More questions re: oversized flash holes

[Kestrel4k]

Questions for Larry Gibson for the most part; my apologies in advance.

I have had considerable success with the #29 flash holes w/ Red Dot & 308Win; cases that had previously shortened to the point where a push-type extractor wasn't even going over the cartridge rim. Really an outstanding solution, and I couldn't be happier.

1. I am about to run the same exercise with belted cases (300H&H, 110gr jacketed @ ~60% load density). Obviously the belted cases can't shorten over time, but was wondering if any other benefit(s) of oversized flash holes w/ Red Dot would justify the minimal effort of modifying the cases? I have an ample supply of cases for this project and would certainly keep them segregated for these loads.
2. Also, would the oversized flash holes be the way to go on Blue Dot (i.e. of "Seafire" fame) loads? Certainly higher pressures, but not traditional centerfire loadings either. I have had success beyond expectations with 223Rem & Blue Dot (using standard flash holes), but I am about to start a 308Win & Blue Dot load series - also w/ light bullets @ ~60% load density. How about the #29 flash hole with those cases ? (and keeping them segregated of course)

Best regards,

[Screwbolts]

Start reading the "Silvercreek Farmers" sticky above on or about post 28 for your answers.

[Bazoo]

Larry did a test where he loaded full pressure rounds in 308 and found that the oversized flash holes do not cause an issue. At least with that particular group of components tested. Here is the link. https://castboolits.gunloads.com/sho...oles-dangerous

[Kestrel4k]

Yes thank you both; have read the 'Is drilling out flash holes dangerous' thread a few times now, and yes good info.

My personal experience is that virtually all of my 308/Red Dot testing (before or after flash hole drilling) was at or above 50% load densities, with Quickload estimates of 30+ksi; and I was still getting case shortening after a series of 6-8 loadings - behavior which the #29 drill eliminated.

I will re-read that thread again; just curious as to any demonstrated accuracy improvements when running these higher pressures with easy-to-ignite Red Dot and Blue Dot. I did note the Fiocchi tests cited in post #40, and the subsequent IMR4895 testing; I was just wondering about any more specific experience here.

I have previously been convinced about the safety of such measures, both by testing by Mr. Gibson and and my own testing of going up to 1/8" with IMR4895 in the M1 Garand.

Thank you,

[charlie b]

I am one who is careful with Blue Dot loads, having had an excursion in a .45Colt.

But, I love light loads of BD in my .308. Bullets around 160-180 and 8gn of BD give me really good groups at 100yd. Vel is ~1250fps. Sounds like a throaty rimfire This was sighting in a load. Most groups aren't that good but are usually 1.5" or so.



If I want higher vel I use 4198, but, many like 2400 instead.

[Larry Gibson]

The use of drilled flash holes in larger capacity cases, such as with the 300 H&H, has the additional benefit of allowing the flash to get into the case quicker while filling the volume more readily. This results in better more uniform ignition and less powder position sensitivity. This is especially beneficial with small charges of fast burning powders.

I use quite a bit of Blue Dot (currently have an 8 lb jug) but that use is in pistol cartridges with close to or at 100% load density. I've not found Blue Dot to work well in reduced loads in pistol cartridges. As to the use of Blue Dot in rifle cartridges; I've been aware of Seafire's and other's trials and tribulations over on another forum noting also some high pressure events have been reported. Seems in smaller cartridges such as the 223 Blue Dot seems to be a viable powder with jacketed bullets and, perhaps, cast bullets.

However, it also appears in larger cases, especially those using LR primers, the use of reduced loads of Blue Dot may lead to high pressure excursions and even an S.E.E. with the use of light weight for caliber jacketed bullets. This is speculation as I've not done any testing with Blue Dot in any rifle case with jacketed bullets. It is based on my understanding of such and experience with such incidences and the ignition and burning nature of Blue Dot.

[charlie b]

Forgot. I am another who has drilled out flash holes for all of my cast loads, including those that come close to jacketed velocities. Even had some good accuracy when using 175gn SMK's in my .308 (sub MOA at 1000yd).

This is where I got the idea for Blue Dot and plinker loads.
http://www.gmdr.com/lever/lowveldata.htm

Also did not mention that going above 8gn resulted in groups opening up. At 10gn they looked like shotgun patterns.

[charlie b]

Larry,

My understanding is that flash holes were sized to accelerate the flash from the primer, not due to peak pressure considerations. Is that your understanding as well?

[Larry Gibson]

Larry,

My understanding is that flash holes were sized to accelerate the flash from the primer, not due to peak pressure considerations. Is that your understanding as well?

With this topic, like many in this game, we tend theorize there is some magical scientific reason. However, my tests with the 308W, the 44 Magnum and the 45 Colt have shown there is essentially no difference in pressure or velocity regardless of the flash hole size from "standard" size up through the maximum size made with a #28 drill. Thus, as with many other things, the size of the flash hole is probably just a case of manufacturing consistency which has led to the "standardization of pretty much the size of flash hole we see today. Note that size (close to a #45 drill +/-) is pretty much standard in all cartridges, handgun and rifle, with loads from mild pressure with fast burning powders to magnums with large charges of slow burning powders....the size of the flash hole remains constant. It is the composition of the priming compound that makes the difference.

[charlie b]

So, it was probably just a random choice by an engineer/experimenter somewhere? I can get behind that one I've made similar decisions on programs before

[Larry Gibson]

So, it was probably just a random choice by an engineer/experimenter somewhere? ..............

Probably was.......

