Case head swipe from a .308 Jp LRP07 .... Help please.

[dlouie87]

Hello,

I took my first reloads out last week and fired them out of the JP for load development. The groups weren't bad but I just examined the cases today and noticed that there was some ejector marks on the case heads. The cases are pretty dirty as well. I don't know if it's over pressured or if it's something else.

My loads were with:

New win brass and LC match brass
COAL: 2.800
Cases trimmed to 2.005
Powder: Varget (started with 42-43.5gr)
Primer: Winchester LRP
Projectile: 168smk

If you need more info, please let me know. Reloading is still new to me so I hope you folks can give me some guidance. What are some possible solutions to fix this? Mess with the gas block? Check other parts of the rifle?

Thanks

***Updated with pics**

Dirty and light marks on the head case.

FGGM 168:



New winchester brass loaded:




LC Match once fired loaded:

 

[BCP]

Was the win brass dirty and the LC brass clean with ejector swipes?

Because winchester brass is rather light and 43.5 varget with a 168 would not be a hot load but in LC brass that same charge would be getting near max especially in a tight chamber.

Plus ejector swipe is somewhat normal for a semi anyways I have piles and piles of brass from my DPMS SASS that had small semi-circular ejector marks and it never gave me any problems. Some of it went 8-10 loads.

 

[dlouie87]

Man, you are right on! The win. brass was dirty and the LC brass was cleaner.

So ejectors strikes mean that the cartridge is near max? And loads that aren't as hot get more dirty?

Also, should I keep the brass from a semi separate from my 700's fired brass?

 

[vinsonr]

I do.

 

[bigedp51]

dlouie87

A case head swipe is caused by the rifle being over gassed and the bolt rotating while the case is still pressed against the chamber walls. The round circular mark on the base of the case is caused by high pressure and the brass starting to flow into the ejector. It can also happen with soft brass at normal pressures.

Military Lake City cases are made to higher standards than commercial cartridge cases and the base of military cases are harder to withstand larger diameter and longer headspaced military chambers.

Any time you have a ejector mark on the bottom of your case it also means the unsupported base of the case can expand also.

Below is a exaggerated example, BUT if brass is flowing into the ejector, the base of the case is also expanding outward due to pressure also. Back off your load you have high pressure or defective soft brass in the base of the case. With normal brass it does not start to flow till approximately 70,000 psi and normal max pressure is approximately 60,000 psi for the .308/7.62.

 

[Xcount]

You have kind of indicated two different problems. The title states case head swipes which can be from just overgassing a mild load but then in the text you mentioned ejector marks which usually indicate over pressure. can you post a pic?

 

[dlouie87]

Oh, I'm sorry. I thought case swipe and ejector marks were the same thing. Whoops. I will get a picture up in the next few days.

 

[Xcount]

typically a ejector mark is a round brass flow into the area around the ejector from extreme overpressure. a case head swipe can be caused by the ejector but can also be from any part of the bolt because it's unlocking so fast and the brass is staying stationary in the chamber. swipes don't really mean overpressure in the case. so the terms are not really supposed to be interchangeable one is much more severe than the other in terms of pressure.

hopefully the picture will help diagnose the problem.

 

[dlouie87]

Updated first post. Let me know if there is any more info you need.

 

[Xcount]

I think you are overgassed. it's kind of hard to definitely tell since there are two different primers but none look overly flat and there no real ejector flow marks. my recommendation is to GET AWAY FROM VARGET first and foremost. If you have an adjustable gas block then by all means trying closing it down some and try again. H4895 is much better in gas guns and has much lower port pressure for comparable chamber pressures.

 

[dlouie87]

Okay. I'll close the gas block a 1/4'' turn.

I'll also give h4895/imr4895 a try. Do you think rl15 or h335/WCwc844 will work as well?

I'll update the thread once I get new loads. I'll start with @ 41gr this time.

 

[Xcount]

If you have any 4895 I would start at 40gr and up to 41.5 you probably won't to search to long. That powder works great in 308 gas guns. There was a saying amongst M1A shooters that "if your rifle doesn't shoot 41.5g behind a 168SMK then it just won't shoot". The cartridge just like's that combo.

RE15 is better than Varget in my opinion but not in this application. Hopefully someone else can chime in about H335/WC844, i've never used them.

 

[dlouie87]

Thanks for the insight Xcount. I'll give that a shot and let you know how it goes. Should I stick with the thicker LC match brass or winchester?

 

[Xcount]

definitely use the LC. you aren't benchrest shooting it right! LC holds up well. Winchester is good if your trying to milk a little extra accuracy for 600yds+ but really LC does a great job. Find a load, load a bunch, practice and have fun. Brass is the smallest part of the game.