Over Pressure Sign or No?

[throwback]

Using Hornady Match Brass I have from shooting a bunch of Hornady 168gr factory loads. My OCW consisted of the following:

Hornady Match Brass
-Shoulder bumped .002
-.002 neck tension via .332 (really .331 result) bushing
178gr A-MAX
-Seated to mag length and well off the lands.
Varget from 42.9gr - 45gr
CCI BR2 Primers

From low end to high end I get an arc cut on to the case. It is the ejector carving a grove into the brass as I open the bolt clearly, but I'm not sure it's a over pressure sign. Case extracts just fine. I looked back at the factory loads I have not reloaded and sure enough, they have the little arc cut in them as well. However, the higher end of the Varget range over 44gr, the grove is more pronounced and deeper. I does not look like 'ejector marks' others talk about as it does not appear that brass is flowing into the ejector. As far as I can tell primers look fine. No other signs of problems. At 45gr the bolt was just marginally harder to open, but would not call it sticky, just barely noticeable. Even my extra light load at 42.9 gr created the mark, just much lighter than the 45gr load. What do you think?

I will try to post pictures tonight. Thanks for the help.

 

[cali_tz]

Re: Over Pressure Sign or No?

I would say if primers are not flattened, and the bolt is not at all sticky on extraction, then you have a problem other than high pressure.

 

[Captain Kirk]

Re: Over Pressure Sign or No?

Generally speaking, if you have difficulty lifting the bolt or have primer flow it is a indicator of over pressure signs, but swipe marks left on the case from the ejector is not that uncommon and may not indicate excessive pressures.

Do you get ejector marks on the case from loading and unloading a live round?

Kirk R

 

[throwback]

Re: Over Pressure Sign or No?

Picture of Scrape. You can see the 'original' scrape from the factor load at 12 o'clock. The 'new' scratch is slight deeper, it took out the H in match. I do not get the mark without sending the round. I think what is happening is once the round fire-forms the chamber holds it tight enough to have the bolt rotate around it. It's too loose to do this when I just chamber and remove the round.

 

[RTH1800]

Re: Over Pressure Sign or No?

If primer pockets are staying tight, drive on. If not back off or get new brass. I do not know if Hornady is soft or not. Your loads are not hot so should be fine.

 

[throwback]

Re: Over Pressure Sign or No?

Thanks for the input. Primer seems fine and no other issues. I'll do another string around my 44.7 node and just keep vigilant.

 

[MitchAlsup]

Re: Over Pressure Sign or No?

This might be a case where the ejector is not flat with the face of the bolt. I took a couple thou off an ejector with a stone and oil to rid a gun of a problem like this.

 

[MEDICGORDO]

Re: Over Pressure Sign or No?

I would usually get ejector swipe before flattened primers with the br2's,they are pretty hard.That was with Lapua brss.

 

[Fuzzball]

Re: Over Pressure Sign or No?

Looks like you have a burr on the bolt face at the ejector cut.

 

[Grump]

Re: Over Pressure Sign or No?

The more I do this, the more convinced I am that the most reliable "pressure sign" is more velocity than factory ammo out of the same barrel.

Yes, Hornady brass is not only quite spacious compared to Lake City and newer FC in .308, but it is not very hard-headed. Even with softer brass, loose primer pockets don't happen until way, way beyond spec pressures.

Boltface impressions *no deeper than from the first firing*, coupled with similar primer cup fill-out to match factory, would suggest that pressures are safe.

But if your reload is 100 fps faster than factory ammo with the same bullet, you're probably not within specs unless using one of the newest uber-powders like SuperFormance or perhaps a few others that have longer pressure curves...unless you're comparing with ammo using that same powder technology.

Now, some people are perfectly willing to ignore specs so long as they don't have stiff bolt lift or sticky-extracting cases, but we're big boys here and are free to use up as much of our case/rifle safety margin as we wish. But that requires a willingness to accept all consequences of that, even long-term.

 

[Clark]

Re: Over Pressure Sign or No?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">The more I do this, the more convinced I am that the most reliable "pressure sign" is more velocity than factory ammo out of the same barrel.</div></div>
The more I do this, the less I care about what the absolute pressure is in strong rifles, and the more I care about one of the effects of pressure, brass life.
I find the threshold of long brass life and back of a powder charge safety margin. That margin may be smaller for my one rifle than the margin required for ammo to be shot in many rifles.
The velocity is function of the integral of pressure over distance, minus friction and rotational energy, and not peak pressure.
Looking at the chrono data for determining pressure and max load for an individual with a strong rifle has <span style="font-weight: bold">two erroneous assumptions:</span>
1) The absolute peak pressure matters.
2) The absolute peak pressure may be inferred from the velocity.

 

[jonbearman]

Re: Over Pressure Sign or No?

What kind of rifle are you shooting and is it a match chamber,what twist is it and length of barrel. Have you had the ejector out to clean the bore it fits into? When I see marks like this,it is usually a problem that needs attention. Remeber as we tighten specs in our rifles ,it may cause pressures that exceed the design. It is always better to err on the side of safety. I dont want you to get injured. Do you neck turn your brass to insure uniformity? That mark is real pecular,like the case isnt rebounding to allow easy extraction.

 

[throwback]

Re: Over Pressure Sign or No?

Again, thanks for the help guys. This is a factory M700 5R Mil-Spec rifle. I went to the range and ran some rounds though the Chrono:

44.4 gr - Avg 2600
44.8 gr - Avg 2625

Max book from Hodgdon 45gr OAL @ 2661 w/ 180gr bullet.

Max speed I saw over 10 rds of 44.8 was one 2635

This seems fairly consistent with velocity in the reloading manual, if not a little low. Ojive is at least .125 away from the lands even though my OAL is 2.83 (typical Remington factory chamber these days). Ejector swipes showed the same as before on all brass.

I am going to really clean the chamber (maybe I have a bur or grit holding the case too tight after firing?) and maybe touch the ejector pin with some polish and see if that helps. Based on velocity and lack of any other signs of issues, I think I'm OK safety wise.