Can excessive copper fouling cause cartridge overpressure in factory ammo?

HandB

Well-Known Member
Hi Everyone, I have noticed signs of cartridge overpressure in 7.62 NATO factory ammo fired in my Parker Hale T4 Lee Enfield. Things like flattened primers, case ringing/separation. It looks at first glance like headspace is excessive but Fultons found it is within specs. I am therefore wondering if such overpressure signs could be caused by a build up of copper fouling narrowing the bore. I have fired about 700 cartridges without using specialised copper remover (I clean the bore using VFG felts and Armistol oil after each session).

Thank you!
 

HandB

Well-Known Member
Thanks very much - that's a strong possibility too. I am going to scrub the barrel and chamber with carbon and copper removers, to get down to the bare steel then reshoot. If the overpressure signs vanish from the cartridge cases then I will know it is not a headspace issue, but a cleaning issue.
 

Rider

Well-Known Member
With 700 or more fired rounds on the clock and no proper cleaning in between please do yourself a favor and use a bore paste.

All srubbing with solvents will be pretty useless in your case, especially with regard to carbon removal.
 

Muir

Well-Known Member
Hi Everyone, I have noticed signs of cartridge overpressure in 7.62 NATO factory ammo fired in my Parker Hale T4 Lee Enfield. Things like flattened primers, case ringing/separation. It looks at first glance like headspace is excessive but Fultons found it is within specs. I am therefore wondering if such overpressure signs could be caused by a build up of copper fouling narrowing the bore. I have fired about 700 cartridges without using specialised copper remover (I clean the bore using VFG felts and Armistol oil after each session).

Thank you!
What 7.62 NATO? Much of it is hot.~Muir
 

Mach IV

Active Member
I had a pressure problem with my 17 Mach IV when it was first built. It was maxing out at a grain under max loads and 500fps short on expected velocity. Stiff bolt lift, sticking cases. I checked everything neck length, headspace, tried different primers all sorts. Copper cleaners, carbon cleaners you name it nothing worked.
It was very accurate but it was meant to be a Mach IV not a Mach 3.5!
In the end I thought it felt a little tight near the throat when patching out so thought f*** it, got some JB bore paste and did about 50 strokes in the first third of the barrel and a few up the whole barrel. After that no problem, load to max loads and 4,000fps with a 20gn Vmax as it should.
I can only think that the barrel had some oil in it and it got burned on at the proof house. What ever the problem was JB bore paste did the trick.
 

Muir

Well-Known Member
What 7.62 NATO? Much of it is hot.~Muir
I have never found that excessive copper fouling in anything above sub-caliber (20, 17, 14) was an issue. Lord knows I have owned military 30-06 that have NEVER had the copper removed yet shot factory ammo well. Likewise, I have an Ishapore / Enfield 308 that has never had the copper removed and doesn't do anything unexpected with 147 grain Ball ammo from SBS or Lake City. The brass always looks stretched and the primers flattened but these are attributed to the chamber dimensions and finish.~Muir
 

Colonel

Well-Known Member
When I was shooting for my regiment I would fire 2-300 in a day practicing once or twice a month and we only had pull throughs to clean our rifles in those days, we didn’t have rods and brushes and no copper cleaners. If it was a hot day we would keep the ammunition out of the sunshine.
 

HandB

Well-Known Member
Thanks everyone - I shot the T4 at Bisley yesterday after a week of daily cleaning of the barrel with Bore Tech Cu+2 copper solvent. This flushed out a lot of blue residue and has reduced the overpressure problems somewhat. There is still a bit of ringing near the cartridge head but there were no case separations and the primers are normal. As a cadet I shot many hundreds of cartridges in .303 Lee Enfield rifles with no overpressure problems, despite cleaning only using a pull through/oil so I reckon that the copper fouling/overpressure problem is a by product of the T4 having a tighter bore than a typical .303 Lee Enfield (presumably it was designed that way to help with target shooting) which makes it more sensitive to copper fouling.
 

HandB

Well-Known Member
Update - I have done more cleaning with a bronze brush and solvent then did another Bisley session on Sunday. The pressure signs are slightly reduced but still present. I have therefore wheeled out the toothpaste to see if it can reach areas that the bronze brushing and solvents can't. The answer is that toothpaste is powerful stuff. The patch on the left is before applying the toothpaste. It is white suggesting that the bore is finally clean. Add some toothpaste and scrub with cotton patches and it's clear there is actually loads more fouling still in the barrel as shown by the dirty patches. You can actually feel the toothpaste biting into the fouling which a bronze brush couldn't touch. The results make me think that toothpaste is too aggressive for sustained use so I have ordered some JB Bore Cleaner paste from Spud reloading.
Toothpaste bore clean.png
 

Top