EDG
12-29-2015, 04:59 PM
This is some of the data that I have gathered from 7.65 Mauser rifles, dies, factory ammo and new factory brass.
Keep in mind that there are NO SAAMI standards for this round. However there are CIP (European) standards for this round.
Because CIP drawings use a different scheme to dimension the drawing I had to change the measurement units to inches and calculate the Gauge dimension using trigonometry in a spreadsheet. The CIP drawings are not toleranced unless there is a seperate reference document so I calculated my own SAAMI go and no go and field dimensions for my own use.
If you are more interested in the subject you can read about the delta L problem with some cartridges. The delta L problem exists where the longest ammo permitted, by the standard, is longer than the shortest chamber permitted in the rifles. This means you could get ammo that is in tolerance that will not chamber in rifles that are also in tolerance. This is not really good engineering practice. Just do a web search for "delta L problem".
Gauge = The dimension from the head of the case to a .375 gauge diameter on the shoulder.
The measurements were taken with a .375 gauge bushing mounted on a set of dial calipers.
The calipers were set using a 7X57 Forster gunsmith headspace gauge. They were set using the dimension marked on the gauge.
This provides for a very accurate gauge setting.
For the rifles I sized a fired .270 Win case until the stripped bolt body would close with a very slight drag.
This case was measured with the gauge set up above. The result is what I considered the chamber length for that rifle.
Notice how uniform the results are.
Rifle
Cal
Gauge
M1891
7.65
1.822
M1891
7.65
1.821
M1891
7.65
1.820
M1898/09
7.65
1.820
The same gauge was used to measure new factory ammo and brass by both PPU and Norma.
Note that Norma is somewhat shorter. Norma ammo was not as consistent as PPU.
The new brass of each brand was very uniform. The 4th and 5th decimal places came from calculating the averages.
Norma ammo will stretch about .010 worst case when fired in my rifles.
Gauge
Gauge
Norma Factory Ammo =
1.812-1.816
Norma brass
1.81520
PPU ammo =
1.819 -1.821
PPU brass
1.81775
These die dimensions were taken as follows.
. 001 increment guage pins - for the neck and base diameter of each die
Brown & Sharpe 0-1 micrometer - Shoulder diameter and pressure ring diameter produced on cases sized by the dies
Caliper with .375 diameter gauge bushing attached - Sizer Headspace = head to shoulder length produced on cases sized by the die.
The last 3 columns are just the GO, NO GO and Field dimensions that I decided upon based on the rifles, the ammo and dies.
These are my preferences based on the data. You are free to use your own calculations.
RCBS
Die
Die
NECK
SHOULDER
BASE
Pressure
GAUGE
SIZER
FIELD
Cartridge
Code
Brand
TYPE
DIAMETER
DIAMETER
DIAMETER
Ring Size
DIAMETER
HEADSPACE
GO MIN
NO GO
MAX
7.65 Mauser
CH
TRIM
.3360
.4260
.4690
.4670
.375
1.7810
1.8160
1.8200
1.8240
7.65 Mauser
Pacific
FL
.3360
.4250
.4710
.4660
.375
1.7970
1.8160
1.8200
1.8240
7.65 Mauser
Lyman
FL
.3320
.4230
.4670
.4660
.375
1.8140
1.8160
1.8200
1.8240
7.65 Mauser
66
RCBS
TRIM
.3390
.4280
.4690
.4670
.375
1.8160
1.8160
1.8200
1.8240
7.65 Mauser
88
RCBS
FL
.3310
.4300
.4670
.4650
.375
1.8180
1.8160
1.8200
1.8240
7.65 Mauser
N
RCBS
FL
.3290
.4250
.4690
.4660
.375
1.8190
1.8160
1.8200
1.8240
7.65 Mauser
LEE
FL
.3250
.4250
.4710
.4660
.375
1.8380
1.8160
1.8200
1.8240
This information is provided to show that there are a few crappy dies out there and some that are dimensioned properly.
Some dies will require some extra time setting them up to maximize case life.
