Pressure Signs Help Needed

TheBoctor

Member
Joined
Oct 11, 2018
Messages
24
Location
UT
I've had loadings that show similar signs regardless of what charge i throw (within reason). For example they'd start showing pressure signs at 2800fps and it really wouldn't be any different until 2 grains later at 2950 fps and then bolt lift would start getting a little sticky. I typically switch powder and start working up with that and see what if it reacts the same way at similar velocities. Sometimes a slower powder will ease up the brass flow problems.
 

Elk Hunter 338

Well-Known Member
Joined
Feb 19, 2010
Messages
1,426
Location
Pocatello Idaho
silly question is there any film left on the brass from resize lube or in chamber?
Like i said before I'm not seeing the OMG stop right now and backer off signs on your cases! the one has more sign than lower but nothing horrible..

on a side note is this chamber a Nosler sammi or an actual PO ACK chamber
 

Rook57

Member
Joined
Feb 16, 2020
Messages
13
Location
Texas
silly question is there any film left on the brass from resize lube or in chamber?
Like i said before I'm not seeing the OMG stop right now and backer off signs on your cases! the one has more sign than lower but nothing horrible..

on a side note is this chamber a Nosler sammi or an actual PO ACK chamber
Using rcbs case lube, but wiping them off with paper towel, and wiping out inside necks with q tips before charging and seating.

Chamber is saami spec
 

YZ-80

Well-Known Member
Joined
Feb 20, 2019
Messages
670
Location
Maryland
remington 700 unless pin has been bushed will always crater the primer and that in no way is a sign of over pressure they all do it..
I have a few rifles that crater primers, even with factory loads. The thing to look at is the annular space around the peripheral boundary of the struck primer, which will go away as pressure increases and it will flatten out. If I see this, I don’t worry too much about it unless it is accompanied by ejector swipes and/or stiff bolt lift.

I think the OPs original pictures look like the cases are OK. Just my .02
 

Elk Hunter 338

Well-Known Member
Joined
Feb 19, 2010
Messages
1,426
Location
Pocatello Idaho
I have a few rifles that crater primers, even with factory loads. The thing to look at is the annular space around the peripheral boundary of the struck primer, which will go away as pressure increases and it will flatten out. If I see this, I don’t worry too much about it unless it is accompanied by ejector swipes and/or stiff bolt lift.

I think the OPs original pictures look like the cases are OK. Just my .02
it will never go away in a factory 700 action the cratering i mean..
 
Last edited:

jebel

Well-Known Member
Joined
Jun 15, 2018
Messages
244
Location
Oregon
I have a factory 700 that shows craters and extractor marks on all charges as well. To my eye, your higher charge is starting to show more pronounced flattening. Given that there are no other signs yet, I'd guess that you were right near the edge with the higher charge.
 

Elk Hunter 338

Well-Known Member
Joined
Feb 19, 2010
Messages
1,426
Location
Pocatello Idaho
Using rcbs case lube, but wiping them off with paper towel, and wiping out inside necks with q tips before charging and seating.

Chamber is saami spec
reason for asking the sammi is shorter than a PO version by .014".. so if you have a Po version using sammi dies you could be sizing to far back if set up per rcbs instructions ! can you put a fired round in chamber and close bolt with little resistance or some resistance?? if so back die out 2 full turns and size try to chamber and repeat until bolt closes with slight to no resistance this will get you right at min spec for sizing.
 

manitou

Well-Known Member
Joined
Mar 14, 2018
Messages
445
Location
Missouri
I am running 59.2 grains of H4831sc in two standard .280s (140 gr Accubond) with no hint of over pressure. Getting 3040 fps with 26" barrels.
 

manitou

Well-Known Member
Joined
Mar 14, 2018
Messages
445
Location
Missouri
Your primers look flattened to me, but all mine do too in my 7mm-08 and .280 cartridges after firing. I use WLR primers, which are on the soft side.
 

Rook57

Member
Joined
Feb 16, 2020
Messages
13
Location
Texas
I appreciate all of your replies. As far as the plan from here, I’m going to back off a .1gr to 61.4 grains. In testing of that load, a Five shot group came in at Avg. 3022 fps ES 17 SD 6.3 and grouped .471” at 100 yds. Going to test seating depth at .10 .30 and .50 off and see what happens, unless anyone has a better idea.
 

fiftybmg

Well-Known Member
Joined
May 16, 2016
Messages
199
Location
Johannesburg, South Africa
"Pressure signs" are not visible to the eye. There is nothing to see untill the primers blow or the bolt is stuck.

What needs to be done is not seeing, but measuring.

Running the rifle with hot loads just wears things out a lot faster, and worst case you find lug setback over time.

Randy Selby has a u-tube on measuring the base of the case after firing, and looking for up to 8 / 10 000 expansion to tell you when you're at an optimum load for max case life.

You can take it higher, if you don't care about brass life, and you can decide how far to go.

When you hit the 8/10000 expansion from new brass, you can see nothing to tell you there is a pressure sign. Not even with glasses.

As a side effect of that method, I found an out of round chamber on my son's PRS rifle, a Sabbatti in 260 Rem. I was looking for expansion from new on different loads, and instead found the bases of the case measured 20+ thou oval. Barrel was sent in to be re-cut, and the gunsmith confirmed 30 thou oval at the mouth of the chamber. The rifle was a 0.5 moa shooter with that oval chamber.
 

tim_w

Well-Known Member
Joined
Mar 25, 2008
Messages
538
Looks like someone needs to bushing the firing pin hole.

IMHO reading primers is one of the least accurate and wildly variable ways to read pressure signs of the case. It can tell you other things but case pressure limit thresholds not so much. Same goes for ejector swipes but to a lesser degree.

I can make prinrers flatten by increasing headspace. Ejector swipes by leaving a bit of lube on the case. etc......

Measuring the groove diameter and case head along with primer pocket seating pressure is the most helpful IMO. Neck growth is another after fl sizing.

Many case manf set the shoulders a good bit under min SAAMI /CIP spec. If you have a mid to max chamber you can have stupid amounts of headspace almost approaching 0.1 in some cases. It always pays to measure headspace on new cases vs your chamber so you know if you need to fireform the cases with a jam.

First firing a mid pressure load seems to have a positive effect on case life. Sure seems to on .223 cases shooting F/tr where you push those little cases to the ragged edge. Seems to carry over.
 

Recent Posts

Latest Classifieds

Nightforce has great tracking capabilities, they are rugged, a bunch of elevation, holds zero forever, and reticles are designed for long range shooting. So if you are looking to shoot long distances constantly, then you need a scope that can take the abuse. -- gilmillan1


Culture Of Excellence At Nightforce Optics
By Len Backus

A high level of quality both in production and in service. Read More


Nightforce is such a solid combo of reticle, available elevation, glass that is good enough to shoot at the longest range you can dial. Nightforce has bullet proof construction that can handle the incidental horse rolling or some other rodeo action. -- bigngreen


Nightforce ATACR Scope Review
By Jeff Brozovich

The new NightForce ATACR is for sure a top choice for any long range shooter. Read More


The total package. Nightforce is the best I have used as far as turret feel and solid detents. I have never had one that didn't track right on and always return to zero. Nightforce NXS is the best value for everything I need. -- Broz


Nightforce Velocity 1000 Reticle Review
By Scott Shreve

I think Nightforce knocked it outta the park with this reticle! Read More

NightForce


Top