Thread: Pressure signs with factory ammo

Originally Posted by gundoc

A wet chamber (oil or water) is the cause of the problem as it prevents the case sealing against the chamber wall and the full pressure is exerted rearwards. Make sure the chamber and bore are dry, and scrap the brass that has the pressure marks.

This. Google and/or make a chamber mop to use as part of the cleaning regime. A slick chamber wall, lubed isn't a good combo with some rifles. Try it dry and see if results differ.

I think probably a combination of wet chamber and that bolt face design leaves a bit less area supported on the base of the case so will show stamping easier.
Very light deburing/ countersinking of those holes would help too.

If it is not a wet chamber? , then it is possible you have a generous but still inside specification chamber . Remember that factory ammunition is supposed to fit in all chambers big and small . So in essence it is essentially a headspace issue .
A test can be to use a fired case that is only neck sized with a mild load and see what happens (not to mild as you can get the same result from low loads) , that is if you are not a nervous Nelly.

To me your primer looks flat as and the stamped brass, tight bolt lift point to over pressure. This should not happen with factory ammo. I agree re head space. Have a smith check it.

Originally Posted by Tankd

If it is not a wet chamber? , then it is possible you have a generous but still inside specification chamber . Remember that factory ammunition is supposed to fit in all chambers big and small . So in essence it is essentially a headspace issue .
A test can be to use a fired case that is only neck sized with a mild load and see what happens (not to mild as you can get the same result from low loads) , that is if you are not a nervous Nelly.

This. Had exactly the same issue zeroing a Z6 on my sons Sako 85 WSM. I bought some Fed blue box to get it on the paper at 100.
Had never experienced firm bolt closure and stiff bolt opening with brass swarf in the action and on the bolt face.
Cleaned, scrubbed everything.
Mate said buy some factory Norma.
Problem solved.
His prior and similar experiences were everything inside SAMMI spec but at each end of the +/- tolerances.

For what it’s worth.

B

Originally Posted by shift14

This. Had exactly the same issue zeroing a Z6 on my sons Sako 85 WSM. I bought some Fed blue box to get it on the paper at 100.
Had never experienced firm bolt closure and stiff bolt opening with brass swarf in the action and on the bolt face.
Cleaned, scrubbed everything.
Mate said buy some factory Norma.
Problem solved.
His prior and similar experiences were everything inside SAMMI spec but at each end of the +/- tolerances.

For what it’s worth.

B

Yes I think you might be onto something here. I just tried to chamber some cases fired with the Sauer in my Tikka, the bolt wont close, I don't think it is the case neck because I got the bolt easily to the point of closing but it wont close the final bit. However cases fired in the Tikka will easily chamber in the Sauer, these are all once fired factory ammo, I don't reload. I know this is a pretty crude way of checking chamber tolerances but I think it does tend to indicate more headspace in the Sauer. i am going back to the range now with a squecky clean barrel and chamber to check the result.

Right, so I just got back from the range and here's what I discovered. Even with a squeeky clean chamber the Hornady superformance 129gn SST's were showing pressure signs. Tight bolt lift and ejector marks on the the base of the case. Grouping also sucked. It seemed to go Ok for 3 rounds and then the pressure signs showed up. So I tried the Fiocchi 129gn SST's which are a more mild load than the Superformance. Grouping was not great, with the odd flyer the bolt was still slightly sticky to lift.
So I then went to some Hornady Precision Hunter with the 143gn ELDX. these are also a mild load, they chronographed at 2530 in my Tikka with a 20" barrel, so I reckon they would be doing around 2600 in the 22" barrel on the Sauer. No pressure signs, nice smooth bolt lift and grouping under the 1" at 100m.
So it looks like those who bagged the Hornady Superformance load are correct, at least for this rifle, this is a shame since I have around 500 rounds of the stuff in stock. However the Tikka does love it so I will be stuck with having to stock 2 types of ammo for the 2 guns. Thanks to all who gave input on this.

Unusual that you get that much difference from it from what doesn't seem to be a major variation, and I compare here to a BSA .308 that was so oversized you couldn't even engage the bolt lugs on another .308 like a Rem M700 with a factory barrel and chamber when trying to chamber a fired case from the BSA. That thing was huge, swallowed a no go gauge but we never knew any different until I started reloading for it. Resizing cases from it to fit anything else wasn't a really going proposition to be honest! Press arm forces were horrendous...

If it was mine, I'd be getting it once-overed just to be sure something isn't weird like a miscut throat that's tapping the pill with the superformance where the other brand is clearing and not giving such a pressure spike. The most likely scenario is the simplest one which is as you report with the chambering of fired cases, but if that's a symptom of another issue then you might have not solved the problem. If it is excess headspace is it due to a pre-existing fault that's causing that issue? Bearing in mind here the Sauer 100 uses a breech ring system where the bolt breeches up on the breach ring and the barrel screws into the action until it contacts the ring which is promoted as being a system that gives more consistent tolerances. I've never heard of that issue in one of these as a factory rifle before...

The SuperPerformance might be the cause of your issue, but it’s the chamber of the Sauer that is most likely your problem.

The SuperPerfomance was fine until the 3rd shot, so if the chamber neck is too tight, the carbon build-up doesn’t allow the brass to expand and allow bullet release. You’ll get typical pressure signs.

If it doesn't shoot well then shoot something else.
Superformace is marketed as a hotrod round, it will be at max pressure the lawyers will allow.
Looking at the pics of your brass and considering it is an American brand factory ammo I wouldn't be the Least bit concerned.
I have had much worse stamping from factor fed blue box 308 in a brand new Sako 308.
Us reloaders can be and mostly are a bit precious about pressure signs.
But the fact of the matter is factorys like Hornady,norma, federal etc etc etc have done the homework and in all but extremely out of the ordinary circumstances it is safe.

I have fed brass that has more stamps than I can count that still holds a primer tight and chambers and fires fine.

Also superformance seems to be heat sensitive. A hot day with ammo in the sun and after a few rounds the rifle is also hot. I use superformance and it's ok out hunting as you only fire a couple of shots, all going to plan. At the range I put ammo box in a small chilly bag with a slicker pad to keep ammo consistent. Works for me anyway.