Primer impulse-bullet movement - hyperlink fixed

[markm]

I seent this on Accurateshooter.com

https://apps.dtic.mil/sti/pdfs/ADA622138.pdf

. The ullage provides a certain amount of freedom
for the propellant bed to compress and move during the initial stages of the interior
ballistic event. With minimal ullage available, the propellant merely transmits the
primer force to the projectile, acting much like an incompressible fluid. Conversely,
a cartridge with more ullage will create a situation where the initial motion of
projectile and propellant act more in unison.

[markm]

The most compelling publication to hit M4C ever, and crickets.

[HKGuns]

The most compelling publication to hit M4C ever, and crickets.

The link you posted requires an account, so I can’t even read the article.

Making assumptions it sounds like it supports your experience with wolf primers perhaps.

[Krazykarl]

Ever since the Brennan demise of Precision Shooting, I have been seeking an alternative to step into the void created. Is Accuratshooter.com the one?

As far as primer behavior upon ignition:

1. Primer brisance varies greatly between manufacturers.
2. Brisance changes within the manufacturer separates standard from magnum classification.
3. Complete burn and utilization of a powder charge is the goal as the solid fuel becomes a gas causing work to happen on the projectile.
4. Efficient conversion of solid to gas has been experimented upon with extended flash holes. Not practical in small arms but US Army tests found extended flash holes to be promising.
5. The duplex load has been used prior to the consistent availability of high quality magnum primers. Even then, not all magnum primers are equal. My testing with 120gr of powder per round revealed Federal to be the hottest and most desirable.

Thank you Markm!! I appreciate you!

[markm]

The link you posted requires an account, so I can’t even read the article.

Making assumptions it sounds like it supports your experience with wolf primers perhaps.

Crap. Not so much the primers.. but maybe. https://apps.dtic.mil/sti/pdfs/ADA622138.pdf

[markm]

Crap. Not so much the primers.. but maybe. https://apps.dtic.mil/sti/pdfs/ADA622138.pdf

The interesting thing they "concluded" (although did not test) was that lower ullage loads (like the H322/77gr load we use) help the primer and powder work together instead of the powder just acting as an energy transfer to the bullet.

The bullet yaw observations when jumping to the lands (which we're all aware of) was interesting too.

[Krazykarl]

Markm,

My apologies, I am now fully grasping the gist of this thread. Yes, I can absolutely believe how a reduced load density powder charge with the proper primer can produce good results. Load density that is too light can exhibit erratic ignition behavior including hang fires and even detonation. Traditional logic dictates that the high density loads produce better precision as the propellant is consistently arranged inside the case. But, what happens when the reduced loads are used? The old school nostalgia of service rifle members tipping the fast burning charge back onto the flash hole before firing? But, what happens if a hot match primer is used? I believe what you already know. A hot match primer can in fact go against traditional logic that low density powder charges are to be avoided.

[markm]

Markm,

My apologies, I am now fully grasping the gist of this thread.

Neither am I. I posted to get some more thoughts on it.

Yes, I can absolutely believe how a reduced load density powder charge with the proper primer can produce good results. Load density that is too light can exhibit erratic ignition behavior including hang fires and even detonation. Traditional logic dictates that the high density loads produce better precision as the propellant is consistently arranged inside the case. But, what happens when the reduced loads are used? The old school nostalgia of service rifle members tipping the fast burning charge back onto the flash hole before firing? But, what happens if a hot match primer is used? I believe what you already know. A hot match primer can in fact go against traditional logic that low density powder charges are to be avoided.

The 77 load I run has higher "ullage", but not so much that it's detonation danger. And if I'm understanding their conclusions correctly, yes. They're saying a high ullage/lower density charge is better. Although they didn't shoot such a load to conclude this.

I'd LOVE to know what their testing would show with the mild WOLF SRM primer.... i.e. does that mild primer push the bullet prior to output charge ignition too? Especially in the context of a higher ullage cartridge...

[markm]

It's also unclear what the story is on the #41 primer. They say the legacy primer was milder despite the spec being the same. I'd love to know more on that. Especially since the very current production primers I have are insane hot.

[MegademiC]

Im confused. How does the bullet move without pressure?

I assume the shockwave from the HE, but would that not register as pressure against the base?

Figure 1 shows movement from primer, figure 5 does not?