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  #1  
Old 01-13-2017, 10:02 PM
dave bulla

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Duramatic barrel swap issues



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OK guys... in the interest of providing all possible useful info for helpful answers this may get a bit windy.

I've got a Duramatic and love it. It's been a bit of a project gun and the first thing to be replaced was the grip due to cracks. Second was the magazine. It had a junky Triple K mag that was worthless. I bought one from Alan and it has worked perfectly out of the box. Need to get a second one soon just because everyone needs a spare magazine.

The original barrel was a 6.5" one with a too short front sight. I did what I could with what I has on hand and built it up and I'm happy with the results. Problem was accuracy from that barrel was a bit lacking. I suspect a recrown will help but in the mean time I happened across a 4.5" Plinker barrel and bought it. Seemed to drop right in. Accuracy was about twice as good as the 6.5" one so I was pretty happy. Several magazines later, the gun stopped ejecting reliably so I went home. I later found that the extractor was broken.

It was at this point I began looking more closely at the "fit"of the two barrels. I found that the plinker barrel seems to sit just slightly lower than the Duramatic. Now, before someone starts saying that there is an M100 and an M101 version, I'm aware of that. I mistakenly bought a second 6.5" barrel and it is totally different in the mounting face area. Honestly I forget which version mine is but I want to say M101.

Looking at the extractor slot, the original barrel top and bottom edges of the barrel extractor slot are evenly spaced to the edges of the slot in the slide. The slot in the barrel is slightly wider so basically there is a slight step up in slot width from the slide side to the barrel side. As far as I can tell, this is normal. When I put the 4.5" Plinker barrel on, the top edges of both slots are even and the difference is all on the bottom side. I think this may be why the extractor broke. It might have just snagged the edge of the lower barrel slot and snapped. I've got some pictures but photobucket always gives me fits with warnings popping up about viruses and such. I'll try to load the pics but it may be a while

Today was the first time I was able to shoot it since I replaced the extractor. Since the short barrel is more accurate, I took it with that one installed. Loaded up a mag full of bulk Remingtons, slapped it in, pulled the trigger and "click". I thought OK, crappy Remington ammo. Cycled out the dud and I see only a tiny little nip mark on the rim. Hmmm, that's odd. Second round, same thing. Third, same thing.

Pulled the mag, emptied the chamber and took the slide off to look at the firing pin. If you know what the firing pins on these models look like, it's waaay over built. No dinky little piece of flat stock in a slot, it's over a quarter inch diameter solid rod with a flat side for alignment and a basically conical tip. Pretty much indestructible and mine looks perfect. There is a flat register/shoulder at of the back of the cone that acts as a stop against the forward face of the slide channel it travels in. I drug my fingernail across this flat face and gouged up some carbon. I kept cleaning, slapped it back together and tried it again. Got about 50% fires but strikes waaay out on the edge. FYI, the pin is positioned to strike the top of the case rim.

Thought a bit more and had the idea I could shim up the barrel a bit, raise the entire thing in relation to the slide and the strikes should be lower and more solid. I had a bank receipt in the console so I cut two strips of paper. Put one forward and one aft of the barrel screw. MAYBE raised the barrel .010" if I had to guess. Next mag I had 100% fire success but still strikes are pretty far out on the edge. Visually, there is still room to go up looking at the extractor slots so I'll probably play with it some more. Maybe try some foil, aluminum can or brass shim stock.

The thing that puzzles me is this. As common as extra barrels are and as often as you can pick them up, surely people swap barrels a fair bit. I'm wondering why I've not heard of this issue before. IS this common or did I just stumble upon a one off situation?

Last edited by dave bulla; 01-13-2017 at 10:19 PM.
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  #2  
Old 01-13-2017, 11:47 PM
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I bought 103 Sport King a few years ago that came with a Tournament barre in the case with the 4.5 in original barrel and 3 magazines.

None of the magazines would work with the 4.5 inch barrel. One mag worked great with the Tourny barrel, but it was a bull barrel and shot about 16 inches low at 15 yd.s. Not much good for anything except burning ammo.

Upon inspection it seemed to ride lower in the SK frame than the OEM 4.5 in. barrel. I had the Tourny barrel D&T'd and put a short rail and a red dot on it. Sounds very much like the same situation the OP experienced.

Through trial and error and a lot of help from RFCers I finally acquired some magazines [some older than my pistol.] which work smoothly with either barrel. The Triple K I received with the pistol never did work. I have 2 with the rather unusual base plate [miitary?] that run smoothly. One of them is one that came with the pistol and was the only one that was functional with the tourny barrel and fair with the short barrel.

