The Accurate Reloading Forums
Pressure and Barrel Cleaning
16 May 2004, 11:43
Dr. DucPressure and Barrel Cleaning
There is a very interesting article in the new Handloader about "pressure signs". Almost as a sidelight to the author's conclusions he mentions that cleaning a barrel produces extreme pressure excursions and poor accuracy until it is fouled again. Conclusion: Don't clean until accuracy suffers.
I'd be interested to know the collective reaction-read the article before you chew my ass out Please!
16 May 2004, 22:57
lonniemikeYea, I want to read that article. Maybe the Swiss military types are right, as they joke that "Americans are cleaning their rifles while we(Swiss) drink beer". Their basic technique is to clean(degrease), shoot, grease, clean, shoot, grease, clean, shoot, grease..... Scubbing or brushing the bores is not supposed to be common. Usually the bores were just swabbed/greased with the old Waffenfett or the newer Automatenfett. Unlike the US, they also used steel jacketed projectiles with a thin Cu/Ni over-plating.
17 May 2004, 02:52
arkypeteThe Swiss are without peer in banking, watch making and being profitably neutral. Not sure just how much experience the Swiss have in military matters, of recent vintage.
The Swiss supply all of their militia with weapons and ammo. I wonder if this cavalier attitude would apply if the firearms were their own?
Jim
I have two strain gage instrumented rifles, which I have shot both clean and dirty. I have not noticed any excessive pressure on the first shot. I do want to read the article, and find out what the author had to say.
17 May 2004, 05:46
ASS_CLOWNI have noticed a pressure differential between a clean well oiled barrel and a barrel with three to 10 shots through it. This differential seems to be somewhat bore sensitive, meaning it seems to increase with bore diameter. The differential exists even when the oil has been "swabbed out" with dry patches.
The result is the errant first shot. The rifles in question do not exhibit errant first shots from fouled barrels, only clean oiled ones. For this reason I only oil a bore if the rifle will be setting for an extended period of time. If I shoot regularly I brush and dry swab, only using a copper solvent if there is significant copper fouling (which seems to be a rare animal in a well broken-in barrel).
ASS_CLOWN
17 May 2004, 22:40
monteroI have just read Norma's reloading manual and there is a very interesting study, made with a large capacity 7mm cartridge.
They started with a clean to the bone barrel and fired it measuring the presure for each shot. After only 30 shots the presure started climbing significantly.
I don't have it here but it didn't take a large number of shots to increase peak presure by 30 percent !!!
Barrel was shot at a constant temperature so presure had nothing to do with a cooking chamber.
Interesting...
montero
18 May 2004, 05:26
RicochetIf true, that sounds like a pretty good argument for leaving 'em uncleaned and loading to a stabilized pressure with an equilibrium-fouled bore.
Read the Norma quote again; They say a barrel that is getting dirty raises the pressure,
not a clean oiled barrel. It does sound like fouling. Of course if you havent hit the Elk
with 30 shots, you could run him down with the pickup.
Good luck1
18 May 2004, 07:22
RicochetQuote:
Read the Norma quote again; They say a barrel that is getting dirty raises the pressure,
not a clean oiled barrel.
Exactly. Read my post again.
18 May 2004, 09:11
Bear in FairbanksDr:
Interesting that you post on this subject. I have the current issue but haven't gotten to the article yet.
I had thought about posting this on the board earlier but wasn't sure I wanted to. At any rate, here's what happened to me with my Ruger .338 Mag last week. I had cleaned the barrel (stainless) and proceeded to resight the open sights & scope. I began with full length resized cases and was using my chronograph. All loads were the same - 70.5 grs. of Rldr-22, 225 gr. Northfork, Fed GM210 primers and all seated to the same depth (measured). The first shot registered something like 2650 fps, as I recall, succeding shots showed gradually increasing velocity. I ran out of the cartridges that were full length sized and went to a box of cartridges that were only neck sized. Everything else was the same. The velocity finally levelled off in the neighborhood of 2780 fps or so (where it should have been). I was just incredulous that such a thing could happen & can't believe that the cause of the lower velocity was the full length sized cases. Think I'm gonna leave the barrel pretty much fouled from now on. This is just what happened to me. Later, Bear in Fairbanks
18 May 2004, 10:51
bigcountryI read that article this morning. I disagree somewhat. It took him 3 or so groups to get MOA accuracy and the ones before that was like 3MOA. I say, if the rifle was broken in, or shot alot, it wouldn't have taken him so long to get accuracy. A rifles velocity should settle out after 2 fouling shots. Not 10. I notice on new rifles the velocities are all over the place before 100 shots. AFter that the accuracy seems to improve and velocity spreads goes down. shooting the 100 shots is same as brake in in my opinion.