Flash hole uniforming and deburr

[Laurie]

It’s like any reloading tool which is adjustable you can decide and fix the amount of the flash hole you remove. Comes with a cone on the handle that acts as a stop on the case neck enterance that you adjust to consistently remove what you don’t want.

Yes absolutely, but as someone has already posted you really do need to trim all cases to a common length beforehand unless they are already very uniform out of the box.


The most I do on new brass (regardless of make) is let the tool virtually hang in the flash hole by its own weight and turn it to see if there is a burr to snag on. If so the lightest touch cuts the burr out. I'm a big believer in NOT altering the flash hole by cutting an internal bevel. I have no proof or clue if cutting it as in some above pics is harmful....but I just don't do it. [M-61]

+ 1 There was period some years ago when many people recommended putting a bevel in to create some sort of 'venturi effect'. I've never seen any proof of such claimed benefits though and now strongly suspect that minimum is much better than too much. As Shynloco says, there is a real danger of preparation overkill here. Even if such an outcome does improve things, it's so marginal it'll never show up in scores, and if it isn't proven to be a good thing just avoid it as who knows of the possible downsides.

 

[jlow]

Yes absolutely, but as someone has already posted you really do need to trim all cases to a common length beforehand unless they are already very uniform out of the box.


The most I do on new brass (regardless of make) is let the tool virtually hang in the flash hole by its own weight and turn it to see if there is a burr to snag on. If so the lightest touch cuts the burr out. I'm a big believer in NOT altering the flash hole by cutting an internal bevel. I have no proof or clue if cutting it as in some above pics is harmful....but I just don't do it. [M-61]

+ 1 There was period some years ago when many people recommended putting a bevel in to create some sort of 'venturi effect'. I've never seen any proof of such claimed benefits though and now strongly suspect that minimum is much better than too much. As Shynloco says, there is a real danger of preparation overkill here. Even if such an outcome does improve things, it's so marginal it'll never show up in scores, and if it isn't proven to be a good thing just avoid it as who knows of the possible downsides.

Yes, the case has to be trimmed to a common length if you are indexing off the case mouth. It's like the Giraud case trimmer that index off the shoulders, shoulder bump has to be consistent.

 

[Comrade Terry]

Yes absolutely, but as someone has already posted you really do need to trim all cases to a common length beforehand unless they are already very uniform out of the box.

The 21st Century flash hole deburring tool indexes off the case floor, so you wouldn't have that issue.

http://www.xxicsi.com/flash-hole-debur-tool.html

 

[Laurie]

I've not come across that tool. It looks good, although that's pretty well the norm for 21st Century - good, well designed products. Unfortunately, small company, small volume stuff like this usually becomes frighteningly expensive by the time it gets over the Atlantic to the UK.

 

[jlow]

The 21st Century flash hole deburring tool indexes off the case floor, so you wouldn't have that issue.

http://www.xxicsi.com/flash-hole-debur-tool.html

Do you have a close-up of the tip where the cutter is. That photo on their website is too small. What I am wondering about is how it index of the case floor?

 

[Comrade Terry]

Do you have a close-up of the tip where the cutter is. That photo on their website is too small. What I am wondering about is how it index of the case floor?

I apologize for the image quality. The brass bushing fits snugly in the case mouth, and the shaft rotates within the bushing. The flat part of the cutting head stops on the case floor when the burr is removed, and the cutter doesn't bevel the hole - it gives it a slight radius.

Hope this helps.

 

[M-61]

From the 21st Century link:

"Built in depth stop, you will feel it stop cutting when proper chamfer is achieved."

What do they mean by chamfer as opposed to say bevel?

 

[jlow]

I apologize for the image quality. The brass bushing fits snugly in the case mouth, and the shaft rotates within the bushing. The flat part of the cutting head stops on the case floor when the burr is removed, and the cutter doesn't bevel the hole - it gives it a slight radius.

Hope this helps.

View attachment 986343

Thanks for the photo. I guess what I was wondering is how the cutting head is stopped. It looks like since the cutting head sits in the bushing and the bushing is not cutting, it’s the bushing that limits the cut.

As it turns out, that is also one way the Sinclair stops the cut i.e. it use a non-cutting bushing. Of course, mine makes a chamfer cut but whether that is good or bad at least to me has not been determined.

