Primer Blow Out with NO Over Pressure Signs?

[BuffCyclist]

Flattened, loose primers also happen from excessive headspace (improperly adjusted dies setting the shoulder back too far). I read the whole post but haven't seen this mentioned or verified.

No idea on this, I haven't tried measuring my rifles headspace. I used Lee Full Length sizing die to size all brass initially before trimming everything to 2.005". I also wouldn't say my primers were flattened, just loose. The 42.8gr has a good 0.025" movement around the primer. The 38.0gr load doesn't have wiggle room, but it will slip out easily.

[C Ward]

The load data in the book is only for that particular component combination and that particular test rifle . Every other rifle and set of components will be different, the book is a guide not the law .

15 years of loading for precision rifles experience tells me your headed down the path to ammo issues . In the end your gonna do whatever you want , the whole lead a horse to water thing , have fun .

[BlasterBob]

I probably shouldn't be making ANY comments in this rather scientific reloading discussion and I have not read each and every post in this thread but someone mentioned that perhaps the swaging was not proper. I thought LR and Match cases did not have the primer pockets crimped so surely swaging would have nothing to do with this matter.

[BuffCyclist]

The load data in the book is only for that particular component combination and that particular test rifle . Every other rifle and set of components will be different, the book is a guide not the law .

15 years of loading for precision rifles experience tells me your headed down the path to ammo issues . In the end your gonna do whatever you want , the whole lead a horse to water thing , have fun .

Exactly. IMR states starting load of like 41gr, max 45gr. Another manual said 38gr-42gr. So that was problems in and of itself.

[BuffCyclist]

I probably shouldn't be making ANY comments in this rather scientific reloading discussion and I have not read each and every post in this thread but someone mentioned that perhaps the swaging was not proper. I thought LR and Match cases did not have the primer pockets crimped so surely swaging would have nothing to do with this matter.

Precisely and this has already been brought up.

Eta. On phone and can't talk much. This has been brought up as a possible cause buy it is long range brass and is not crimped.

[TheBelly]

OAL is used to tune for accuracy not pressure . The chamber on that gun will not let you get 5 - 10 thou from the lands with ammo that will be reliable so it makes no since to compromise the reliability of the ammo to load it long . The Match King bullets are very jump tolerant and distance from the lands is a non issue .

99 times out of 100 too much pressure equals too much powder , back the powder charge down . Brass is simply a container for the combustion process and the only affect it has on the pressure is the space available inside for it to happen . Also as of late Lapua brass has had less case capacity then the newer LC brass so the powder charge will need backed down even more .

doesn't pressure change when you have more/less case capacity? Can't case capacity change due to the amount of bullet seated into the case? (I'm not trying to be a jerk, just seeking clarification on this point.)

[BuffCyclist]

doesn't pressure change when you have more/less case capacity? Can't case capacity change due to the amount of bullet seated into the case? (I'm not trying to be a jerk, just seeking clarification on this point.)

Yes but it is the percentage of change. The minimal amount the case capacity would decrease when seating deeper is so small, my understanding is that it won't affect the pressure as greatly as say on a pistol. on pistol, sear deep and you have more bearing surface. On rifle, ar one point the bullet bearing surface will be below the shoulder and not affect the friction required to unseat the bullet. On phone so can't be clearer than that lol

[TheBelly]

Yes but it is the percentage of change. The minimal amount the case capacity would decrease when seating deeper is so small, my understanding is that it won't affect the pressure as greatly as say on a pistol. on pistol, sear deep and you have more bearing surface. On rifle, ar one point the bullet bearing surface will be below the shoulder and not affect the friction required to unseat the bullet. On phone so can't be clearer than that lol

my questions wasn't in reference to bearing surface, but rather about the physical volume taken up by the projectile as it is seated at different depths. The volume occupied by the bullet changes the percentage of available volume, and thus can change the pressure curve... Is that mathematically possible, BC?

[BuffCyclist]

my questions wasn't in reference to bearing surface, but rather about the physical volume taken up by the projectile as it is seated at different depths. The volume occupied by the bullet changes the percentage of available volume, and thus can change the pressure curve... Is that mathematically possible, BC?

Yes, but the volume that changes is minimal so it won't affect it.

[BuffCyclist]

Just when everyone thought this thread was buried, here's more DATA!!!

I measured the chamber length with 15 different bullets, then averaged the results.

Actual Length (base to ogive) = 2.3655"
Chamber Length = 2.9455"
Average Bullet Bearing Surface (ogive to ogive) = 0.5025"
Average Base to Ogive - 0.005" back from Lands = 2.3605"
Average COAL - 0.005" back from Lands = 2.9405"

Amount of bullet bearing surface below brass lip (bullet to brass contact) = 0.1490" = 29.65%

I then seated 5 bullets to a length of 2.3605" base to ogive and attempted to unseat the bullet by hand for about 1min each bullet. I then measured again and was unable to determine a change in length of any of the 5 bullets. Which makes me believe that seating the bullets this long does not make fragile-as-eggs ammo. After that, I chambered each bullet, closing the bolt hard, then remeasuring and again, could not detect the bullet seating deeper (due to touching the lands).

If the only problems I will have in seating the ammo this long is the internal hinged floorplate magazine length, then perhaps I will load up to this length when I get my Lapua brass (if SWA ever ships it) and retest.

On the other hand, I just found Alpha Industries Type 1 Magazine (an AICS pattern magazine) and they claim a max COAL of 2.920". If I seated to this depth, I would be 0.020" back from the lands.

Or, I could seat to 2.880" length which AICS mags, and be 0.045" back from the lands.

The options are endless!!