Fire forming pierced primers

[Jeff Von Rosenberg]

I was fire forming 100 Br cases to BRX yesterday and I had fire formed about 80 cleaning every 25 rnds . Everything was great all the sudden it started piercing primers and a couple of stuck cases. could it be the heat in the chamber as I was just cleaning between strings, not really setting rifle aside. . These were fireformed by seating bullet long into lands. 105 scenar backed with 30.0 grains of Varget. JVOn

 

[ShootDots]

That sounds exactly like what happened... I also bet you have somewhat of a looser primer pocket in those particular cases..

 

[4xforfun]

Two thoughts.

Maybe developed a carbon ring that got bad enough to bump PSI. When you clean do you go after the carbon or just trying to zap the copper and powder?

Headspace problem?? Maybe the you need more than a jam. Try a couple with a false shoulder.

Good luck.

 

[ShootDots]

Two thoughts.

Maybe developed a carbon ring that got bad enough to bump PSI. When you clean do you go after the carbon or just trying to zap the copper and powder?

Headspace problem?? Maybe the you need more than a jam. Try a couple with a false shoulder.

Good luck.

I agree>>>the false shoulder method is considerably better..

 

[Jeff Von Rosenberg]

New brass so primer pockets the same not likley to change suddenly after 80 rnds. Carbon ring possible as I was just doing minimal cleaning after 25 shot strings. As far as turning false shoulders, no need as I have around 200 rnds now, just trying to figure out what happened? Could residual heat built up in chamber have caused this? First couple 3 strings I let rifle cool awhile , last string I began firing immediately after cleaning.

 

[bigedp51]

The majority of pierced primers are caused by excess head clearance and the primer being pushed back over the firing pin. This action turns the firing pin into a cookie cutter and it punches the center out of the primer.

From the Sierra manual

Below the anvil is plugging the hole in the primer, .223 case with excess head clearance fired in a AR15 .

The firing pin strikes the primer driving the case forward, the cartridge goes bang and the primer is forced back over the firing pin and the primer is pierced.

 

[4xforfun]

"turning false sholders"??

No turning nessessary, unless you are running a tight neck..then you need to turn regaurdless.

As far as heat...if you simply load and shoot, heat has ZERO bearing...unless you let the loaded round sit in the hot chamber for a long time.

 

[Jeff Von Rosenberg]

Still don't know why this started after I had already done 80 rnds? Same cases , rifle , powder charge , oal. How could the headspace change mid stream ? This is a Savage Target action blueprinted by Fred at SSS and a new McGowen 6BRX barrel. This is the first time I have shot thru it. Shot 5 and cleaned 3 times than proceeded to clean about every 20, how ever as stated before after last cleaning I didn't let rifle set and cool as on previous strings. Have plenty of brass just want to know what happened after successfully forming 90% of the cases?

 

[Erik Cortina]

It's definitely excessive headspace. The primer strike drove the case forward just like bigedp51 described.

Maybe the heat expanded the brass which in turn gave you less neck tension? Or maybe you left some cleaning solution in the throat area allowing bullet to jam further into the rifling? I really don't know what did it, but I know that it was excessive headspace that caused your pierced primers.

 

[fdshuster]

JVON: Yes to all of the above suggestions, but, after reading your posts several times, cannot find anywhere that you told us what primers you are using. Fed. 205 at .019" cup thickness, CCI 400 at .020", Winchester small rifle at .021"? OR CCI BR4, 450, Remington 7 1/2 all at .025"? Big difference !

 

[Jeff Von Rosenberg]

I agree with all suggestions including primer type and I agree Erik( good spelling huh!) it's excessive headspace , but why after 80 good rnds. Erik the cleaning solution sounds plausible. I'll keep searching , you guys are great!!! JVON

 

[bigedp51]

The firing pin hitting the primer has enough force to actually shorten the case and decrease cartridge headspace. In one of my milsurp .308/7.62 rifles if I repeatedly left the fired cartridge in the chamber and pulled the trigger the case would be .001 shorter every time I pulled the trigger.

For case forming and seating your bullets into the rifling you need a good bit of neck tension to keep the bullet and case from moving forward when hit by the firing pin.

If any cleaning solution is left in the chamber it will increase the backwards thrust of the case and apply more force to the primer. Using Lighter fluid, rubbing alcohol, etc on your last patch through the chamber and bore will remove the majority of cleaning solvents and dry the chamber and bore.

On my milsurp rifles with throat erosion and excess headspace I would leave the expander button out of the sizing die for maximum neck tension. I would also have to load the bullets backwards so the base of the bullet would touch the rifling. (boat tail maximus)

 

[jonbearman]

Ed,bullets backwards? Do you fire them that way? Back in the forties guys would use fmj bullets and pull them and load them backwards to make a hollow point sort of.

 

[bigedp51]

Ed,bullets backwards? Do you fire them that way? Back in the forties guys would use fmj bullets and pull them and load them backwards to make a hollow point sort of.

Yes backwards because a surplus Enfield rifle that fired cordite ammunition has a throat length twice as long as a Weatherby due to high temp erosion. (if it has a throat at all)

On many of the older Enfield rifles you just slip a rubber o-ring around the rim to hold the case against the bolt face and fire form the cases. This is because the throats are gone and the false shoulder method doesn't work due to the size of the chamber and causing split necks.

Below, fire forming fun, American companies don't know where to put the shoulder of the case. The case rim below is resting on a lip inside the Wilson gauge and the shoulder is actually a 1/4 inch too short of proper location. And at maximum military headspace you can have .017 head clearance depending on rim thickness. (headspace maximus)

 

[Jeff Von Rosenberg]

Thanks guys got a chance to check things out and it appears although it seemed tight , that the barrel and barrel nut must have backed out some. This was 1st time on new barrel. I rechecked headspace and though it appeared tight, at some point during the 80 rnds it backed out! Thanks for all the input JVON

 

[Steve Ladino]

I've had primer piercing on occasion but recently i failed to clean all the solvent out of the chamber and the first three rounds pierced then all subsequent shots were fine, same brass and primers etc. etc. This gun has never pierced and hasn't done so since .