Help me troubleshoot unexpected pressure signs

[RmeJu]

I have a relatively mild load that has worked well in my rifle, but yesterday, I took out this exact same load and it started to show some slight pressure signs (faint ejector mark, but no wipe or heavy bolt lift). It also had significant carbon buildup around the case mouth and shoulder, web, and headstamp, none of which I have ever seen before. I don't whether this is a pressure sign, but I suspect it might be. You can see in the third pic the carbon outline of the ejector mark, but most of this is actually just carbon. The last pic (after wiping down with case head with solvent) shows the actual pressure mark is much fainter, but you can just make it out if you look closely.

A little background: the brass is virgin Nosler 7mm rem mag. The load is 61.5 gr of RL-22 under a 162 gr ELD-M, WLRM primer, and set to 0.005" jump. Last week, I took my rifle out for the first time this season, and got less than stellar grouping with a load that I know can hammer if I do my part (I got none of the above pressure signs, btw). I suspected it was either fundamentals, or that my rifle was too dirty (hasn't been cleaned in a little while). So mid-week, I did some light cleaning, which consisted of cleaning out the chamber with a few dry stick patches until they came out clean, and pushing a solvent patch down the bore (using a bore guide), and following up with a few dry patches (I did this latter process twice). No copper solvent.

I also suspect, but don't know, that I might have carbon rings. The reason I suspect this (and I could be wildly wrong) is that when I used a Hornady OAL gauge to set my CBTO for a 0.005" jump, I got what looked like little scrapes on the ogive that looked like the bullet had been pushed into the lands, even though I doubt the light finger force I used on the gauge when pushing the bullet to the lands could have jammed the bullet. I also suspect carbon rings, because this is a mild load that has never shown signs of pressure, and now it suddenly does.

I don't have access to a borescope. If carbon rings are a potential issue here, I found there is frustratingly inconsistent information about (1) whether, (2) when, and (3) how to get rid of them. I do have some KG #2 paste should that be needed, but I've never used it.

So, my questions are:

1. Is the carbon build up in the pics a pressure sign?
2. What could have caused it, given that it normally does not occur in this load?
3. Based on the information I provided above, what are some potential solutions?
4. Should I trash this brass?

 

[Supersubes]

Only had a moment to peruse your post, but is the charge weight a typo? If it’s not a typo then the carbon is a pressure sign, a sign of low pressure. Carbon to the case head is caused by a case not sealing the chamber. Wipe that “ejector mark” with some solvent, my guess is there’s no mark there at all.


Alliant doesn’t show a 162 grain bullet in their data but they do have a 160/165. They don’t even post a reloader 22 load for them but they do for the faster burn reloder 17, and the charge is where you’re at now basically.

 

[Bandit320]

The maximum load for RL-22 and a 160gr bullet on the Nosler site is 84 grains. I agree, it looks like the case isn’t sealing.

 

[RmeJu]

Wipe that “ejector mark” with some solvent, my guess is there’s no mark there at all.

That's what I did between the third and fourth picture in the original post. As noted there, the mark was mostly carbon, but there is a faint, but definite, ejector mark after I wiped it down with solvent. In the last pic, you can see it just to the left of the "G" in "MAG"

Alliant doesn’t show a 162 grain bullet in their data but they do have a 160/165. They don’t even post a reloader 22 load for them but they do for the faster burn reloder 17, and the charge is where you’re at now basically.

The maximum load for RL-22 and a 160gr bullet on the Nosler site is 84 grains. I agree, it looks like the case isn’t sealing.

I'm going by the Hornady 10th Ed book, which lists RL-22 max as 62.9gr for that bullet... I suppose there could be some slight variations based on COAL, but 21.1 grains is way more difference than that could account for. I don't have the Nosler book, but the fact that I actually got an ejector mark--faint as it was--leads me to believe there was a high pressure situation. Again, this was the first and only time I got any indication that something might have been off pressure-wise (high or low) in using this load for 18 months or so.

On the other hand, I lost about 30 fps between yesterday and shooting this same exact load last week, even though it was 10 degrees warmer yesterday. I would've expected the opposite MV change. Losing ~60fps, along with the carbon all over the case, is certainly something that could be explained by a failure to seal.

But if that's true then:

1. Why have I never seen this happen before despite shooting ~400 hundred rounds with this load?; and
2. Why did I get an ejector ring?

 

[Bandit320]

First of all, I need to correct myself. I was getting the Nosler Load Data off their website and I must of mis-read it. It shows 63 grs as a maximum. Sorry about that.