Notice the old CH and Pacific dies are too short and the Lee die is too long. The Lyman is a little under my min chamber length and the RCBS dies are just about perfect.
Keep in mind that there are NO SAAMI standards for this round. However there are CIP (European) standards for this round.
Because CIP drawings use a different scheme to dimension the drawing I had to change the measurement units to inches and calculate the Gauge dimension using trigonometry in a spreadsheet. The CIP drawings are not toleranced unless there is a seperate reference document so I calculated my own SAAMI go and no go and field dimensions for my own use.
If you are more interested in the subject you can read about the delta L problem with some cartridges. The delta L problem exists where the longest ammo permitted, by the standard, is longer than the shortest chamber permitted in the rifles. This means you could get ammo that is in tolerance that will not chamber in rifles that are also in tolerance. This is not really good engineering practice. Just do a web search for "delta L problem".
Gauge = The dimension from the head of the case to a .375 gauge diameter on the shoulder.
The measurements were taken with a .375 gauge bushing mounted on a set of dial calipers.
The calipers were set using a 7X57 Forster gunsmith headspace gauge. They were set using the dimension marked on the gauge.
This provides for a very accurate gauge setting.
For the rifles I sized a fired .270 Win case until the stripped bolt body would close with a very slight drag.
This case was measured with the gauge set up above. The result is what I considered the chamber length for that rifle.
Notice how uniform the results are.
Rifle
Cal
Gauge
M1891
7.65
1.822
M1891
7.65
1.821
M1891
7.65
1.820
M1898/09
7.65
1.820
The same gauge was used to measure new factory ammo and brass by both PPU and Norma.
Note that Norma is somewhat shorter. Norma ammo was not as consistent as PPU.
The new brass of each brand was very uniform. The 4th and 5th decimal places came from calculating the averages.
Norma ammo will stretch about .010 worst case when fired in my rifles.
Gauge
Gauge
Norma Factory Ammo =
1.812-1.816
Norma brass
1.81520
PPU ammo =
1.819 -1.821
PPU brass
1.81775
These die dimensions were taken as follows.
. 001 increment guage pins - for the neck and base diameter of each die
Brown & Sharpe 0-1 micrometer - Shoulder diameter and pressure ring diameter produced on cases sized by the dies
Caliper with .375 diameter gauge bushing attached - Sizer Headspace = head to shoulder length produced on cases sized by the die.
The last 3 columns are just the GO, NO GO and Field dimensions that I decided upon based on the rifles, the ammo and dies.
These are my preferences based on the data. You are free to use your own calculations.
RCBS
Die
Die
NECK
SHOULDER
BASE
Pressure
GAUGE
SIZER
FIELD
Cartridge
Code
Brand
TYPE
DIAMETER
DIAMETER
DIAMETER
Ring Size
DIAMETER
HEADSPACE
GO MIN
NO GO
MAX
7.65 Mauser
CH
TRIM
.3360
.4260
.4690
.4670
.375
1.7810
1.8160
1.8200
1.8240
7.65 Mauser
Pacific
FL
.3360
.4250
.4710
.4660
.375
1.7970
1.8160
1.8200
1.8240
7.65 Mauser
Lyman
FL
.3320
.4230
.4670
.4660
.375
1.8140
1.8160
1.8200
1.8240
7.65 Mauser
66
RCBS
TRIM
.3390
.4280
.4690
.4670
.375
1.8160
1.8160
1.8200
1.8240
7.65 Mauser
88
RCBS
FL
.3310
.4300
.4670
.4650
.375
1.8180
1.8160
1.8200
1.8240
7.65 Mauser
N
RCBS
FL
.3290
.4250
.4690
.4660
.375
1.8190
1.8160
1.8200
1.8240
7.65 Mauser
LEE
FL
.3250
.4250
.4710
.4660
.375
1.8380
1.8160
1.8200
1.8240
This information is provided to show that there are a few crappy dies out there and some that are dimensioned properly.
Some dies will require some extra time setting them up to maximize case life.
Notice the old CH and Pacific dies are too short and the Lee die is too long. The Lyman is a little under my min chamber length and the RCBS dies are just about perfect.