barrel fouling, pressure and accuracy

[SPAK]

Hey guys,

Lately my barrel has been acting kind of funny. After 15 shots through the bore, my accuracy goes to crap and I start getting crazy pressure signs (EJ marks on case head). My cases are coming out really sooted as well.

After I run my bore snake through the bore, my accuracy returns again but only for another 10-15 rounds or so.

I usually only run a bore snake after each shooting session, and "moderately" clean every 500 rounds or so. However, I did start using Iosso bore cleaner paste as part of the regimen. That has been the only change as of late.

I thought maybe my barrel needed to be cleaned really well?? I started to clean tonight and it seems to be much more difficult to get clean and it's taking me a lot longer than usual to get a clean patch to come out.

Any thoughts? Round count is about 2000, .30-06 running 208 amax bullets around 2650-2700fps, 22" mcgowen barrel nitrided, with a suppressor.

Powders used: 56.7gr RL22 or H4841sc, or 53gr H4350. Accuracy for the first several shots with either charges have been phenomenal, but then after 15 slow fire shots it all goes to crap.

Any thoughts??

 

[memo43]

Re: barrel fouling, pressure and accuracy

I would get in there an give it a good scrubbing.
Cleaning with a bore snake is like wipeing a counter with coffee spills, you are just cleaning the surface. You need a good brush an good powder/copper solution of your choice. this will help break up all the build up you have in the lands an grooves. Especially after 2k rounds.
That way you can get some life back as well as your accuracy.

memo

 

[Stonewall2]

Re: barrel fouling, pressure and accuracy

Buy a proper cleaning rod and brass brushes from a benchrest supply shop such as Sinclairs .

Use a boreguide with insert i.e. a Lucas bore guide .
http://www.accurateshooter.com/forum/index.php?action=profile;u=367039

I bet that you still have carbon in the throat.

Glenn

 

[SPAK]

Re: barrel fouling, pressure and accuracy

I normally use a dewy rod and universal bore guide. Hoppes 9, brake cleaner and then just 2-3 patches of kg12 copper solvent, let it sit for a few minutes then patch it out with hoppes 9 again until i get a clean patch.

I started using Iosso paste as a reccommendation on the hide, wet a patch wrapped over a brush, run it through about 6 times or so, then patch it out...

I try not to clean too often and my accuracy has been really good. It's still good except I can't shoot more than 10-15 shots without getting sooted cases and pressure signs.

I'll give it a good scrubbing and see what happens..

 

[Greg Langelius *]

Re: barrel fouling, pressure and accuracy

OK, after 2000 rounds, the bore is not the same one as when the load was perfected. Specifically, I care less about what the differences are than about the fact that they have become significant.

I would redevelop the load, and do my testing with a warm, fouled bore; since that seems to be the more important fouling state in your shooting regimen.

I would also suggest that the bore is getting on some, and not count on any load's relationship to an ideal bore transit time as having a long life expectancy. Me, I'd consider rebarelling the next time it goes out of tune with the new load.

This is behind one of the reasons I prefer L-W barrels. Their stringent testing and record keeping allows a far better chance to order a replacement barrel which is most likely to prefer the loads I developed for its predecessor. My pair of 'identical' L-W barrels (no two barrels are truly identical, but some get pretty close) work best with loads that are only different by .1gr of propellant. I consider that very desirable.

Greg

 

[former naval person]

Re: barrel fouling, pressure and accuracy

I'll bet you have enough throat erosion to cause the problem you are having. Try determining the throat length. You may need to either rebarrel or set the barrel back a couple of inches and rebarrel. A bore scope could give you some answers on the throat condition.

 

[SPAK]

Re: barrel fouling, pressure and accuracy

I see if I can't get a smith to scope the bore for me...I've got a rebarrel in the plans right now...I wonder if the suppressor is making the bore foul more...


I've been soaking and patching out with Hoppes 9 for the last couple hours and the dry patches still have some darker brown residue and one black streak on the patch....does that sound like carbon build up???

I'm sure there are better cleaners out there though..Any reccomendations??



on a side note, has anyone used david tubbs final finish on their barrels??

