Peened Case Mouths

[Cardboard Assassin]

I have two sets of Lapua 6BR brass which is once fired. I loaded up some rounds (which would be second firing on the brass) and found that when I tried to chamber them the bolt would stop just short of closed.

I inspected the rounds and could see no obvious issues, and I found that if I lightly tapped the bolt forward I could then close it. I shot the ammo like this (it was annoying but shot great with the normal level of accuracy.

I figured I had messed up on headspace and hadn't bumped the shoulders back enough (I measured the original fired cases and bumped them back two thousandths). I use custom Whidden dies (this was my first time using them).

When I got home I looked over the fired brass and took some measurements, I also picked up a Whidden BR case gauge which has measurements and Go / No Go markings. I found that I had bumped the shoulder back but I was still ~ 0.001" shy of the GO length (easy fix, I tried to chamber some prepped brass (no bullet) and it was slightly tight but barely noticeable.

I also noticed that the prepped cases had some peening and I started to wonder if that was a factor. The extra force it took to load a prepped case was definitely less than it took me to load the loaded rounds so I got to thinking if the raised lip on the peened area was what was causing the issue (bullet would expand that area when seated which would explain the extra force required to seat between a loaded case and an unloaded case). To be clear the bullets are not in the lands (measured / confirmed as 0.075" jump).

I used a wet tumbler to clean them with no stainless steel pins. Even without the pins there is still peening on the mouthes (can feel a lip with my finger nail). I will reduce the time from here forward to see if that helps.

I still feel that headspace was the issue but how are others dealing with peening? I have a Giraud and could chamfer it off but I dont want to do this every time (even removing a very minimal amount of material is bound to add up over time.

 

[acourvil]

You are probably either overloading your tumbler or running it too long. Unless the peening is extreme, a quick chamfer should take care of it.

 

[Cardboard Assassin]

You are probably either overloading your tumbler or running it too long. Unless the peening is extreme, a quick chamfer should take care of it.

Don't feel like it was overloaded (only 100 rounds / one lot of brass in the tumbler), as mentioned previously I will try reducing the time.

Reducing the time will help I'm sure but I'm still expecting peening (albeit a reduced amount).

 

[918v]

I have two sets of Lapua 6BR brass which is once fired. I loaded up some rounds (which would be second firing on the brass) and found that when I tried to chamber them the bolt would stop just short of closed.

I inspected the rounds and could see no obvious issues, and I found that if I lightly tapped the bolt forward I could then close it. I shot the ammo like this (it was annoying but shot great with the normal level of accuracy.

I figured I had messed up on headspace and hadn't bumped the shoulders back enough (I measured the original fired cases and bumped them back two thousandths). I use custom Whidden dies (this was my first time using them).

When I got home I looked over the fired brass and took some measurements, I also picked up a Whidden BR case gauge which has measurements and Go / No Go markings. I found that I had bumped the shoulder back but I was still ~ 0.001" shy of the GO length (easy fix, I tried to chamber some prepped brass (no bullet) and it was slightly tight but barely noticeable.

I also noticed that the prepped cases had some peening and I started to wonder if that was a factor. The extra force it took to load a prepped case was definitely less than it took me to load the loaded rounds so I got to thinking if the raised lip on the peened area was what was causing the issue (bullet would expand that area when seated which would explain the extra force required to seat between a loaded case and an unloaded case). To be clear the bullets are not in the lands (measured / confirmed as 0.075" jump).

I used a wet tumbler to clean them with no stainless steel pins. Even without the pins there is still peening on the mouthes (can feel a lip with my finger nail). I will reduce the time from here forward to see if that helps.

I still feel that headspace was the issue but how are others dealing with peening? I have a Giraud and could chamfer it off but I dont want to do this every time (even removing a very minimal amount of material is bound to add up over time.

How many cases are you tumbling at once? Many people overload the tumbler and there is too much weight in brass and not enough pins to cushion. Case necks are soft and they will peen.

 

[Cardboard Assassin]

How many cases are you tumbling at once? Many people overload the tumbler and there is too much weight in brass and not enough pins to cushion. Case necks are soft and they will peen.

100 cases (1 lot) at the time. No pins. Interesting to hear you say pins help to cushion as many times I have read that pins cause peening.

Recently I have not been using pins so much, it makes the process much easier and I find it removes enough dirt to keep the dies clean but still leaves a little carbon in the neck which makes seems to seating more consistent (vs squeaky clean brass).

 

[918v]

100 cases (1 lot) at the time. No pins. Interesting to hear you say pins help to cushion as many times I have read that pins cause peening.

Recently I have not been using pins so much, it makes the process much easier and I find it removes enough dirt to keep the dies clean but still leaves a little carbon in the neck which makes seems to seating more consistent (vs squeaky clean brass).

