Practical Scrap Metal Small Arms Vol.3 the Diy Sten

The DIY STEN Gun

Practical Scrap Metal Small Arms Vol.3

By Proessor Para!ellum

Plans on pa"es ## to #$

Intro%uction

The DIY STEN Gun is a simplified 1:1 copy of the British STEN MKIII sumachine !un" The main differences ho#e$er include the numer of components ha$in! een !reatly reduced and it%s o$erall construction made e$en cruder" &sin! the simple techni'ues descried( the need for a millin! machine or lathe is eliminated ma)in! it ideal for production in the home en$ironment #ith $ery limited tools" *or o$ious le!al reasons( the demonstration e+ample pictured #as uilt as a non,firin! display replica" It%s dummy arrel consists of a hardened steel spi)e #elded and pinned in place at the chamer end and a separate solid front portion protrudin! from the arrel shroud for display" It%s olt is also inert #ith no firin! pin" This document is for academic study  purposes only.

(Disassembled: Back plug, recoil spring, bolt, magazine, sear and trigger displayed)

(Non-functioning dummy barrel present on display model)

Tools & construction techni'ues

 - fe# $ery $ery asic and and ine+pensi$e ine+pensi$e po#er tools tools can e e used to simulate machinin! machinin! actions usually reser$ed for a millin! machine" &sin! a cheap an!le !rinder the a$era!e hoyist has the aility to perform speedy remo$al of steel usin! a $ariety of cuttin! and !rindin! discs" .ather than tediously usin! a hac)sa# to cut steel sheet( an an!le !rinder fitted #ith a 1mm slittin! disc #ill accurately cut a strai!ht line throu!h steel of any thic)ness in mere seconds" *itted #ith a /mm disc it can e used to easily %sculpt% thic) steel into any shape in a fraction of the time it ta)es to manually use a hand file" It%s most useful application for this pro0ect is to cut and !rind the olt to it%s re'uired profile" This is a relati$ely 'uic) process and #ith care can produce a olt 0ust as !ood as a factory made ori!inal"

Inexpensie arc !elders are aailable for purc"ase oer t"e Internet:

 - rotary tool tool or Dremel Dremel is hi!hly hi!hly useful useful for delicate delicate !rindin! !rindin! and and cuttin! cuttin! operations" operations" *itted *itted #ith a %reinforced cuttin! disc% it ecomes a mini an!le !rinder( ideal for cuttin! out and !rindin! openin!s in pieces of tue 'uic)ly and neatly #ithout ha$in! to manually use a hand file" This is particularly effecti$e #hen used in comination #ith a %chain% of drill holes to 'uic)ly remo$e an openin! mar)ed on the STEN recei$er" .otary tools can e purchased cheaply online #ith a lar!e $ariety of cuttin!( !rindin! and sandin! its a$ailale for #or)in! #ith metal"

 -ll tools mentioned can e found found $ery cheaply online( or or ein! practically practically !i$en a#ay at any s#ap meet"

(seul tools An"le "rin%er  )ac*sa+ , co!alt tippe% !la%es -o!alt or titanium tippe% %rill !its Drill press or han% %rill com!ine% +ith a stan% el%er  Dremel / rotary tool , reinorce% cuttin" %iscs )an% iles

Materials 0ecei1er2 # #/4 53$mm / #.6mm +all7 mil% mil% steel tu!e Ma"a8ine9+ell2 #4 : 4 56;mm : 6mm7 steel !o: section Tri""er housin"2 #< "au"e 5mm7 steel sheet Stoc*2 3/<4 5#=/;mm7 steel tu!e Barrel collars2 3/<4 shat loc* collars 536mm outer %iameter7 #;mm aluminum plate 36mm mil% steel !ar stoc*

Bolt construction

 - typical sumachine sumachine !un olt olt copy can e constructed constructed #ithout #ithout the use use of a lathe lathe or millin! millin! machine y usin! a comination of drillin! and slittin! usin! a cheap an!le !rinder to remo$e the unneeded material" - 12mm len!th of 3mm diameter round steel ar stoc) is re'uired to construct the olt for the STEN" Many ori!inal STEN olts #ere casted from soft ron4e later on in 55/( so e$en a fairly soft %machine,ale% or %leaded% !rade of mild steel ar stoc) is perfectly suitale"

The centre of the olt is first mar)ed and drilled usin! a 16mm drill it until mm deep" This is est achie$ed usin! a numer of smaller drill its startin! at 7mm" If misali!nment is e+perienced( the piece ein! #or)ed on can e manually tilted y hand and drilled at an an!le until the drill it #anders ac) to the centre" The resultin! hole can then e le$elled flat usin! a second 16mm drill it modified y remo$in! it%s tip usin! an an!le !rinder" - sli!ht e$el is made around the hole usin! a 17mm8 drill it or rotary tool !rindin! it"

