barnbwt
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- Joined
- Aug 14, 2011
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- 7,340
I traded into this kit a year or so back from a builder who had done most of the hard work (filling the ~3/8" gaps in the torch cuts & installing a denial bar), and I just recently got around to actually knocking out the semi-auto conversion, final assembly, and test fire. Final Bondo & paint remains to be completed (obviously) as well as the eventual SBR conversion back to the length Tullio Marengoni intended --at present it is a fraction of an inch shorter than an FN30 (improved 1919) I have tie-wrapped together at home 
I'm not showing the reverse angle since the bolt is still covered in ugly blue Dykem
Link to a link to the test fire vidja
History:
The M38A was a veritable Alfa Romeo of 9mm SMGs in its day, very nice quality for the late thirties, when SMGs were rapidly ditching build quality for mass production from the high-dollar hey-day of the "first generation" models in the 20's & early 30's. The M38A possessed a number of desirable features vs. its peers like the MP38/40 German guns, and was highly prized by all the Axis fighters, but war demands would ultimately see nearly all of them stripped from the design later in the war by necessity;
-Captive internal return spring/guide rod system for very easy assembly/service & pushbutton-locking endcap
-Lever-actuated open-bolt firing pin for safety & reliability
-Manual safety lever that would not allow a cocked bolt to jar free on its own inertia if dropped
-Dual triggers for full & semi-auto fire
-Full size rifle barrel & stock along with muzzle compensator for extremely controllable/accurate fire, along with a fairly heavy bolt mass
-Quality rifle-style ramp blade sight indexed out to 500m or so
-Fully shrouded barrel that was actually tensioned to a small degree by the muzzle compensator
-Non-reciprocating charging handle with integral sliding dust cover
-Sliding dust cover for empty magazine well
-Full-profile bolt body to effectively seal the ejection port when decocked
-Extremely large ejection port, opened right at the breech for very good chamber access
-Intimidatingly large stick magazine of 40 round capacity; especially considering that paratroopers each wore a vest that carried 5 sticks horizontally on the front, 7 on the back, and six stick grenades!
German soldiers greatly preferred the guns over their domestic issued SMGs to the point they were highly prized items eventually reserved for elite units; the reliability of the M38A recoil spring plunger assembly vs. the MP40 and far better stock arrangement are what I imagine endeared them the most.
The Build:
I'm sure I've mentioned it before, but striker conversions of these old burp guns to semi-auto closed-bolt operation generally suck. The triggers are too often irredeemable garbage, and frequently end up breaking because they are not designed strong enough to snag the striker as it reciprocates at full speed in the long run. They also are often a bit on the finnicky side for builders, especially when the striker comprises a good portion of the bolt mass (i.e. chopping off the tail of the bolt to make the striker) So, I wanted to do a hammer system, which incidentally allowed me to maintain a far more 'authentic' look & operation of the gun in the end...except for the funnest part of course
My first thought was AR15 FCG, because it's cheap & well understood, but I've come around to the belief that the wound spring arrangement really is a weak link unless you have the ability to tweak and optimize a design. Far too often AR FCG conversions wind up with light strikes and require heavier hammer springs or hammer modifications. They also take up a lot of room when you don't have very much to play with for these conversions. After learning about the 10/22 and how powerful, small, cheap its FCG units were, I decided to go that route instead.
I won't go into too many details of the conversion for a number of reasons, but I welded two 'sideplates' on either side of the receiver between the magwell and trigger group housing inside the stock, and installed the 10/22 trigger & hammer pivots between them. A simple pivoting linkage on the outside of the left side plate pushes up & down on the trigger tail, causing the trimmed trigger to rotate in & out of sear engagement when the other end of the lever is pressed by either trigger (so both are now independent semi-auto triggers). No original trigger guts besides the two trigger levers were used (the M38A is the epitome of overly complicated Italian trigger groups). I haven't designed the safety yet, but it will likely either block the linkage from moving (therefore locking the sear against release) or retract the bolt 3/8" so the firing pin cannot be struck by the hammer.
The bolt assembly was half-ready for closed bolt operation from the factory, because of that lever-operated firing pin I mentioned earlier. I removed the OEM firing pin (a giant, heavy bar that doubled as a spring guide rod) and welded up the pivot lever's mounting holes so that open-bolt system could never be installed again. Then the bottom of the bolt was slotted wider so the 10/22 hammer could swing through, and the back side of the firing pin channel was bored out & relined with a steel tube shaped for a standard AR15 firing pin. A hook-shaped retainer engages the collar of the firing pin so it cannot fall out against its return spring. The original return spring tube/plunger that fits into a hole at the rear of the bolt was retained, but the narrow original spring inside the tube was replaced with an AR carbine spring that fits around the tube as though it were a guide rod. Lastly, the semi-auto modified bolt was slotted to match the denial bar welded into the receiver, so it could fit inside and rear full battery position. Very important that this part comes last.