 

[Kevlars]

Re: barrel fouling, pressure and accuracy

That black or brown stuff may be your barrel. In the pay section they were talking that more barrels have been runied by over cleaning. If you think that your barrel is really that dirty ... I would use Patch in - Patch out (http://www.sharpshootr.com/patchout.htm) foam -- you spray it in and let it sit over night ... 4 patches later its absolutly clean.

There are plenty of other really great products-- if you really want to pull out all the stops and go with the nuclear option you can use Sweets 7.62 but be careful with that one and dont let it sit in the barrel more than 5 to 7 min. like the label says. Make sure you follow up with some oil afterward as sweets is amonia based and attracks moisture. Good luck

 

[SPAK]

Re: barrel fouling, pressure and accuracy

Yeah, I try not to clean too often....but maybe I went a little too long without cleaning??

I'll see if I can find some spray in foam....

Can the hoppes 9 really start removing barrel material???

 

[SPAK]

Re: barrel fouling, pressure and accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">I'll bet you have enough throat erosion to cause the problem you are having. Try determining the throat length. You may need to either rebarrel or set the barrel back a couple of inches and rebarrel. A bore scope could give you some answers on the throat condition. </div></div>

FNP if the throat is eroded, would I have any accuracy at all? The rifle is still very capable of .25moa groups...just after 15 or so rounds it all goes to hell. I got a hold of a local smith who's gonna run the scope in for me. I guess I'll find out soon enough..

 

[jeepguy242]

Re: barrel fouling, pressure and accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Apophas</div><div class="ubbcode-body">That black or brown stuff may be your barrel. In the pay section they were talking that more barrels have been runied by over cleaning. If you think that your barrel is really that dirty ... I would use Patch in - Patch out (http://www.sharpshootr.com/patchout.htm) foam -- you spray it in and let it sit over night ... 4 patches later its absolutly clean.

There are plenty of other really great products-- if you really want to pull out all the stops and go with the nuclear option you can use Sweets 7.62 but be careful with that one and dont let it sit in the barrel more than 5 to 7 min. like the label says. Make sure you follow up with some oil afterward as sweets is amonia based and attracks moisture. Good luck </div></div>

I used that sharpshoot-r- on a rem 700 that i thought was clean, WOW did that stuff prove me wrong, after a day of soaking the patch came out navy blue!

that is all i use now to glean my guns!

 

[former naval person]

Re: barrel fouling, pressure and accuracy

With the soot blackening you mention on the necks and shoulder, I suspect blow by, plus a rapid carbon buildup in the eroded throat. What do I know?

 

[SPAK]

Re: barrel fouling, pressure and accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">With the soot blackening you mention on the necks and shoulder, I suspect blow by, plus a rapid carbon buildup in the eroded throat. What do I know? </div></div>

I'm definitely not questioning your knowledge!

I'm just trying to learn and understand the thought process. Unfortunately I have my suspicions you might be right.

I checked the distance to the lands today with my dummy round and looks like the rifling has advanced about .016". Seems like a lot for 2000 rounds...

Getting borescoped tomorrow.

 

[Leaddog]

Re: barrel fouling, pressure and accuracy

You are not really getting the bore clean. Use a brush. Patches alone just don't clean well. After the bore is scrubbed (one stroke for each shot) and patched dry, use some bore paste and give it a go about every 100-200 rounds. Clean the bore at least weekly if you are shooting alot. Copper isn't good to leave in the bore. Copper is the culprit, not carbon soot.

Saying all of that, check your throat and seating depth. You'll find that the 30's are forgiving if you stay on top of the changes over time.

 

[Clark]

Re: barrel fouling, pressure and accuracy

I started out trying to clean out Copper fouling 15 years ago with Sweet's 7.62.

