Flash hole deburr question

[Uncle Ed]

Many deburring tools have the cutter enclosed in a metal tube, and the mouth of the tube stops the depth of cut like the one at the link below. Meaning no matter how thick the flash hole web is the cutter always removes the minimum amount.

K&M Replacement Flash Hole Uniformer Cutter 0.080"
https://ads.midwayusa.com/product/714802/k-and-m-replacement-flash-hole-uniformer-cutter-0080?utm_medium=shopping&utm_source=google&utm_campaign=Reloading+-+Metallic+Reloading+Equipment+(Not+Presses)&utm_content=714802&cm_mmc=pf_ci_google-_-Reloading+-+Metallic+Reloading+Equipment+(Not+Presses)-_-K&M-_-714802&gclid=EAIaIQobChMInrz7uIvH4gIVCI_ICh13DAyzEAQYCCABEgIpAPD_BwE

Below deburring tools with adjustable stops at the case mouth will remove more brass from the case on the right, if adjusted for the case on the left.

Below another example of deburring tools that will not remove too much brass because of the stop on the cutter.

 

[spclark]

was size spring? post a pic of the setup thanks

Have to wait a bit... on road to MN LR Regional right now.

Size ~ twice dia. of ball point pen spring, maybe 1-1/2 x length, heavier spring wire. I’ll get you a Hillman products part number maybe Monday, post it here w/pic.

 

[D-4297]

One very important part of this discussion that hasn't been mentioned is trimming the cases to length before doing anything else . Seems that most or all the inside deburring tools work in relation to case length , so trimming to length should be a no-brainer . Then set your stop after some careful adjustment to get a "clean" corner-break , and you should be good to go . Haven't changed the stop on my Lyman tool for three years now , but it only ever gets used for new cases once . After they are all trimmed to the same length to start with . Short-cuts create more problems than they fix .
Grand-Dad told me when I was about 12 years old . "Never time to do it right , But always time to do it twice".

 

[Straightshooter1]

One very important part of this discussion that hasn't been mentioned is trimming the cases to length before doing anything else . Seems that most or all the inside deburring tools work in relation to case length , so trimming to length should be a no-brainer.

This is one of the reason I went with the 21st Century tool. It only uses the neck as a vertical guild rather than a stop guild.

Then set your stop after some careful adjustment to get a "clean" corner-break , and you should be good to go . Haven't changed the stop on my Lyman tool for three years now , but it only ever gets used for new cases once . After they are all trimmed to the same length to start with . Short-cuts create more problems than they fix .

Though deburring the flash holes is a one time step for newly acquired brass, trimming cases to length is always the last step for me (I use a Tri-Way trimmer) so that all my cases are always the same length (well, within .001 anyway).

But, you make a good point . . . and the steps in the process depends to the particular tools you use.

 

[fatelvis]

Can you guys mark a measurable difference in group size or ES,SD, etc., after deburring flash holes? I haven't done this yet, and was wondering how much difference it makes.

 

[spclark]

Can you guys mark a measurable difference in group size or ES,SD, etc., after deburring flash holes? I haven't done this yet....

I have.

I de-burr flash holes ‘cause I was looking for less vertical dispersion.

Uneven powder column ignition will affect velocity consistency. Burrs that aren’t symmetrical will affect primer flame pattern, which in turn affects how powder ignition occurs.

(The adage ‘less is more’ fits here too.)

I know when I de-burr new cases that the swarf coming off the tool, and that falls out of each case, isn’t the same from case to case. Yet the tool has a stop to keep it from cutting too far, so the variances have to be coming from differences in how much brass sits proud of the flash hole in each case before it gets cut away.

 

[chkunz]

Can you guys mark a measurable difference in group size or ES,SD, etc., after deburring flash holes? I haven't done this yet, and was wondering how much difference it makes.

Bryan Litz reported on the test that he did on this subject in his "Modern Advancements in Long Range Shooting" Volume II. Since he ran a test and presents data it is worth reading.

 

[rardoin]

I don't uniform my primer pockets until twice fired...I wait for things to get situated down at the base after fire forming.

Me too....except after the second, third, fourth.... etc. I still don't uniform them...anymore. That tool takes it's place next to the pocket uniformer in the 'Land of Misfit Reloading Tools'.

