Gunsmithing Barrel fouling/pressure problems

[RTO]

I am hoping maybe someone has seen this before and can add some insight.
Rebarreled my 6.5 creedmoor and did standard break in process for first 50 rounds. I did a ladder test to find node for this barrel. After finding node I ran 50 rounds through it without a problem. No pressure signs and rifle shoots .5" groups at 300 yards. Another hide member on here was with me when I was doing load development and both of us checked brass and for signs of pressure. I went back to the range today. Previous to today rifle had about 100 rounds through it. Today was cooler than previous day of shooting and pressure was lower. After shooting about 10 rounds today groups opened up and started getting heavy bolt lift and base of cases really showing pressure. Several cases even sliced around ejector. Thinking this was a carbon ring forming cleaned barrel really good. Started shooting again. First 10 rounds showed no signs of pressure. After 10 rounds pressure signs came back with heavy bolt lift and pressure signs like before on case head. Cleaned again with butches bore shine this time and sweets, ran a bore scope through the barrel to check to make sure there wasn't anything I was missing or any throat issues. Everything looked good. First 25 rounds were perfect shooting great groups and then groups opened up after 25 rounds and heavy bolt lift and pressure signs came back. I cleaned again and first ten fine then it came back again. This time I cleaned it and took 20 rounds I ran the other day with this same load neck sized only and fireformed which should gain some case capacity. I also dropped the load by a full grain of powder. First ten shots were great then it reared its ugly head again. Now all of these cases are from the same lot, same keg of powder, same box of bullets, same box of primers etc etc. Barrel has about 200 rounds through it now and it shoots great after cleaning until it gets several rounds through it.
Chamber is not a tight neck and I am neck turning brass and doing full brass prep on all cases. The chamber does not require necks to be turned I just do it for consistency. Im at a loss I have checked headspace, I came home and pulled the action off the barrel this evening to check dimensions of chamber and make sure chamber didnt have anything in it etc etc. All looks good and checks out.

At this point I can only assume its fouling quickly and causing pressure and going to have to rebarrel again and make this one a tomato stake.
If anybody has any ideas or have seen this I would love suggestions at this point.

 

[buffybuster]

Re: Barrel fouling/pressure problems

That load might just be too hot.

I don't know what your rate of fire was or how hot you got your barrel but I'm thinking your chamber is heating up and in turn heating up your rounds which is giving you the increase in pressure. That's my WAG.

Never seen a carbon ring form in 20rds of shooting.

 

[3oh8er]

Re: Barrel fouling/pressure problems

I recently had a similar problem with one of my bolt guns in 7mm Rem Mag. I found I needed to give some extra attention to the neck area of the chamber and the bolt face.

 

[RTO]

Re: Barrel fouling/pressure problems

Its not too hot, I ran several strings with this load earlier in the week and no signs of pressure. I also ran .6 grains hotter than this load and still no real pressure signs. Dropping it a full grain and using fireformed brass was just another step to make sure that was the case.

 

[Rthur]

Re: Barrel fouling/pressure problems

I was a witness to the ladder test with loads ranging over a grain @ 300. The nodes were clearly defined ad the brass was checked at each load weight. I also did some of the shooting to try to eliminate shooter error in the test. The rifle was behaving as expected and was showing a reasonable climb over the chrono as the load weight increased. Even at .6 over the load choice I was barely noticing primer flattening.

 

[Grott]

Re: Barrel fouling/pressure problems

Are your turned necks too far under spec allowing fowling in the neck area, making the chamber tighter?

I'm new to this stuff so I'm just spitballin' here.

 

[turbo54]

Re: Barrel fouling/pressure problems

What powder is being used?

How sooty are the (outsides of the) case necks, and how far down the neck does the soot go?

 

[mdesign]

Re: Barrel fouling/pressure problems

You might want to check the length of the chamber as compared to the length of the case. Maybe your cases are running a little on the long side creating pressure as they bind on the mouth of the chamber during firing.

 

[RTO]

Re: Barrel fouling/pressure problems

Update reduced load by another grain today. It took longer for the pressure signs on the case head to appear but after 36 rounds the pressure showed up on the case head where the ejector was. It took longer with a lighter load to show up but severity is the same as with the hotter loads.
Cases are not even turned 100%. They are just turned to cleanup about 75%. Necks do have a lot of soot but that is common for turned necks.

