Case trimming question

[caustic]

Hey All, I've been lurking for a while on the hide, I did a search and didn't find what I was looking for, my question is , is there any benefit in accuracy in keeping your cases closer to the maximum length rather than trimming them down the full .01" these cases will be for a 300WM.

thanks in advance

 

[Guest]

Re: Case trimming question

Most folks trim slightly under max to avoid repeated trimmings.

 

[Winchester 69]

Re: Case trimming question

Not in accuracy, but some with custom barrels like to keep their cases as long as possible to minimize barrel erosion.

You can count on a factory chamber being longer than spec. There are ways to measure chamber length. Then you need to trim to be shorter than the chamber rather than meeting some book spec. Sinclair has a gauge piece for about $7 that fits in a shortened case neck. You measure your chamber length with a caliper.

 

[Hummer]

Re: Case trimming question

A number of years ago there was a article in Precision Shooting about this. I don't remember the details but it was geared toward letting the necks get longer. I never got around to playing with it but am getting ready.
I made up a case length gage for several of my rifles. After installing barrel I took a section of the cut off from the muzzle and ran the same reamer in it so that I could take a fired case and push it into the same chamber. I ran the ream until the neck section was almost out the other side. Then I faced off that piece so that I could see under the lip left with a case in it.
As Win69 says, they are longer and from what I have seen on the three to five that I have made up so far they are about .020" longer.

I keep the little section of barrel in the die box.

With that revelation I started trimming mine at the max length and letting them run over so now when I start to reload them I run the fired case and the resized case into the little gage I have and I know where I am.

There is another way to determine how close you are. Chuck up a case and drill a 1/4"-3/8" hole in base and insert in action. Run a borescope up into bottom and see how close you are to the end of the neck section.

 

[Victor N TN]

Re: Case trimming question

The shorter your cases are trimmed, the more the propellant gas will deteriorate the throat of the chamber. That's especially useful for cartridges that have a lot of powder like the 300 WinMag. There's a lot of flame going down the barrel.

I use a fired case with a ring cut off of it and a bullet seated to find the max length of that particular chamber. Knowing where the case mouth in the chamber is located helps know where to trim.

 

[Suasponte]

Re: Case trimming question

I use these to determine my trim length! Sinclair sell them too.

Terry

 

[Victor N TN]

Re: Case trimming question

Looks like a neat kit. But I started making the ring on the case neck a long time ago.

 

[caustic]

Re: Case trimming question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">

I use a fired case with a ring cut off of it and a bullet seated to find the max length of that particular chamber.. </div></div>

I'm not sure that I understand,could you post a pic please

 

[caustic]

Re: Case trimming question

Suaponte, So I know, are those basically aluminum slugs that fit in to the case neck snug but not too tight with a slight shoulder the same diameter as the case neck, I take it that you leave it sticking out long put your case in the chamber close the bolt extract case and measure the overall length?

once you have this measurement how much should one trim to be safe? or does one make cases to that measurement?

 

[Suasponte]

Re: Case trimming question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: caustic</div><div class="ubbcode-body">Suaponte, So I know, are those basically aluminum slugs that fit in to the case neck snug but not too tight with a slight shoulder the same diameter as the case neck, I take it that you leave it sticking out long put your case in the chamber close the bolt extract case and measure the overall length?

once you have this measurement how much should one trim to be safe? or does one make cases to that measurement?
</div></div>

Correct! You have to sacrifice a case by trimmming it pretty far back! Then you just chamber it with the gage in it and measure!

The measurement you get from the case and plug will me you max trim to!


Terry