9mm Wise Lite Arms “Colefire Magnum” – Sterling type pistol

WLA (Wise Lite Arms) made a Sterling type pistol they called the “Colefire Magnum.” It was made with a lot of Mk4 Sterling parts and chambered in 7.62x25mm. At the time 7.62x25mm was cheap. When the cheap ammo dried up people started parting out these pistols. I found the stripped receiver and decided to make a 9mm. I found some of the parts and made or converted the rest.

https://www.milsurps.com/images/impo.../cole201-1.jpg

A MK4 Sterling bolt being converted to a MK6.

https://www.milsurps.com/images/impo.../cole202-1.jpg

Copying a Mk6 firing spring retainer.

https://www.milsurps.com/images/impo.../cole203-1.jpg

The Mk6 firing spring retainer was too long. I copied this one from a picture on the net.

https://www.milsurps.com/images/impo.../cole204-1.jpg

I made the barrel from a blank.

https://www.milsurps.com/images/impo.../cole205-1.jpg

The short recoil makes a stiff spring necessary. The long cocking handle makes it easier and adds weight to the recoiling mass.

https://www.milsurps.com/images/impo.../cole206-1.jpg

There’s still a little left to finish up. I need to make the ratchet parts for the barrel nut, knurl the barrel, Parkerize the barrel & cocking handle & firing spring retainer.

This one is giving me a hard time. It’s not ejecting reliably.

It always chambers the next round. But the casing from the fired round doesn’t always get ejected.

I checked the extractor, plunger and spring. Also checked the ejector. They look fine.

The barrel is 4 ¼” long. I started out with the Mk7 pistol springs. It has a 4 ½” barrel and the bolt has the same weight. Then I trimmed the springs by taking one coil off and test firing. Then one more, test fire and so on. Eventually the return springs were so short they wouldn’t overpower the firing pin drive spring enough to close the bolt.

I tried 4 different magazines that work fine in other Sterlings.

I tried 115gr, 124gr, 147gr and 158gr rounds. All had the exact same problem.

The bolt moves freely. It’s not binding.

Dummy rounds hand cycle fine.

If you have any thoughts please let me know.

I will try a single spring tomorrow.

On the bright side it’s pretty accurate for having such a short barrel. :D

Usually blow back autos will eject without need for an extractor...maybe try firing a round with the extractor removed?

Did you try a known good extractor? perhaps the existing extractor was modified in some way for 7.62mm...


and the alternate question is, did you polish the chamber? perhaps there is a burr at the bottom of the chamber or throat...


How much shorter is that receiver tube than a Mk7 ? maybe there isn't enough travel for the bolt?

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Originally Posted by Lee Enfield

Usually blow back autos will eject without need for an extractor...maybe try firing a round with the extractor removed?

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Good idea. I will give it a try.

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Did you try a known good extractor? perhaps the existing extractor was modified in some way for 7.62mm...

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No, it’s the first time I have used it. I will try another one.

There is no modification for the extractor for 7.62x25mm.

It extracts fine by hand.

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and the alternate question is, did you polish the chamber? perhaps there is a burr at the bottom of the chamber or throat...

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The chamber looked good. I didn’t polish it, just the feed radius.

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How much shorter is that receiver tube than a Mk7 ? maybe there isn't enough travel for the bolt?

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It’s 1.75” shorter than a Mk7. There’s plenty of room for the bolt to travel.

I have fired one of these in 7.62x25mm and it never missed a beat.

Thanks for the input. I will give them a try this coming weekend.

You're correct in that a blow back will extract without an extractor but to say it will eject without an extractor is like saying that a car will self corner when it detects a camber in the road. Yes, it will, AFTER A FASHION! But you can't rely on it. The actual extractor gives the spent case its definite direction. This is because there is a direct relationship between the radial angle of the extractor on the reciprocating breech face relative to the radial angle of the stationary* ejector which we used to call the mathematical (or angular?) tipping point and the direction of ejection.

There is a simple test you can follow to prove or illustrate this point. Ironically, we used to show it using a Sterling SMG on single shot, fired from the Enfield mechanical rest with a paperr screen a metre or so away from the ejection port. With the ejector all of the spent cases form a distinct group mark on the sheet. No ejector....... it's mayhem! Trying the same with a Browning L9 pistol also proves the point with plenty of jambs too

* Not strictly correct as the ejector IS moving in relation to the breech block or vice verca, depending on how you are presenting the lesson to the class - or writing your answer!

