Expedient Homemade Firearms - BSP 9mm SMG - P.a Luty

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Expedient Homemade Firearms. BSP-SMG.

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(2)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S M G BSP-SMG SCHEMATICS

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Expedient Homemade Firearms -1-

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(4)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S -2 - 1. 15.88 x 3.25mm tubing. 2. ½” BSP Socket. 3. ½” BSP nipple. 4.

½

” BSP lock nut 5. 1 ¼” x ½” BSP reducer. 6. Magazine Catch. 7. Magazine. 8. Trigger. 9. Trigger Bar. 10. Bolt. 11. Sear. 12. Mainspring.

13. Stock anchor point. 14. 1” Diameter x 1/8” tube. 15. Rubber buffer. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

(5)

Expedient Homemade Firearms. BSP-SMG

-3-

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A

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(Internal Components. Hole Diameters Arrowed)

Sear. 1/8” Plate. Trigger Bar. ¼” Plate. Trigger. ¼” Plate Magazine Well. 40 x 20mm Tube. Trigger Guard. 14 gauge sheet steel. Magazine Catch. 20 gauge

spring steel. Magazine Stop. 40 x 20mm Tube.

66 m m 6mm 3.8mm 3.8mm 4mm 4mm

(6)

E xp ed ie nt H om em ad e F ire ar m s. B S P S -4 -

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(Hole diameters shown in millimetres)

The lower receiver is composed of two receiver side- plates, each being 9¾’’ in length.

Each plate is identical. Each side - plate is cut from a length of 2.5mm thick steel sheet

to the shape of the above template. The square recess shown in figure ‘A’ is the anchor

point for the shoulder stock. This measures ½’’ square.

Note: If the template is not 9¾’’ in length when printed, it may be enlarged using a

9

¾

’’

6mm 4mm 4mm 6mm

2.5mm steel Sheet.

(7)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S M G . -5 -

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To create the lower receiver assembly, the two receiver side- plates are joined together by spacing them between two 6mm studding connectors, (A and B). Four dome head cap screws are then screwed into the connectors and thoroughly tightened, effectively holding the assembly together. The two connectors must be exactly 20mm in length.

As bought, 6mm connectors are usually this exact length, but if they are not, they may be trimmed on a lathe until the required length is achieved.

A section of steel plate measuring 20 x 20mm is now silver soldered between the two side- plates in the position shown at ‘C’ below. The plate should be ¼” thick. A gap of 2mm should now exist between the plate and the end of the receiver.

Top View Side View

STIDDING CONNECTOR ‘A’ STUDDING CONNECTOR ‘B’ 2.5

m

m

(8)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S -6 -

The lower receiver template is attached to a section of 2.5mm steel plate.

Two receiver side - plates are required. Two studding connectors are used to

hold the side - plates together

(9)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S M G

-7-L

L

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The magazine well is inserted into the receiver and welded in place along points ‘A’ and ‘B’.

Note: Do not weld along opposite side of point ‘B’. It must be ensured before welding that

the top edge of the well is 7mm above the top edge of the receiver.

7mm B A C D 27mm 103mm 5/8 Trigger Guard 9x7mm 3mm

The trigger guard is made from a 103mm length of 5/8” steel sheet. This sheet should be 5/8” wide. The guard is formed to the shape of the template on page 3.

A hole measuring 9x7mm is cut through the guard, 27mm from its front edge. This hole will accept the lower leg of the trigger. The guard is silver soldered in position at points ‘C’ and ‘D’.

(10)

Expedient Homemade Firearms. BSP-SMG

P

P

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The grip is the next part to make.

It is made from a 112mm length of 40 x 20mm tubing.

A 5.8mm diameter hole is drilled through the grip in the position

shown in the accompanying grip template.

Before the grip is fixed to the receiver the sear must be made and

fitted.

See page 8.

11 2m m 5.8mm Grip Template

(11)

Expedient Homemade Firearms. BSP-SMG

-9-

S

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The sear is cut from a section

of 1/8” thick steel plate. See

templates, page 3.

A 4mm diameter dowel pin is

tapped into the sears 3.8mm

hole.

The pin should protrude 8mm

from the sears right side

when fitted.

The sear is made from mild

steel and should be case

hardened after final shaping.

4mm dowel pin TOP Right Side 6mm 8mm Sear- Right Side.

(12)

Expedient Homemade Firearms. BSP-SMG

T

T

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I

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The trigger is made from a section of ¼” thick steel

plate. A 4mm diameter dowel pin (a spring pin could be

used as a substitute) is tapped into the 3.8mm hole.

The pin must protrude 6mm from each side of the

trigger when fitted.

4mm Dowel Pin

Rear

Rear View

Pin must protrude

6mm from each

side of trigger.

