What to do with case mouths when the brass doesn't grow

[dgeesaman]

My reloading experience is with 6PPC and 6BRA using less than match loads. So after fireforming, the brass doesn't grow much if at all. This leads to a few questions:
1) Should I trim the cases periodically anyway to keep the lengths uniform?
2) If not, should I chamfer the inside edge periodically to ensure the inner edge doesn't get rough?

Thanks,

David

 

[Lefty Trigger]

I run all my brass for my 6BR and 6BRX through the trimmer about every 5th reload, only ever find a few that got slightly longer. I anneal them every 4th reload and chamfer the inside every other time but just a slight touch. Now that I'm sonic cleaning my brass the stainless pins don't beat up the case mouths when I would wet tumble.

 

[Rsadams]

This is just what I do.... I trim to equal length everytime....

 

[JMayo]

My 6bra doesn't grow enough to trim. I've got some fired 20 + times.
I suppose I need to measure them again, find the shortest, make em all that length.

 

[strat81]

I run my brass through the trimmer after every firing because it's fast and easy. I figure it gives me consistent neck lengths, which should aid in consistent neck tension.

 

[mikecr]

It's common for necks to pull back on fire forming. Especially when outright improving shoulders. They'll grow with sizing.
Trim them as they get within the chamber end clearance you desire. Eventually they'll all be where you want. No reason to re-chamfer until you've trimmed your chamfer.

 

[golong]

Pretty much already been said...

FLS will eventually get them to grow. If you are not using an expander it will take longer - no need to be in a hurry. Also keep in mind that most SAAMI chambers have more room than the book. You may want to gauge your chamber or get a look at it with a bore cam while an empty sized piece of brass is in the chamber. Trimming too short is not the best.

I chamfer the entire batch if they have been tumbled wet or dry. I currently do not trim until they get to where they need to be trimmed. However, I have a Giraud on order so within the next couple of weeks I will probably just run everything past the trimmer.

 

[dgeesaman]

My 6bra doesn't grow enough to trim. I've got some fired 20 + times.
I suppose I need to measure them again, find the shortest, make em all that length.

Like he said: the brass doesn’t grow.

Fire formed brass: 1.548, 1.546, 1.547, 1.545, 1.547.

10x fired, some w loose pockets: 1.545, 1.546, 1.547, 1.547, 1.546. Full length sized only.

My Wheeler 6BRA reamer print says 1.570 chamber length, and I clean the neck with a 7mm bronze brush to remove carbon buildup in the gap.

So I could trim down to 1.545, but it will basically stay there.

David

 

[garandman]

How does one trim brass that doesnt grow? Is that like ppl who wear a wig getting a haircut ? Or using a lawn mower on astroturf?

 

[Twicepop]

Case design has more to do with brass "growing" than any other factor, doesn't it? The aforementioned cartridges all have at least 30 degree shoulders and minimal body taper, to maximize internal capacity and reduce brass growing, right? A friend of mine shoots a 22-250 AI, he says after the first fire-forming and prepping he no longer has to trim brass for this gun.

 

[wildfowler]

My 6bra doesn't grow enough to trim. I've got some fired 20 + times.
I suppose I need to measure them again, find the shortest, make em all that length.

I’ve always wondered how competition shooters handle odd sized lengths. Is this what everyone does or do some try and keep size variation to no more than a certain amount? Say +/- .002” of a number?

Thanks.

 

[Joe Salt]

Once the brass is fired at least three times, then I sort by length then trim to the shortest length and hope they grow together, good luck there! But I always put them in the Wilson trimmer to see if they need trimming. then chamfer the inside, and DE-burr.

Joe Salt

 

[garandman]

I dont trim unless out of spec. I check to make sure they have a good case mouth chamfer.

Then I put primer, powder and bullet in them.

 

[Brians356]

If all you want to do is avoid roughness, don't chamfer, just twirl the end of the case against a wad of 0000 steel wool. It will be as smooth as a baby's bee-hind.
-

 

[dgeesaman]

I dont trim unless out of spec. I check to make sure they have a good case mouth chamfer.

Interesting because a secondary question is what are the spec brass lengths for 6PPC made from Lapua 220R and 6BRA. The PPC brass tops out around 1.490 and the “book” says 1.500.

The 6BRA doesn’t have a published trim length and looking at my reamer print, it’s a long way for the mouth to reach the end of the chamber neck. Based on my numbers above I’m guessing 1.545.

As for visually inspecting a chamfer that’s only a few thou in size, I’d like to know your method. It sounds a bit like trying to sort gnats by their ass size in the dark.

 

[garandman]

Interesting because a secondary question is what are the spec brass lengths for 6PPC made from Lapua 220R and 6BRA. The PPC brass tops out around 1.490 and the “book” says 1.500.

The 6BRA doesn’t have a published trim length and looking at my reamer print, it’s a long way for the mouth to reach the end of the chamber neck. Based on my numbers above I’m guessing 1.545.

Non scientific I know, but if it chambers, it chambers. And if it groups good, then I'm happy. I'd guess consisency in case length is more important than being "spec" so long as it chambers.

As for visually inspecting a chamfer that’s only a few thou in size, I’d like to know your method. It sounds a bit like trying to sort gnats by their ass size in the dark.

I dunno. Never really had a problem with that. Visual inspection in good light / how the bullet seats tells me what I need to know. I'm not a real fuss-budget in my loads. I'm looking for 0.25 - 0.45 MoA.

When it doubt, re-chamfer.

 

[mikecr]

A few thou in case OAL variance means nothing to anything. But trimming way short of the chamber end can affect things. There is no credible reason to do it.

 

[dgeesaman]

A few thou in case OAL variance means nothing to anything. But trimming way short of the chamber end can affect things. There is no credible reason to do it.

How short is way short? Because my Lapua brass is .025 short after forming. It seems reasonable but on the large end of things.

When it doubt, re-chamfer.

My experience so far is if your chamfer tool is a dull handheld “rocket” type it won’t do much damage. If it’s a nice sharp VLD chamfer tool, you could end up with a knife edge after a few cycles.

One reason I’ve asked is because I considered buying a VLD chamfering tool. But when seating boattail bullets it takes almost no chamfer at all. So that trimmer may be a solution in search of a problem.

 

[garandman]

@dgeesaman ... I use the mechanical hand help type. Its not dull, I dont think.

 

[dstoenner]

@dgeesaman ... I use the mechanical hand help type. Its not dull, I dont think.View attachment 1132440

As Einstein said “dull is relative”. I use the same tool but with a light hand just to break the edge

one thing about case growth is that it can be uneven. I see this in my 6br cases where one side of the case mouth is bright and the other isn’t. I trim every firing to keep the mouth of the case as square as i can get.

David