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scratchbuilt roller locking

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#1 ·
[from a thread of mine elsewhere, that died out. Reposted here FYI]

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Has anyone done a scratchbuild with a roller locked bolt?

I've been looking at a book that covers the Enfield EM-1 prototype from the 1950s. It was a gas operated, roller locked setup. The bolt consisted of a tube that held two rollers, looks like they were about 5/16 x 3/8", and an inner wossname, firing pin carrier, with a wedge face to force the rollers out. The firing pin rode inside the carrier.

The gas system moved the firing pin carrier, which moved the outer sleeve. It looks like it was a very long stroke gas system.

From the drawings, it looked like about 1/3 of the roller was in the front trunnion when locked, so when the firing pin carrier moved back, the rollers just popped out of the trunnion of their own accord. There's no indication of anything like the fancy ramp angles a G3 or CETME uses. The trunnion otherwise looked pretty much like a G3 part.

The bolt tube carried the entire locking load; the carrier just kept the rollers pushed out. When in battery, the rollers were on a perpendicular surface on the carrier, so the camming action from the gas load just tried to pinch the bolt carrier; there was no angularity to move anything back.

The length of the carrier nose and the firing pin protrusion appear to be designed so that there's no chance of a firing pin strike until the bolt is fully locked.

I've been pondering this setup for a couple of weeks now. It looks like it would be easier to build than a turnbolt setup. The "lug" area of the bolt sleeve looks reasonable. You can buy proper roller bearing rollers from several sources; they're usually 8620 alloy or something similar.

The gas load on the locked bolt will try to spread the ears on the trunnion a bit. Theoretically, enough spread and you could blow the bolt right out. I found a G3 trunnion on GB for $15 to take a look at; it isn't here yet. The G3 is a roller-delayed setup instead of roller-locked, but I'd like to see how beefy they felt they needed to go with a .308.

Anyway, has anyone done this from scratch? Results? Comments?

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I found "Full Circle: A Treatise on Roller Locking" by R. Blake Stevens while searching for roller locking stuff on the web. The going price seems to be $80-ish, so I logged onto the local library's web site and ordered it via Inter-Library Loan. Hopefully some library out there has a copy to share. If not, I guess I'll buy it.

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Definitely let us know what's in "A Treatise on Roller Locking"--an awesome name, if nothing

10-4 I'm hoping it has some real information and not just pictures of guns that happened to use the system...

Roller locked uses the rollers to hold the barrel and breech together at the instant of firing; the locked-together barrel/breech assembly recoils backward until some sort of trunnion pulls out the rollers, and the chamber is opened.
The EM-1 used an ordinary gas setup with a piston. It slotted into the firing pin sleeve, which formed the locking wedge. When the gas pushed the sleeve back, the rollers popped back in, and then the whole assembly moved back.


The EM-1 sounds like roller *locked*, so I'm not sure how much the G3 parts are going to help you.
Yes, locked. I'm not sure about the G3 trunnion either; when I ordered it I didn't realize the G3 was just delayed and not locked. If nothing else I can get the roller size and send it off to a friend who has access to various testing equipment to get the hardness and alloy.

Tricky part about scratch-building a useful roller locked gun would be that damn moving barrel--getting any accuracy would take some pretty sweet trunnions for the barrel to seat back into...

The EM-1 used an ordinary fixed barrel. I'm starting to get the impression that it was, if not unique, an unusual implementation of roller locking.

At the moment the only detailed roller locking information I have is the pictures in the book "EM-2 Concept and Design" by Dugelby, which has to go back to the library tomorrow. The EM-1 prototypes were roller locked, the EM-2 used lever locks. Doable, but way more complex to build than rollers. There was no explanation as to why they picked the EM-2 over the EM-1, but there was considerable politics involved. And as far as manufacture... the Brits were never afraid of complexity. Where an American car would join two parts together with a single coarse-thread bolt, a British car would use three fine-thread studs with flat washers, lock washers, castle nuts, and cotter pins...

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might be easyer to use the locking flaps like the Ruskies used in the DP-28 and a lot saner.

I discovered those while googling for roller stuff. I've seen some pictures of the bolt assembly, but just external pictures of the receivers. If you can point me to some detailed views I'd sure like to see them.

I'm guessing the backs of the flaps are shaped to cam out of their recesses, and do so when [a locking wedge?] releases them. I've managed to sketch a few designs that might work, but they would all be impossible to machine without building customer machinery to cut the flap recesses. Obviously the Russians and Germans had a better idea...

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The G3 trunnion showed up today. It's sitting on the desk next to a Yugo AK trunnion. They're about the same size, but the Yugo trunnion is noticeably beefier. They both use barrels of similar diameter, and the G3 barrel is pinned in place like (most) AKs.