(13)

Expedient Homemade Firearms. BSP-SMG

-11-

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F

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Before the sear is fitted, a slot is cut through the rear and

front of the grip wall. The slot is 15mm deep and 4mm wide.

The sear is inserted into this slot and retained with a 6mm

diameter dowel pin. This pin should be 20mm in length.

Grip

Sear Fitted 5.8mm Cut 4mm x 15mm Slot

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Spring Fitted

The sear spring is formed from 20g spring wire to the shape illustrated opposite.

It should have between four and six coils.

(14)

Expedient Homemade Firearms. BSP - SMG

G

G

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M

M

B

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T

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D

D

The grip and sear assembly is in

serted into the receiver and

retained with two dowel pins.

The magazine catch is bolted to the front of the receiver using a 6mm diameter dome head socket screw.

Receiver Top

2.5mm

Note:

It is very important that

the top edge of the grip is positioned 2.5 – 3mm below the top

ed

g

e of the receiver.

Grip

(15)

E xp ed ie nt H om em ad e F ire ar m s. B S P - S M G -13 -

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We can now begin construction of the

upper receiver!

(16)

Expedient Homemade Firearms. BSP-SMG

P

P

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N

T

T

S

S

The upper receiver assembly consists of a 1

¼

” BSP tube (screwed at both ends) and fitted with a Cap and Reducer, as photo ‘A’ below illustrates. Photo ‘B’ shows the reducer and cap screwed onto the receiver tube and the barrel assembly ready for fitting.

‘A’

(17)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S M G -15 -

U

U

P

P

P

P

E

E

R

R

R

R

E

E

C

C

E

E

I

I

V

V

E

E

R

R

T

T

E

E

M

M

P

P

L

L

A

A

T

T

E

E

The upper receiver template must be enlarged using a photocopier until it is 12 ½” in length.

Once enlarged, the template is glued around the 1 ¼” BSP upper receiver tube. The recesses for the ejection port, magazine well (EP&MW), bolt handle, and sear can then be marked onto the receiver tube. 12

½

EP& MW Bolt Handle Sear Sling Loop Holes 5

¼

(18)

E xp ed ie nt H om em ad e F ire ar m s. B S P -S -16 -

U

U

P

P

P

P

E

E

R

R

R

R

E

E

C

C

E

E

I

I

V

V

E

E

R

R

S

S

H

H

O

O

W

W

N

N

W

W

I

I

T

T

H

H

T

T

E

E

M

M

P

P

L

L

A

A

T

T

E

E

BSP- 9mmSMG.

(19)

Expedient Homemade Firearms. BSP-SMG -17-

P

P

H

H

O

O

T

T

O

O

O

O

F

F

T

T

E

E

M

M

P

P

L

L

A

A

T

T

E

E

A

A

T

T

T

T

A

A

C

C

H

H

E

E

D

D

T

T

O

O

U

U

P

P

P

P

E

E

R

R

R

R

E

E

C

C

E

E

I

I

V

V

E

E

R

R

T

T

U

U

B

B

E

E

The template is attached to the upper receiver tube to allow the necessary recesses to be marked onto the tube.

(20)

Expedient Homemade Firearms. BSP-SMG 12

½

1

¼

” B SP Tubing Thre ad Length: 1 -1/8 14 -3/8 1

¼

x

½

Reducer 1

¼

Ca p

U

U

P

P

P

P

E

E

R

R

R

R

E

E

C

C

E

E

I

I

V

V

E

E

R

R

(21)

Expedient Homemade Firearms. BSP-SMG

-19-

The BSP nipple, socket, and lock nut assembly are screwed into the reducer. The assembly is then thoroughly tightened.

The barrel tube is inserted into the BSP barrel assembly.

A

(22)

Expedient Homemade Firearms. BSP-SMG

P

P

H

H

O

O

T

T

O

O

O

O

F

F

B

B

A

A

R

R

R

R

E

E

L

L

C

C

O

O

M

M

P

P

O

O

N

N

E

E

N

N

T

T

S

S

The barrel is assembled from a 9” length of 15.88 x 3.25mm

hydraulic tubing, a 1

¼

” BSP Reducer,

½

” BSP Lock nut,

½

” BSP Socket, and a

½

” BSP Nipple (threaded tube).

Screwing the barrel assembly onto the upper receiver.

Hydraulic tube

Reducer Nut Socket

(23)

Expedient Homemade Firearms. BSP-SMG

-21-

B

B

O

O

L

L

T

T

A

A

S

S

S

S

E

E

M

M

B

B

L

L

Y

Y

The bolt is machined to the following dimensions from a

suitable section of round steel stock.

