Another trimming question.

[RangerBrad]

After watching Shawn Calocks video on long range hunting I have a question. In the video he made sure to trim cases till each got a full cut. My question is after doing this each brass will be a diffrent length. Should all brass be trimmed to the shortest brass so that they are all the same length or is that of little consequence? Thank's Brad

 

[RangerBrad]

I also use a run of the mill RCBS trimmer that is not micrometer adjustable thus when trimming I'm pretty much just guessing at the length till trimmed. Would I do much better with accuracy if using a trimmer that I can measure for while trimming? Thank's, Brad

 

[Tikkamike]

I cant speak for shawn but in my opinion. I like to trim brass so there is a complete ring so that the case mouth is square and the bullet leaves the case on all sides at the same time. Typically your trimmer is set to one length. But maybe he trims more or less on each one depending on the length.
I reccomend the redding 2400 trimmer or if you really want precision the Sinclair ultimate trimmer.

 

[Hookturnr]

I use a lyman trimmer and set it up with a case trimmed to proper dimension. I mic one and trim SLOWLY without the stop locked until I get to the length I want. Then I use that case as my gauge to set the stop and go onward from there. I will trim to .010 shy of max length for my chamber every loading cycle for consistency. I also anneal every 2-3 cycles depending on caliber.

 

[Bullet bumper]

Cases should be trimmed as a "batch " . Measure all the cases untill you find the shortest case and set up to square that case up and all the rest should end up the same. If the batch is large then it could be quicker to pick a length and trim to that then put aside any that don't square up all the way around .
Then measure the batch that did not square up and find the short one and reset and trim all to that. Trimming is more interesting and productive than measuring is.

 

[Gene]

Trimming brass too far below the barrel chamber length encourages formation of a carbon ring just in front of the case mouth. Eventually this carbon build up will result in severe loss of accuracy if not removed. To keep carbon ring to a minum, trim all cases within about .003" below the SAMMI casre length for your caliber.

There are several methods to remove carbon ring, just google it.

 

[Lefty7mmstw]

Trimming brass too far below the barrel chamber length encourages formation of a carbon ring just in front of the case mouth. Eventually this carbon build up will result in severe loss of accuracy if not removed. To keep carbon ring to a minum, trim all cases within about .003" below the SAMMI casre length for your caliber.

There are several methods to remove carbon ring, just google it.

If you use a bronze brush when cleaning your rifle and use powder solvent, this is a non-issue. It's those who choose to clean with patches only or nylon brushes that have odd issues like this. I trim .010" to.015" down from max. and have fired thousands of rounds with everything from 5.56 nato to 405 win with some really nasty bore eaters like the 7rum in the mix. I've never gotten a "carbon ring" in my chamber.
I tried going to shooters choice only for a while(after I ran out of Hoppes) and actually nearly filled the rifling on the 7rum with carbon deposits for the first few inches, but one heck of a scrub down with hoppes #9 and a bronze brush solved that little problem. The shooters choice is reserved for copper fouled bores only now. Funny how the new bottle(shooters choice) says to use powder solvent also, but I don't remember the old one saying that.

 

[J E Custom]

Cases should be trimmed as a "batch " . Measure all the cases untill you find the shortest case and set up to square that case up and all the rest should end up the same. If the batch is large then it could be quicker to pick a length and trim to that then put aside any that don't square up all the way around .
Then measure the batch that did not square up and find the short one and reset and trim all to that. Trimming is more interesting and productive than measuring is.

+1

Cases should allways be at least .010 thousandths shorter than the neck chamber and no more
than .030 to .040 thousandths for best performance.

If they are shorter a thorough cleaning of the chamber each time you clean the rifle is recomended.

I trim/uniform all new cases before loading then before each loading I check to see how much
they have grown and trim back to the first trim length.

This will/should keep the load fairly consistant. A lot of times ,if trimming,annealing and other
practices are not maintained, Groups,pressure,POI may change and also shorten brass life.

J E CUSTOM

 

[cornchuck]

So, I have a question. I have always trimmed my cases to max trim length. Is this good or bad? I have asked this question to someone I used to shoot with and he said he does the same, trim to Max length for decreased throat erosion. Should I get some chamber length gauges? Yes, I do trim my cases at each loading. I don't mind the process. But I could get away from doing it less frequently.

Jason

 

[Hookturnr]

The chamber length gauge can be a big eye opener. I have one rifle that I don't trim to less than .012 over book max length to keep it .010 under the chamber length. Other rifles I've got with min spec chambers almost always end up trimmed .010 under the book spec. As long as you are aware of the carbon ring possibility, you have some options. You won't know just what those options are until you measure the neck of your chamber in some manner.

 

[RangerBrad]

On shawn's video he trimmed case's back till they got a full cut (squared). He did not mention that he trimmed all cases to the shortest length but, that may have been an over sight on his video. He did mention that he wasn't concerned that they were under recommended length as much as he wanted them squared and mentioned that after a few firings they would grow back out to intended length which leads me to believe that he would like to see them all at max length but more importantly squared. What say yal? Thank's, Brad

 

[Hookturnr]

You definitely want them all squared. That being said, I choose to not trim too short or to cull a few if they are too short. I have a 280AI that just doesn't seem to grow cases when FL sizing but it's a **** tight chamber and custom dies too..

A few others I've got you could wait for the life of the brass for them to stretch to a particular length.
I don't let the culls go to waste, they become fun range day ammo, 100yd zero confirmation/foulers etc.

I just like to have as much neck holding the bullet as I can in the big boomers to maintain seating depth through a recoil cycle or rough field handling so I try to keep them longer.

 

[Bullet bumper]

On shawn's video he trimmed case's back till they got a full cut (squared). He did not mention that he trimmed all cases to the shortest length but, that may have been an over sight on his video. He did mention that he wasn't concerned that they were under recommended length as much as he wanted them squared and mentioned that after a few firings they would grow back out to intended length which leads me to believe that he would like to see them all at max length but more importantly squared. What say yal? Thank's, Brad

Squared up is way more important than length. The stuff about carbon rings , well if you are going to get a carbon ring then it is going to form no matter what length the case is. It will just form in a different place give or take a few thou.
Clean properly and you don't get carbon rings.
It is also important to not over chamfer the case mouth . You don't want the mouth edge like a knife as it will start the brass fretting at the case mouth and that encourages nicks and splits if they are going to happen in most cases they will not . Think of the internal case mouth chamfer as the muzzle crowing on the first barrel in the gun. That's a bit extreme because most bullets from bottle neck cases using slow powders are started into the bore by a tube of unburnt powder but it does have some similarities .

 

[Mikecr]

I absolutely disagree with notions about trimming excessively from chamber as a good action.
Yes, it contributes to carbon deposits, but worse and immediately with most cartridges, it increases ES.
This due to varying volume for gas, getting around case necks, that seal with differing timing.
If your shooting a hunting cartridge, and you really really want lower ES, you'll mind & manage your trim length, and neck tension, to reduce variances to your pressure peaks.

I shoot for under 5thou from chamber end. It's not always a choice with factory chambers, but it is with customs. My custom throats are also coaxial and tight(<.0005 over bullet).
With this, and turned necks, my neck soot extends maybe 1/8th" from mouths, and my ES gets into single digits.
That's consistent chamber sealing.