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Posted: 10/11/2007 5:33:17 PM EDT
I would like to do a 605 clone.
I would like to use ALL Colt parts and make it correct as possible(except for the NDS lower and semi auto FCG).

I have talked to 45Bravo about it a bit and have concearns about reliability with the gas system.

I know I can use the Bushy dissapator barrel (midlength gas system) and cut it to correct length, but, again I want it to be as original as possible.

Any ideas?

Worst case is that I will build it, and have it as a wall hanger if the recipe cant work.

This will be a SBR build.

Link Posted: 10/11/2007 6:01:48 PM EDT
Coctailer,

Great Minds think alike

I have two barrels that 45Bravo is working on right now. You may check with him again, I sent him some ammo with the barrels so he could fine tune the gas port size. He has been able to get both of them to function well in the original 605 lenght and gas system. He is aslo permanetly pinning the 3-prong flash hider on them so the total lenght will be 16"

I should have everything back soon to assemble on a NDS lower with a real 605 upper receiver with the milled off forward assist. Will definatly post pics.

Good luck with your 605 build...fell in love with that model after member tgus posted pics of the real deal he bought.

Link Posted: 10/11/2007 6:14:28 PM EDT
you could also go with a dedicated .22LR barrel cut to look like a 15" .223 barrel(605 style), but will be 16" legal because of the chamber setback...just another option
Link Posted: 10/11/2007 6:27:52 PM EDT

Originally Posted By Critical-Mass:
Coctailer,

Great Minds think alike

I have two barrels that 45Bravo is working on right now. You may check with him again, I sent him some ammo with the barrels so he could fine tune the gas port size. He has been able to get both of them to function well in the original 605 lenght and gas system. He is aslo permanetly pinning the 3-prong flash hider on them so the total lenght will be 16"

I should have everything back soon to assemble on a NDS lower with a real 605 upper receiver with the milled off forward assist. Will definatly post pics.

Good luck with your 605 build...fell in love with that model after member tgus posted pics of the real deal he bought.



Can't wait for the pics and range report.

I have a couple of the "milled off" recievers and all of the other parts.
I'm excited about this build.

Gunna have to use one of my M VP 12 barrels for the build. Kinda hate cutting it though.



Link Posted: 10/11/2007 6:35:32 PM EDT

Originally Posted By gunnut003:
you could also go with a dedicated .22LR barrel cut to look like a 15" .223 barrel(605 style), but will be 16" legal because of the chamber setback...just another option

Good idea. I'm big into .22 right now.
Damn you for giving me an idea for another build!!!!!

Still wanna make it as absolutely correct as possible.
Link Posted: 10/11/2007 6:38:06 PM EDT

Originally Posted By Critical-Mass:
Coctailer,

Great Minds think alike

I have two barrels that 45Bravo is working on right now. You may check with him again, I sent him some ammo with the barrels so he could fine tune the gas port size. He has been able to get both of them to function well in the original 605 lenght and gas system. He is aslo permanetly pinning the 3-prong flash hider on them so the total lenght will be 16"

I should have everything back soon to assemble on a NDS lower with a real 605 upper receiver with the milled off forward assist. Will definatly post pics.

Good luck with your 605 build...fell in love with that model after member tgus posted pics of the real deal he bought.



On a 605 with pinned FH, won't the barrel length be 1/2" too short if I make it original length?
I thought the barrel had to be cut a hair longer to be 16"
Link Posted: 10/11/2007 6:39:36 PM EDT
[Last Edit: 10/11/2007 6:40:57 PM EDT by Morg308]
The 605 had a lot of reliability problems, because of the gas system, which is probably why the carbine length gas system came about. I opted for a fluted Bushy Dissipator barrel I got here off the EE. If it's not quite original, it should at least run well. I have no room for weapons that don't function. I have heard that some people have gotten the rifle length gas system to run pretty well, but I understand that air density, in other words temp and humidity are big factors in their reliability. I'm building this as if my life may someday depend on it - the only way to build a gun IMO. Just my .02

Oh, and I think the Bushy barrel has a carbine length gas system, although CMMG makes both middy and carbine 'dissipator' barrels.

