trim to length accuracy

[goblbustr]

I have a couple buddies telling me I'm crazy but. When trimming I try to keep them all within - .001 of each other anything outside that i continue to trim or set it to the side. What tolerances are acceptable when full length trimming? Thanks

 

[Seabeeken]

Does it make a difference on target? The few i have that need trimming i let grow to .010 short of chamber and measure and that is my trim length. My AI cases have never needed a trim.

 

[Rick Richard]

To be honest in my experience anyway, I have NOT noticed any SIGNICANT difference in accuracy if they are not all the same length.

 

[Bob Wright]

Consistency is the prize. Keep up the good work. Sometimes, If it's a few thousands short, shoot them (Stuff happens). Too long and I recut to correct size.

 

[RegionRat]

Here is a suggestion or food for thought....

Most chambers are cut generous in the zone of the neck length. It is best to know your exact chamber details and the keep that zone clean, but my point in bringing this into the discussion is to point out that your trim length is based on specs that may or may not reflect your actual reamer and chamber. Zoning in on your max trim length is more important than holding the tolerance to 0.001".

This opens up the discussion space for trying the following.
If you save up about 15 to 20 cases and postpone the trim on this set to your maximum, and create a test of an equal number trimmed to your minimum, you can then test to determine if trim length makes any difference to you at all.

I would never suggest neglecting case length or that allowing carbon residue is not asking for trouble, but more to point out that several other factors are far more important than the case length tolerance when it comes to precision and accuracy.

Many guns don't shoot tight enough to detect the difference between max and min. Many chambers are cut longer than specs.

One of the only reasons to agonize over case length tolerance is to make sure your dies and set-ups are always happy and that you are not pushing a longer case into a wedge. The effect of that tolerance on accuracy or precision is subject to testing. YMMV

 

[WapitiBob]

Your ID chamfer is going to vary more than .001.

 

[Varmint Hunter]

Providing that your cases don't get so long that they bind the bullet when chambering, the effect of varying case length is negligible. You probably couldn't tell the difference unless you were a hall of fame benchrest shooter. Just my 2 cents.

A helpful idea to determine what length is tolerable is to chamber an empty case and to then insert a bore scope through the muzzle and see how much room you have left. You can also see if carbon is becoming an issue at the junction.

I never cut my cases more than .005" even if they get too long. Cutting them to minimum specs just leaves more room for carbon to deposit.

 

[lancetkenyon]

You are not crazy. Or anal.

You are detail oriented. Of which I applaud. Trim to exact. It definitely doesn't HURT amything.

 

[Elk Hunter 338]

One simple step after FL sizing i do almost always. I run a the Hendersons trimmer now, so simple, its a no brainer.

 

[Mikecr]

I'm sure that people go crazy with trimming -because it's so easy to do that.
But for hunting capacity cartridges, you should not trim too short of chamber.
That means measuring chamber length to know you're inside of your trim length goal.
If you trim too short you will have carbon build up in the chamber neck. This, because you make it easier for gas/carbon to curl around backwards. Add high neck clearance, and watch sooting deposits go all the way to shoulders.
This can affect quick & consistent neck sealing.

I don't trim unless within 5thou of chamber end, and leaving no more than 10thou clearance.
I don't FL size, so my sizing doesn't lengthen cases. And most of the time my case OAL shortens with fire forming.
So with a factory chamber it's unusual that I ever need to trim cases.
With custom chambers I intentionally set the chamber end close, so that I will trim all to same length (after fire forming).

I haven't seen nor suspected an issue with a relatively wide tolerance on this.
But where I've seen more than 10thou chamber clearance, I've seen a carbon ring build in the neck, and it's no fun to manage.

 

[Reelamin]

I have a couple buddies telling me I'm crazy but. When trimming I try to keep them all within - .001 of each other anything outside that i continue to trim or set it to the side. What tolerances are acceptable when full length trimming? Thanks

You do what you want. When someone tells me what I have to do or must do 99% of time I never do it. I seldom as in almost never trim for length. Just keep loading and shooting them. Easily go 5 or more loadings and never consider if I should even check.

 

[David_h]

So what are some good ways to determine max case length for a particular chamber? I can see using a bore scope for a non quantitative indication. Trial and error using progressively longer pieces of brass?

 

[338 dude]

So what are some good ways to determine max case length for a particular chamber? I can see using a bore scope for a non quantitative indication. Trial and error using progressively longer pieces of brass?

SINCLAIR INTERNATIONAL Sinclair Chamber Length Gage | Brownells

Check out the SINCLAIR INTERNATIONAL available Online at Brownells Today and many more Case Length Gauges products are available in our Reloading Department.

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[cape cove]

So what are some good ways to determine max case length for a particular chamber? I can see using a bore scope for a non quantitative indication. Trial and error using progressively longer pieces of brass?

SINCLAIR INTERNATIONAL Sinclair Chamber Length Gage | Brownells

Check out the SINCLAIR INTERNATIONAL available Online at Brownells Today and many more Case Length Gauges products are available in our Reloading Department.

www.brownells.com