The original barrel was drilled as part of the demilling process, and could not be saved. The large-diameter threaded 'trunnion' section of the barrel at the breech with the feed ramp & extractor cut was cut off from the rest of the tube (which was discarded), then bored out and internally threaded for a 5/8" Green Mountain 9mm blank to be torqued in place. The chamber was reamed to proper headspace, and the muzzle threaded for the compensator (which was also bored & re-threaded due to damage). I made the ugly spacer tube that sits between the shroud and compensator so the shroud can be properly secured by the brake despite the extra ~4" of barrel length to get to 16". If eForms & 41F ever get fixed, it will be removed after a 200$ lop & chop.
Here is the action bereft of its wooden finery, before the (third) trigger was trimmed & the linkage fitted on this side. You can (easily) make out the side plate by the nasty MIG "bead" on its three sides. Were I to do this again, the plates would not extend all the way to the mag well, because then I wouldn't have had to clean up burn-through inside the magwell
At last the mechanically functional gun was completed for final assembly. The rear sight base (which had been chiseled off the receiver --this kit was in really rough, nasty shape before I got it, which I've come to learn in this hobby means it was likely imported from an Italian-affiliated nation in Africa) was reattached by drilling out & retapping the damaged holes in the receiver, and replacing the ruined metric screws with #10 pan-heads with reduced heads. Phillips, not slotted, since slotted screws are terrible & this is not a 'reproduction' job, but an homage to the original of no historical value. Last but not least, the stock was inletted for all the new additions until the action nestled down to the proper position without binding, and could be secured with the barrel band and one stock bolt in my possession (I'll need to make another at some point, but these have little retainer screw notches cut into them that makes fabrication slightly more annoying).
Test Fire:
First test fire showed the trigger conversion worked reliably and was powerful enough to set off primers. But function, not so much. Remember how I said the barrel was replaced with a blank then chambered? Yeah, that should have been "chambered and chamfered to match the feed ramp" but this guy skipped a step! Some quick & dirty Foredom Rotary Tool work with a carbide bur got that transition cleaned up enough that round-nose bullets would not hang up as they fed from the magazine.
Second test fire was far more successful, and conducted with more than six bullets. Ejection started out a bit sluggish with one stove pipe, but after a half dozen shots it became far more consistent & assertive. I unfortunately don't have much experience with 'normal' straight blowback guns since I find them crude & unpleasant to shoot, but this Beretta is *very* tame compared to them, as gentle as any 223 (only much quieter). Once I get the sights dialed in & the compensator lok-tited, it should be pretty accurate too. I enjoyed the roughly doubled sight radius vs. any other subgun.
Link to a link to the test fire vidja
The trigger(s) was a bit disappointing. I mean, it's not like it matters on a blaster like this, but I'd hoped for something nicer since this was hammer fired (and it usually is). I think a couple of factors conspired to make the trigger heavier and creepier than it could be. Owning to the confined space I had to work with, the rear of the hammer strut sits lower relative to the hammer pivot than on the actual 10/22. I think when cocked, this gives the hammer spring more leverage, so the sear/hammer are under higher pressure and harder to disengage. I did use the original trigger pack to locate the hammer & trigger holes, but any error there could also increase sear engagement noticeably. The way the disconnector is designed, it requires a rather long trigger travel before resetting. Next, my linkage has its own return leaf spring that's fairly strong to drive the sear reset, and each trigger has its own small return coil spring & plunger (similar to how Beretta did it originally), which all contribute to the trigger pull weight and friction. Lastly, the two Beretta triggers are shaped differently where they contact the linkage lever, and also apply different levels of off-axis torque to the linkage. The end result is a long ~5lb 1/16" takeup ~8lb rough break for the front trigger (the 'good' trigger) and ~6lb 1/4" spongy takeup and >10lb inconsistent break for the back trigger (the one in the most convenient position on the stock). The roughness & friction will undoubtedly decrease with enough time & oil, but I'm still overjoyed it works at all since these projects are often exercises in aggravation when it comes time to test fire . This one was pleasantly painless come range time.
