Would excessive headspace cause pierced primers and loose primers?
- Thread starter 1911nut
- Start date
jackieschmidt
Gold $$ Contributor
Excessive headspace can cause primers to “back out”, if the case grips the walls of the chamber really tight and the case head never actually comes in contact with the bolt face.
Loose primers are either caused by cases simply being fired too many times under upend loads, or too hot of a load to begin with.
Pierced primers are usually caused by too hot of a load, but a ragged firing pin tip can also contribute.
You need to do some precision measuring and find out just how much clearance there is between the face of your loaded round and the bolt face.
Do not rely on “feel”.
Loose primers are either caused by cases simply being fired too many times under upend loads, or too hot of a load to begin with.
Pierced primers are usually caused by too hot of a load, but a ragged firing pin tip can also contribute.
You need to do some precision measuring and find out just how much clearance there is between the face of your loaded round and the bolt face.
Do not rely on “feel”.
Thanks Jackie, I’ll work on the measurements.
Old Navy
Gold $$ Contributor
I have two target actions. I simply screw the barrel on snug with the go gauge and a couple raps with the hammer and I am go to go. I can put one layer of scotch tape on the gauge and it will be snug closing. This works perfectly for me.
Pieced and loose primers, along with hard bolt lift certainly indicates high pressure but in my experience not an excessive head space.
A split case case leakage has been the result that I've seen.
Emmett Dibble
Gold $$ Contributor
I do the same as Old Navy with Remage barrels... go gauge, 1 layer of scotch tape and the bolt should "just" engauge the lug ramps. Scotch tape is about .001-.002". Remove the ejector on the bolt for a better feel. If your really cheap (not recommending) some people use a peice of sized brass or a commercial match round as their go gauge. Some guns/loads just piss off primers I think. I have a thread about a 6X45 that blows primer shoulders out with no real pressure signs then I have a 6CM that will flatten a primer smooth but never rupture them. Pierced though, would check fire pin depth/sharpness... all other things being equal.
Same barrel, removed and reinstalled. Barrel may have tightened, barrel nut seemed loose.
Was also a bolt problem. I now know a lot about setting up Savage bolts with both ends of the firing pin threaded for adjustment. One end adjusts firing pin protrusion, the other end to set cocking piece pin clearance to the bolt body. Adjust the cocking piece pin clearance first…….
Had the same thing on my Savage model 12 action 3 years ago. Was getting primer cratering and some piercing. Did some research and discovered that the firing pin hole was to large and would cause the firing pin to wiggle and cause cratering and piercing. I had two options:
1. send the bolt and pin to a gunsmith down south and he would put a bushing in the bolt face to stop the wiggle.
2. Try a harder primer (in my case I am using small rifle primers).
Went to a CCI #41 and problems went away.
This years I experienced a different issue with the same action and barrel. Round .chambered easily fired but had a very hard bolt lift and extraction.
Checked the chamber with a bore scope and noticed a yellow film in the chamber. Took a shot gun brush wrapped some scotchbrite pad around it (green color) and Hoppies #9
Placed the rod in a drill and ran the brush into the chamber about 30 seconds of scrubbing the chamber the film was gone and so was my hard extraction..
My conclusion as to the yellow film was I was not wiping the sizing lube off the cases before I reloaded them and the heat of the chamber cause the lube to transfer onto the chamber and cause the sticking.
That was 2 months ago and have not had this problem re occur since I am now wiping the excess lube off the formed case.
Below is a picture of the cratering and piecring.
1. send the bolt and pin to a gunsmith down south and he would put a bushing in the bolt face to stop the wiggle.
2. Try a harder primer (in my case I am using small rifle primers).
Went to a CCI #41 and problems went away.
This years I experienced a different issue with the same action and barrel. Round .chambered easily fired but had a very hard bolt lift and extraction.
Checked the chamber with a bore scope and noticed a yellow film in the chamber. Took a shot gun brush wrapped some scotchbrite pad around it (green color) and Hoppies #9
Placed the rod in a drill and ran the brush into the chamber about 30 seconds of scrubbing the chamber the film was gone and so was my hard extraction..
My conclusion as to the yellow film was I was not wiping the sizing lube off the cases before I reloaded them and the heat of the chamber cause the lube to transfer onto the chamber and cause the sticking.
That was 2 months ago and have not had this problem re occur since I am now wiping the excess lube off the formed case.
Below is a picture of the cratering and piecring.
Attachments
ckaberna
Gold $$ Contributor
I once had some cases that I set back too far. About .005-.006” and had the popped primers. Not sure of the mechanics of it. I wound up putting scotch tape , I don’t remember 1-2 layers, and fired the remaining cases without issue. Folks don’t realize how important that process is. I have on hand a 100 or so Lapua 220 Russian for a ppc that the previous owner set back about .008” too far. I’ve been told by some respected folks to load long and fire them.?? My logic tells me, without enormous neck tension, I will stretch the case at the .200 line and wind up with separating case heads. ?
I still have questions but maybe this is of use to you.
IME, excessive headspace can cause pierced or cratered primers and other false signs of excessive pressure but I don't think it'll cause loose primer pockets. Sounds like you have high pressure. Cratered and/or pierced primers are most often too much clearance between the pin and the fp hole, but light spring pressure, excess headspace as well as high pressure can cause them. Light spring pressure and excessive headspace are sorta related, or similar. Both cause the spring to back out and bounce. The primer brass flows rearward, unsupported at all and can flow into the pinhole during this short period....acting much like too much pin clearance. It looks much the same and lead you to believe the bolt needs bushed. It might, but it can also be the weak sping or excess headspace leaving the fp hole open very temporarily, allowing the unimpeded brass flow. The pin bounces back and the primer looks just like a cratered primer from excess clearance. Actually, excess pressure can but is a pretty rare cause for cratered or pierced primers, ime. There's even more to this that I can not explain as some powders/loads do it worse than others even at lower pressures. I've never figured that one out. Varget in a 6BR with heavy bullets seems to do this quite commonly, even at mildish loads while powders/loads that make more pressure don't show it at all. I won't guess as to why this is but I've seen it a lot more than coincidentally or randomly....on both several custom actions as well as bushed and unbushed remington and savage bolts. There's something to it but I'm not sure what it is.
Answer is yes to most of your problems but loose pockets is probably pressure.
Excessive headspace will cause the case togrip the wall , primer will start to back out ( pressure increasing , primer hits the bolt face ) and hits the bolt face , then the case stretches and hits the bolt face reseating the primer .
So ,with no coffee in me yet , I hope it makes sense.
Wow! That's over pressure.
NorCalMikie
Gold $$ Contributor
Would excessive headspace cause pierced primers and loose primers?
YES!!!
But, not chamber/barrel headspace as much as the "brass too short for that chamber".When fired, case gets pushed forward, primer tries to back out, gets pierced and or flattened.
Usual cause? Shoulders got pushed back too far when resizing OR if new, brass too short from the factory.
Once fire formed, good to go as long as you don't push the shoulders back too far and create the same problem all over again.
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