Dirty gun = Pressure issues?

[greyghostnw]

do you trim your brass? Do you push your shoulder back properly? Make sure your brass is trimmed within .002 of each other 10-15 thousandths less than max in chamber. Have you taken fire control apart like plungers out as well sized brass till bolt handle just has a slight touch before it falls to bottom? Should measure around .002 less than fired case. If your not full length sizing at all its harder on your brass and bolt lugs and can create hard bolt lift. The list goes on. Case base swells if you let it get away…. Consistent redundant practice equals results on paper. Good luck.

 

[General RE LEE]

Filthy cans dropping chunks of carbon in a bore when bumped at the range or field will spike pressure.

I clean my Banish Backcountry ~ 300 rounds and I like to run a few Hoppes patches every other range trip. I also brush out the chamber every few hundred rounds to get the carbon ring.

I seldom go after copper unless there is a consistent change in groupings.

 

[Neilbob]

Bumping this thread just because the same thing happened to me the other day. During load workup for a new 7MM Sherman Short barrel, I worked up to pressure (slight ejector mark and a little sticky bolt lift) with N555 and 175 grain ELDX using virgin ADG brass. I figured I'd gain a slight amount of case capacity once fired, but I still dropped 0.5 grains and shot a few more groups that didn't show any pressure signs. Thought I was good to go and loaded up quite a few. Then after a few range trips, I got significant ejector mark and difficult bolt lift. I cleaned the gun, backed down another 0.5 grains, and also seated the bullet another 0.01 off the lands. I was already 0.030 off. Everything seems happier, but I'll keep an eye on it.

 

[wind gypsy]

Bumping this thread just because the same thing happened to me the other day. During load workup for a new 7MM Sherman Short barrel, I worked up to pressure (slight ejector mark and a little sticky bolt lift) with N555 and 175 grain ELDX using virgin ADG brass. I figured I'd gain a slight amount of case capacity once fired, but I still dropped 0.5 grains and shot a few more groups that didn't show any pressure signs. Thought I was good to go and loaded up quite a few. Then after a few range trips, I got significant ejector mark and difficult bolt lift. I cleaned the gun, backed down another 0.5 grains, and also seated the bullet another 0.01 off the lands. I was already 0.030 off. Everything seems happier, but I'll keep an eye on it.

Loading close to pressure signs on a fresh barrel and virgin brass typically means you'll be well into pressure once the barrel is seasoned and brass is on subsequent firings.

 

[Tanner]

Found this doozy of a thread after some research and wanted to chime in and pick some brains.

My tikka 6 CM is about the most consistent rifle I’ve shot in the last 10 years. Just consistently hammers with every bullet I’ve tried.

I’ve got a well proven load of 109 ELDMs over 39.5gr of H4350 that makes about 2870. Today that same load was showing pretty noticeable pressure issues that were way out of the norm for it. My first inkling was be a super dirty barrel as it’s been shot 100% suppressed for about 350 rounds, so I went ahead and ran 2 rounds of a foaming bore cleaner down it, as painful as that was as I’m generally in the “don’t clean until something looks very wrong camp”. Kinda’ wondering if I don’t also need to grab a can of C4 and see what sort of carbon ring I’ve got built up.

Anywho, I will shoot it again soon and see what shakes out. This was a fun read!

 

[wind gypsy]

Found this doozy of a thread after some research and wanted to chime in and pick some brains.

My tikka 6 CM is about the most consistent rifle I’ve shot in the last 10 years. Just consistently hammers with every bullet I’ve tried.

I’ve got a well proven load of 109 ELDMs over 39.5gr of H4350 that makes about 2870. Today that same load was showing pretty noticeable pressure issues that were way out of the norm for it. My first inkling was be a super dirty barrel as it’s been shot 100% suppressed for about 350 rounds, so I went ahead and ran 2 rounds of a foaming bore cleaner down it, as painful as that was as I’m generally in the “don’t clean until something looks very wrong camp”. Kinda’ wondering if I don’t also need to grab a can of C4 and see what sort of carbon ring I’ve got built up.

Anywho, I will shoot it again soon and see what shakes out. This was a fun read!

Shooting into the wind by chance? Were velocities on par with expectation?

 

[Tanner]

Shooting into the wind by chance? Were velocities on par with expectation?

Both good questions, wind was about 5mph full value off the left so no head wind. I’ve shot this load so much now that I didn’t even chrono, but dope was perfect to 800 and it still shot well.

