Home Forums Reloading Big Game Rifles A clean barrel's effect on pressure?

I shot many rounds in my 7mm ultra of 140 ab, cci250, rem case, 95.5 gr RL25, oal 3.670. Until today my results were always the same; 3520 fps ave and about 1 in groups at 100 and sub 2" groups at 300 yd. Today bofore going out to shoot I spent some time to get the barrel really clean. Overnight with wipeout and then repeated brushing and patching to remove alot of black powder fouling. At first after the wipeout the bbl appeared to be pretty clean but as I got aggressive with the brass brush and regular solvent I kept getting black out of it. I finished with a coat of tetra lube on the bore. I thought I patched any excess out of it. Anyway my first shot scared the crap out of me. 3470 fps and very very heavy bolt lift with the extractor scraping away brass from the case head. Brass had actually flowed back into the ejector somewhat causing the heavy lift. The case extracted ok and primer still where it should be. Being the idiot that I am I thought it over and squeezed off another one. Still pressure signs but much less so somwhat heavy bolt lift. A third shot had no abnormal bolt lift and only the slightest extractor mark. by the 5th and 6th shots all signs had dissappeared and the gun was back to acting normal. I can only think that my cleaning the barrel and using the tetra in the bore was the culprit. The gun is a rem 700 LSS. I will probably back the load down as it must be on the ragged edge. Of course it shoots best right where its loaded to right now. So weird that the load behaves so well with a slightly fouled bore yet not so with a clean bbl. I did not clean the barrel so thoroughly before shooting this load in the past. What should we put on our bore after cleaning? Any thoughts or experiences on this phenomenom is appreciated.

Dufur, If I use Tetra lube to lube the barrel, for me its usually at the end of the season for hunting, and is being put away for the winter. I'm not familiar with lubing the barrel after cleaning. I would wonder if the enormous heat generated from firing would affect the cooked lube and hinder performance.
At the range we always discount our "clean shots", seems to figure that the micro grooves in the barrel get "lubed" by the copper. Always tighter groups after the first 2-3.

Some barrels may shoot a little better fouled but this isn't always so. Also, a clean barrel shouldn't give you higher pressure UNLESS you have left an oil residue in the barrel. If you remove all oil from the barrel prior to shooting with a good solvent, you'll probably find that the first few shots aren't high and all over the place.

In addition, I think there are bore cleaners out there much better than Wipeout. One is KG 12 Big Bore Cleaner. You'll not have to use any brushes with this one to get your barrel really clean. Another I've just started using that may be the equal of KG 12 is Prolix. Also, rather than using oil to coat my barrels, I use Microlon Gun Juice.

I'm with Grumulkin on this. I think there was enough lube left in the barrel that the bullet became a "squeagy". To inexperienced shooters they would think that a high velocity comes from the lube being "slippery" therefore the bullet goes faster. BUT, we all know that speed only comes from pressure.

A couple years back we were siting in guns for Wis deer season. A buddy showed up with his 30-06 BAR and some 165 factory loads. I had the chrony set up and I proudly proclaimed he'd clock about 2750 with his factory 165's. His first one landed 5" high and clocked about 2900. The next a little lower and clocked about 2850. The next a bit lower and clocked about 2800. Then everything went to normal and he was clocking about 2775. Anyhow I asked how he stored his barrel. He said "I don't want it to rust so I "slop alot of oil" down the barrel." I told him he was playing with fire....especially if it was really cold out and the oil got really thick. Anyhow.....it's the way he always took care of the gun.....he hadn't sited it in in 4 years....and the funny thing is that he got 3 reeally nice bucks in those 4 years on the first shot of the season.

thanks for the opinions guys. Yes I think that having a little copper in the bore to smooth things up a bit must help keep the pressure down. I can only assume that the clean barrel with the lube in it was responsible for my pressures going into orbit. The thing that really scared me about it was that the velocity was actually lower at 3470 but the pressure signs had skyrocketed on that first shot. As the pressure signs lessened with each subsequent shot, (shoot 3, cool down, shoot 3 more)the velocity worked its way back up around 3520 where I expected it to be. It was about 72 degree weather. I have shot this load and a round loaded at 96 gr in weather that was 85 with no signs of excess pressure. I guess it could have been worse like having to pound the bolt open or blowing the gun up. Just so I understand; if I clean a bbl really well before shooting after removing the copper, I should just use solvent and patch out then go shoot the nekked bore--no lube in bore except for storage-- I used to swab a little break free down the bore after cleaning but I don't know if thats a good idea either. I think I'll use up some of my factory load supply as foulers. Like shoot about 3 through a clean bore before sitting down with the serious reloads. The 7 rum is about performance but still I want to acheive that performance safely.