[charlie b]

Yep, we'd probably have to ask Col Boxer. Probably cause it was a convenient drill size Funny that the Brits adopted the Berdan primer, invented in the US and the US adopted the Boxer primer, invented in the UK.

[MostlyLeverGuns]

Tool life and other production considerations probably play into what punch size is used in today's production environments. Some of the 'new LEAD FREE' primers do have larger flash holes than the tradition .081 plus/minus.

[GregLaROCHE]

With this topic, like many in this game, we tend theorize there is some magical scientific reason. However, my tests with the 308W, the 44 Magnum and the 45 Colt have shown there is essentially no difference in pressure or velocity regardless of the flash hole size from "standard" size up through the maximum size made with a #28 drill. Thus, as with many other things, the size of the flash hole is probably just a case of manufacturing consistency which has led to the "standardization of pretty much the size of flash hole we see today. Note that size (close to a #45 drill +/-) is pretty much standard in all cartridges, handgun and rifle, with loads from mild pressure with fast burning powders to magnums with large charges of slow burning powders....the size of the flash hole remains constant. It is the composition of the priming compound that makes the difference.

This answers the question I’ve been wondering about since reading this post. So all flash holes are more or less the same size. Does this hold true for cases that take small primers? How about foreign cartridges?
I opened up some for BP in 45/70, but didn’t see any difference.

[Ford SD]

This answers the question I’ve been wondering about since reading this post. So all flash holes are more or less the same size. Does this hold true for cases that take small primers? How about foreign cartridges?
I opened up some for BP in 45/70, but didn’t see any difference.

the smallest flash hole I have seen was in S&B 9mm pistol brass smaller than the depriming pin .... it was a pain I drilled out 500 pcs of brass


I normally do not measure holes

There is a practical size limitation I have no idea what it is for Brass

But for mild steel plate rule of thumb is ... thickness of the plate is the smallest hole you can punch
1/4 hole in 1/4 inch thick plate if you have thicker plate you have to drill etc
....... 1 inch hole in 1/8 plate is no problem

I was working one place and one of the fitters forgot and tried to Punch a 1/4 hole in 5/8 plate and shattered the punch and parts of the punch went flying.... there are reasons why guards are on equipment

[charlie b]

The only time I ran into smaller flash holes was with the Lapua 6BR brass. They use a .059 (1.5mm) flash hole. They are also known for very small SD/ES. I have heard that some other Lapua brass using small primers are treated the same.

[Kestrel4k]

OP checking in here; haven't posted an update but have certainly read all the replies with great interest.
Thanks to all; will keep in mind this knowledge base as I move forward. :thumbsup:

I was inclined to open up the flash holes for my 300H&H / Red Dot, and feel confirmed after reading here.
Will most likely do the same with 30-30 & Green Dot (just using up old powder inventory).

Was certainly undecided on the upcoming 308Win / Blue Dot loads, and see that there is no good reason to use oversized flash holes there. Thank you,

[charlie b]

I'd open up the .308 brass as well. Not a good reason not to. They will still work well with full powder jacketed loads as well.

[Kestrel4k]

[...] I use quite a bit of Blue Dot (currently have an 8 lb jug) but that use is in pistol cartridges with close to or at 100% load density. I've not found Blue Dot to work well in reduced loads in pistol cartridges. As to the use of Blue Dot in rifle cartridges; I've been aware of Seafire's and other's trials and tribulations over on another forum noting also some high pressure events have been reported. Seems in smaller cartridges such as the 223 Blue Dot seems to be a viable powder with jacketed bullets and, perhaps, cast bullets.

However, it also appears in larger cases, especially those using LR primers, the use of reduced loads of Blue Dot may lead to high pressure excursions and even an S.E.E. with the use of light weight for caliber jacketed bullets. This is speculation as I've not done any testing with Blue Dot in any rifle case with jacketed bullets. It is based on my understanding of such and experience with such incidences and the ignition and burning nature of Blue Dot.

Thank you for your perspective on BD; based on my personal experience I am reasonably confident in it, but after reading the 'favorite powder for handgun / reduced rifle' thread, I realized I've got some older 2400 to use up before I go further into my nearly-new keg of BD. So I could run some 308Win QL models on that 2400 as well ...

[Kestrel4k]

Revisiting this thread; I just read through it again, there is much good info posted thanks to all here.

I use quite a bit of Blue Dot (currently have an 8 lb jug) but that use is in pistol cartridges with close to or at 100% load density. I've not found Blue Dot to work well in reduced loads in pistol cartridges. As to the use of Blue Dot in rifle cartridges; I've been aware of Seafire's and other's trials and tribulations over on another forum noting also some high pressure events have been reported. Seems in smaller cartridges such as the 223 Blue Dot seems to be a viable powder with jacketed bullets and, perhaps, cast bullets.

However, it also appears in larger cases, especially those using LR primers, the use of reduced loads of Blue Dot may lead to high pressure excursions and even an S.E.E. with the use of light weight for caliber jacketed bullets. This is speculation as I've not done any testing with Blue Dot in any rifle case with jacketed bullets. It is based on my understanding of such and experience with such incidences and the ignition and burning nature of Blue Dot.

My other option besides Blue Dot is 2400, that I've run some Quickload models on; (257 Roberts, light bullets).
Larry, any specific opinions about going down to 50% loading density with 2400, in bottlenecked rifle cartridges w/ jacketed bullets ?

I am already very comfortable with Red Dot for these loading densities, and have had some limited but satisfactory experience with Blue Dot as well.
Just curious as to 2400 compared to BD - there is most likely more experience with 2400 on this forum than anywhere else.

Thank you,