Unexplained pressure increase

[GSSP]

Pressure increase: unexplained

Shooting my new 338 Edge, 300 OTM, Rel 33, CCI 250, 30" Bartlein, Surgeon 1086 action.

Treated barrel with DBC then ran about 10 rounds down to smooth up the reamer marks at the throat. Cleaned with Hoppes #9 for powder fouling then Barnes CR10 for copper which was nil.

10 round ladder from 97.5 to 102 with no chromo results but very nice node at 101, 101.5 and 102. No pressure signs what so ever except barely noticeable increased bolt lift at 102 gr; expected this.

Back to the range with Oehler 35p which netted 2984 (101 gr ), 3004 (101.5) and 3049 (102 gr). Wow! I thought.

Went on to shoot some 3 shot groups. 100 gr = .45 moa and 101.5 gr = .35 moa. Man, I was a happy camper except starting to see ejector marks.

Shot a seating depth test (likes .015" off) and more ejector marks. Backed off to 100 gr. Still ejector marks. Ran primer test and got ejector makes with all 4 brands of primers.

Now, with WLRM primers, 97.5 gr giving 2850 fps i'm getting ejector marks.

Two things come to mind

1) A possible build up of copper fouling though I just now cleaned the barrel and barely got any copper out. Has anyone seen a copper build up that increased pressures?

2) Could the ejector springs be so strong that's it's somehow pushing up against the case and causing the eject marks even at lower pressures?

You opinions please.

Alan

 

[dkhunt14]

Probably carbon in the throat. Matt

 

[dmoran]

My answer to your Q.1: copper no, but carbon yes
And agree with Matt "Probably carbon in the throat"
Donovan

 

[GSSP]

JB Bore Paste and some judicious scrubbing in front of the throat?

Alan

 

[GSSP]

Online gent at Sinclair suggests

509-350-040WB C4 Carbon Remover by BoreTech

Just let it sit and

 

[243winxb]

DYNA-BORE COAT- Could it reduce friction like moly? Reducing pressure till it was shot out or cleaned from the barrel ??

2) Could the ejector springs be so strong that's it's somehow pushing up against the case and causing the eject marks even at lower pressures?

If your ejector is like a Rem 700, the mark is produced when brass flows into the hole the ejector sits in. The pin itself does not make a mark, in my experence.

 

[Jeff Conover]

The problem you are seeing is caused by carbon fouling. The pressure is hitting peak when the bullet is 3-4 inches down the barrel and the curve is is on the downward slope. Copper doesn't build until further down the barrel and in extreme cases you will see the velocity drop in a copper fouled barrel while the pressure remains constant. To fight the pressure issue you need get the bullet pass the 4 inch mark in the barrel and of course working within the limits of the case chamber.

Jeff Conover

 

[/VH]

What? Seems purdy long seated, even for an edge.

 

[justpassinthru]

How does the brass show high pressure but the primers look so good?

 

[jlow]

Although a carbon ring can cause high pressure, it is not the only thing other than an over max charge that can result in brass that gives you that “high pressure” look.

Other things include too much head space, lube on the case, water on the case, soft brass case like FC, too long neck to cause a crimp on the bullet, jamming, thin case primers (i.e. CCI 400) etc. Not all of the above are actually high pressure situations, and so the primers and brass will respond differently.

 

[bigedp51]

Although a carbon ring can cause high pressure, it is not the only thing other than an over max charge that can result in brass that gives you that “high pressure” look.

Other things include too much head space, lube on the case, water on the case, soft brass case like FC, too long neck to cause a crimp on the bullet, jamming, thin case primers (i.e. CCI 400) etc. Not all of the above are actually high pressure situations, and so the primers and brass will respond differently.

