Re: Quick question on Sinclair chamber length gauge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">I don't trim until I get to .010, if you have a butt loads of rounds down range in the chamber it may be pretty long. </div></div>Well, the barrel has 2600 rounds (.308) and I measured the chamber length as 2.043. But if I subtract .024, I end up real close to Saami spec (2.015) at 2.018.

In any case, in this last batch of brass (2x fired but never trimmed) I noticed a range of 2.08 to 2.18, so I trimmed all that I was loading to 2.08 for uniformity.

 

[ChrisGarrett]

Re: Quick question on Sinclair chamber length gauge

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bm11</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 427Cobra</div><div class="ubbcode-body">I don't trim until I get to .010, if you have a butt loads of rounds down range in the chamber it may be pretty long. </div></div>Well, the barrel has 2600 rounds (.308) and I measured the chamber length as 2.043. But if I subtract .024, I end up real close to Saami spec (2.015) at 2.018.

In any case, in this last batch of brass (2x fired but never trimmed) I noticed a range of 2.08 to 2.18, so I trimmed all that I was loading to 2.08 for uniformity. </div></div>

Back when my Savage 10FP was newish, I could go out to 2.020" with my brass and not get any pinching around the mouth.

I would think that the .024" number is somewhat arbitrary, don't you?

Why .024" and not .025" or .020"?

Chris

 

[Rover31]

Re: Quick question on Sinclair chamber length gauge

I am sure the note about not exceeding SAAMI is their Lawyers talking.
I am not a bechrest guy but don't those guys run the neck length way out there to the measured specs?

FWIW I think this is a great under-used cheap tool!

 

[bm11]

Re: Quick question on Sinclair chamber length gauge

Ok, I have the complete instructions in front of me. The warning is as follows:

<span style="font-style: italic"><span style="font-weight: bold">WARNING!</span>
Excessive case length will cause dangerous chamber pressures resulting in personal injury. We do not recommend increasing case length beyond published SAAMI specifications. <span style="font-weight: bold">DO SO AT YOUR OWN RISK!</span> If you do increase your case length maintain the case length so that it is a minimum of .024" shorter than the chamber length.</span>

Again, I think that is just the lawyers talking, as I understand what I am accomplishing here- determining the true length of my chamber so that I can let my brass grow longer than spec without repercussions. The only thing that threw me for a loop is that the .024" seemed rather specific, but perhaps that was the intention, to make the reader more likely to follow the instructions.