6BRA Brass Issue

[a-dog]

I need some help with my brass prep. After I trim, chamfer, and deburr, I am left with this slight burr on the outside of the case mouth. Sometimes it is so minor that it's no big deal. However, sometimes it's just bad enough to cause an issue with chambering. It's noticable enough that my fingernail will catch on it. I'm shooting this from a Defiance Deviant single shot action in my F-class rifle. I'm using a Frankford Arsenal trimmer and then separate chamfer and deburring tools. I have attached a pic that points to the problem area. Has anyone ever experienced this?

 

[Bill Norris]

Saw this with my Lyman deburring tool. Started just letting the tool weight lay against it and not put any undue pressure on it. Solved my issue.

 

[Rick300]

My Lyman tool did this also. I ended up getting the RCBS carbide chamfer tool and that cured it.

 

[gunsandgunsmithing]

Possibly over annealed. That would leave the case mouth "dead" with no springback, which will very slightly bell the case mouth enough to do it. Part of the reason I mention it is because, IMHO, the brass has the slightly over cooked look, too. It's not trash but if that's the issue, it'll go away after firing it a couple or three times without annealing again. Easy enough to verify, either way.

You should have at least .002 and closer to .003 clearance but I bet if you check it, the "burr" is actually a tiny flare.

Seldom saw this kinda thing before annealing became "mandatory" to shooting well. See it pretty frequently now though.

It could be something else but that's my bet, which is tough without having it in my hands.

 

[a-dog]

Possibly over annealed. That would leave the case mouth "dead" with no springback, which will very slightly bell the case mouth enough to do it. Part of the reason I mention it is because, IMHO, the brass has the slightly over cooked look, too. It's not trash but if that's the issue, it'll go away after firing it a couple or three times without annealing again. Easy enough to verify, either way.

You should have at least .002 and closer to .003 clearance but I bet if you check it, the "burr" is actually a tiny flare.

Seldom saw this kinda thing before annealing became "mandatory" to shooting well. See it pretty frequently now though.

It could be something else but that's my bet, which is tough without having it in my hands.

Interesting. I never thought annealing could be the issue. I just assumed it was an issue with my trimmer going dull or something. I'll try your recommendations!

 

[gunsandgunsmithing]

Interesting. I never thought annealing could be the issue. I just assumed it was an issue with my trimmer going dull or something. I'll try your recommendations!

Whatever it is, I hope you find it easily and know for sure but it sure does look like it's over baked, just a little bit and that could do it.

Measure behind the "lip" and if your clearance is right behind it, shoot it and narrow it down one thing at a time. Another thing that I see and I simply don't know the physics behind is, when I neck my new Lapua brass down from 6.5 to 6mm, it leaves a similar bell mouth that goes away entirely after the first firing and never comes back. I can't explain that but it just does. It normally chambers fine but is really close in that regard until I get it fired once...problem solved, and it shoots pretty danged good on the fire forming shot too. Got second place in a br match a couple of weeks ago shooting ammo that had been loaded since last September, about half of which was unfired! Go figure. Lol

 

[jxb]

I would check them after trim to assure it's what is expected, little to none as that may be where it's occurring and need a new or sharpened trim head.

I had your issue on new brass where it came with a pretty good amount and I was having issues removing with my old deburring tool, I got a new one which works noticeably better and quicker. A good sharp deburring should take it off without any real pressure or effort. Side note, I do mine after using my expander mandrel which assures they are round/concentric, can really notice the difference when using a hand deburring tool as it feels/looks like even cutting all around.

 

[Straightshooter1]

I need some help with my brass prep. After I trim, chamfer, and deburr, I am left with this slight burr on the outside of the case mouth. Sometimes it is so minor that it's no big deal. However, sometimes it's just bad enough to cause an issue with chambering. It's noticable enough that my fingernail will catch on it. I'm shooting this from a Defiance Deviant single shot action in my F-class rifle. I'm using a Frankford Arsenal trimmer and then separate chamfer and deburring tools. I have attached a pic that points to the problem area. Has anyone ever experienced this?
View attachment 1547276

Yes, I've experienced this. . . as a result of my deburring tool not being sharp enough. Once I got a good sharp deburring tool, problem solved. I also had the same issue with the 3-way cutter on a Trim-it II and once I got a new cutter, no more burr left.

 

[a-dog]

I would check them after trim to assure it's what is expected, little to none as that may be where it's occurring and need a new or sharpened trim head.

I had your issue on new brass where it came with a pretty good amount and I was having issues removing with my old deburring tool, I got a new one which works noticeably better and quicker. A good sharp deburring should take it off without any real pressure or effort. Side note, I do mine after using my expander mandrel which assures they are round/concentric, can really notice the difference when using a hand deburring tool as it feels/looks like even cutting all around.

