Am I doing it wrong?

[Tex S]

I have been deburring flash holes for as long as I can remember. I have the Sinclair tool that indexes on the case web and prevents removing too much material. I have always chucked it in a low speed drill and ran it in the case until the tool bottoms out on the case web.

I was talking with a buddy the other day and he said he just gives the tool "a twist or two", because he is afraid that even with the built in stop the tool can remove too much material. He said that after all, you are trying to knock off a burr, not "ream" a champher inside the case.

Am I doing this right, or should I not let the tool bottom out?

[Hunter0924]

For me, I have the RCBS hand tools to deburr the flash hole and a few turns does a fine job to deburr and true the flash hole.
I don't know if you really run the risk of opening the hole too much as the tool does have a stop and will only cut so much, I just don';t think it takes that much to do the job.
When I have a lot to do, I add the deburr tool to the RCBS casemaster which is driven by electricity and that has not given me any issues.

[Bart B.]

I too, think what you're doing is OK if you want to do it.

But I don't debut them. Never was able to see any improvement in performance with debuted flash holes after doing it.

[hooligan1]

I use the Lyman handtool, just a few turns and done.
Having said that I dont think this step is necessary either, cant tell any difference except,,,,,,,,in confidence.

[Magnum Wheel Man]

I have the Lyman hand tool in my RCBS case prep center...

there was a thread a while back, where someone had posted some nice pictures of cut away cases, & yes, you can chamfer the flash hole, if the stop is set too deeply...

also agree with what's been posted about noticing a difference, with one difference, I do think it matters more on smaller cartridges... I do it on my 25 ACP revolver loads, & on 17 & 22 Hornet cartridges...

[old roper]

Sinclair tool can be used both ways and no way to go pass the stop. Sinclair tool is called Primer Pocket Uniformer so it cuts same depth and that is SAAMI Spec.

As Magnum Wheel Man mention you can chamfer flash hole, so depth may not be SAAMI Spec using Sincliar tool.

[Unclenick]

Old roper,

I think you're on a different tool. The primer pocket uniformer, used from the back end of the case, is a different tool from the flash hole deburring tool discussed here, which cuts burrs off the lip of the flash hole from the inside of the case.


Tex S,

As the others have said, the method of cutting is your choice. Just don't overdo it. The recent thread on this topic showed the deburring tool actually puts its own burrs on the perimeter of its cut. However, someone once had some flash profile photos from cut down cases—I think maybe in the defunct Precision Shooting Magazine—that showed the deburred cases really did produce a more uniform flash shape. I think this is because the slight chamfer, even though it has burrs, has them aside from the main gas path.

Whether that improved uniformity translates to anything you can see on target or not depends on the powder, IME. I once got a significant accuracy improvement in an M1A from deburring flash holes, but I was using a charge of spherical powder that filled the case poorly, and I was using a mild primer. Poor case fill and a mild primer with a spherical propellant are a recipe for inconsistent ignition. Deburring the flash holes seemed to go a long way toward fixing that, but, looking back, I might have got the same improvement by going to a magnum primer to better pressurize the empty case. That gun's barrel and that lot of powder are long gone, so I can't exactly replicate the experiment, now. I will add that I tried deburring with several stick powders I also loaded with in that gun with the same barrel and same bullet (168 grain SMK) back then and never saw any improvement. The stick powders all tuned to the same group size as the spherical powder needed deburring to achieve. Other things limiting accuracy were dominant in those instances.

As a result of the above, I concluded that in a benchrest precision level, say, 1/4 moa shooting or tighter, deburring might still show up as an advantage, but for most good loads with precision any less than the bughole range, the difference it makes is likely to be swamped out by other error factors. I do it for cases I am doing load development with, just to eliminate another variable, but once I have the load I drop it, see if I see a difference or not. So far, I haven't, with the exception of that one experience. But I avoid the older spherical propellants, for the most part, and I don't shoot benchrest rifles, so I'm not giving myself a lot of opportunity to see a difference, either.

The only negative to the deep deburring is that when you follow case life, you find the floor of the primer pockets gradually gets pushed out. The hotter the loads level, the faster this happens. This is why some folks use a primer pocket depth uniformer to clean primer pockets. It cuts them back to the same depth each time. However, if you thin that web too much with a deburring tool, it seems to me you might expect it will push out more quickly. I haven't followed that over the life of a case. It seems like it might be worth tracking, just to see.

[Bart B.]

Where can I find SAAMI specs on any primer pocket dimension? Flash holes and primers, too, if they exist.

There are none in cartridge dimension specs on SAAMI's web site I can find. An old Sinclair International reloading book claims to have them in it. There's nothing in SAAMI's old and new documents I can find to support it.

Thanks in advance.

[cw308]

Just make sure the cases are all trimmed to the same length when deburring the flash hole.

[243winxb]

http://thefiringline.com/forums/show...=553086&page=3 And a Poll http://www.thehighroad.org/showthread.php?t=764492

[Jim243]

I use a 5/64th drill bit by hand to ream rifle cases and clean out the flash hole basically because I tumble them after sizing and trimming to insure no stuck media and uniform size.

Just what I do.
Jim