 

[dolek]

I have.

I de-burr flash holes ‘cause I was looking for less vertical dispersion.

Uneven powder column ignition will affect velocity consistency. Burrs that aren’t symmetrical will affect primer flame pattern, which in turn affects how powder ignition occurs.

(The adage ‘less is more’ fits here too.)

I know when I de-burr new cases that the swarf coming off the tool, and that falls out of each case, isn’t the same from case to case. Yet the tool has a stop to keep it from cutting too far, so the variances have to be coming from differences in how much brass sits proud of the flash hole in each case before it gets cut away.

Same findings here. I wonder how many folks have actually tried deburring before forming such a strong opinion against doing it. I think not many...

 

[RDavies]

Bryan Litz reported on the test that he did on this subject in his "Modern Advancements in Long Range Shooting" Volume II. Since he ran a test and presents data it is worth reading.

I don't have a copy of this book. What are the basics of what he found?

 

[spclark]

I don't have a copy of this book. What are the basics of what he found?

I have his first three works at home, will see if I have that one once I get back later. If it’s there I’ll summarize here tomorrow.

 

[fatelvis]

After doing some digging online, it looks like Brian found that drilled flash holes get no benefit from reaming, but punched ones improved two out of three cases.

 

[Kracken McGraw]

I Deburr my Hornady brass, but the Lapua I formed my 6x47 out of was so pristine. Common sense told me to leave it as is!

 

[chkunz]

I don't have a copy of this book. What are the basics of what he found?

It would not do the subject justice for me to try to summarize. It is not an exhaustive study but enough to give you some data to base your decision on as to if it would be beneficial for you in your application. If you are interested it would be worth reading and studying the entire chapter. I have always deburred my cases but never saw a creditable test to see if it is important. After reading the chapter in Bryan's book I decided to keep on doing what I am doing for my aplication.

 

[duanepa]

I guess if you want to shoot gophers and chipmunks, chucks and yotes, it doesn’t matter. If, on the other hand, you want to bang one hole dots at a BR match, your brass damn sure better be uniform. That is the descriptive word and basically the bottom line here.

 

[coldboreshot]

Don't assume anymore that high quality brass is going to be flawless out of the box. I have recently seen (Name withheld) quality brass out of the box with deformed necks and burrs in the flash holes. Started deburing all my new brass regardless. I have to add...not one bit of difference in the performance when the inside edge of the flash hole is chamfered. I have tested side-by-side. As long as you keep all the brass consistent with each other, there should be no variations.

 

[coldboreshot]

Don't assume anymore that high quality brass is going to be flawless out of the box. I have recently seen (Name withheld) quality brass out of the box with deformed necks and burrs in the flash holes. Started deburing all my new brass regardless. I have to add...not one bit of difference in the performance when the inside edge of the flash hole is chamfered. I have tested side-by-side. As long as you keep all the brass consistent with each other, there should be no variations.

Let me elaborate...I'm not talking about a massive chamfer. I use the Redding tool which eases the edge and auto-guides to the bottom of the case.

 

[Straightshooter1]

After doing some digging online, it looks like Brian found that drilled flash holes get no benefit from reaming, but punched ones improved two out of three cases.

I used to think that drilled flash holes didn't really need the deburring until I ran some with my 21st Century deburring tool (Lapua brass) and I found material being cut away on quite a few of them (not all). When there's no burr, this tools will not cut away any material nor create a beveled crater. It was a bit of a surprise as I've heard so many say that it wasn't necessary. Then I got to thinking about my experience as a Sheetmetal Mechanic where I used to do a LOT of drilling of somewhat soft material (e.g. alloys of aluminum, magnesium, copper, tungsten) and it was common to have burrs on both sides of a drilled hole and in some cases somewhat of a dimple effect on the back side depending on the material and just how it was drilled. So, it's really not such a surprise to me that drilled flash holes will have some burring that should be removed.

 

[spclark]

I have his first three works at home, will see if I have that one once I get back later.

Nope... have Vol. I, not Vol. II.
Somebody else is gonna have to fill us in on what Brian wrote.

As for that spring...



Specs are: 1.375” L, 0.280” OD, 0.223” ID, 0.029” dia. wire.

Hope this helps.