Ne+t a series of drill holes are made in order to aid in remo$in! material from the olt( e$entually formin! the ma!a4ine feedin! cuts" The positions of si+ holes are mar)ed and drilled usin! a 9mm it until 92mm deep" &sin! a cheap drill press and a #ell oiled it( each hole only ta)es  minutes or less to ore #hen #or)in! #ith re!ular mild steel" nce each hole has een drilled( an an!le !rinder fitted #ith a 1mm slittin! disc is used to cut throu!h the sides of the holes as close to the ed!es as possile( enalin! the t#o pieces of e+cess material to e easily remo$ed" - drill hole can e made at each end to aid in plyin! each piece out #ith a scre# dri$er and hammer"

nce the main ul) of material is remo$ed( the remainin! lo#er section is cut off at a mar)ed point lea$in! mm of material remainin! to e formed into the feed lips" This area is !round in#ards into a sli!ht ramp profile usin! a dremel fitted #ith a !rindin! it" This section should fit et#een the lips of a sten ma!a4ine #ithout any friction( thus may re'uire additional

!rindin! until around 3mm in #idth" nce complete( the e0ector channel is cut into the olt usin! a 1mm slittin! disc then #idened usin! a /mm disc until enterin! 1mm into the 16mm center of the olt" - dremel fitted #ith a cuttin! disc can e used to score a strai!ht line efore hand in order to aid in accuracy"

The sear contact point is cut into the olt y usin! a hac)sa# to mar) a line( after #hich material in front of this point is remo$ed usin! a /mm or mm !rindin! disc aimed at a 92 de!ree an!le to %sculpt% out a !or!e" *inally( a sprin! !uide at the rear of the olt can e made y drillin! a ;mm hole in the center and tappin! it to accept an m3 olt and fi$e 1< #ashers #ith an 3mm hole" The olt is finished y ali!nin! it inside the recei$er #ith the ma!a4ine and mar)in! the point to drill for the olt handle"

Tri""er "roup

The tri!!er !roup has een simplified to t#o $ery easily constructed components( each made usin! a section of 16mm aluminum or steel plate #ith a fe# additional modifications" Bein! typical of an open,olt desi!n( the tri!!er acts as a le$er( pi$otin! the sear out of the #ay of the olt #hen pulled( only to e pushed ac) into en!a!ement #hen the tri!!er is released due to continuous sprin! tension actin! upon it" This assemly allo#s for fully automatic fire only"

0ecoil sprin"

 - le$er type type !rease !un almost almost al#ays al#ays contains contains a near perfect compression compression sprin! sprin! for an SMG" Dependin! on manufacturer( you may need to loosen up the sprin! sli!htly y repeatedly compressin! it rapidly #ith a firm slammin! motion" - lar!e = cell flash li!ht is usually a perfect fit inside the !rease !un tue to perform this action" The sprin! #ill usually e 1< to 6mm in outer diameter and around ;< lon!"

Desi"n notes

The ori!inal STEN desi!n includes a remo$ale stoc) #hich also doules as the ac) plu! of the recei$er" The DIY STEN Gun has een simplified y instead ha$in! a permanently fi+ed stoc) #elded in place and a much stron!er ac) plu! retained y t#o olts" This is $astly easier to construct and #ill result in a much more secure assemly" The ori!inal si!hts ha$e een sustituted for a 1;< lon! steel ar #elded in place to simulate the 'uic) tar!et ac'uisition properties of the ori!inal top ri seam" The dust co$er present on the ori!inal has een left out as it is unneeded" - cartrid!e e+tractor is also not essential for function and can e left out( thou!h a template for the ori!inal has een included should one e desired" This desi!n uses ori!inal unmodified STEN ma!a4ines"

Plans  -ll pa!es pa!es included included should should e printed printed out on on 3"2 + 11 11 &S letter letter paper" paper" Each componen componentt template is dra#n to scale and can e cut out and !lued to their respecti$e thic)ness of material or used as reference for measurements" Ma)e sure the ruler at the ottom left of each sheet is / inches in len!th" -lternati$ely( ta)e a screen,shot and enlar!e the plans usin! a computer pro!ram until the ruler is the correct len!th( then trace the parts needed onto a sheet of paper taped o$er your computer%s screen"  - recei$er template for for -9 paper paper has also also een included" included"

0eerence photos

Original cast bronze STEN bolt:

Top: cast bronze, bottom: machined steel:

Original STEN bolt face:

Original STEN chamber feed entrance:

STEN MK magazine!"ell and latch:

#iring se$uence illustrated:

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