 

[Wjesswheel]

It depends on the brass. I never deburr Lapua, Norma, or RWS. I will uniform the flash-hole from behind using the Sinclair tools to 0.061" / 0.081". With these makes, that's usually wasted effort, but just occasionally an undersize one appears that needs a lot more effort to ream. One box of Lapua 223 had three really, and I mean really, undersize flash-holes that would have ruined ES/SD values in this little cartridge. The small diameter holes in 220 Russian / BR / 6.5X47L are really consistent though IME.

Some American makes though ........ Deburr? Hell, yes. I find it astonishing that people say they've never seen a burr - a small intense flashlight beam at an angle though the flash-hole from the primer pocket end usually shows some burrs, and often some very large spikes left - they will angle the jet of flame and hot particles from the primer to one side of the powder column.

Primers are explosives and won't be affected by a burr or two as claimed in post #13. You think this pair here getting on for 1/8th inch length and both partially covering the flash-hole would have had no effect?

So iam the op. Admittedly new to reloading. I basically was doing as Laurie stated above was reaming from behind only and when I looked thru the Flashole I thought I was seeing a burr that I could not feel with the reamer, but I was seeing it I thought it was in the flash hole, so I did as another poster said I went to work and got the bore scope out and there is a significant burr on all my federal cases as in Laurier pictures, couldn't feel it but could see it. The amount of material being removed was similar to the pics so it alarmed me. Well anyways I loaded up 8 rounds at 42.3,42.6,42.9,43.2,43.5 with 175smks. 4 at each weight with the burrs and 4 with the burrs removed and a little bit of chamfer. Shot thru my savage ftr. Shot at 200 yards. The SD on every weight tested was smaller, and my groups were smaller. No signs of high pressure everything looked normal after shooting. So I guess all my brass is getting cleaned up and a small chamfer put in it.

So on another note I use a Rcbs digital scale that I thought was going to do a good job for me but I have resorted to picking up kernels of powder one at a time with tweezers, till my scale settles and flips to the tenth iam trying to get. Are there another reasonably priced digital scales that are better or should I go to some sort of balance scales?

 

[jlow]

So iam the op. Admittedly new to reloading. I basically was doing as Laurie stated above was reaming from behind only and when I looked thru the Flashole I thought I was seeing a burr that I could not feel with the reamer, but I was seeing it I thought it was in the flash hole, so I did as another poster said I went to work and got the bore scope out and there is a significant burr on all my federal cases as in Laurier pictures, couldn't feel it but could see it. The amount of material being removed was similar to the pics so it alarmed me. Well anyways I loaded up 8 rounds at 42.3,42.6,42.9,43.2,43.5 with 175smks. 4 at each weight with the burrs and 4 with the burrs removed and a little bit of chamfer. Shot thru my savage ftr. Shot at 200 yards. The SD on every weight tested was smaller, and my groups were smaller. No signs of high pressure everything looked normal after shooting. So I guess all my brass is getting cleaned up and a small chamfer put in it.

So on another note I use a Rcbs digital scale that I thought was going to do a good job for me but I have resorted to picking up kernels of powder one at a time with tweezers, till my scale settles and flips to the tenth iam trying to get. Are there another reasonably priced digital scales that are better or should I go to some sort of balance scales?

Not familiar with RCBS digital scale but if it is the RangeMaster 2000, it only can weight accurately to +/- 0.1 grains. If you want as consistent MV as possible at least removing the effects from powder weight variation, you want something that can weight accurately to +/- 0.02 grains. For that, I would suggest either the GemPro 250 which cost around $100 or the A&D FX-120A which cost more like $500. Both works well and depends on your budget.

 

[rardoin]

If you can afford it I would go with the FX-120A. I have a Gempro mothballed as I could not get it to stop drifting. Others have had similar problems/quality control problems/interference problems. That being said, there are many reloaders that report great service from the Gempro 250. You will gamble a little on the Gempro; it may or may not be the last scale you will buy. If you can afford the A&D (or a Sartorius for twice the $), you will be set for life IMO/IME.

Edit- My comments are in regards to digital products only. A good balance beam will get it done too if you have it tuned.

 

[jlow]

A buddy of mine told me about the book by Bryan Litz that showed that it actually hurt SD. To me the concept of uniforming and chamfering makes compete sense. Having all of the burrs in the bottom of the case just doesn't sound like it would make for consistent ignition.

That's an interesting comment as I just finished reading that chapter in Bryan's "Modern Advancements in Long Range Shooting".