Link Posted: 10/11/2007 6:45:02 PM EDT
I have tried building several and can't get any to be reliable below 50 degrees Fahrenheit. Let me know if you get a working solution.
Link Posted: 10/11/2007 6:48:04 PM EDT

Originally Posted By Morg308:
The 605 had a lot of reliability problems, because of the gas system, which is probably why the carbine length gas system came about. I opted for a fluted Bushy Dissipator barrel I got here off the EE. If it's not quite original, it should at least run well. I have no room for weapons that don't function. I have heard that some people have gotten the rifle length gas system to run pretty well, but I understand that air density, in other words temp and humidity are big factors in their reliability. I'm building this as if my life may someday depend on it - the only way to build a gun IMO. Just my .02

Oh, and I think the Bushy barrel has a carbine length gas system, although CMMG makes both middy and carbine 'dissipator' barrels.



Exactly what I heard.
On this build I am going for form over function. It would be nice to have both.
If I must choose..............It will be correct even if it wont run reliably.
Kinda silly from a practical point, but I have a dream...............
Link Posted: 10/11/2007 6:52:58 PM EDT

Originally Posted By uxb:
I have tried building several and can't get any to be reliable below 50 degrees Fahrenheit. Let me know if you get a working solution.


When you opened up the ges port, did you do it to the FSB also? I thought that may be the key.
Link Posted: 10/11/2007 7:14:15 PM EDT

Originally Posted By Critical-Mass:
Coctailer,

Great Minds think alike

I have two barrels that 45Bravo is working on right now. You may check with him again, I sent him some ammo with the barrels so he could fine tune the gas port size. He has been able to get both of them to function well in the original 605 lenght and gas system. He is aslo permanetly pinning the 3-prong flash hider on them so the total lenght will be 16"

I should have everything back soon to assemble on a NDS lower with a real 605 upper receiver with the milled off forward assist. Will definatly post pics.

Good luck with your 605 build...fell in love with that model after member tgus posted pics of the real deal he bought.



Indeed, I have had success with the two barrels that Critical-Mass sent me. I was concerned as the one I did originally didn't run but then I never could get the pins out to remove the FSB. The pins were rusted in place, it's an old Sarco barrel.

I will make a measurement next time I'm at the shop and let you all know what the port size is that I used. I can't remember right now.

I chopped the lugs and turned the barrel back, threaded, and will pin and weld on the three prongs sometime after a short weekend vacation. I'll see if I can get some pics up soon.

Now, for the down and dirty. Between the two barrels I fired 60 rounds of Malaysian 55 grain and 60 rounds of LC 01 M855 green tip 62 grain ammo.

I had only one malfunction out of each barrel, both with the 55 grain ammo. The Colt barrel had one failure to eject. Easily cleared by utilizing SPORTS. The CMMG barrel had one failure to feed, which could have been magazine related, but not likely. Both barrels worked flawlessly with 62 grain ammo.

When shooting on semi the recoil was very soft on both barrels with 55 grain ammo. It wasn't much stouter with 62 grain ammo and was still less than with the 20 inch barrel. The biggest difference was noticed when shooting full auto. The cyclic rate was much slower with 55 grain ammo than it was with 62 grain ammo.

My thoughts are that this would be a fairly reliable system when using full power military ammunition. Reloads, commercial, and some surplus just might not cut it.

Anyway, I hope that I'll be able to give you guys an update sometime in the near future. I will probably leave the photos to Critical-Mass as these are his projects.
Link Posted: 10/11/2007 7:26:49 PM EDT
[Last Edit: 10/11/2007 7:27:02 PM EDT by Kalahnikid]
Ive posted this picture before for the guys interested in the 605

It ran 100%, custom work done by KKF.

Link Posted: 10/11/2007 7:28:36 PM EDT

Originally Posted By uxb:
I have tried building several and can't get any to be reliable below 50 degrees Fahrenheit. Let me know if you get a working solution.


I know it won't be visually correct, but there was a vendor here a couple years back who was developing & marketing an adjustable gas tube...it had a kind of needle valve that was externally adjustable...you would open up the barrel orifice/sight base port and fit the adjustable tube w/Allen key adjustable valve...it was mostly hidden under the handguard...

Has anyone tried this system??? I've been away a while and don't recall who it was who had it...

Sounded worth a try, though...
Link Posted: 10/11/2007 7:30:38 PM EDT

Originally Posted By postino:

Originally Posted By uxb:
I have tried building several and can't get any to be reliable below 50 degrees Fahrenheit. Let me know if you get a working solution.


