Jump to content
SASS Wire Forum

Reloading ?: Flash hole diameters

Widder, SASS #59054

Recommended Posts

I know that flash holes seem to be of 2 diameters:  small at .0625  and  large at .081.


Before anyone post that the small diameter is for small primers and the large diameter flash holes are for large primers, that isn't always so.

.454 Casull brass uses small primers (pistol or rifle) yet the flash hole is the larger size.


Anyhow, while reloading some brass, even with the same headstamps of R-P, FC, Speer, etc..... most of the brass from each of these headstamps had small flash holes while about 1 in 10 had a large flash hole.


And if your decapping pin is of the larger size, you will find out quickly that A Lot of your brass has the small flash hole..... ;)


Thanks for any insite you may have.




Link to comment
Share on other sites

Interesting. The only  brass I know of that always has small primer holes is the Lapua we use to make 6 or 6.5PPC.   Sinclair(now owned by Brownells)  sells a primer hole reamer that can be used to enlarge primer holes to .081 or precision ream small ones to .0625.  It only fit small primer pockets. What caliber was the brass you found with small primer holes??

Link to comment
Share on other sites

I have yet to encounter any different diameter flash holes in my .45Colt, or 45ACP brass.  Or, for that matter, .223/5.56, .30-30, .30-06, 7mm RM, .40S&W, .40-90SBN, .375Win or .45-70 brass.  (Although I have bent a couple of decapping pins in the past... tho' I never found the exact cause, as once I replaced the pin, it decapped the case fine).


The only difference I've run across in 40+ years of reloading is in .38Spl.  I have some brass ( down to about 2,000 cases now) that have large primer pockets... and a slightly larger flash hole than the modern, standard small primer pocket brass. But, the decapping pin in my standard .38Spl/.357 Mag die set works. 

Link to comment
Share on other sites


In trying to resize/decap a few hundred pieces of .357 SIG brass, about 9 out of 10 had the smaller flash hole.  These were headstamped R-P,  Speer, and FC (Federal).


Aprrox 1 out of 10 had the larger flash hole.



Here is what happened:

I was using my .40/10mm CARBIDE resize/decap die to resize my .357 SIG brass.   This keeps me from having to use case lube to resize/decap with a NON-Carbide .357 SIG die.

Anyhow, it didn't take me but a handful of .357 SIG brass to realize the ram wouldn't push the brass fully up into the die because the recap pin was catching on the inside flash hole.   I mik'd the recap pin, which was the correct size.  It worked great with .40 and 10mm brass.   Not so with the .357 SIG brass.


I also mik'd the recap pin in the .357 SIG die, and it was of the small size.


Anyhow, after checking over 350 pieces of .357 SIG brass of various headstamp, approx 10-12% of various headstamps (mentioned above) were of the larger flash hole.  The other approx 90% were small flash holes, of which some of those were REALLY TIGHT when pushing the small recap pin thru.


I have since drilled out those small holes with a 5/64 (.078) drill bit and polished the diameter of the recap pin accordingly.    Now all works well together.


BUT, I still don't know why this type brass had both flash hole sizes.


Thanks  for your comments.




Link to comment
Share on other sites

357 SIG  NO surprise.   That case is well known for different flash hole sizes. No real spec on the flash hole size. Just that it is a small pistol primer.  When Federal first made the cases the walls were thin. After problems they increased the wall thickness and all other mfgrs. use the thicker wall due to the 40,000# pressure limit. There seems to be no specific reason for the different flash hole diameters.

Link to comment
Share on other sites

.454 C cases are set up for small rifle primers. When I load full end loads, I use SR. When I load 'lite' loads, I use SP.

I have found using the smaller diameter decap pin made from drill rod to work the best.


Link to comment
Share on other sites

Small Primer 45 ACP will generally have a larger than normal flash hole.  It will also be marked "NT" on the case head for non toxic.  Is there a NT on the case head?

How does the 357 sig load?

I have a friend that wants to start loading that caliber and I have resisted because of the short bottleneck.



Link to comment
Share on other sites

Happy Jack:   that makes sense.


Lumpy:  that drill rod would work well.


J.Frank:  My SIG loads work really good.  I use the Hornady carbide resize/decap die for .40/10mm caliber to resize the SIDE BODY of my SIG brass.   Then I use my Non-Carbide SIG resizing die to resize the case neck and barely bump the shoulder back.  I would say that the shoulder is 'kissed'.    This keeps me from having to use any case lube.


Then I expand the case neck appropriately.  


My seating die is set to seat the bullet and allow for an approx .002 slight crimp.

I'm lucky in that my neck sizing die gives excellent tension on my newly seated bullets and the smallest crimping of the case mouth is all that is needed.  


I have been told, and I have read literature, that the .357 SIG will headspace on the case mouth.   AND, I have also read that the .357 SIG will headspace on the shoulder.


Frankly, I don't know.   But in all my reloading years and experience with bottleneck cases, I personally think my .357 SIG headspaces on the shoulder.


If your friend would like to call me, I will be glad to share load info with him.


My number is:   865 / 696-1996.




Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.