Yes I trim only after I size and expand to ensure concentricity as well.

 

[Owens85]

I would take a real good look at the faint line in the middle of that case.

Believe that's just from the FA trimmer . There's a plastic sleeve the case goes into and the top of the sleeve leaves a cleaned area where it rides when trimming. Does the same to my cases if the sleeve is tight on case.

 

[DJSBRS]

I always chamfer the outside last to eliminate any possible inside chamfer burr's left from dull tools or misalignment while chamfering inside.

DJ
DJ's Brass Service

 

[bugman]

sharper tools with finer flutes, followed by 0000 steel wool.
Lot less force....you just need to uniformly break the edge and remove the burs from trimming...not sharpen a knife.

 

[ASbobcat]

I need some help with my brass prep. After I trim, chamfer, and deburr, I am left with this slight burr on the outside of the case mouth. Sometimes it is so minor that it's no big deal. However, sometimes it's just bad enough to cause an issue with chambering. It's noticable enough that my fingernail will catch on it. I'm shooting this from a Defiance Deviant single shot action in my F-class rifle. I'm using a Frankford Arsenal trimmer and then separate chamfer and deburring tools. I have attached a pic that points to the problem area. Has anyone ever experienced this?
View attachment 1547276

Chamfer/debur tools all do an inadequate job. I see it every time. I remove this lip with Scotchbrite brown pad, followed by a Dremel hard rubber polishing on inside and outside of mouth. It is laborious, but will prevent another problem.

If you don't remove this, small brass chips will eventually gall your sizing die and or bushings, Removing this galling is far more laborious than dealing with the lip. Redding TiN bushings are the worst. They are magnets for these chips. Your indications of this problem are scratches on the brass.

Polishing the inside will prevent scratching of bullet jackets.

 

[a-dog]

Chamfer/debur tools all do an inadequate job. I see it every time. I remove this lip with Scotchbrite brown pad, followed by a Dremel hard rubber polishing on inside and outside of mouth. It is laborious, but will prevent another problem.

If you don't remove this, small brass chips will eventually gall your sizing die and or bushings, Removing this galling is far more laborious than dealing with the lip. Redding TiN bushings are the worst. They are magnets for these chips. Your indications of this problem are scratches on the brass.

Polishing the inside will prevent scratching of bullet jackets.

I was hoping to avoid having to add another step to the process but I guess it's unavoidable. I should probably upgrade to a higher quality trimmer like a Giraud or Henderson.

 

[Rick300]

I was hoping to avoid having to add another step to the process but I guess it's unavoidable. I should probably upgrade to a higher quality trimmer like a Giraud or Henderson.

A good SHARP tool will eliminate the problems you are having. The issue with good SHARP tools is adapting to how much LESS pressure you need to do the job. The first couple of cases you might get necks that are knife edge sharp, but you soon learn the proper technique.
The cases I had with the problem became so bad that I finally resorted to running them all through my neck turner again to knock off the lip. No problems after that and a valuable lesson learned.

 

[a-dog]

A good SHARP tool will eliminate the problems you are having. The issue with good SHARP tools is adapting to how much LESS pressure you need to do the job. The first couple of cases you might get necks that are knife edge sharp, but you soon learn the proper technique.
The cases I had with the problem became so bad that I finally resorted to running them all through my neck turner again to knock off the lip. No problems after that and a valuable lesson learned.

What trimmer do you use and recommend?

 

[Rick300]

I use PMA trimmer and neck turner, but 6BRA rarely needs trimming. As I stated above, the RCBS carbide outside chamfer tool works great. I use these mounted on a Lyman prep center.

Amazon.com

https://www.amazon.com/RCBS-Trim-Mate-Carbide-Chamfer/dp/B0063IDGBS/ref=pd_bxgy_d_sccl_2/130-2084422-7247129?pd_rd_w=Br2XL&content-id=amzn1.sym.9713b09e-9eac-42a7-88bb-ecfe516a6b92&pf_rd_p=9713b09e-9eac-42a7-88bb-ecfe516a6b92&pf_rd_r=18G3GWYJB1BMA29BSFMH&pd_rd_wg=GrFzz&pd_rd_r=c10ba617-9b25-4dcf-8157-37f35ef0e99e&pd_rd_i=B0063IDGBS&psc=1

 

[JEFFPPC]

I would take a real good look at the faint line in the middle of that case.

That ring can also come from riding in the cartridge box. See if it mates up.

 

[Fuj]

I just replaced my carbide trim to length cutter. Even carbide
wears out. A fresh cutter will not leave much of a burr. A dull
cutter will push material to the side and not cleave it off the edge.
And use the tightest fitting pilot you can get your hands on. A loose
in the neck pilot will do you no favors.

 

[a-dog]

The ring you see in the middle of the case is just rubbing from the trimmer.