Individual pins weigh nothing relative to what a case weighs. Pins hitting the case mouth don't cause peening. Cases hitting case mouths cause peening.

 

[marchboom]

Individual pins weigh nothing relative to what a case weighs. Pins hitting the case mouth don't cause peening. Cases hitting case mouths cause peening.

I agree. Water provides very little to slow down the cases when they are tumbled. The reason you don't hear about peening with media tumbling is that the cases don't fall onto other cases. They just slide around and don't hit each other with enough force to damage other cases. Other than cases coming out REALLY shiny I don't see any benefit to the wet tumbling method.

 

[GONE BAD]

Fill your tumbler brim full with water and then tumble

 

[CK1.0]

As mentioned above, the peening is from cases crashing into other cases, period, full stop. It has nothing to do with the pins vs no-pins.

That said, the SS pins are considered "cushoning media", so they actually help by taking up volume and in that if you want the greatest cleaning action in the shortest tumbling time, it might make sense to use them... YMMV.

You need to slow down the cases when they're flying around in the tumbler...

I had heard of some old benchresters using tennis balls... it worked better than without, but was pretty heavy handed and threw some of the cases around worse, could've been better. I ended up cutting up some Pelican foam I had kicking around and using it to take up some of the extra volume in the tumbler once I've filled it up 3/4 of the way.

I try to only do 100 cases at a time and use all the pins I've got (5lbs) and never tumble longer than 1 hour. No more peened case mouths.

Honestly though, if someone could come up with a way to slow down tumblers, that'd be even better, because excessive speed is part of the problem. IMO my Frankford Arsenal tumbler would be a bunch better if it had a half-speed setting.

 

[Wheres-Waldo]

I messed with this in my STM tumbler before finally fixing it to my satisfaction.

I fitted a larger diameter driven wheel to reduce the gear ratio and effectively slow the drum down by 33%, and also I run a shit ton of pins, double what they send with the kit… I want to say 5 lbs but not sure. I also let cases soak in the drum beforehand and do the soak/tumble with HOT HOT water/dish soap/Lemi-Shine/car wash & wax.

I also only run for a maximum of 60 minutes. My stuff comes out blingy.

Still trim, chamfer & deburr every time, but the rolled over case mouths are gone.

 

[2aBaC̶a̶]

Franklin tumbler user. Ive minimized the peening by using a double dose of pins, full water, under 1hr run time. I can do up to 200 6.5cm cases at a time. I almost think more is better.

Still needs a chamfer, debur.

 

[918v]

I am overjoyed to hear that.

 

[Cardboard Assassin]

So I ran the same set of brass and used the pins this time.

I also only ran them for 30 minutes. The brass was clean enough (not crazy clean but ok for such a short cycle).

There was the faintest hint of peening but it was virtually non existent compared to the the longer session with no pins, much better.

The rounds being hard to chamber was 100% from the peened case mouths and not from headspace.

Lesson learned.

 

[marchboom]

If you can see peening that means the brass has been work hardened. Unless the brass was designed to be peened (work hardened) every time it is cleaned, IMO the brass has been damaged.

I have looked at every possible benefit of wet cleaning and besides getting the brass really clean, the negatives greatly outweigh the benefit of really clean brass.

 

[Cardboard Assassin]

If you can see peening that means the brass has been work hardened. Unless the brass was designed to be peened (work hardened) every time it is cleaned, IMO the brass has been damaged.

I have looked at every possible benefit of wet cleaning and besides getting the brass really clean, the negatives greatly outweigh the benefit of really clean brass.

Not sure what to say except that I used one batch to shoot an F class match on Sunday and it worked great (it chambered perfectly with very stable speeds).

With regard to the work hardening I anneal the brass after cleaning / before sizing every time.

 

[marchboom]

Glad it's working for you. Yeah, annealing would be the way to counter the work hardening issue, not to mention keeping the neck tension the same as much as possible.

 

[tlsmith22]

I had this exact same problem and I use no pins also. I cut the run time down to 30 minutes and because I have a Henderson trimmer, I trim every time. I have had zero issues since. I was tumbling for 2 hrs before.

 

[acudaowner]

need pics .

 

[acourvil]

If you can see peening that means the brass has been work hardened. Unless the brass was designed to be peened (work hardened) every time it is cleaned, IMO the brass has been damaged.

I call BS on this. Tumbling a reasonable amount of brass for a reasonable time will not have any meaningful effect. At the worst, you will work-harden a micro thin layer at the surface of the metal. To work-harden a piece so that you gain measurable hardness, you would need to apply pressure to penetrate the surface and change the grain structure of the metal below the surface.

