trimming cases

[garyrapp55]

I know the book states a trim length. I understand you can get away with longer, and I have. How do I know when longer is too long?

Sorry if I broke a rule asking this here instead of the ammo section. These cases are in bolt gun only, specifically H mini.

[jasper2408]

These might help.

https://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx

CaseChamberLengthGage.PNG

[grayfox]

If you stray beyond saami max length then the brass does not have room to expand forward during the firing stage. Other than your caliper saying >1.520", the next notification you might get is a kaboom. This also applies to whatever dimension your chamber is actually cut at, max brass length I mean.
Why o why do you even want/"need" to go there. If this is coming up then I would suggest a different issue is really happening, and it's leading you into dangerous territory.

In short, I personally disagree with your premise "you can get away with...". You can of course, think what you like.

[jasper2408]

I agree with grayfox on trimming no longer than book max but I have also read where some shooters trim longer than book max to keep carbon build up to a minimum in the chamber neck area in front of the case neck. Sinclair also doesn't recommend use on semi-auto rifles. This might cause a big stink but here is what Sinclair has to say on their web page in the description part for the chamber length gage. Notice the text in bold. Don't shoot the messenger here, just sayin'.

The Sinclair Chamber Length Gauges are designed so the handloader can determine the true length of his rifle's chamber when measuring from the bolt face to the end of the chamber's neck. This measurement will tell you how much excess case length your chamber may have over published trim lengths in reloading handbooks.

The Sinclair Gauges are inserted into a fired, unprimed shortened case and then chambered into your rifle. The insert pushes back into the case when it contacts the end of your chamber. You then extract the case and measure the overall length. The gauge is made of 12L14 soft steel so it will not damage your chamber. Step-by-step instructions accompany each gauge. The gauges can be used over and over again.

The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.

The 22 caliber gauge will not work on thin-necked cases such as the 22 Hornet, 218 Bee, or cartridges based on these cases. The 30 caliber gauge will not work on teh 30-30 Winchester. None of the gauges listed will work on tight-necked chambers except for the G-243T. Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles.

[Klem]

Gary,

I agree with everyone here, and Sinclair's explanation makes sense but is arguable. As you know necks creep forward over a number of firings and if not checked will eventually crimp into the bullet. You don't want this for safety reasons. Some necks will be longer than others and as they start to crimp into the bullet the pressure builds and velocities are all over the place, plus the obvious safety hazard.

How long your neck is depends on the reamer used on your chamber - every chamber is different. One way to figure it out is to take a cast of your chamber (I have never done this). Another way is to use the Sinclair inserts in Jasper's post, or make your own if you have access to a lathe.


Sheridan rifle gauges are apparently reamed with a normal chamber reamer so this picture shows typically how much clearance you might have before the necks hits the forcing cone of the barrel.


As for the Sinclair advice, it is fair but I would not use it as an excuse to let your cases creep forward as there's arguably no advantage in letting this happen - even on a semi-auto. With Grendel, there is typically plenty of grip on 6.5 bullets so being even more generous with neck length is of no advantage. Sinclair's idea of keeping cases clean by letting the necks grow up to the forcing cone is arguable. Risk/reward is just worth it. Regardless, carbonised necks or stained cases don't affect accuracy anyway. Cleaning cases is more cosmetic than useful. Unless you trim your cases to a stupid shortness they are always going to obdurate and seal barrel gasses.

Best-practise is to trim cases to SAAMI and then you don't have to worry about it. In Grendel they don't creep forward too much anyway. Whatever case length you settle on it pays to keep all cases as consistent to that length as possible for accuracy.

[Harpoon1]

I know the book states a trim length. I understand you can get away with longer, and I have. How do I know when longer is too long?

Sorry if I broke a rule asking this here instead of the ammo section. These cases are in bolt gun only, specifically H mini.

[Kosh65]

[Harpoon1]

[jasper2408]

How do I know when longer is too long?

When I was doing some research for your question I came upon an F-Class post about this subject. What that person said was that he would do different case lengths, beyond book max, so that he could find the one that gave him the best ES. He claimed that you could help decrease ES by lengthening the case. He said that he never went closer to the end of the chamber than 10/1000. This distance is supposed to allow for case expansion.

I am not saying this method is safe or even if it works and I am not telling you to try it. Just some info I found.

Decided to add this:
Just so you are aware that if you miss checking just one case and it gets too long to where the case neck gets past the chamber and up into the throat you could blow up your rifle. If you don't want to check the length of your cases then maybe you should just shoot factory ammo. I will state again that I totally agree with grayfox that I think you are playing with fire. So there you go, if you blow something up I warned you.

[garyrapp55]

I ordered a bore scope, mostly for seeing carbon build up but it might give me an idea of where I'm at in there. Considering the chamber length gage as well. Thanks for all the input.

[Zeneffect]

Playing with trim length in quickload will change the chamber pressure modeling. Enough so that there is significant difference between 1.520 and 1.518. Just food for thought... bearing surface on the neck will change the pressure profile of a given charge. longer can push into the "dangerous" territory with the same max charge developed with a shorter trim length.

[Harpoon1]

Playing with trim length in quickload will change the chamber pressure modeling. Enough so that there is significant difference between 1.520 and 1.518. Just food for thought... bearing surface on the neck will change the pressure profile of a given charge. longer can push into the "dangerous" territory with the same max charge developed with a shorter trim length.

Very interesting, thanks for the heads up!

[jasper2408]

I emailed Sinclair about their statement on case length below:

The differences between published trim lengths and the actual length of your chamber can be quite significant. You could be over trimming your cases by .030 inch or more.

This is the explanation they emailed me today:

By allowing your neck to remain longer than published trim to lengths. You can gain better support for your bullets if you are trying to load bullets to reach or come close to lands of your rifle chamber.

Also the information I posted previously about going past max book case trim length was taken from several posts on the "AccurateShooter dot com" forum under Reloading. There are multiple threads there on the subject. Just search for "rifle max case trim length".

One thing I have noticed is that not in one of the threads or the email that I received has anyone mentioned anything about pressure or if it is dangerous to do unless you get the case neck up into the throat. Just an observation of mine.

[olasvadas]

I solved the problem using Lee Case Trimmer and Cutter with Lee Case Length Gages and Shellholders for the 6.5 Grendel. Every 2 or 3 shopping sessions I check the cases, if necessary, because the Trimmer works on brass, I work on all the lot. I'm Always work to semplice my Life.

[BowChamp]

If you stray beyond saami max length then the brass does not have room to expand forward during the firing stage. Other than your caliper saying >1.520", the next notification you might get is a kaboom. This also applies to whatever dimension your chamber is actually cut at, max brass length I mean.
Why o why do you even want/"need" to go there. If this is coming up then I would suggest a different issue is really happening, and it's leading you into dangerous territory.

In short, I personally disagree with your premise "you can get away with...". You can of course, think what you like.

Did someone say KABOOM!!!! LOL!!!!

This was my exact thoughts on his question.


It's really very easy.


Long.............................................. .................................................. ..........................Trimmed