The idea that chamfering/deburring can hurt SD is true but taken a bit out of context. His conclusions is that it helps with MV and SDEV for cases with primer holes that are punched out. Conversely, there is a slight increase in SDEV for cases that are drilled. I am not going to go into details and let the "cat out of the bag". Anyone interested should get the book and read it as there is a lot of interesting stuff in there. not all of which I agree with, but interesting reading regardless.

 

[LHSmith]

FWIW- to my knowledge no manufacturer "drills" flash holes. Lapua punches from both ends to eliminate "flashing".

 

[Shynloco]

FWIW- to my knowledge no manufacturer "drills" flash holes. Lapua punches from both ends to eliminate "flashing".

LH,
I too had read some time ago that there are a few brass manufacturers who "drill" their flash holes. Honestly can't remember who they might be as I use mostly Lapua brass for my BR's and Lake City for my AR. But I do use a KN Flash hole reamer, but lightly on even new Lapua brass and usually get very little fallout or burr material.

Alex

 

[LHSmith]

The primer is a high explosive. It doesn't ignite it detonates. I doubt a few burs around the primer hole slow down a shock wave traveling at over 15,000 fps. I am not willing to remove metal from the inside of the case for some unproven guess work. If Tony Boyer doesn't see a difference with a rail gun in an atmosphere controlled tunnel that's good enough for me. I think a lot of the best shooters in the country don't worry about things discussed on this website. Read the articles in the TechnicalShooter section of this website and see what the the best in the country do. Too much worry about I need to do everything that's possible to a case and no talk about bench and shooting skills. Records are made at the range not in your basement measuring 10 different things on a cartridge case.

First of all Neary's test was on Lapua .220 Russian cases. TB only shoots at 100 and 200 yards. Stretch that distance 5 and 10 fold and the little things begin to matter. Tony also throws charges which probably vary by 2 tenths of a grain, and I doubt he segregates by case volume.

 

[jlow]

FWIW- to my knowledge no manufacturer "drills" flash holes. Lapua punches from both ends to eliminate "flashing".

Only quoting what Brian Litz said in his book which was on page 135 "There are two basic methods of making flash hole sin brass cases: drilling and punching." and then on page 139 he said "Lapua brand which has drilled flash holes". If you think these are in fact incorrect, you should tell him. He has a thread on the "ballistic" page.

 

[LHSmith]

Only quoting what Brian Litz said in his book which was on page 135 "There are two basic methods of making flash hole sin brass cases: drilling and punching." and then on page 139 he said "Lapua brand which has drilled flash holes". If you think these are in fact incorrect, you should tell him. He has a thread on the "ballistic" page.

Kevin Thomas addressed it here: http://forum.accurateshooter.com/threads/lapua-brass.3780898/#post-36036572
How's that for memory....4 year old post....now if I could only remember in a match which sighter represents which condition
Norma, however, may be drilled...at least that's the notation in Sinclair's catalog in their description of Norma brass.

 

[jlow]

Kevin Thomas addressed it here: http://forum.accurateshooter.com/threads/lapua-brass.3780898/#post-36036572
How's that for memory....4 year old post....now if I could only remember in a match which sighter represents which condition
Norma, however, may be drilled...at least that's the notation in Sinclair's catalog in their description of Norma brass.

Congrats on the brief reprieve from Alzheimer! You’ll have to remember to visit the rest of us at the home sometime!

Joking aside, good memory but the point of the article/my post was not whether Lapua brass was drilled vs. punched but the fact that brass manufactured properly i.e. without the burr but what chamfering/deburring will or will not do with that brass.

 

[rmist]

So...bottom line is that you should do some sort of cleanup on your flash holes. Is that correct ? I've been using the K&M tool since my PPC days. I don't get overly aggressive with the tool but it always makes the flash hole a couple thou bigger and slight de-burr on the inside.

 

[MagnumManiac]

Interesting fact few have touched on. Most, if not all, European manufacturers, particularly Lapua, Norma, RWS and S & B all use a slightly smaller DRILLED flash hole that measures .078" compared to US manufactured brass that measures .081". This info about drilled flash holes came from each manufacturer, not hearsay.
I use both Lapua and Norma in comp, increasing the flash hole size to the US .081" hurt groups, ES and SD. I no longer touch these brands, they are very good as is from the factory.
My 6.5x47 Lapua uses the tiny .061 size flash hole and small rifle primers. Can't wait to see how it performs on range, still working out a few gremlins on powder selection. Initial results on grouping is very promising. Looks like it likes RL17.

Cheers.