 

[turbo54]

Re: Barrel fouling/pressure problems

Well, either you:

1. Have a scale that is drifting while you load, and you're firing the cartridges in the same order you loaded them in (unlikely)

Or

2. You're developing a bore obstruction from either powder or copper fouling.

H4350, if that's what you're using, burns very, very clean with midrange and high pressure loads. H4350 should not be leaving much soot on case necks, turned or not. H4831 and its SC variant burns nowhere near as clean until it's at high pressure.

If you're not using H4350, you should start. If you already are, either live with early/often cleanings or get a new barrel.

 

[RTO]

Re: Barrel fouling/pressure problems

I am using 4350 and your guess about powder or copper fouling was my first guess as well but after looking at it through a bore scope that is not the case. At this point another barrel is pretty much going to happen but it still doesnt explain what is going on with this barrel.
Scale is accurate and has been double weighed using two scales to elimate that already.

 

[Blueboat]

Re: Barrel fouling/pressure problems

Did you check the length of your cases? You might have some long cases and building pressure with them. WAG

 

[slick1177]

Re: Barrel fouling/pressure problems

tagged

 

[KingCountry LRS]

I am hoping maybe someone has seen this before and can add some insight.
Rebarreled my 6.5 creedmoor and did standard break in process for first 50 rounds. I did a ladder test to find node for this barrel. After finding node I ran 50 rounds through it without a problem. No pressure signs and rifle shoots .5" groups at 300 yards. Another hide member on here was with me when I was doing load development and both of us checked brass and for signs of pressure. I went back to the range today. Previous to today rifle had about 100 rounds through it. Today was cooler than previous day of shooting and pressure was lower. After shooting about 10 rounds today groups opened up and started getting heavy bolt lift and base of cases really showing pressure. Several cases even sliced around ejector. Thinking this was a carbon ring forming cleaned barrel really good. Started shooting again. First 10 rounds showed no signs of pressure. After 10 rounds pressure signs came back with heavy bolt lift and pressure signs like before on case head. Cleaned again with butches bore shine this time and sweets, ran a bore scope through the barrel to check to make sure there wasn't anything I was missing or any throat issues. Everything looked good. First 25 rounds were perfect shooting great groups and then groups opened up after 25 rounds and heavy bolt lift and pressure signs came back. I cleaned again and first ten fine then it came back again. This time I cleaned it and took 20 rounds I ran the other day with this same load neck sized only and fireformed which should gain some case capacity. I also dropped the load by a full grain of powder. First ten shots were great then it reared its ugly head again. Now all of these cases are from the same lot, same keg of powder, same box of bullets, same box of primers etc etc. Barrel has about 200 rounds through it now and it shoots great after cleaning until it gets several rounds through it.
Chamber is not a tight neck and I am neck turning brass and doing full brass prep on all cases. The chamber does not require necks to be turned I just do it for consistency. Im at a loss I have checked headspace, I came home and pulled the action off the barrel this evening to check dimensions of chamber and make sure chamber didnt have anything in it etc etc. All looks good and checks out.

At this point I can only assume its fouling quickly and causing pressure and going to have to rebarrel again and make this one a tomato stake.
If anybody has any ideas or have seen this I would love suggestions at this point.

Did you every find out what was causing the pressure ?? I’m having the same trouble

 

[CanSniper]

What is the load you are running and the velocity?

 

[Tnc]

Did you every find out what was causing the pressure ?? I’m having the same trouble

It was over 8 years ago so I bet he figured it out by now.

 

[CanSniper]

Friggin dang zombie thread!

 

[Steel head]

 

[rayvandervort]

Friggin dang zombie thread!

My simple opinion: neck turning not always a good thing when gasses slip past the neck to chamber seal and gum up the chamber - the one place to cause chamber aberrations.

 

[KingCountry LRS]

The loads 142 Sierra match kings , 42.7 grains reloader 16 , hornady brass and federal LRP. It’s only really in competitions when I get past about 6 shots and everything is heating up that it appears . I dropped to load back a little and it stopped doing it but just couldn’t understand why it would appear. Bullets weren’t sitting in the chamber very long to heat up but that few seconds in there could of been enough to spike the pressure