Is chamfering necessary ?

[hounddawg]

F Class John has posted a video using the new AMP press and one of his first tests involved chamfering. Oddly enough the best groups came from the non chamfered cases. Anyway that got me to thinking, always a dangerous thing that thinking. I asked myself what is the purpose of a inside neck chamfer? The answer is obvious of course, it provides a wedge effect for allowing the bullet to expand then neck. It also removes any burrs which could gouge the copper jacket. But consider this , the boat tail bullet is a natural wedge and even the flat base target bullets have a slight bevel at the base. As far as the burs are concerned unless you have trimmed the case there should be no burrs. Even if the case has been trimmed if it was tumbled afterward any burrs would be peened smooth by the pins or dulled by the walnut media.

anyway just curious as to whether you guys think a chafer is necessary, I am going to try some with a very light chamfer or or no chamfer just to see.

My own pet theory is the chamfers can be uneven and when the bullet exits the case and result in a uneven release of the bullet and venting off the gas in the case which could cause a wobble in the bullet the as it enters the throat.

Link to F Class Johns video

https://www.youtube.com/watch?v=yhD8nSEwJ2c

 

[STORM2]

This thought has crossed my mind also but then what might the neighbors think? Who am I to talk about brass time, I check the solution ph with litmus paper…every batch.

 

[GJeffB]

hounddawg, I've never measured the neighbors ph, but that notwithstanding ...
we may be discussing different issues. But I load 99% cast lead. Almost always have. Having said that, I've found a chamfer to be a fine compliment to a slight case mouth bell. Less bell I assume results in less case mouth split over time. I don't know if the chamfer reduces or increases splits. I just know that I've been doing both, in moderation, for many many years.

Having said that ... the efficacy when using jacketed, especially boat tails, I can't really speak to.

-jb, kind of a "yes, but ..." reply

 

[GeauxTide]

I only chamfer when I trim.

 

[Don Fischer]

This frost's my butt. I've been champhering case's for over 50 years and now your telling me it's not necessary? Well best I know it never caused me a problem other than early on when I did to much. Think I'll keep it up!

 

[44 AMP]

I will tell you with certainty that sometimes it is necessary, even when there are no burrs.

With some brass and bullets it doesn't matter much but with others it can.

Do you know how much .22 Hornet brass costs?

and do you know that case mouth brass is darn near paper thin and loves to buckle when seating a bullet, no matter how slow and careful you are? (and boattails didn't make a noticeable difference) I found that those cases actually survived better when given MORE chamfer than I usually used on other larger cases. What is of no real concern with a large .30 caliber case with a sturdy neck is a different matter with a small case and a very thin neck.

My own pet theory is the chamfers can be uneven and when the bullet exits the case and result in a uneven release of the bullet and venting off the gas in the case which could cause a wobble in the bullet the as it enters the throat.

I thought about this for a bit, and I think your theory needs some rethinking.

First off, I think its overfocused on minutae, but consider this, when you chamfer (and assuming its done correctly) all you are doing is removing a little metal so there is no sharp 90 degree edge on the inside of the case mouth. You make no change to anything else. The entire length of the case neck in contact with the seated bullet is the same, chamfer or no chamfer.

That sharp edge you "break" with the cutting action of the chamfer tool doesn't touch the seated bullet, because its not there to do so. The "final point of contact" between the bullet and the case isn't that chamfered edge, its the case neck just below that, and you don't touch that when you chamfer the case mouth. I think any uneveness in the case neck releasing the bullet would be due to factors other than the chamfer. Brass elasticity, variance in neck tension even differences in neck thickness might cause it, but none of those things is affected by chamfering.

I might be wrong, I'm not a guy who builds ammo for Nth degree accuracy, my guns wouldn't know it if I did, and for me there's no point, my ammo shoots better than I can, anyway.

Point here is, there are some circumstances where a good chamfer extends case life and also many situations where potential accuracy differences between chamfered and unchamfered brass is irrelevant.

If your game is the smallest groups possible, go for it, and enjoy it. Is a fun game. My game is what hits what I aim at. And if I don't have to do extra work to get what I want, I don't do extra work. I'm lazy that way.

As a friend is fond of saying, "that's interesting. How does it help me put an elk in my freezer with my Model 99 .300 Savage??

 

[Metal god]

The answer is obvious of course, it provides a wedge effect for allowing the bullet to expand then neck. It also removes any burrs which could gouge the copper jacket

This is NOT directed at you dawg .

I'm SO sick of these F-class bench rest guys thinking they know everything as if what they are doing and why is EXACTLY the same as every reloader in the world . This comes up especially when talking annealing .

I chamfer the insides of my necks after trimming for two reasons 1) It removes the shavings of brass left behind . Anyone that has sized a LC 308 or even a 5.56 case with a small base die that was fired in a machine gun knows there is so much material being removed do to the case extruding out through the neck when being FL sized the case length can grow .010 to .015+ . So much so at times the shavings on the insides of the neck looks likes there's sheets of brass stuck to the edges , even to the point of jamming up the pilots on the trimmer . lol yeah F-class John , seat a bullet in a case neck like that and tell me how well it shoots

This points out how these F/Bench guys think . Totally ignoring that they are likely using a custom cut chamber and sized brass that pretty much fits it PERFECTLY so it expands minimally when fired resulting in very little if any extruding brass forward when being resized . It seems more and more of these experts live in there own world and think everyone else lives there with them

The second reason is simple , I called chamfering "deburring the insides of the necks" once in a thread years ago and was quickly told/reminded by several posters that you de-burr the outside of the neck and and it's called chamfer if doing it to the inside . So the second reason I chamfer is because that's what it's called when de-burring the insides of your necks after trimming . For me it has ZERO to do with seating a bullet , bullet release , bullet hold or concentricity . It's all about getting the shavings out from the insides of the neck after trimming . Note I have chamfered some necks in specific handgun cartridges a little more to help with seating soft lead bullets . Hell I've even tried double chamfering , first with a VLD then a standard to see if that helped . Oh I just heard the ghost of Unclenick say "get a damn M-Die already" lol

END RANT
MG

 

[hounddawg]

Thanks for some interesting thoughts. Point taken on different situations. I can absolutely see where with cast bullets it would be necessary. Not sure how taking away brass from the neck would prevent splitting with a boat tail though.

