What causes this and would you reuse the brass?

[rayporter]

i would keep a close eye on that ammo. i have a feeling lube is not the only culprit.

 

[A382DWDZQ]

Check your primer pocket and see if you can push a primer back into it with just your finger.
Weigh your spent casings and see if they are close in weight or if that blown out one is a lot heavier than the others.

With the unfired ammo, I’d break them all apart and weigh each powder charge and each case. I know that seems like money down the drain, but it’s probably worth it to find out that there is / is not a problem with that batch. If there is, then you get your money back from Hornady, and if not, you know it’s something with your rifle.
I’d also get some temp strips and put them on your barrel and see how hot it’s getting with a rapid three round group, after you clean your chamber.

 

[gbflyer]

That’s what I was hoping to hear. My dumbass mistake.

Thanks for all the replies.

Maybe the first round. Not after that.

Being a custom, I’d bet you have a non-SAAMI throat in the rifle giving you pressure. Call the builder let them know what’s going on. It sucks to have to hammer your bolt open in the field. That’s where you’re headed next.

 

[prm]

Lube in the chamber would increase bolt thrust, but not chamber pressure causing primer to pop, would it? I’m asking as much as stating.

Stuff in the bore would of course increase pressure. I’m not referring to that.

 

[ResearchinStuff]

Technically, yeah. But without a pressure trace, just looking at the case after firing, it looks like typical overpressure.

Does lubricant or water increase pressure on handloads?

One of the most commonly asked questions and theories around hand-loaded ammunition is if leaving lubricant or getting water on cases increases pressure. The reason this speculation or theory has taken off is that commonly many individuals will shoot in geographical locations where it rains very...

www.reloadingallday.com

 

[49ereric]

Maybe the first round. Not after that.

Being a custom, I’d bet you have a non-SAAMI throat in the rifle giving you pressure. Call the builder let them know what’s going on. It sucks to have to hammer your bolt open in the field. That’s where you’re headed next.

This^
try a smaller grain bullet is the only other option imo.

 

[GreyBeck]

This^
try a smaller grain bullet is the only other option imo.

the handloads are actually a few more grains and faster fps but didn’t do this but same 175g. I have every piece of brass this rifle has cycled and looked over each box. Four of the first 5 rounds today had ejector marks and the 4th was the one with the primer coming out and black marks near the ejector. They get better as I progressed and the 2nd box was fine. My son was shooting next to me with the same ammo and had no issues. I THINK - after reading the article above that my rounds were getting oil on them or I failed to remove all the oil from the chamber from the last cleaning - or both. The spring in the mag felt like it would catch and I lubricated it at the last cleaning and I think some of that oil got on the first several rounds - especially the 4th at the bottom of the mag. The first round I inserted into the chamber - it was ok. The next 3 I cycled and that 4th round was at the bottom of the mag and got the most crap/excess oil on it I suspect. Too much oil is bad, lesson learned. I do need to find more articles about bad signs on cases and what to look for. I appreciate all the feedback.

 

[49ereric]

the handloads are actually a few more grains and faster fps but didn’t do this but same 175g. I have every piece of brass this rifle has cycled and looked over each box. Four of the first 5 rounds today had ejector marks and the 4th was the one with the primer coming out and black marks near the ejector. They get better as I progressed and the 2nd box was fine. My son was shooting next to me with the same ammo and had no issues. I THINK - after reading the article above that my rounds were getting oil on them or I failed to remove all the oil from the chamber from the last cleaning - or both. The spring in the mag felt like it would catch and I lubricated it at the last cleaning and I think some of that oil got on the first several rounds - especially the 4th at the bottom of the mag. The first round I inserted into the chamber - it was ok. The next 3 I cycled and that 4th round was at the bottom of the mag and got the most crap/excess oil on it I suspect. Too much oil is bad, lesson learned. I do need to find more articles about bad signs on cases and what to look for. I appreciate all the feedback.

If no oil in the chamber then the rifle has a tight chamber as gbflyer wrote and bullet ogive making contact or seated to long(whatever the proper wording is) for the chamber is the issue. Smaller grain bullet will or should be shorter and pressure signs will go away.
i have two Savage rifles with tight chambers and found out the hard way as you did.
I didn’t have the primer pop out but ejector marks big time and the LC LR brass was trash. My hand loads work in the other rifles fine.
I certainly do hope it is oil though so you can shoot the factory ammo you want.

 

[packer58]

Technically, yeah. But without a pressure trace, just looking at the case after firing, it looks like typical overpressure.

Does lubricant or water increase pressure on handloads?

One of the most commonly asked questions and theories around hand-loaded ammunition is if leaving lubricant or getting water on cases increases pressure. The reason this speculation or theory has taken off is that commonly many individuals will shoot in geographical locations where it rains very...

www.reloadingallday.com

Good find and good read ....

 

[OutdoorEdventure]

Blown primer with extractor mark! Definite pressure signs. I’d have to inspect webbing and measure pocket to see if reusable.

 

[EdP]

Here is a site with good info on pressure signs.

Understanding Pressure :: Primal Rights, Inc

Reading pressure is a required skill that all shooters must have. Whether you are shooting factory ammunition or your own handloads, you absolutely must be able to detect and interpret pressure signs on your fired brass.

www.primalrights.com

 

[Axlrod]

If the primer falls out on ejection you are at an extreme over pressure.

