conversion from 7x57mm to 7.62x51 NATO
-barrel modification, safety, sear, lug races, bolt handle notch-
Applies to models made by Deutsche Waffen - und Munitionsfabriken (DWM) as well. Those rifles manufactured by Ludwig Loewe
are considered antique (pre-Jan.1, 1899) by the U.S. BATF, but the DWM are classified as "Curio-Relic" (modern) even if the
stock is dated 1898, which many DWM are.
The rear receiver bridge is marked:
7.62 N, denoting the
7.62x51 NATO cartridge. This is not same as the commercial .308 Winchester.
See below for added text.
I have several of these rifles in my collection in the original caliber of 7x57mm and enjoy shooting them.
They are beautifully built rifles, but they are not suitable of endless thousands of rounds of 7.62 NATO
ammunition, nor even token amounts of .308 Winchester.
This sectioned barrel shows the chamber insert and solder joint. This barrel was originally 7x57. It is now chambered in 7.62 NATO.
This is not a particularly prudent conversion as the action was not designed for subsequent use with commercial .308 Winchester ammunition.
The gap in front of the chamber is thought to be caused from gas cutting of the soft solder joint.
This close-up shows the tearing of the chamber by a dull chambering reamer, just below
the neck and in the neck area. The "smushed" rifling in front of the chamber neck is the leade,
or throat. The longitudinal lines in the grooves are from the rifling cutter, and the radial marks
on top of the lands are from the precision reaming of the bore diameter prior to rifling.
The barrel threads were cut off revealing the bolt lug races.
Notice the uneven wear on the lower lug race compared to the upper race.
Top lug race
Lower lug race
This is the so-called safety lug for the bolt handle.
The 1895 Chileno is the only
Mauser to have this feature.
This safety lug is only utilized if the two bolt locking lugs should happen to completely shear off.
Its not much of a safety shield between the bolt and the shooter's eye.
Add to this the fact that the 1895 model Mauser has -zero- gas escape features designed into it.
The safety lever cams the cocking piece away from the sear and blocks its forward movement.
In many rifles the safety is difficult or impossible to engage. This can sometimes be adjusted
by stoning the camming angle to allow it to pick up the cocking piece. The Mauser system safety
is about as perfect a safety as can be devised. Initially utilized via a patent by Paul Mauser on
the Infantry Gewehr 1871 it has remained virtually unchanged throughout the entire series of Mauser
military rifles. Personally, I dislike those sporting safeties that act on the trigger, as the cocking
piece is still engaged with the sear and accidental discharge can occur.
The following was kindly supplied by Kyrie Ellison:
.308 Winchester chamber headspace gauges:
GO: 1.630"
NOGO: 1.634"
FIELD REJECT: 1.638"
US Army 7.62x51 chamber headspace gauges:
GO: 1.635"
FIELD REJECT: 1.6455"
SAAMI .308 Winchester chamber pressures:
MAP: 62,000 psi
MPSM: 66,000 psi
Minimum Proof Pressure: 83,000 psi
Maximum Proof Pressure: 89,000 psi
US Army 7.62x51 chamber pressures:
Maximum: 50,000 psi
Proof pressure: 67,500 psi
7.62x51 NATO pressure data from: TM 43-001-27 "Army Ammunition Data Sheets Small Caliber Ammunition" and
headspace data from Kuhnhausen's M1/M1A shop manual.
.308 Winchester data from ANSI/SAAMI document Z299.4-1992, "Pressure and Velocity, Centerfire Rifle Sporting Ammunition".
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Copyright 2004 Dutchman
No reproduction without written
permission.