36 m m 83mm 50mm 20mm 13.5mm

B

B

U

U

F

F

F

F

E

E

R

R

A

A

N

N

D

D

S

S

P

P

R

R

I

I

N

N

G

G

G

G

U

U

I

I

D

D

E

E

The buffer is made from a section of hard rubber stock to

the following dimensions.

The spring guide is nothing more than a length of 1”

diameter tubing.

The tubing should have a wall thickness of 1/8”.

1” diameter tube (Spring Guide) 66mm 25mm 12 35 19 25 Buffer

(24)

Expedient Homemade Firearms. BSP- SMG

A

A

L

L

T

T

E

E

R

R

N

N

A

A

T

T

I

I

V

V

E

E

B

B

O

O

L

L

T

T

C

C

O

O

N

N

S

S

T

T

R

R

U

U

C

C

I

I

O

O

N

N

M

M

E

E

T

T

H

H

O

O

D

D

An alternative to machining the SMG bolt would be to assemble it from the components illustrated below.

The components are fitted to the 8mm bolt section as shown below.

8mm bolt section and nut

‘J’ / Hook bolt

½” spring pin Stack of washers

(25)

Expedient Homemade Firearms. BSP- SMG

-23-

The ½” spring pin is two inches in length and is silver soldered to the end of an 8mm diameter high tensile bolt. The end of the bolt section being fitted with the firing pin prior to this.

A stack of 1 ½” diameter washers (with 8mm holes) are then inserted over the bolt section and retained with a nut.

Around 52 washers are necessary to provide the bolt with the required length and weight.

(26)

Expedient Homemade Firearms. BSP-SMG

F

F

I

I

T

T

T

T

I

I

N

N

G

G

T

T

H

H

E

E

M

M

A

A

I

I

N

N

S

S

P

P

R

R

I

I

N

N

G

G

After placing the bolt into the upper receiver, the mainspring

can be inserted, followed by screwing on the BSP cap.

(27)

Expedient Homemade Firearms. BSP-SMG

-25-

Magazine Template

A 34.93 x 15.88mm plastic tube cap is used to seal off the bottom of the magazine.

Drill two 2mm diameter holes through the

Magazine body and cap to retain the cap in position.

Th

e

m

ag

az

in

e

bo

dy

is

9

in

le

ng

th

. I

f i

t i

s

no

t t

hi

s

le

ng

th

w

he

n

pr

in

te

d,

th

e

te

m

pl

at

e

sh

ou

ld

b

e

en

la

rg

ed

u

si

ng

a

p

ho

to

co

pi

er

un

til

th

is

m

ea

su

re

m

en

t i

s

ac

hi

ev

ed

.

Th

e

te

m

pl

at

e

is

a

tt

ac

he

d

to

a

le

ng

th

o

f 3

4.

93

x

1

5.

88

m

m

tu

bi

ng

.

9”

(28)

Expedient Homemade Firearms. BSP-SMG

As shown in Expedient Homemade Firearms -The 9mm Sub-Machine Gun, the magazine is made from a section of 34.93 x 15.88mm

rectangular tubing.

As a design improvement i have added a plastic tube cap, retained with two pins, to act as the magazine base plate.

Tube Cap Pins

(29)

Expedient Homemade Firearms. BSP-SMG

-27-F

F

I

I

T

T

T

T

I

I

N

N

G

G

A

A

S

S

H

H

O

O

U

U

L

L

D

D

E

E

R

R

S

S

T

T

O

O

C

C

K

K

I

It

t

i

is

s

q

qu

ui

ie

et

t

p

po

os

ss

s

ib

i

bl

le

e

t

to

o

c

co

on

ns

st

tr

ru

uc

ct

t

a

a

s

si

im

mp

pl

le

e

f

fo

ol

ld

di

in

ng

g

s

s

ho

h

ou

ul

ld

de

er

r

s

s

to

t

oc

c

k

k

f

fo

or

r

t

th

he

e

B

B

SP

S

P

m

ma

ac

c

hi

h

in

ne

e

g

gu

un

n

u

us

s

in

i

ng

g

n

no

ot

th

hi

in

ng

g

m

mo

or

re

e

t

th

ha

an

n

a

a

m

mo

od

di

if

fi

ie

ed

d

3

3

/8

/

8

r

r

at

a

tc

c

he

h

et

t

s

s

pa

p

a

nn

n

ne

er

r

a

a

nd

n

d

a

a

l

le

e

ng

n

gt

th

h

o

of

f

s

st

te

ee

e

l

l

t

tu

ub

bi

in

ng

g!

!

T

Th

he

e

f

fo

ol

ll

lo

ow

wi

in

ng

g

p

pa

ag

ge

es

s

i

il

ll

lu

us

st

tr

ra

a

te

t

e

h

ho

ow

w

t

th

hi

is

s

i

is

s

d

do

on

ne

e

.

