weak hammer spring and accuracy issues

grumpyvette

Administrator
Staff member
one of my neigbors has a rather vintage marlin 35 remington, thats his one and only big game rifle caliber,firearm.
over the years he has had a few miss fires and accuracy tends to be about 3" at 100 yards off a good bench rest , it maters not a bit if its factory ammo or my hand loads.
well several week's ago he goes to the local range and he had two miss fires and accuracy was the for him, typical 3"-4" groups so he decides too mention this, when hes over watching me trouble shoot his sons car during a tune -up.
I suggested he bring over the rifle and the unfired cartridge that did not fire as he saved it!
well the rifles had obviously had minimal cleaning in decades, he says he generally gets it soaked in WD 40 on the metal parts and runs a bristle brush with a patch or two soaked in hoppes #9 bore solvent, thru the bore on returning from a trip to the range or hunting but that's the extent of maintenance care!
thats a bit like not changing the fuel, oil or spark plugs in an engine for 30 years ,just washing and waxing the car once a year and expecting it to run like new


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SO, step one was a careful cleaning internally on the action and a very careful bore cleaning. looking at the primer, on the cartridge it was obvious the firing pin indentation was minimal at best, (mostly the result of built up dirt and grease in the action, )which always leads to inconsistent ignition of the powder in the ammo, I disassembled and cleaned a good amount of surface rust, dirt and greasy crud from the action and cleaned the bore and chamber and had him order a new main spring from brownells for $10 as the original spring was weak and well worn and rusted.
well it came in and was installed last Friday and he went to the range, he swears , the rifle never ever shot that well before it shot several 1.2" five shot hundred yard groups, and the reason is obvious, hes no longer getting a semi consistent ignition on the primers,and the bores clean, now the rifle firmly indents the primers insuring a consistent and brisk full ignition.
all primers need to be hit fairly hard and consistently , firing pins normally need to protrude about .040 into the primer surface for a good ignition.
 
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