The roller ramp area in the G3 is contained within "wings" off the back of the trunnion. They're joined by a flat web across the bottom. I guess you could also look at it as a 3/4 circle opened at the top; either way, the tops of the wings are unsupported.

There are marks from the rollers. They're much smaller than I expected.

There are machining marks on the outside of the G3 trunnion. I can't tell if it started off as an investment casting or bar stock, but the OD was finished off with dull tools. The roller ramps and inside areas of the trunnion are very smooth, apparently ground. The "wings" are tall enough to handle the roller tracks and sufficient overtravel for a small grinding wheel to finish the ramp area.

I *think* I see a pair of Rockwell dimples on the back of the right wing.

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The library emailed me back; that book is not available by Inter-Library Loan.

I've added it to the "discretionary budget" list, but it's pretty far down, considering the bits I need to finish various gun projects.

I'm still going to keep an eye out for roller locking stuff, though. It seems like such an elegant solution...
 
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#2 ·
Hello TRX,
The Stevens book may be a "reference room only" text. So you would have to go to that library in person perhaps with a pocket full of change for copies of key items.

G-3 parts could be retro engineered back into the original Stg-45(M) to make a cool semi-auto carbine in 8mm kurz. The original tube size was nominally like that of the Sten. Curious !!! The first prototype was very much like a Sten on steroids with the roller locks.

VD
 
#3 ·
TRX i have a book that has drawings of a sten converted to a roller locking 8mm kurz design.

Let me know and i can try to scan it.


A while ago I drew up a fully roller locked gas powered design for a 10mm or 45 win mag design. Just never got around to cutting it
 
#4 ·
There was a guy on practicalmachinist [I forgot if that's the right site, I always remember "roderus gunworks" as them] making a Calico MAC upper, he made a roller delayed trunnion. Really cool way of making the recesses too, he drilled holes in the block and then milled out the bolt pocket so it intersected the drilled holes and made them into the roller pocket things.
 
#7 · (Edited)
Doing a roller locked action could be rather trying expectantly with limited tooling. Given how thigh the tolerances would have to be and having to retain symmetry. Cutting the locking recesses so that they have a uniform contact with the rollers and not only small porting would be rather tedious.

To me for a locked semi from scratch with It would be less trouble to go with a bolt with locking flapper lugs like in the G43, EM-2, Degtyarev DP-27, RPD, ect G 43 Disassembly In theory a trunnion or barrel extension could have the locking recesses cut in it with a key-way cutter (woodruff cutter, t-slot cutter).

Another option is a tilting bolt like the FAL, SKS, SVT40 ect.. SVT-40 Disassembly

I would bet that a person could build a hybrid of the Chinese Stamped sheet steel receiver sks and the ak style receiver. Pictures of the receiver about half way down. Yooper John Note see how the front trunnion extends back from the barrel to the locking step for the bolt. It is both riveted and spot welded in place.

There has been some discussion about this over on homegunsmith.com. I did bring up a neat little straight pull SR30 that uses ball bearings instead of rollers. Though it is a little complex, hard to machine with limited tooling, and the tight tolerances required would cause problems with any dirt or debris.
The thread. iB::Topic::Anyone make a roller locking pistol or rifle?

I have been thinking about both the stamped steel tilting bolt and the flapper lug bolt for quite some time, and some day I hope to getting around to making some chips.
 
#8 ·
Cutting the locking recesses so that they have a uniform contact with the rollers and not only small porting would be rather tedious.
I think I have that part sussed out. To do an EM-1 style roller lock I'd drill and ream the trunnion from above to create the lock recesses, drill the sleeve and file the roller recess square. The roller wedge would be simple lathe and mill work. The attraction of a roller lock is that it's *much* simpler than a turnbolt.

To me for a locked semi from scratch with It would be less trouble to go with a bolt with locking flapper lugs like in the G43, EM-2, Degtyarev DP-27, RPD, ect
Looks like the EM-2 was a derivative of that. I've been calling it a "lever lock" since I hadn't come across any pictures of the "flap" setup.

That's the thread I was thinking about.

I have been thinking about both the stamped steel tilting bolt and the flapper lug bolt for quite some time, and some day I hope to getting around to making some chips.
I'll scan some of the EM-2 pictures I got out of that book. They might help you.
 
#9 ·
EM-1 locking system

Enfield EM-1 roller lock:

Unfortunately, nothing about the extractor and ejector bits. I've been scratching my head on how to fit something into the available space.