I have never seen too much headspace that ever gave an over pressure indication, all that happens is the case stretches and thins in the base web area which leads to case head separations. And lube and water will increase bolt thrust but will not raise the chamber pressure to the point of causing the brass to flow unless the neck doesn't have room to expand or get in front of the bullet. Meaning your talking about a lot of grease and water that a blind man could see and accusing the case greasers of gross ignorance. (of which I know a little about torquing them off) :

The OP is talking about hard bolt lift and ejector marks on the base of his cases, and he didn't say he was shooting in the rain or not wiping the case lube off his cases, and denting his case shoulders from over lubing his cases.

And the biggest danger of too much headspace is foam on your upper lip and overly loud belches when reducing said headspace.

Trust me, the Enfield rifle in the photo below has had the headspace adjusted from just kissing the rear of the case (.006 shorter than the GO gauge) to .010 over normal military maximum meaning .027 head clearance and also the war time emergency headspace maximum. And "NO" the case did not show excess pressure signs and the case did stretch more but did not separate.

And just one of the reasons military rifles have longer headspace settings is to "reduce" bolt thrust because the case stretching acts like a shock absorber and reduces the dwell time the case is applying pressure to the bolt face.

And now back to our case greasers in the forum. :

 

[jlow]

As usual, bigedp51 you are quintessence of know-it-all with enough rudeness for all of us - thanks!

 

[bigedp51]

As usual, bigedp51 you are quintessence of know-it-all with enough rudeness for all of us - thanks!

And headspace jlow is also the distance between your ears and how you use it. Now any of you please show me ejector marks from a rifle with "excess" headspace that will cause brass to flow into the ejector. You can't because headspace doesn't cause the chamber pressure to increase to the point that brass begins to flow.

And if you think correcting your error is rudeness then you better hope I don't get real technical and even more informative.

Brass begins to flow when the chamber pressure exceeds the strength limitations of the brass and has NOTHING to do with headspace.

And thank you for your error.

 

[jlow]

Just wondering how many times you are going to act this way before you get banned....?

 

[bigedp51]

As usual, bigedp51 you are quintessence of know-it-all with enough rudeness for all of us - thanks!

It will depend on what the moderator considers what is being rude and which person gave the correct information.

So like I said before "show me" how headspace can increase chamber pressure and make brass flow, without YOU being rude.
So jump right in and show us jlow I'm waiting and so is the rest of the internet. :

 

[jlow]

Well, if you can calm down enough for a meaningful discussion, I will answer your question. If you don’t think you are rude, read your post in Repy#11 carefully. It is not the fact that you disagree but how you do it that people have a problem with. If after reading your reply and you still don’t see how you are rude, then I can’t really help you.

First, I was not answering the OP’s question but poorboy’s question in Reply #9.

Second, if you look at my post, I never said headspace can increase chamber pressure and make brass flow. What I said was in fact quite the opposite. I said carbon ring was “not the only thing other than an over max charge that can result in brass that gives you that “high pressure” look”. The key word there is “Look”.

If you have too much headspace, that means the case is too short. So when the firing pin hits the case, it pushes the case forward. When ignition happens, the case stretches out again like you say, but since the head is in fact no longer next to the bolt head like it is normally but moving towards the bolt face, depending on how far and how fast it moves, if it moves far and fast enough it will cause what looks like an ejector mark on the case.

 

[bigedp51]

GSSP

Question, were you loading and firing a single round at a time or were you feeding from the magazine?

Meaning could your loaded rounds be moving under recoil closer to the lands when loaded in the magazine?

So could your loaded rounds possibly have the bullet moving at the range or while transporting your ammunition to the range. Meaning were you driving over a bumpy road and could your neck tension be at fault.

 

[Kings X]

I might check case length on fired cases. Might be getting long and gripping bullet.
Quick check is old trial of dropping a bullet down a fire case.

 

[GSSP]

Single feed. Each round was seated just before the shot.

 

[Deleted old_dood]

I have to agree with those who suspect carbon. see this thread started by me http://forum.accurateshooter.com/index.php?topic=3844630.0

pay particular attention to my entry of 9/13