I know it won't be visually correct, but there was a vendor here a couple years back who was developing & marketing an adjustable gas tube...it had a kind of needle valve that was externally adjustable...you would open up the barrel orifice/sight base port and fit the adjustable tube w/Allen key adjustable valve...it was mostly hidden under the handguard...

Has anyone tried this system??? I've been away a while and don't recall who it was who had it...

Sounded worth a try, though...


Hmmm, thats interesting
Link Posted: 10/11/2007 7:50:52 PM EDT
[Last Edit: 10/11/2007 8:16:55 PM EDT by coctailer]

Originally Posted By postino:

Originally Posted By uxb:
I have tried building several and can't get any to be reliable below 50 degrees Fahrenheit. Let me know if you get a working solution.


I know it won't be visually correct, but there was a vendor here a couple years back who was developing & marketing an adjustable gas tube...it had a kind of needle valve that was externally adjustable...you would open up the barrel orifice/sight base port and fit the adjustable tube w/Allen key adjustable valve...it was mostly hidden under the handguard...

Has anyone tried this system??? I've been away a while and don't recall who it was who had it...

Sounded worth a try, though...


Was it Mack Gwinn from MGI?
Link Posted: 10/11/2007 8:54:07 PM EDT
Personally I don't think an adjustable gas port would do much for you, as you would need more gas, not less, so you wouldn't want to shut the port down, but be able to open it up. I guess it depends on what the adj. range was, and how big the port was originally. I totally respect wanting to build something that is as close to original, but mine will double as a KISS go-to weapon, so I didn't want to go that way.

Anyone who knows that a 605 didn't have a .750 journal at the FSB will spot mine as a 'fake' when it's done, but I can live with that. It's cool that you have the milled FA upper - I'm using a 604 upper for mine. (Apparently both types were used.) I've been kicking myself in the ass for not buying the 'weird' upper I saw at a gunshow a year or so ago (milled FA upper). Good luck with the build - These weapons are still very compact (34") light and simple. The 605 appeals to me a lot. Mine will be a little heavier because of the barrel, but no heavier than an M4, and essentially the same internally. Seems to balance well when I hold it in a mock-up. I'm essentially building a VN era weapon with the characteristics of an M4. I can't wait to see pics of your clone, and hear how the gas system works out for you.
Link Posted: 10/12/2007 3:59:02 AM EDT
[Last Edit: 10/12/2007 4:55:47 AM EDT by Critical-Mass]

Originally Posted By coctailer:

On a 605 with pinned FH, won't the barrel length be 1/2" too short if I make it original length?
I thought the barrel had to be cut a hair longer to be 16"


No problem, here is a side by side comparison. The bottom is a Colt 20" barrel, the one on the top is a standard 16". Even without the split ring washer, the 3-prong will bring total length to 16 1/4 or more when permanently pinned tight against the FSB like the original.

If the flash hider is permanently mounted, it is included/added to the barrel lenght. Might as well save 200.00 if you can test for function on a RR or SBR before pinning and welding. (would be a great retro-build for non SBR states)




Below, gun and photo credit; Member tgus-original 605B



Link Posted: 10/12/2007 5:10:55 AM EDT
Link Posted: 10/12/2007 6:21:12 AM EDT
Anybody have a picture or link to this milled 605 upper ...I have never seen one.
Link Posted: 10/12/2007 6:28:25 AM EDT
[Last Edit: 10/12/2007 9:15:38 AM EDT by postino]

Originally Posted By coctailer:
Was it Mack Gwinn from MGI?


Pretty close...It was Tom Lyons from MGI...

www.mgimilitary.com/gastube.htm



And it's stocked in Brownell's catalog, pg 55, as -

AR-15/M16 REGULATED GAS TUBE

www.brownells.com/aspx/NS/store/productdetail.aspx?p=9947&st=AR-15/M16%20REGULATED%20GAS%20TUBE&s=

741-000-001
Rifle Gas Tube $59.95

741-000-002
Carbine Gas Tube $59.95


The point made above by Morg308 about opening up the gas port is a valid one. There was discussion here at that time (back in '05) that you needed to open up both the barrel orifice/gas port to the same diameter as the tube, which seems to be ~.120" on the gas tube I just grabbed, to get increased gas flow, and *then* regulate it with the valve.
Link Posted: 10/12/2007 8:24:03 AM EDT
Just a wild idea.....