The ammo is probably fine. The case will not hold enough of the correct powder to blow primers. If it were the wrong powder it would blow every primer. If it was the rifle/chamber it would blow every primer. The most likely cause is lube in the chamber or some other partial obstruction.

 

[30338]

May want to check your bolt face for erosion at some point. I'd contact the builder as well.

 

[TaperPin]

The rifle is a McWhorter 7prc with a Borden action.

As you look into pressures and handloading, it’s good to keep in mind what the goal is. We want pressures to produce good velocity, but with the rifle/barre/bullet/case/powder/primer combination brass needs to last a reasonable amount and extract reliably. Case will eventually fail - loaded to really high pressure they may only last a few reloads before the primer pocket expands too much or the case head separates. Loaded to extra low pressure cases last almost indefinitely. Loads that allow a case to last 10 loads is my personal goal. That provides lots of velocity, but good extraction and overall reliability.

The shiny mark is normal - brass was under enough pressure to flow into the ejector slightly. That is a sign of high pressure, but not necessarily overpressure by itself. Some brass will fail without showing a single ejector ring, while other brass will have a dozen rings showing how many times it’s reloaded.

As others have said, it’s uncommon to have the primer leak into the ejector. Leaking primers are somewhat common with high pressure loads - benchrest shooters often talk about this as a necessary part of the game, even though escaping gases will eventually cut a ring into the face of the bolt. While hunters are generally more conservative and consider this a sign of over pressure.

The stiff extraction is a sign of pressures on the high side - the higher the pressure, the more the brass is forced into every tiny irregularity and the less it springs back. Rough spots in the chamber can be smoothed out to reduce this. It’s also somewhat more common with the design of the PRC because of it’s straighter sides.

Case heads don’t separate all at once, but thin a little at every shot. Many reloaders use a bent paper clip to feel for the thinning spot and toss the case before it separates. A full separation with half the case stuck in the chamber can put you out of business until the case can be removed.

 

[prm]

If the throat is cut a tad bit short the front of the brass neck (on longer ones) may be getting pinched when you close the bolt. Or, the throat is fine and a few pieces of brass had slightly long necks. Absolutely contact the builder.

 

[hereinaz]

Technically, yeah. But without a pressure trace, just looking at the case after firing, it looks like typical overpressure.

Does lubricant or water increase pressure on handloads?

One of the most commonly asked questions and theories around hand-loaded ammunition is if leaving lubricant or getting water on cases increases pressure. The reason this speculation or theory has taken off is that commonly many individuals will shoot in geographical locations where it rains very...

www.reloadingallday.com

The issue sounds like oil on the rounds and in the chamber.

OP said that he heavily oiled the bolt and it dripped on the brass in the mag. The pressure was worst for the rounds in the magazine under the oily bolt. The last round in the mag was worst, probably got oil accumulating with each oily round. Then it would get better as he shot more dry rounds that would slowly take away oil.

The issue slowly went away, and he finished as normal sounded like it went back to normal.

Oil and water do not compress like air. When it fills in the spaces between the chamber wall and brass there is higher pressure spike because the brass can’t initially expand.

There also could be some other reason that the rifle is that close to pressure in that chamber that the oil pushed it over the edge.

 

[GreyBeck]

Asking this question makes me realize how little I know about ballistics and makes me want to start reloading all the more. So I know the contents of each round and inspect all cases. I have several hundred Hornady 7mm PRC cases now that will all get inspected and eventually reloaded if still good. Again thanks for the replies

 

[Vern400]

If you're fairly new to this, just be aware that the higher performance rifles are susceptible to copper buildup in the first five or six inches of the barrel, and also carbon fouling. That alone can drive pressures way up. Oily chamber or oily cartridges can surely cause signs of high pressure also. You might want to read up on cleaning practices for the higher performance rifles particularly those with tight Chambers. I don't like to use it, but if I do have a problem with copper build up I have used Sweets 7.62 ammonia based copper solvent. You can potentially damage a barrel with it but if your job is done in 15 minutes it's pretty safe as long as you clean it out good and hit it with oil directly afterwards. Don't use any bronze components for the cleaning because it'll give you a false positive on copper. Using sweets, when a patch comes out clean, there's no copper left.

 

[Marbles]

Seeing as oil and water increase case head thrust against the bolt, but do not increase pressure (as demonstrated in the testing linked by @ResearchinStuff), and a blown primer occurs due to pressure in the primer pushing outwards towards the circumference of the case head, I doubt a blown primer is a false pressure sign.

My guess is something was off with the round, perhaps a combination of a slightly long case neck and a tight chamber. Personally, I would keep an eye on it and if having pressure signs with known dry chamber and rounds I would consider that an issue.

 

[35WhelenAI]

Correct, it's not doing anything to raise pressure by having oil in a chamber. The cartridge has nothing to grip so all the force goes backwards giving a visual sign of pressure even when there's not.

Vern400, what do you mean by a "higher performance" rifle? Most every bolt rifle and cartridge operates at relatively the same max pressure threshold and barrels are made within bore and groove tolerances for the caliber no matter who the manufacturer is.