Curious - Blown Primer effect on the fired round?

[QQgunstuff]

Mostly a curiosity question. Was at practice range the other day with AR Service Rifle. Shot 20 rounds prone, stopped and picked up brass. Found two rounds with missing primers (uh-oh). Quickly checked gun for the primers etc. While firing I had not noticed any effect of the blown primers.
Then I went down to paste up the target and found 2 shots missing? (I do admit I am not a great shooter, but a MISS on a slow-prone shot at 200yd target?).
So the question is, if you blow a primer does it dramatically affect the bullet's trajectory?

 

[mgunderson]

Seen it both ways. It can show up on call, but most often it is a low shot.

 

[dcali]

I had one head off about 8 minutes to the right if memory serves. It went way to the side.

 

[JayBeeYou]

Way back when Hornady released the superperfomance 178 BTHP ammo I was shooting it at a 1000 yard F class match. Blew about 3 to 4 primers every 20 shots and each time round went to 8 ring high elevation. The rounds that didn't blow the primers held a decent for factory ammo waterline.

Remaining ammo was sent back to Hornady and they told me that it was prone to overpressure in a gas gun. When I told them it was a bolt gun the reply was "are you sure it was a bolt gun?" That was the day I decided to start reloading.

 

[Dusty Stevens]

Way back when Hornady released the superperfomance 178 BTHP ammo I was shooting it at a 1000 yard F class match. Blew about 3 to 4 primers every 20 shots and each time round went to 8 ring high elevation. The rounds that didn't blow the primers held a decent for factory ammo waterline.

Remaining ammo was sent back to Hornady and they told me that it was prone to overpressure in a gas gun. When I told them it was a bolt gun the reply was "are you sure it was a bolt gun?" That was the day I decided to start reloading.

shoulda told em it was an AR lookin bolt gun

 

[R.Olds]

Isnt the case held against the bolt face during ejection a lot longer than it will take for the bullet to exit the barrel.

 

[D-4297]

To @R.Olds : The answer is yes . But the pressure to blow out , or partially collapse the primer to make it "loose" in the pocket occurs at , and during the detonation process , as the bullet is "releasing" from the neck and travelling down the barrel , and gone . Thus having a effect on POI . It all occurs in mili-seconds .

 

[D-4297]

Understood . I was trying to provide a viable explanation to the "process" , that normal people who aren't ballistic scientist could understand , without excessive techno-babble .

 

[QQgunstuff]

To R.Olds

I have had others outside this forum agree with you, that the bullet is already launched by the time the primer is affected to the point of “failure”. I’m not technical enough to repeat the details of the discussion but it had to with how, when and where peak pressure occurs.

 

[Laurie]

If you read Glen Zediker's original book, The competitive AR15

https://www.zediker.com/books/ar15/ar15main.html

he covers this issue of blown primers in this rifle type, in his experience usually caused by charge weights worked up in a chilly spring being over-pressure in hot summer conditions.

The comment that struck me (given that we're not allowed semi-auto ARs in the UK, only manual straight-pulls that tell you everything you ever needed to know about pressures when you come to yank the bolt open) was about the unwary US XTC shooter who is happily shooting rapids, when the trigger assembly stops working. Field stripping the rifle shows its internals are full of spent primers some of which inevitably end up affecting the trigger. He points out that this is often the first indication to the unwary handloader that he/she has a problem with loads in this type of rifle.

 

[spclark]

Several years ago shooting my 6HAGAR spacegun at NRA Highpower Nationals 600 yards at Camp Perry I had a nice clean going when at about round fifteen the last shot fired came up 9 @ 3, mid-ring.

Hmmm I thought, looked good in the sights when it left the gun.

Wonder why that happened?

Loaded next round, closed bolt... no, wouldn’t close... YANK.

S#!+

Round ejects, lands on mat, with the front half of the fired case from that wide nine jammed over the part that should have scored for shot #16.

S#!+

Deep breath. Load another, fire when ready.

(199.12 I think, but maybe Amanda Eisenboss remembers better? She was scoring for me.)

I found the back half of that separated case later on, inside my shooting stool’s bag with some other otherwise intact empties.

 

[QQgunstuff]

If you read Glen Zediker's original book, The competitive AR15

https://www.zediker.com/books/ar15/ar15main.html

he covers this issue of blown primers in this rifle type, in his experience usually caused by charge weights worked up in a chilly spring being over-pressure in hot summer conditions.

The comment that struck me (given that we're not allowed semi-auto ARs in the UK, only manual straight-pulls that tell you everything you ever needed to know about pressures when you come to yank the bolt open) was about the unwary US XTC shooter who is happily shooting rapids, when the trigger assembly stops working. Field stripping the rifle shows its internals are full of spent primers some of which inevitably end up affecting the trigger. He points out that this is often the first indication to the unwary handloader that he/she has a problem with loads in this type of rifle.

 

[QQgunstuff]

You’re right on about the spent primer. I dug in and around the trigger assembly best I could soon as I found the spent cases. Luckily nothing in there.

 

[QQgunstuff]

Several years ago shooting my 6HAGAR spacegun at NRA Highpower Nationals 600 yards at Camp Perry I had a nice clean going when at about round fifteen the last shot fired came up 9 @ 3, mid-ring.

Hmmm I thought, looked good in the sights when it left the gun.

Wonder why that happened?

Loaded next round, closed bolt... no, wouldn’t close... YANK.

S#!+

Round ejects, lands on mat, with the front half of the fired case from that wide nine jammed over the part that should have scored for shot #16.

S#!+

Deep breath. Load another, fire when ready.

(199.12 I think, but maybe Amanda Eisenboss remembers better? She was scoring for me.)

I found the back half of that separated case later on, inside my shooting stool’s bag with some other otherwise intact empties.

 

[QQgunstuff]

That’s what makes this sport so entertaining!

 

[spclark]

That’s what makes this sport so entertaining!

Case head separations?

Blown primers?

Yeah, entertainment's a state of mind one can pay dearly for.