It could be a lot things. Since this is you’re first time out I’d try a very good cleaning of the weapon. You also said you used new brass. Did they all do this? If not how does the offending brass compare (weight, dimensions, etc.) to the others. If they all did this, do you have some of the old brass you could try loading up to see if it does the same thing. Lastly, I’d check the seating depth again if you think you’re getting marks on your bullets. If you want to be sure cover one bullet you’re going to test with black marker so there is no doubt.

You’re Load doesn’t sound over pressure. I’d just check one , or a few, variables on loads and make note of which variation gives you the results you’re looking for

Mike

 

[Supersubes]

You didnt really explain the brass situation except to say that this was virgin. What was it previously? Have you just been working through a bunch of virgin? Switch brass make? There’s a whole bunch of possibilities. Condition of the necks, and neck tension differences between the two sessions could explain. The fact that the load got softer/slower, and stopped sealing definitely points towards too low pressure. The ejector mark could simply be too much headspace.

 

[RmeJu]

First of all, thank you both for taking the time to help! It is very much appreciated!

You didnt really explain the brass situation except to say that this was virgin. What was it previously? Have you just been working through a bunch of virgin? Switch brass make? There’s a whole bunch of possibilities. Condition of the necks, and neck tension differences between the two sessions could explain. The fact that the load got softer/slower, and stopped sealing definitely points towards too low pressure. The ejector mark could simply be too much headspace.

All prior loadings have either been Nosler virgin, or up to 3 firings of that same brass. Neck tension is as close to 0.0015" as I can get it (I have previously tried 1-2 thousandths). The necks on this batch were turned a little beefier than normal, set to 0.01375" +/- 0.00015 (i.e. I'm super anal with my neck turning... 3 ten thousandths total variance between each of four measurements around the neck). Other batches were 0.001175" to 0.001275". Whatever the thickness, I use a Redding bushing die to set the tension to 1.5 thousandths.

I still have all of my old brass. Given that this batch of Nosler brass was new, there was very likely more headspace than I normally have (usually set back 0.0015" when reloading), which is a good point on the ejector mark. Still doesn't explain why I got low pressure this time, when I haven't gotten it before. If it was the problem, I suppose the next batch should (in theory) shoot normally...

Is it possible it was the cleaning I did mid-week? Could the thicker neck have caused it?

First of all, I need to correct myself. I was getting the Nosler Load Data off their website and I must of mis-read it. It shows 63 grs as a maximum. Sorry about that.

No apologies needed! Thank you for taking the time to help!

It could be a lot things. Since this is you’re first time out I’d try a very good cleaning of the weapon. You also said you used new brass. Did they all do this? If not how does the offending brass compare (weight, dimensions, etc.) to the others. If they all did this, do you have some of the old brass you could try loading up to see if it does the same thing. Lastly, I’d check the seating depth again if you think you’re getting marks on your bullets. If you want to be sure cover one bullet you’re going to test with black marker so there is no doubt.

The offending brass is pretty much the same weight as the other Nosler brass I've used. Slight differences, of course, but nothing that would explain what I saw yesterday. I'm pretty anal with my brass prep, but since it was virgin brass, I couldn't "fix" the high headspace until I got at least one firing in. I never had a problem before, and didn't measure the difference between the headspace on that batch of virgin brass and the other virgin brass I've used (which I also didn't measure for headspace prior to the first firing). I know the headspace is going to be too much prior to the first firing, but since I never had a problem before, I never measured to see how much it actually was. I suppose it's possible that this batch could have just had excessive headspace from the factory for some reason, which should (theoretically) be fixed now. Maybe it's as simple as that?

Maybe neither here nor there, but as for the marks on the jackets, I could actually see the copper jackets with slight etches after I "seated" the bullets with the Hornady OAL gauge. However, for the actual loads, I dialed back 0.005" from this, so (although I didn't check with the live rounds) I'm fairly sure they were not touching the rifling, and thus not getting marked up.

 

[Supersubes]

What are your velocities? How high a charge weight have you tested to with this combo?

 

[RmeJu]

What are your velocities? How high a charge weight have you tested to with this combo?

Last week: 59 degrees, 29.06 in Hg. MV was 2861 (measured with a Lab Radar), std 13.5. That brass was on its third firing, also Nosler.
Yesterday: 71 degrees, 28.78 in Hg. MV was 2826, std 23.4. This was the virgin Nosler brass from the pictures above.

Both batches were the same recipe except that, as noted above, the necks on yesterday's brass were thicker, although both batches were set to the same neck tension.

I've tested this load up to the Hornady book max of 62.9 (or maybe .1 gr over for an even 63.0, can't remember). I never went over the published max to see if there was a better node that didn't show pressure signs. Of the loads I tried, 61.5 was my best, so that's what I stuck with.