But what about moving the gas port back under the handguards and making a very compact clamp on gas block with a regulator built in. It could be hid under the handguards no?
Link Posted: 10/12/2007 9:38:53 AM EDT

Originally Posted By rotchooah:
Anybody have a picture or link to this milled 605 upper ...I have never seen one.


Here you go
This is also member tgus rifle and photo.


Link Posted: 10/12/2007 10:35:34 AM EDT

Originally Posted By Critical-Mass:
Here you go
This is also member tgus rifle and photo.


That's a Colt upper; correct??? Did they mill the FA off *before* the rest of the machining, or is there a plug in the FA that is machined off *with* the FA after final machining (or during arsenal refinishing or whatever)???
Link Posted: 10/12/2007 10:40:40 AM EDT
[Last Edit: 10/12/2007 10:41:40 AM EDT by uxb]
Milled off when the rest of the forging was finished into the receiver.
Link Posted: 10/12/2007 8:49:52 PM EDT
[Last Edit: 10/12/2007 8:53:58 PM EDT by Morg308]

Originally Posted By Heatnbeat:
Just a wild idea.....

But what about moving the gas port back under the handguards and making a very compact clamp on gas block with a regulator built in. It could be hid under the handguards no?


Good idea, but if you shorten the gas system enough to get it under the HGs (as Bushmaster & CMMG have done for example) You already essentially have a carbine, which will run well without work. An adjustable gas system, ala FAL would cure the 'overgassing' on M4 carbines, but that's already been cured with heavier buffers or 'enhanced' BCG. FWIW the rifle buffer which would be used on a 605 clone is already a 'heavier' buffer, and I plan on using an LMT enhanced BC.

I think however that the OP's desire is to have something as close to original as possible, in which case you end up opening up the gas port - but I still think that's a poor excuse for having enough barrel in front of the port to create anough pressure.

One thing I wondered about was using a lighter buffer in a cut-down 20" - in other words, modify a carbine length buffer tube, with longer screw and spacer - probably custom made, in order to cycle the action better with less dwell time. I think this is really a 'lesser' way to do it, but if you were looking to keep the look original, it might just work. You'd have to have a TIG on hand to modify the receiver extension properly though - to add a nut to the end. Very fine wire, low heat. Welding a nut on a buffer tube would be no biggy for most guys here though. A spacer should be even easier. I am not going to drag out anything to measure, but it sure would be convienient if a standard A2 spacer would fill the void between a CAR tube and an A1. This in conjunction with a slightly bigger gas port might be the answer - after all, you have to fill less space with gas using a carbine extension, not to mention the lighter buffer (standard carbine buffer) Just a thought after several beers...
Link Posted: 10/12/2007 8:52:14 PM EDT
Is there a reason you cant use a Dissy barrel and install a low-profile gasblock?
Link Posted: 10/12/2007 8:57:32 PM EDT

Originally Posted By Kalahnikid:
Is there a reason you cant use a Dissy barrel and install a low-profile gasblock?


I think he wants it as original as possible. FWIW, I agree with you - that's my route, but each to his own. I can understand wanting everything to be 'right'. No different than having the right bolt release on a 601 clone. Boy, this forum has come a long way!

God is in the details - does that apply to retro rifles?
Link Posted: 10/12/2007 9:21:52 PM EDT

Originally Posted By Morg308:

Originally Posted By Kalahnikid:
Is there a reason you cant use a Dissy barrel and install a low-profile gasblock?


I think he wants it as original as possible. FWIW, I agree with you - that's my route, but each to his own. I can understand wanting everything to be 'right'. No different than having the right bolt release on a 601 clone. Boy, this forum has come a long way!

God is in the details - does that apply to retro rifles?


Well, they were scrapped because they wouldnt run worth a shit. Might as well go dissy style, IMHO. Each to their own though.

And yes, this forum rocks!
Link Posted: 10/13/2007 8:10:46 AM EDT

Originally Posted By Morg308:

Originally Posted By Heatnbeat:
Just a wild idea.....

But what about moving the gas port back under the handguards and making a very compact clamp on gas block with a regulator built in. It could be hid under the handguards no?