Now that I know the gun runs & is safe/fun to shoot, I'll work on getting that safety knocked out and getting the gun ready for its finish. I believe the originals were parkerized, but I will most likely be filling the weld divots with Lab Metal (aluminum-bearing conductive epoxy) and powder coating the thing semi-gloss black or very dark blue since I think the gun's classy enough to pull off the fine polished blue look. I've also seen one of these stocks restored nicely with a gloss oil finish, so I may strip off the lacquer & do something similar (although it really isn't that terrible as-is, considering)
TCB
I'm not showing the reverse angle since the bolt is still covered in ugly blue Dykem
Link to a link to the test fire vidja
History:
The M38A was a veritable Alfa Romeo of 9mm SMGs in its day, very nice quality for the late thirties, when SMGs were rapidly ditching build quality for mass production from the high-dollar hey-day of the "first generation" models in the 20's & early 30's. The M38A possessed a number of desirable features vs. its peers like the MP38/40 German guns, and was highly prized by all the Axis fighters, but war demands would ultimately see nearly all of them stripped from the design later in the war by necessity;
-Captive internal return spring/guide rod system for very easy assembly/service & pushbutton-locking endcap
-Lever-actuated open-bolt firing pin for safety & reliability
-Manual safety lever that would not allow a cocked bolt to jar free on its own inertia if dropped
-Dual triggers for full & semi-auto fire
-Full size rifle barrel & stock along with muzzle compensator for extremely controllable/accurate fire, along with a fairly heavy bolt mass
-Quality rifle-style ramp blade sight indexed out to 500m or so
-Fully shrouded barrel that was actually tensioned to a small degree by the muzzle compensator
-Non-reciprocating charging handle with integral sliding dust cover
-Sliding dust cover for empty magazine well
-Full-profile bolt body to effectively seal the ejection port when decocked
-Extremely large ejection port, opened right at the breech for very good chamber access
-Intimidatingly large stick magazine of 40 round capacity; especially considering that paratroopers each wore a vest that carried 5 sticks horizontally on the front, 7 on the back, and six stick grenades!
German soldiers greatly preferred the guns over their domestic issued SMGs to the point they were highly prized items eventually reserved for elite units; the reliability of the M38A recoil spring plunger assembly vs. the MP40 and far better stock arrangement are what I imagine endeared them the most.
The Build:
I'm sure I've mentioned it before, but striker conversions of these old burp guns to semi-auto closed-bolt operation generally suck. The triggers are too often irredeemable garbage, and frequently end up breaking because they are not designed strong enough to snag the striker as it reciprocates at full speed in the long run. They also are often a bit on the finnicky side for builders, especially when the striker comprises a good portion of the bolt mass (i.e. chopping off the tail of the bolt to make the striker) So, I wanted to do a hammer system, which incidentally allowed me to maintain a far more 'authentic' look & operation of the gun in the end...except for the funnest part of course
My first thought was AR15 FCG, because it's cheap & well understood, but I've come around to the belief that the wound spring arrangement really is a weak link unless you have the ability to tweak and optimize a design. Far too often AR FCG conversions wind up with light strikes and require heavier hammer springs or hammer modifications. They also take up a lot of room when you don't have very much to play with for these conversions. After learning about the 10/22 and how powerful, small, cheap its FCG units were, I decided to go that route instead.
I won't go into too many details of the conversion for a number of reasons, but I welded two 'sideplates' on either side of the receiver between the magwell and trigger group housing inside the stock, and installed the 10/22 trigger & hammer pivots between them. A simple pivoting linkage on the outside of the left side plate pushes up & down on the trigger tail, causing the trimmed trigger to rotate in & out of sear engagement when the other end of the lever is pressed by either trigger (so both are now independent semi-auto triggers). No original trigger guts besides the two trigger levers were used (the M38A is the epitome of overly complicated Italian trigger groups). I haven't designed the safety yet, but it will likely either block the linkage from moving (therefore locking the sear against release) or retract the bolt 3/8" so the firing pin cannot be struck by the hammer.
The bolt assembly was half-ready for closed bolt operation from the factory, because of that lever-operated firing pin I mentioned earlier. I removed the OEM firing pin (a giant, heavy bar that doubled as a spring guide rod) and welded up the pivot lever's mounting holes so that open-bolt system could never be installed again. Then the bottom of the bolt was slotted wider so the 10/22 hammer could swing through, and the back side of the firing pin channel was bored out & relined with a steel tube shaped for a standard AR15 firing pin. A hook-shaped retainer engages the collar of the firing pin so it cannot fall out against its return spring. The original return spring tube/plunger that fits into a hole at the rear of the bolt was retained, but the narrow original spring inside the tube was replaced with an AR carbine spring that fits around the tube as though it were a guide rod. Lastly, the semi-auto modified bolt was slotted to match the denial bar welded into the receiver, so it could fit inside and rear full battery position. Very important that this part comes last.