Most of the weird monkey motion is due to the bullpup arrangement. Enfield chose to use a somewhat, ah, unusual arrangement. The sear is offset to the right, very long, and reaches down to the trigger assembly. They also used a striker and a rocker arm, unique, as far as I know. Fortunately I'm not interested in duplicating any of that part.

The centerlines of the rollers ride on the sleeve. Around 1/3 of the roller sticks out into the trunnion. Gas load makes the roller push against the nose of the firing pin sleeve; there's no rearward thrust through the roller action. Gas load goes from the front of the sleeve to the forward sleeve cutout, across the roller, and to the trunnion.

The firing pin sleeve moves back, the rollers cam in through the sleeve, everything unlocks. I'm not particularly thrilled at how the rollers can touch the firing pin. I imagine the unlocking would be somewhat brisk, even though theoretically the left and right rollers wouldn't put any bending force across the pin.

You could drill and ream the roller slots in a round chunk, then bore and hone it to size. Voila, trunnion.
 

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#10 ·
EM-2 locking system:

Enfield EM-2 lever lock:

Both the EM-1 and EM-2 used stamped steel receivers. There was no useful information about that in the book; I couldn't even tell if the rollers locked into a trunnion piece or against the sides of the receiver itself.
 

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#14 ·
A square hole minimizes the distance the rollers have to move from locked to unlocked. With HK-sized rollers (look to be somewhere between 3/8 and 1/2") a round trunnion and bolt sleeve would add, oh, maybe half again as much travel.

For a roller-delayed setup like a G3 this would be bad - the ends of the trunnion hole and the center of the bolt sleeve would see high localized pressure as the centerline of the roller moved from locked to unlocked. It'd probably beat up the parts.

With gas operation I don't see that this would be a big problem as long as the gas system wasn't too violent. All the gas system needs to do is cam the roller out of the trunnion and kick the carrier far enough back to cycle another round. I noticed the EM-1 had a really long spring and a lot of carrier travel, probably so it only needed a relatively gentle kick from the gas system.


I guess it *would* be possible to do a square trunnion - other than a mill step, it would work just the same as my round idea. Drill and ream the locking lug recesses, bore the inside, then add an extra step to mill flats along the inside of the recesses. With a 1/4" end mill the overtravel would work out okay. I've been sketching with the bolt sleeve locating the rollers vertically, so a longer roller track than needed wouldn't hurt.

Hmm... might just as well go with a square trunnion then.
 
#15 ·
I see what you mean about the extractor; for some reason I didn't pick it out of the drawing. The sliding block setup seems to be popular on high-end rifles nowadays. Running a tiny little cutter to do the notches would take a few practice parts to get the speed and feed right. It'd be a snap with EDM... out of my price range, though.

I bet you could just buy the extractor piece from Numrich.
 
#16 ·
On your drawing you show the roller locking area as smaller than the barrel hole. It would be easier to make the other way around - and that's how my $15 G3 trunnion is arranged.

The G3 trunnion, by the way, looks positively flimsy compared to a Yugo trunnion.
 
#18 ·
With a boxy or square trunnion I was thinking of a receiver along the lines of the QBZ-03 or Beretta AR70. ÖйúQBZ03ʽ5.8ºÁÃ××Ô¶¯²½Ç¹Ïê½â[19P]_©IÆÜÔÆЦЦÉú_°Ù¶È¿Õ¼ä Weaponeer.net Forums: Beretta AR70 kit build Arizona Response Systems, LLC. Notes. Building an AR-70

The reasoning for the roller locker area being smaller then the barrel journal was so it could be cut with broaches. It would be a bit easier to cut the locking interface with a end mill and have it the same diameter as the barrel journal. Doing it that way wouldn't limit the adjustment of the head space. Haveing it be a rounded square would save time and not cause any adverse effects.

You may want to check out Gun Parts - RTG International Surplus Gun Parts and Militaria Could also think of using the HK rollers and retainer plate.
If I remember right the CETME trunnion isn't as light as the G3, but not by much. When they build them with the heaver barrels they are forced to do longer trunnions or a trunnion extension. I would love to know the safty factor of an ak...:)

I would bet the ejector would be similar between the EM-1 and EM2. On the drawings of the EM2 bolt it has a grove for the extractor at the 4:30 location. It isn't the full length back so it can't be a fixed ejector. I would bet it is a lever like what is used on the CETME and it's H&K derivatives.
 

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#21 ·
The bolt is going to be awful busy with the rollers and the firing pin and the cam to engage the rollers.
Yes; that's the downside. But probably cheaper than the EM-2 bolt. According to the Dugelby book the EM-2 bolt cost almost fifty pounds sterling to make;. The exchange rate was one pound to three 1950 US dollars; $150 went a long way in 1950.
 