I will say I was pretty surprised to see how much gunk came out after a round of Gunslick.

Interesting note, this same charge of 4350 showed zero pressure signs with a 115 DTAC load about 150 rounds ago. Hard to say if the HBN coupled with short bearing surface of the 115 was keeping pressures acceptable, or if I’ve just gunked up the bore enough to see pressure with a bullet 6gr lighter with the same charge.

 

[Castle Rock]

Found this doozy of a thread after some research and wanted to chime in and pick some brains.

My tikka 6 CM is about the most consistent rifle I’ve shot in the last 10 years. Just consistently hammers with every bullet I’ve tried.

I’ve got a well proven load of 109 ELDMs over 39.5gr of H4350 that makes about 2870. Today that same load was showing pretty noticeable pressure issues that were way out of the norm for it. My first inkling was be a super dirty barrel as it’s been shot 100% suppressed for about 350 rounds, so I went ahead and ran 2 rounds of a foaming bore cleaner down it, as painful as that was as I’m generally in the “don’t clean until something looks very wrong camp”. Kinda’ wondering if I don’t also need to grab a can of C4 and see what sort of carbon ring I’ve got built up.

Anywho, I will shoot it again soon and see what shakes out. This was a fun read!

You didn’t mention using a brass brush, but all the witches brew in the world isn’t as good as 2 minutes of scrubbing

 

[Tanner]

Just a quick update, shot a few rounds on my way home from work and pressure/velocity/accuracy seems to be back in a good place.

Certainly not anything but anecdotal evidence and I’d love to never clean anything but it does appear that a heavily gunked up barrel in this case was causing some extra pressure.

 

[TOLeary]

Just a quick update, shot a few rounds on my way home from work and pressure/velocity/accuracy seems to be back in a good place.

Certainly not anything but anecdotal evidence and I’d love to never clean anything but it does appear that a heavily gunked up barrel in this case was causing some extra pressure.

Did POI stay the same after cleaning and shooting a few? Would assume it would but curious what you actually saw

 

[Chris in TN]

I really wanted to get higher muzzle velocity given cooper bullets need higher impact velocities to perform. So pushed it Too far I guess!

Learning!

There's a great way to deal with that next time:

Throw the copper bullets in the trash and buy some cup/cores to run at lower pressures/speeds. You can thank me later.

Also - I don't like the idea of loading ammo to 0.02" or less off the lands. Or running right up to max pressures and then backing off a hair and thinking this is 'close enough'.

 

[Chris in TN]

No, but only because “don’t use too hot loads”. Yes, if someone is running ammo at 70,000 plus PSI- EVERYTHING matters. Running your bullets in or right on the lands- EVERYTHING matters. Not full length resizing- EVERYTHING matters.


Doing any of those, and holy Pete- all of them, you WILL have issues in field guns eventually. The answer is “don’t do it”.

^^This is exactly why I will find 'max' in my rifles then back off. Bullets seated to some reasonable depth from lands, usually ~0.060ish. Find powder charge that shows pressure signs in summertime then back off a grain. You'll never miss that last 50' but you'll never FORGET if a blown primer locks up a bolt, or with gas guns, drops out into the receiver and you think it's OK until three shots later it gets jammed somewhere it shouldn't be and the gun stops working.

I can beat 2600' in my 5.56/77 loads but run 2575. I can hit 2925' with my 280ai180s but stopped at 2870'. Slight pressure signs at 2660' with the kids' 6.5cm/147 but I settled at 2610'.

Better barrel life, less drama, less wonder if the next shot will be the one that pops a primer and squirts gas in my child's face. If you want more speed, buy a bigger cartridge but first ask yourself *WHY*.

 

[Tanner]

Did POI stay the same after cleaning and shooting a few? Would assume it would but curious what you actually saw

Yeah, first round was out in right field but then it went back right to stacking them.

 

[justin davis]

Just a quick update, shot a few rounds on my way home from work and pressure/velocity/accuracy seems to be back in a good place.

Certainly not anything but anecdotal evidence and I’d love to never clean anything but it does appear that a heavily gunked up barrel in this case was causing some extra pressure.

Yea I’ve seen this too. Despite what people say about cleaning. I think cleaning is important at times and needed. Guns get dirty and can cause issues Especially when using a suppressor. Suppressors hold in a lot of carbon I think.