 

[marchboom]

I call BS on this. Tumbling a reasonable amount of brass for a reasonable time will not have any meaningful effect. At the worst, you will work-harden a micro thin layer at the surface of the metal. To work-harden a piece so that you gain measurable hardness, you would need to apply pressure to penetrate the surface and change the grain structure of the metal below the surface.

Did you notice my disclaimer? "IMO". You can believe whatever you want and clean your brass however you want. I stated MY OPINION.

 

[acourvil]

Facts are important in forming an opinion.

 

[marchboom]

Facts are important in forming an opinion.

And these are the facts as I understand them. Do your loading as you want to and stop trying to convince everyone else that there is ONLY one way to do something...........Your way! Shooting matches are won by shooters who do things differently than some other shooters do them. And they win too. Bother someone else.

 

[918v]

Did you notice my disclaimer? "IMO". You can believe whatever you want and clean your brass however you want. I stated MY OPINION.

Your opinion is based on nonsense.

 

[acourvil]

And these are the facts as I understand them. Do your loading as you want to and stop trying to convince everyone else that there is ONLY one way to do something...........Your way! Shooting matches are won by shooters who do things differently than some other shooters do them. And they win too. Bother someone else.

I didn’t express any opinion about what way to do anything, I simply pointed out that what you said is factually incorrect. Stating something that is demonstrably not true is not justified because it is your “opinion.”

 

[2aBaC̶a̶]

Seriously?

 

[CK1.0]

Occam's razor: It's not work-hardening, it just plain fucks up the mouths because the brass is thin there and they're crashing into each other, plus, we keep it that way by chamfering our case mouths every loading.

Has anyone ever tried a variac on a rotary tumbler..? I'm thinking of buying one to see if I can slow down my tumbler so it rolls them through the pins slow-dance style instead of a mosh pit. I have a suspicion slow might actually clean faster (if that makes sense), and be easier on the case mouths.

Figure the worst that could happen is I fry a tumbler... but it might work, IDK?

 

[CK1.0]

Behold, I may have found the end to peened case mouths:

Search for a "fan speed controller", this one was like $12 off Amazon.

I've only run 1 batch of cases so far, but the device allowed me to slow my Frankford Arsenal Rotary Tumbler down to half-speed, and the results were great, no peening whatsoever.

I ran the cases for 2 hours at half-speed (instead of my usual 1 hour), using all the pins I have (~5lbs).

FWIW, turns out the timer built into the FART is just a passive timer (like a kitchen timer) so lowering the voltage to the tumbler's motor didn't affect the timer and it still worked as usual.

Still too early to tell for sure whether this thing hurts the tumbler or not long-term, and only time will tell if this thing lasts... but slowing down the tumbler to actually tumble the cases, and not whip them around and crash them into each other, seems to have done the trick.

 

[Haney]

Great idea , going to order one up . Thanks for posting .

 

[2aBaC̶a̶]

I've been running mine with 12lbs of pins and full water 30min-1h. no more peening

 

[just browsing]

As everyone else has said, more pins and chock full of water makes the biggest difference. Fill that bitch up with brass too.

30-45 minutes is all you need. Enough time for the pins to clean the interior and exterior surfaces without stripping them completely.

 

[acudaowner]

rebrand that answer , and lable it as you product charge 600 dollars for it make a couple mill and never need ammo ever again unless you want to . also to point out I myself am more than happy to recieve money as a thanks for the idea , as a poor person one can never have enough to buy more ammo or tp .

 

[CK1.0]

Think I’m going to order some more pins, as I think that can’t hurt (might clean better actually), and of course the added weight slows the tumbling down some. Slowing the tumbling down seems to keep the cases more in the pins at the bottom and less floating all around, really it’s as simple as that I think.

Just beware guys, I haven’t tested this thing for cycles and cycles, but the results sure look promising!

 

[CK1.0]

These were:
> fired
> annealed (AMP Aztec)
> deprimed
> FA 7L tumbler, ~5lbs SS pins, 98% full of water, splash of Armor All Wash & Wax and pinch of Lemi-Shine, 90 minutes, speed turned down to around half of its normal speed with the “fan speed control“ thingy mentioned earlier.

I probably don’t have a good enough camera to show it, but the necks look great, no real peening to speak of.

It probably helps that I only deburr the outside of the case-mouths/necks once when new, and whenever I trim. Otherwise, I just chamfer the inside of the case-mouths every time. I think leaving the outside of the necks alone and not thinning them out unnecessarily helps protect them a little better when they’re bashing around in the tumbler.

Anyways, so far, so good…

 

[DeathBeforeDismount]

This is why you hit them with the henderson before loading. Chamfer the necks so they are easier to size as well as keeping them from getting peened.