#22 · (Edited)
I don't mean cost wise, with using the rollers you are going to be using a lot of room in the bolt head directly behind the bolt face. Even when you overcome the engineering problems related to that you have to make it. I for one would dread the though of making the bolt head getting it setup that the rollers work perfectly. Then when you are setting up the ejector there is an error in alignment ect.. and you have to start over.
 
#23 ·
with using the rollers you are going to be using a lot of room in the bolt head directly behind the bolt face.
True. The rollers wind up about 1/2" behind where a regular bolt's lugs would be, and the nose has to be extended to get room for the extractor. Not a big deal to me.

I for one would dread the though of making the bolt head getting it setup that the rollers work perfectly.
The only important dimension is the distance from the loaded area of the square roller hole to the front of the bolt. It would probably best be broached. The locking recesses in the trunnion are no problem; either move the table the proper distance or use a rotary fixture and just flip the part over.

Then when you are setting up the ejector there is an error in alignment ect.. and you have to start over.
Well, that's all part of development! I was imagining that if I built one I wouldn't bother with an ejector or extractor, just build something I could strap to an old tire and fire with a string. I'm more worried about the camming effect of the rollers spreading the trunnion and letting the bolt pop out than anything else. But looking at the G3 trunnion, it couldn't really be much of a problem...
 
#28 ·
locked vs. delayed

I think some people are getting confused by the way a G3 works vs. the way the EM-1 worked. The difference is in the firing pin carrier (EM-1) or locking piece (G3).

The rollers on the EM-1 ride on a flat that's parallel to the barrel when the bolt is locked. The rollers just sit there in compression when the rifle is fired; there's nothing making them move. A gas system moves the firing pin carrier back to unlock the rollers.

The G3's rollers sit on a ramp on the front of the locking piece. When the rifle is fired, friction keeps it locked for a split second, then the ramp angles spit the rollers inward. The bolt spring increases the delay.

Hmm, I bet you could just use a G3 trunnion and make a new bolt head and locking piece without the ramp... the G3 roller recesses are more complex than simple semicircular cutouts, but that might not be a problem.
 

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#30 ·
What's why I was thinking about extending the nose and using a Savage-type pin ejector. That eliminates any drillings or cuts in the loaded area... of course, you wind up lengthening the bolt stroke to compensate. No free lunch.


In the pictures, it looks like the roller cutouts in the bolt head are simple rectangular holes with no cam angles. If true, it might be possible to just make a new locking piece for a G3 trunnion and bolt head. Anyone have a G3 bolt head for sale cheap?
 
#38 · (Edited)
Hopefully I can attach a picture of the early Gerat 06H prototype etc. It reveals a stark simplicity dating from 1943 that was evolved by 1945 by Mauser. This system became the CETME and G-3 series of today. Note the smooth receiver tube of the early version !!! I recall that they measured about 1.5 inche OD like the G-3 etc.

VD
 

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#39 ·
There must be some pieces tack welded inside; at least, from the pictures I've seen, it looks like the purpose of the stamped grooves is to keep the rollers from falling out as the bolt travels back.
 
#41 ·
On a CETME/G3 the rollers are retained in the bolt head by a small plate with two dimples in it, they fit down in a recess on top of the rollers. The plate is secured in the bolthead with a small roll pin. The purpose of the grooves in the receiver is to keep the rollers retracted, otherwise when the bolt leaves the trunnion the pressure shoving it rearward would make the bolt head shove back against the carrier and pop the rollers out into the "locked" position.
 
#46 ·
the 17 hmr is a no go for the boy, after looking at failures of rugers I cant put the boy at risk. Vorq(cant spell it right now) made workable 17hmr semi's but drilled a vent hole at a "secret" location on the barrel to relieve the sharp pressure spike that was blowing guns.

That said It is going to be a 22 magnum and that being held up by a new lathe I am putting in, the upstairs being refinished and the wife wants a garage......




On the roller locker, I have some drawings of what I want to and likely will build that was designed for safety and easy of milling. Will try to find and post those too.
 
#47 ·
Vz, I certainly understand about the safety factor. Last fall I could only find 2-3 places that still made the 17hmr in a semi. My 17HMAR upper has also been on hold until I get my sheldon lathe up and running (I'm real close), got side tracked by a basement remodel and currently we're moving out of state. It'll be a while until I'm making chips again. I also was holding off on the 17 hoping to find an easy locking bolt design that would work with the small gas volume of the rimfire case. Good luck on your honey do list and I'll keep and eye out for your drawing pics!
 
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