The original barrel was drilled as part of the demilling process, and could not be saved. The large-diameter threaded 'trunnion' section of the barrel at the breech with the feed ramp & extractor cut was cut off from the rest of the tube (which was discarded), then bored out and internally threaded for a 5/8" Green Mountain 9mm blank to be torqued in place. The chamber was reamed to proper headspace, and the muzzle threaded for the compensator (which was also bored & re-threaded due to damage). I made the ugly spacer tube that sits between the shroud and compensator so the shroud can be properly secured by the brake despite the extra ~4" of barrel length to get to 16". If eForms & 41F ever get fixed, it will be removed after a 200$ lop & chop.
Here is the action bereft of its wooden finery, before the (third) trigger was trimmed & the linkage fitted on this side. You can (easily) make out the side plate by the nasty MIG "bead" on its three sides. Were I to do this again, the plates would not extend all the way to the mag well, because then I wouldn't have had to clean up burn-through inside the magwell
At last the mechanically functional gun was completed for final assembly. The rear sight base (which had been chiseled off the receiver --this kit was in really rough, nasty shape before I got it, which I've come to learn in this hobby means it was likely imported from an Italian-affiliated nation in Africa) was reattached by drilling out & retapping the damaged holes in the receiver, and replacing the ruined metric screws with #10 pan-heads with reduced heads. Phillips, not slotted, since slotted screws are terrible & this is not a 'reproduction' job, but an homage to the original of no historical value. Last but not least, the stock was inletted for all the new additions until the action nestled down to the proper position without binding, and could be secured with the barrel band and one stock bolt in my possession (I'll need to make another at some point, but these have little retainer screw notches cut into them that makes fabrication slightly more annoying).
Test Fire:
First test fire showed the trigger conversion worked reliably and was powerful enough to set off primers. But function, not so much. Remember how I said the barrel was replaced with a blank then chambered? Yeah, that should have been "chambered and chamfered to match the feed ramp" but this guy skipped a step! Some quick & dirty Foredom Rotary Tool work with a carbide bur got that transition cleaned up enough that round-nose bullets would not hang up as they fed from the magazine.
Second test fire was far more successful, and conducted with more than six bullets. Ejection started out a bit sluggish with one stove pipe, but after a half dozen shots it became far more consistent & assertive. I unfortunately don't have much experience with 'normal' straight blowback guns since I find them crude & unpleasant to shoot, but this Beretta is *very* tame compared to them, as gentle as any 223 (only much quieter). Once I get the sights dialed in & the compensator lok-tited, it should be pretty accurate too. I enjoyed the roughly doubled sight radius vs. any other subgun.
Link to a link to the test fire vidja
The trigger(s) was a bit disappointing. I mean, it's not like it matters on a blaster like this, but I'd hoped for something nicer since this was hammer fired (and it usually is). I think a couple of factors conspired to make the trigger heavier and creepier than it could be. Owning to the confined space I had to work with, the rear of the hammer strut sits lower relative to the hammer pivot than on the actual 10/22. I think when cocked, this gives the hammer spring more leverage, so the sear/hammer are under higher pressure and harder to disengage. I did use the original trigger pack to locate the hammer & trigger holes, but any error there could also increase sear engagement noticeably. The way the disconnector is designed, it requires a rather long trigger travel before resetting. Next, my linkage has its own return leaf spring that's fairly strong to drive the sear reset, and each trigger has its own small return coil spring & plunger (similar to how Beretta did it originally), which all contribute to the trigger pull weight and friction. Lastly, the two Beretta triggers are shaped differently where they contact the linkage lever, and also apply different levels of off-axis torque to the linkage. The end result is a long ~5lb 1/16" takeup ~8lb rough break for the front trigger (the 'good' trigger
) and ~6lb 1/4" spongy takeup and >10lb inconsistent break for the back trigger (the one in the most convenient position on the stock). The roughness & friction will undoubtedly decrease with enough time & oil, but I'm still overjoyed it works at all since these projects are often exercises in aggravation when it comes time to test fire . This one was pleasantly painless come range time.Now that I know the gun runs & is safe/fun to shoot, I'll work on getting that safety knocked out and getting the gun ready for its finish. I believe the originals were parkerized, but I will most likely be filling the weld divots with Lab Metal (aluminum-bearing conductive epoxy) and powder coating the thing semi-gloss black or very dark blue since I think the gun's classy enough to pull off the fine polished blue look. I've also seen one of these stocks restored nicely with a gloss oil finish, so I may strip off the lacquer & do something similar (although it really isn't that terrible as-is, considering)
TCB
