Is drilling out flash holes dangerous?

[swheeler]

Larry , I see you finally edited your data to 4895 powder instead of 4350, rookie mistake!

[JimB..]

I ran the same tests with a fire formed case and inert primers; headspace was not changed. I then used the same fire formed case with live primers. In as little as two firings there was a measurable decrease in headspace. After five live primers the fired primer was noticeably backed out after firing.

I’m not sure why, but I had believed that you were using your powder puff loads for this stage of the testing as well as for the next stage where you drilled out the flash holes and fired 50 rounds from each case. Thank you for the clarification.

I’m still curious about what happens if you stake the primer. My expectation is that there will be no setback as there are no material forces pushing the case forward.

[Larry Gibson]

Larry , I see you finally edited your data to 4895 powder instead of 4350, rookie mistake!

Yup, that's me....a rookie for sure......

[swheeler]

Probably just a senior moment, I have mine every so often.

[Larry Gibson]

Additional test also in 44 Magnum and 45 Colt at; http://castboolits.gunloads.com/show...cylinder/page2

Post #34

Drilled Flash Hole Test; 44 Magnum and 45 Colt

Completed the test yesterday 29 April, 2019. Test firearm was a Contender with a 8.4” barrel in 44 Magnum and a 10” barrel in 45 Colt. A 2.5X scope is on the Contender. All measured data except group size (ctc widest shots) was obtained via the Oehler M43 PBL. I had prepared 10 cases, as previously posted, for each test string; 10 with standard flash holes and 10 with the flash holes drilled out with a #28 drill. Winchester WLPs were used in all cases for both cartridges.

Testing was conducted from the bench with a Hoppe’s Pistol Rest with the target at 50 yards.
Temperature was 80 degrees.
Humidity was 30%
Barometric Pressure was 29.63

44 Magnum;
Bullet was a 429360 cast of COWW +2% tin, AC’d and aged 10+ days before sizing .430 and lubed with BAC.
Cases were Remington R-Ps sized and loaded in RCBS dies.
Powder charge; 22 gr of Alliant 2400
OAL; 1.638

With Standard flash holes;
Velocity; 1622 fps (muzzle)
SD/ES; 13/41 fps
Pressure; 35,800 psi(M43)
Pressure SD/ES; 500/1,700 psi
Group; 3.1”

With flash holes drilled;
Velocity; 1599 fps (muzzle)
SD/ES; 17/47 fps
Pressure; 34,500 psi(M43)
Pressure SD/ES; 1,400/3.900 psi
Group; 3.2”

45 Colt:
Bullet was a 452-230-TC cast of COWW +2% tin, AC’d and aged 10+ days before sizing .454 and lubed with BAC.
Cases were CBC 45 Colt sized in RCBS steel FL sizer and loaded in Hornady dies.
Powder charge; 7.3 gr 700X
OAL; 1.598”

With Standard flash holes;
Velocity; 1060 fps (muzzle)
SD/ES; 7/23 fps
Pressure; 16,300 psi(M43)
Pressure SD/ES; 400/1,500 psi
Group; 2.9”

With flash holes drilled;
Velocity; 1059 fps (muzzle)
SD/ES; 4/15 fps
Pressure; 16,000 psi(M43)
Pressure SD/ES; 400/1,100 psi
Group; 3.15”

From the measured data we see there is essentially no difference. Again the sky did not fall, California did not slide off into the Pacific and still no Trump collusion with Russians……

Here’s the fired primers…..no difference in “flattening”…….

Attachment 240878

Essentially, after thorough testing, there appears to be no detectable "danger" based on the size of the flash hole when using LP or LR primers at low or high pressures.

[Ramguy]

Wow!!! That's a lot of info. I was looking to load some plinking loads in a .45LC with some brass that had enlarged flash holes, and that very question was answered in the very last post!!! Thank you for sharing your knowledge and testing information.
felipe

[megasupermagnum]

If you think about it, percussion cap muzzleloaders use a .028", sometimes smaller orifice to delay blowback to the cap, and that's with blackpowder pressures. The .060"+ flash hole on new brass is already beyond delaying anything.