What could cause this?

[Elite Precision]

curious as to what could cause this to happen? blew the bolt back, powder blasted the shooter, blew the bottom metal off. bullet went on target at correct aim. previous 3 shots fired from same box of ammo shot fine. rifle was cleaned thoroughly. then this round did this. Nosler factory made trophy grade ABLR 142gr. trued remi SA, bartlien barrel in 6.5 creedmoor.

 

[Nightraider]

curious as to what could cause this to happen? blew the bolt back, powder blasted the shooter, blew the bottom metal off. bullet went on target at correct aim. previous 3 shots fired from same box of ammo shot fine. rifle was cleaned thoroughly. then this round did this. Nosler factory made trophy grade ABLR 142gr. trued remi SA, bartlien barrel in 6.5 creedmoor.





View attachment 1105594

Unsupported case head?

 

[Elite Precision]

Unsupported case head?

as in the bolt nose recess is too deep? and the bolt nose isnt supporting the case enough?

 

[Coyotefurharvester]

So the round before the brass in the pic, blew the bolt open. And then the rifle was fired again, without the builder inspecting it for damage?

 

[Bill K]

How did the bolt blow back, if it was closed and lugs did not shear ? The ring around that base would indicate a over load/charge. Maybe this one round somehow got extra powder when it was loaded. Just some thoughts.

 

[KMart]

The way I am reading your write-up is:
3 shots fired from a box of factory ammo
Then the rifle was thoroughly cleaned
Then the 4th shot from the same box of ammo separated and caused damage.
Is this correct?

 

[Nightraider]

as in the bolt nose recess is too deep? and the bolt nose isnt supporting the case enough?

Yup or a flat face breech with too much gap. Could also be as simple as a bad case, like a case head separation type deal.

 

[NZ_Fclass]

Unsupported case head?

bump

 

[Dusty Stevens]

Thats a shoddy chambering job at best. Even a severely overpressured load wont blow down the feed ramp. Please dont shoot this rifle anymore until a qualified rifle builder corrects it. Scary stuff coming out of garages these days.

 

[gunsandgunsmithing]

Hard to be sure from the pic but it does look like too much unsupported case.

 

[hoz53]

curious as to what could cause this to happen? blew the bolt back, powder blasted the shooter, blew the bottom metal off. bullet went on target at correct aim. previous 3 shots fired from same box of ammo shot fine. rifle was cleaned thoroughly. then this round did this. Nosler factory made trophy grade ABLR 142gr. trued remi SA, bartlien barrel in 6.5 creedmoor.





View attachment 1105594

Didn’t leave an obstruction in the barrel did you.

 

[theallcineyes]

so many variables its hard to give a definite answer. some of the more likely are, over charged load, bullet set back, bad case. my guess would be either a bad case.

 

[Ggmac]

curious as to what could cause this to happen? blew the bolt back, powder blasted the shooter, blew the bottom metal off. bullet went on target at correct aim. previous 3 shots fired from same box of ammo shot fine. rifle was cleaned thoroughly. then this round did this. Nosler factory made trophy grade ABLR 142gr. trued remi SA, bartlien barrel in 6.5 creedmoor.





View attachment 1105594

Firing pin was stuck in the fired position , when closing bolt it fired the case WITHOUT the lugs being in battery ( fully locked ). Hope everyone is okay .

Or the trigger didn't hold the cocking piece and it followed the bolt , again firing the case while not in battery ( fully closed).

 

[Elite Precision]

The way I am reading your write-up is:
3 shots fired from a box of factory ammo
Then the rifle was thoroughly cleaned
Then the 4th shot from the same box of ammo separated and caused damage.
Is this correct?

yes this is correct.

 

[Elite Precision]

Thats a shoddy chambering job at best. Even a severely overpressured load wont blow down the feed ramp. Please dont shoot this rifle anymore until a qualified rifle builder corrects it. Scary stuff coming out of garages these days.

whats your definition of "shoddy"? whats something you recommend checking for? chamber run-out? concentricity? yah this is way scary. not sure where to start other that a complete tear down and check. thanks for your input..

 

[Elite Precision]

Firing pin was stuck in the fired position , when closing bolt it fired the case WITHOUT the lugs being in battery ( fully locked ). Hope everyone is okay .

Or the trigger didn't hold the cocking piece and it followed the bolt , again firing the case while not in battery ( fully closed).

from what i know of the situation. this wouldnt be the cause.. the shooter said he had placed bolt into battery and had plenty of time to settle crosshairs on target and execute a proper trigger press.

thanks for your input..

Matt

 

[Elite Precision]

Didn’t leave an obstruction in the barrel did you.

no, the shooter said the bullet exited the barrel and actually was on target accurately.

 

[243winxb]

Excessive chamber headspace is my guess. Caused case head separation.

 

[J355]

Pics of the previous cases would be nice, may show a bulge from a overdone feed ramp

 

[Elite Precision]

i tore apart the barreled action and checked to make sure everything was still intact internally. the bolt lugs, bolt face, extractor, ejector, firing pin are all fine. the bolt face did have a huge over pressure sign of the entire case end imprinted on it with legible writing! ( ive never seen that before) the internal lug abutments are fine, not cracked or sheared or missing a corner. i did get the first three fired nosler rounds, and a previously shot 20 rnd box of ammo that was shot from this rifle that was all of the initial break in rounds used. the first box of 20 was hornady match 140s. all fired brass looked fine. there were a couple of the hornady brass that had a real faint horizontal line scratched into it on half of the circumference that matches up to the blow out line of the nosler brass pictured. the 3 other fired nosler brass showed a more distinct scratch mark, and it was more prevalent than on the hornady brass. i took 1 round of the nosler ammo and fired it out of a factory remington aac-sd that i have, and there was no mark.

i ran a go/no go gauge thru it, and it passed fine. closed effortlessly on the go, and was locked out on the no go just as it should. i measured the action and bolt and checked those measurements on the barrel and chamber for blueprinting specs and all the measurements (tenon length, go gauge protrusion, bolt face recess) came out within -/+ .0001"

I chucked the barrel up in my lathe and dialed it in to .00015" of true. checked the chamber run out from throat to entry, and it is running true as well.

im not sure what to do at this point. knowing all those measurements are as good. maybe it was an overcharged round. but why would those marks be on the brass? i checked the chamber entry for a burr, or a sharp edge that would be the thing that touches the brass there, and it was clean, had a small chamfer, and was smooth.



is there anything else i can check for while this is apart? any other tests? someone from another forum mentioned to just set the chamber back and re-cut it myself. Thoughts?

thanks everyone for their input! i really appreciate it. keep them coming.


Matt.