 

[Milo 2.5]

Last week: 59 degrees, 29.06 in Hg. MV was 2861 (measured with a Lab Radar), std 13.5. That brass was on its third firing, also Nosler.
Yesterday: 71 degrees, 28.78 in Hg. MV was 2826, std 23.4. This was the virgin Nosler brass from the pictures above.

Both batches were the same recipe except that, as noted above, the necks on yesterday's brass were thicker, although both batches were set to the same neck tension.

I've tested this load up to the Hornady book max of 62.9 (or maybe .1 gr over for an even 63.0, can't remember). I never went over the published max to see if there was a better node that didn't show pressure signs. Of the loads I tried, 61.5 was my best, so that's what I stuck with.

Can you measure how much your brass grows? Measure a new case base to shoulder, then a new fired case, then one fired 3 times. You are definitely not getting a seal off, not enough powder, and now the shoulder in your chamber has a buildup and it needs to come out. A 50 cal nylon brush chucked up in a drill may work, I myself use a 1" circle of scotchbrite jammed onto a 2 cal up brush, chucked up also, the over size brush will clean the carbon ring area in the throat at the same time.

 

[RmeJu]

You are definitely not getting a seal off, not enough powder, and now the shoulder in your chamber has a buildup and it needs to come out. A 50 cal nylon brush chucked up in a drill may work, I myself use a 1" circle of scotchbrite jammed onto a 2 cal up brush, chucked up also, the over size brush will clean the carbon ring area in the throat at the same time.

Do you recommend the brush because solvent isn't good for the action? If I need the brush, is hand power not sufficient? The idea of chucking something in a drill and using it in my chamber seems like I could end up hurting the gun...

 

[Milo 2.5]

Do you recommend the brush because solvent isn't good for the action? If I need the brush, is hand power not sufficient? The idea of chucking something in a drill and using it in my chamber seems like I could end up hurting the gun...

Moderation with a anything chucked up works, Doubt a bronze or a nylon brush spinning will damage too much. The scotchbrite could, but if you had a borescope, you will find caked on shit in a chamber or neck isn't that easy to get out if hard.

 

[RmeJu]

if you had a borescope, you will find caked on shit in a chamber or neck isn't that easy to get out if hard.

Any way to know without one?

 

[Milo 2.5]

Soak solvent or Boretech C4 in the area, monitor by patch color when cleaning it is all I have.

 

[supercorndogs]

I see a couple things that might be worth exploring. .005 is super tight as far as jump goes. If you aren't sorting bullets it would be easy to get some in a batch that jump .005 and some that jam. The other is belted mag, you will often have shoulder grow .01 or more on the first during in belted mags. Sometimes this will lead to ejector marks as you would see with excessive headspace.

Also light hand pressure can easily jam a bullet well into the lands. Its impossible to know without having hands on it, but it sounds to me like you are probably jammed well into the lands. It takes zero pressure to find where the bullet touches the lands.

 

[supercorndogs]

A picture of all the case heads may show more marks that are very hard to see with the naked eye.

 

[Deleted member 10043]

On my rifle it turned it would close on a no go. That was my last rifle built by a "custom" builder. A barrel nut is cheap.

 

[PinesAndProjectiles]

What rifle? Who set the headspace? Are you bumping brass too far? What's the difference at the datum between fired brass and FL sized brass?

 

[RmeJu]

If you aren't sorting bullets it would be easy to get some in a batch that jump .005 and some that jam. The other is belted mag, you will often have shoulder grow .01 or more on the first during in belted mags. Sometimes this will lead to ejector marks as you would see with excessive headspace.

I sort bullets for bullet base to ogive length. That way I know how far to seat them to get them exactly consistent on the jump. I get some that are +/-0.0005. I don’t think this is the issue.

Also light hand pressure can easily jam a bullet well into the lands. Its impossible to know without having hands on it, but it sounds to me like you are probably jammed well into the lands. It takes zero pressure to find where the bullet touches the lands.

I agree that it doesn’t take any force to get the bullet to touch the lands. If you’re right that light finger pressure can jam a bullet into the lands, I guess that makes me less concerned about carbon rings, as I may be been jamming the bullet into the lands rather than the rings.

What rifle? Who set the headspace? Are you bumping brass too far? What's the difference at the datum between fired brass and FL sized brass?

Stock Rem Sendero SFII. Brass wasn’t bumped (virgin brass), but I’m guessing the headspace was too far back from the factory on this batch, but I didn’t measure it out of the box, so can’t say for certain now that it’s been fired.