On splitting hairs and minutia, yep it is what long range shooters do. When something may give one more point out of 200 in a game where first or second are often decided on the X count it is worth thinking about. If that does not apply to your style shooting, no problem

edited for civility

 

[gwpercle]

After trimming a case neck I will give it a light inside and outside chamfer to remove burrs or any rough edges and call it a day .
I have seen some "experts" on the you tube putting a chamfer on the inside like they were making a funnel ... I don't get the reasoning of that and see no need . Cutting away all that metal inside the neck can't help with neck tension at all .
Rather than excessive chamfer funneling a Lee Universal Neck Expanding die or a Lyman M-die will create a nice flare and not cut away any neck thickness .
I don't get it and I don't subscribe to the excessive inside chamfering method .
Gary

 

[Unclenick]

Houndawg,

Commercial ammo makers don't chamfer, but they generally do tumble the case for a good bit after the trimming saw has done its thing, and this rounds the edge of the mouth. When they fail to do that, the edge stays sharp and shaves copper off the bullet. Here's a close-up photo of a round of the old Winchester Supreme S308M ammunition. The circled area shows the worst shaving, but there is a little bit all around the neck:

So, now here's a dirty little secret: The edge of a freshly chamfered case where it meets the straight part of the neck wall can do the same thing, despite its obtuse angle. You just don't see it because of the small gap between the brass and the bullet created by the chamfer at the case mouth. I didn't discover this until I pulled a moly-coated bullet from a loaded round and saw all the moly below the case mouth position was completely scraped clean. I mean, no trace of moly below the neckline. I also found that if I followed chamfering up by dulling that edge, it stopped, and moly bullets would seat and pull with the coating intact.

To do the dulling, at first I put a half-inch hardwood dowel in my drill press and sharpened it like a pencil with a file. Pushing the case mouths up onto the spinning wood point would quickly dull the sharp corner. But it also quickly wore the wood down, so it wasn't a permanent solution. I also applied Craytex tips on my Foredom tool and a couple of other tricks. One was simply running the case mouth onto and of a carbide expander a couple of times. This was pretty good, though I still got a couple of scratch lines here and there.

The person who gave me a permanent solution was Bart B. He'd run into this before and knew the cure: take an EZ Out, with its coarse left-hand twist, and polish it up and run the case mouths onto the smooth, spinning steel. It's fast and stops the scraping. The left-hand helix in a right-hand spinning drill tries to climb out of the case mouth rather than dig in, so the cases don't mind. It's advantage over wood is it doesn't wear out and doesn't seem to need cleaning. I tried a simple pointed piece of steel, but the brass accumulated on it.

I haven't tried the EZ-out on an unchamfered case, but suspect it would work to dull a freshly trimmed edge, too.

 

[Bart B.]

After trimming resized cases then deburring with a standard tool, I have run the case neck on then off a bronze bore brush spinning in a drill press, this rounds off the inside sharp edge so it doesn't scrape off bullet jackets.

Use a magnifying glass to look for tiny strips of jacket peeled off seated bullets.

 

[Unclenick]

Do you like that better than the EZ-out? I've seen a couple of things to suggest a brushed inside neck gives more uniform hold. Also, an example of someone using alcohol and graphite to lube that brushed surface.

 

[hounddawg]

I like the bore brush idea better than my idea of burnishing the edge, thanks Bart

I use the Imperial graphite already, a bit messy but I dip the neck then wipe the outside of the case with a paper towel before adding powder so the mess is minimal

 

[Bart B.]

Unclenick,

I've seen the least amount of jacket peelings that way. Least amount of scratches on pulled bullets, too.

 

[7.62 man]

I don't really champher the inside of the case after trimming I try to just remove the burr that drags down the side of the round. I think if the jacket material is even around the projectile it will give a better truer flight.

 

[kilotanker22]

My VLD chamfer tool works better than my standard tool, but still leaves the scratches. I have been thinking of a way to solve this and I am glad I saw this thread. The Bronze brush in the case neck seems perfect for me.

 

[1100 tac]

Have been using the bore brush method after vld chamfer for over six years now. A few things to consider though, new brushes cut a little too aggressively, so it helps to break one in with something beside your cases. I just drilled an appropriately sized hole in a chunk of brass that I had around the shop. an already worn brush works fine. I also use a bore mop with de-natured alcohol to clean the inside necks after brushing.

I have experimented with Neolube # 2 after brushing, but haven't had time to do much testing with that yet, feels pretty consistent seating bullets though.

It is interesting to look at the before and after processing condition of the inside of the case necks with a bore scope, and the texture of new case necks of different brands before processing.

Don't know how all this affects bullet weld yet, my ammo doesn't get a chance to sit around for a long enough time.

 

[Bart B.]

Lake City ammo plant made 30 caliber match ammo case neck ID's a few thousandths larger than match bullets. It was smeared with black asphaltum before the bullet was seated. When dry, the "glued in" bullet needed at least 260 psi in the case to start pushing it out.