I have tried:
*Sweet's 7.62
*Shooter's Choice
*GT-40 from Calhoon
*50BMG
*Montana Extreme
*Wipe Out
*Butch's Bore Shine
*Pro Shot Copper Solvent II
*KG-12

I was hunting in the 2010 season with a bunch of guys who are handloaders, amateur gunsmiths and self appointed gun experts, yours truly included.
We had a Copper fouled barrel cleaning contest.
I saw myself as the clear winner with my fast technique:
1) Clean out the bore with a wet patch of any solvent, to get the Carbon fouling out.
2) Dry patch
3) Wet patch of KG-12 to etch the edges of the Copper.
4) Wait a couple minutes.
5) Dry patch.
6) Patch with Flitz on top and Kroil around the edges.
7) Stroke 10 times with a Bronze brush that measures, with calipers, larger than the groove diameter of the bore.
8) Dry patch
9) Inspect muzzle, with broad spectrum light entering the muzzle at 45 degrees, look for Copper or any red color.
10) If any red is found, start over.

At 15 minutes per cycle, I could clean badly fouled bores in 30 or 45 minutes of hard work.

Another faction of hunters put Hoppe's No 9 in the bore and waited 24 hours...repeat...repeat
They claimed that I was wearing out the barrels and brushes, and refused to admit defeat.

What does it all mean?
1) If you have had enough anecdotal non sense from me, you can read something more objective:
link to snipers hide thread where Kombayotch does controlled test of Copper solvents

2) I used to not believe in break in procedures. I now believe that if the barrel fouls more when it is new, and I clean out the Copper more often when it is new, I am following a break in procedure whether I believe in it or not.

 

[SPAK]

Re: barrel fouling, pressure and accuracy

ok, the update.

Had the bore scoped and yes there is some erosion in the throat area. The smith didn't think it looked that bad but I could see what looked like....well, a dried up river bed for a lack of better description. I've never seen barrel erosion first hand through a bore scope before, so I couldn't tell you relatively how bad it is as I don't have anything to compare to...

I cleaned the rifle up really well and shot about 20 rounds the other day. I didn't have any more time to do any more shooting.

results, first 5 shots out of a clean barrel went into a nice group about .3 dead in the center. I was actually surprised...

the next 15 all grouped low about 1 minute right around .6MOA

Clean shots definitely "seemed" more accurate, but I'm going to go with Greg's advice and work up my load with the barrel fouled...

It's intersting to note my clean cold bore shots are so consitent and accurate, until the barrel gets fouled up ...I always figured it would be the opposite....Shows you how much I've actually cleaned my rifle really well...

I know there's a few schools of thought floating around about how often to clean the bore. I definitely did not clean this barrel very much at all...I wonder if I could have prevented some of the throat erosion by cleaning a little bit more often??? Rifle seems to like shooting clean, at least from the last few outings.

 

[SPAK]

Re: barrel fouling, pressure and accuracy

Latest update,

Reworked my load..sort of..I basically did another ladder test, nothing crazy, just to see where the pressure limit was on a semi fouled barrel (just boresnaked) and then back down 1 grain.

same symptoms. I can go about 10 rounds with good easy extraction, no pressure signs on the brass and then from the 11th shot forward I start getting shiny extractor and ejector marks on the case head and heavy bolt lift.

I think the throat is toast..I'll see if I can't set the barrel back some and go from there.

Thanks for all the input guys.

 

[Notso]

Re: barrel fouling, pressure and accuracy

I didn't catch that you were shooting suppressed on the 1st read through. The suppressor, most likely, is your culprit - NOT the barrel being clean or not. Accuracy might degrade as the barrel gets dirty, but I doubt that would cause your pressure signs that quickly.

I have two shooting partners that shoot suppressed .308s and they see the exact same issue as you describe. If they take the can off or let it cool for w while, the gun goes back to shooting fine. But as the can heats up right around the 15 round point, they get noticeable pressure signs and accuracy drop off.

Someone smarter than me can probably chime in and tell you WHY the hot can causes the problem - but I'd bet you $$ to donuts thats your problem. Maybe look for carbon buildup in the can as your problem.

Edit: meant to add that I'd bet the reason why you get accuracy back for 15 rounds after running a bore snake through is not because it's cleaner, but because you allowed the barrel and can to cool down while you're cleaning it.

 

[SPAK]

Re: barrel fouling, pressure and accuracy

Intersting....I didn't think the can would limit the number of shots. I figured that mirage would be more of an issue than the can inducing pressure.

I've had the can for over a year now, and I can't remember having any problems shooting over 15 rounds before now....I guess I'll do some more research into this...