.

F

F

o

o

l

l

d

d

i

i

n

n

g

g

S

S

h

h

o

o

u

u

l

l

d

d

e

e

r

r

S

S

t

t

o

o

c

c

k

k

.

.

(30)

Expedient Homemade Firearms. BSP - SMG

P

P

H

H

O

O

T

T

O

O

O

O

F

F

S

S

H

H

O

O

U

U

L

L

D

D

E

E

R

R

S

S

T

T

O

O

C

C

K

K

C

C

O

O

M

M

P

P

O

O

N

N

E

E

N

N

T

T

S

S

The shoulder stock is assembled from a 3/8” ratchet spanner, a length of

5/8” round tube, a section of

½

” box tube, four washers, a cotter pin, and

(31)

Expedient Homemade Firearms. BSP-SMG -29 -

A

A

S

S

S

S

E

E

M

M

B

B

L

L

I

I

N

N

G

G

T

T

H

H

E

E

S

S

H

H

O

O

U

U

L

L

D

D

E

E

R

R

S

S

T

T

O

O

C

C

K

K

M

MA

AT

TE

ER

R

IA

I

A

LS

L

S

R

RE

EQ

QU

UI

IR

RE

ED

D

1. 3/8” ratchet spanner. 2. 5/8” x 16g steel tube.

3.

½

” x 16g box section tube.

4. 1

¼

” washers x

¾

” hole. 5. Cotter pin x 1.

3/8” Ratchet spanner.

The ratchet spanner is cut down and shortened until it has an overall length of around 4 – 5”.

½

” tube

Insert tube onto ratchet and retain using high strength bearing adhesive.

4- 5”

Slide washers onto tube.

A series of washers are placed

over the

½

” box section. These

may consist of either four

standard ‘light’ washers or two to three thick ‘heavy’ washers. Either way, the stack of

washers must result in a combined length of 4 – 5mm.

Washers 4 – 5mm

(32)

Expedient Homemade Firearms.

BSP-SMG-R

R

E

E

A

A

R

R

V

V

I

I

E

E

W

W

O

O

F

F

W

W

E

E

A

A

P

P

O

O

N

N

S

S

H

H

O

O

W

W

I

I

N

N

G

G

S

S

H

H

O

O

U

U

L

L

D

D

E

E

R

R

S

S

T

T

O

O

C

C

K

K

A

A

T

T

T

T

A

A

C

C

H

H

E

E

D

D

T

T

O

O

R

R

E

E

C

C

E

E

I

I

V

V

E

E

R

R

Upper

Receiver

Insert cotter pin

into hole to hold

shoulder stock

in place.

Shoulder Stock

(33)

Expedient Homemade Firearms. BSP-SMG -31-

S

S

H

H

O

O

U

U

L

L

D

D

E

E

R

R

S

S

T

T

O

O

C

C

K

K

T

Th

he

e

c

cl

lo

oc

ck

kw

wi

is

se

e

a

an

nd

d

A

A

nt

n

ti

i-

-c

cl

lo

oc

ck

kw

wi

is

se

e

s

se

el

le

ec

c

to

t

or

r

s

s

wi

w

it

tc

c

h.

h

.

The selector switch is rotated either clockwise or anti-clockwise to allow the stock to be extended or closed; in just the same manner as if undoing a nut or bolt !

Braze or Weld

5”

The butt plate is made

from a 5” length of ¾” x

1/8” steel plate. The butt

plate is welded or brazed

to the stock tube.

A length of 5/8” x 16g steel

tubing is placed over the

shortened ratchet spanner

and retained using bearing

adhesive.

(34)

Expedient Homemade Firearms. BSP – SMG.

C

C

o

o

n

n

s

s

t

t

r

r

u

u

c

c

t

t

i

i

o

o

n

n

n

n

o

o

t

t

e

e

s

s

:

:

1. Mainspring/ recoil spring; a suitable mainspring for the BSP machine

gun can be acquired by stripping down a side lever grease applicator gun and removing the spring.

The spring illustrated below measures 216mm (8 ½”) in length and 30mm in diameter. The wire the spring is made from being 2mm in diameter.

This spring is almost perfect in dimensions for the BSP machine gun and was removed from the grease gun shown below. Spring sizes do vary depending on grease gun manufacturer.

2. Magazine; The magazine for the BSP machine gun is identical to that

shown in my book ‘Expedient Homemade Firearms’ - The 9mm machine

Gun. See book for details.

3. Stock; The length of the shoulder stock can be adjusted to suit

individual requirements by simply increasing or reducing the length of the stock tubing prior to final assembly.

Figure

Updating...

References

Updating...