VH
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Old 01-14-2017, 12:28 PM
dave bulla

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OK.

Finally got the pics loaded. This first is the original barrel trying to show the relationship of the extractor groove in the receiver to the groove in the barrel. The lighting is not the best but you can see that the top of the groove on the barrel side (on the right) is a bit higher than the top of the slide side groove. Bottom edge offset is about identical.


This one is the replacement barrel "The Plinker". The barrel seems to sit lower. You can see the top edge is about dead even and all of the extra width is offset to the bottom.

Last edited by dave bulla; 01-14-2017 at 01:20 PM.
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Old 01-14-2017, 12:33 PM
dave bulla

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Now for some cases. I tried to sort these after the fact based on pin strikes. These are some of the worst offenders as far as nearly missing the rim. Way out there on the edge. Most are likely from after I scratched some carbon off the pin but before I added the paper shim.


These should be from after the shim was added. I don't think I had any fails to fire after adding the shim but I think it still needs more shim.


Last edited by dave bulla; 01-14-2017 at 01:23 PM.
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Old 01-14-2017, 12:39 PM
dave bulla

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And of course being Remington bulk 22's,there's always at least one that just won't fire no matter what. This one still has the bullet but took 3 strikes.


And last, my simple paper shim. Made on the spot at the range with what I had available.

Last edited by dave bulla; 01-15-2017 at 10:49 AM.
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Old 01-14-2017, 12:53 PM
dave bulla

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Now, for comparison sake, here is one of the more marginal hit cases from before the shim. I put the original barrel back on, loaded the case and dropped the pin to get a "normal" strike mark. That strike is on the right. You can see quite a difference between the two.

Last edited by dave bulla; 01-14-2017 at 01:29 PM.
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Old 01-14-2017, 01:12 PM
dave bulla

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I mentioned the M100 and M101 barrel interfaces being different. Here is s pic of the two side by side. The one on the left is the M100 and the right is the M101. By the way, anyone need an M100 6.5" barrel with no front sight and a good bore? I think I paid $70.


End view of the same two barrels. Notice the taller overall profile of the one on the right.

Last edited by dave bulla; 01-15-2017 at 10:46 AM.
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Old 01-14-2017, 01:15 PM
dave bulla

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Last pic. The M100 barrel installed on the M101 frame. Extractor grooves no where close to lining up.
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Old 01-14-2017, 08:06 PM
dave bulla

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Time to build a shim. Gonna need a clean hole in the center. Just happen to have a home made punch to make 45 caliber wads. Looks about the right size.


Looks like it's a fit!


One oversize shim.

Last edited by dave bulla; 01-15-2017 at 10:51 AM.
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Old 01-14-2017, 08:11 PM
dave bulla

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Press down on both ends to mark locations of base block ends.


Trim to length.


Install barrel, compress aluminum shim. Check out that gap improvement already!
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Old 01-14-2017, 08:28 PM
dave bulla

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Fold edge to mark trim line.


Snip snip snip!


One of the empty cases with a poor strike re-struck 180 out. New strike looks a LOT better.



Thats about it for now. I ended up making a second shim and spsuper glued them both to the bottom of the barrel. Gap may be very slightly high on the barrel now but very close to centered. Have not fired it yet but I think the problem is solved.

Last edited by dave bulla; 01-14-2017 at 08:33 PM.
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  #12  
Old 01-14-2017, 10:28 PM
dave bulla

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So, anyone else had to do anything similar to their Duramatic?

See anything I did wrong? Comments or suggestions?
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  #13  
Old 01-16-2017, 08:51 AM
dave bulla

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Boy tough crowd eh?
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Old 01-16-2017, 09:38 AM
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Dave,
I found this to be an interesting read. Thank you for taking the time to detail the issue and your process to remedy it. I look forward to reading how well it shoots.
Regards,
Greg
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Old 01-16-2017, 04:42 PM
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Dura-Matic M-100 and M-101 pistols

Attached is a link to a manual for the Dura-Matic. http://www.histandard.info/manuals/dura/0144D150R.pdf
You will note that certain M-100 parts and not interchangeable with M-101 parts. This includes the barrels of the two designs. While shimming the M-100 barrel may make it usable on a M-101 frame, the use of a M-100 barrel was not intended to be used on a M-101 pistol. So the best fix is to obtain a M-101 barrel for a M-101 Dura-Matic.

These pistols are durable guns for the type of shooting they were intended for
(plinking, informal target shooting).
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