Are we 100% certain that the ejector is unchanged between the caliber conversions?

Thinking about the OAL of each of the two cartridges 9mm @ 29.69 (1.169") and 7.62x25mm @ 34.0 mm (1.34 in) is it possible that the ejector was trimmed a little short to adjust the 'timing" to allow the longer Tokarev round to clear the ejection port, and if so, is this adjustment causing a spent 9mm casing to eject too late in the cycle of operations and it gets caught by the bolt on the return to loading?

Honestly no, experience, with this platform but thinking out loud, based on some troubles I experienced with a Kel-Tec Sub 2000 (Blow back 9mm carbine with some vague similarities to this gun). My issue was similar, but my resolution was not in the ejector. Mine was a thorough de-greasing, over lubrication was slowing the cycling and causing weak/no ejection in cold weather. I now run it very lightly oiled and have not had any issues. But inspecting the actual ejector blade was part of my problem solving with that gun.

https://www.milsurps.com/images/impo...k6breech-1.jpg

https://www.milsurps.com/images/impo...3/STR026-1.jpg

That was a pretty astute observation Darren. Just such a case was the cause of a major problem with the UK Military L85A1 during its morph from whatever it started as up to 5,56mm.

On slo-mo video every so often a case would JUST tip the top right corner of the ejection opening port and go........ Well, it'd go anywhere....., even spinning back through 180 degrees and back into the ejection opening backwards where it could be rammed home in the chamber, backwards. I kid you not. Easily solved by machining .014" from the face of the opening.

Incidentally, back to the 'no-need-for-an-extractor scenario. Been reading my Shrivenham student notes re-extractors, ejectors and tipping points. I know it's a bit sad but it is a rainy Thursday afternoon here in Oxfordshire. If you rely on blow back to extract and eject, there WILL come a day, that after having loaded the weapon and fed the live round into the chamber, that the next order will be '.......UNLOAD.....!' And that round is slightly distorted and will not fall out of the weapon.

From that point onwards and for the next 15 minutes the weapon will have to be left on the ground, facing the butts to cool off or cook off. Nope! No extractor....... works in theory but not in the real world

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Originally Posted by Sentryduty

Are we 100% certain that the ejector is unchanged between the caliber conversions?

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Yes.

Also, the ejector is from a Mk4 (9mm) parts kit.

Thank you for giving this some considerable thought.

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Originally Posted by Peter Laidler

You're correct in that a blow back will extract without an extractor but to say it will eject without an extractor is like saying that a car will corner when it detects a camber in the road. Yes, it will, AFTER A FASHION! But you can't rely on it. The actual extractor gives the spent case its definite direction. This is because there is a direct relationship between the radial angle of the extractor on the reciprocating breech face relative to the radial angle of the stationary* ejector which we used to call the mathematical (or angular?) tipping point and the direction of ejection.

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This described the problem exactly and got me to thinking. The spent cases were not spinning when they were ejected like you normally see with a Sterling. You can see them spinning in slow motion in this Mk5 video.

https://www.youtube.com/watch?v=ZRLcEHD2K5E

So, something was interfering with the relationship between the extractor and the ejector. But what? And why did not do it when hand cycling rounds?

By hand I could cycle the bolt and all 30 rounds would fly out spinning. Something was changing the extractor ejector relationship only when rounds were fired.

When a round is fired the firing pin tip protrudes through the bolt face as it travels back past the ejector. That doesn’t happen when cycling rounds by hand. Then the firing pin is held back by the sear and the tip doesn’t protrude through the bolt.

When I checked the firing pin protrusion it was more than double of what it should have been. It’s an aftermarket part. There are at least four different copies and they all differ slightly in length.

With the new firing pin it ejects flawlessly. I wouldn’t have guessed the problem was the firing pin, but there you have it.

Thanks for the help figuring it out.

I am glad to hear you got it figured out, firing pin protrusion is not something I would have thought of either. However it does make perfect sense, if the firing pin were riding in the fired primer dimple it would inhibit the case from being ejected cleanly, and the issue couldn't be replicated by hand because the sear was holding the pin back.

That is an unusual problem but a great learning experience.

Seems that the problem would have been present in the 7.62x25mm configuration if all part were equal in that build.