Good idea, but if you shorten the gas system enough to get it under the HGs (as Bushmaster & CMMG have done for example) You already essentially have a carbine, which will run well without work. An adjustable gas system, ala FAL would cure the 'overgassing' on M4 carbines, but that's already been cured with heavier buffers or 'enhanced' BCG. FWIW the rifle buffer which would be used on a 605 clone is already a 'heavier' buffer, and I plan on using an LMT enhanced BC.

I think however that the OP's desire is to have something as close to original as possible, in which case you end up opening up the gas port - but I still think that's a poor excuse for having enough barrel in front of the port to create anough pressure.

One thing I wondered about was using a lighter buffer in a cut-down 20" - in other words, modify a carbine length buffer tube, with longer screw and spacer - probably custom made, in order to cycle the action better with less dwell time. I think this is really a 'lesser' way to do it, but if you were looking to keep the look original, it might just work. You'd have to have a TIG on hand to modify the receiver extension properly though - to add a nut to the end. Very fine wire, low heat. Welding a nut on a buffer tube would be no biggy for most guys here though. A spacer should be even easier. I am not going to drag out anything to measure, but it sure would be convienient if a standard A2 spacer would fill the void between a CAR tube and an A1. This in conjunction with a slightly bigger gas port might be the answer - after all, you have to fill less space with gas using a carbine extension, not to mention the lighter buffer (standard carbine buffer) Just a thought after several beers...


I will be using an Edgewater buffer. They are very light.
Link Posted: 10/13/2007 2:55:16 PM EDT
Didn't colt use carbine buffers in each end of a rifle length spring and buffer tube in their .222 rem. AR's? Using the back buffer as a spacer? If so, it might be worth a try.
Link Posted: 10/13/2007 5:15:22 PM EDT

Wat do you think about this?
Opening the gas port, FSB, and gas tube entry hole.
Has this been tried?
Wouldn't Colt do this when they encountered problems in the first place?

Link Posted: 10/13/2007 7:02:05 PM EDT
I think it was the .gov that nixed the 605, not Colt. They did the same thing to the 607, 608, and 609

gas port in fssb is already plenty large enough.

I think you'll need a heaier buffer, not a lighter one. The idea is to slow down the bcg that is overaccelerated be violent pressure spike caused by the larger gas port.
Link Posted: 10/13/2007 7:27:33 PM EDT
I disagree....
I may be wrong, but I thought the pressure would be lighter than normal because of the length of the barrel in front of the gas port.
I think the BCG is going too slow with the 20"bbl port size.
Link Posted: 10/14/2007 6:54:54 AM EDT

Originally Posted By coctailer:
I disagree....
I may be wrong, but I thought the pressure would be lighter than normal because of the length of the barrel in front of the gas port.
I think the BCG is going too slow with the 20"bbl port size.


I agree - the problem is, there's not enough dwell time - the 605 is undergassed. That's why I thought a modified carbine receiver extension might help - less volume to fill. A light buffer would also help, as you're moving less mass. Just my .02

I'd like to hear Randall chime in on this one...
Link Posted: 10/14/2007 6:59:45 AM EDT
[Last Edit: 10/14/2007 7:01:15 AM EDT by ranchhand]
10" barrels have essentially the same measurement from gas port to muzzle. They too suffer from cycling issues. Once you open the gas port you have to add a heavier buffer. I know it seems counter-intuitive but that is the only fix.
Link Posted: 10/14/2007 7:37:45 AM EDT
I see what you mean now.

Now, I cant recall what the actuall symptons are on the 605. I assumed short stroking, due to not enough gas pressure.
Once the port is opened up, then it is over accelerating. What failure occurs then? FTE?

Link Posted: 10/14/2007 8:49:08 AM EDT

Originally Posted By ranchhand:
10" barrels have essentially the same measurement from gas port to muzzle. They too suffer from cycling issues. Once you open the gas port you have to add a heavier buffer. I know it seems counter-intuitive but that is the only fix.


I agree with the dwell time issue on the 10" vs the 605 but the gas pressure is much less at the front sight base on the 605 vs the 10" carbine.

The reason for the heavier buffer in the 10" carbine is because of the extreme bolt velocity with the high gas pressure. It is a fine balancing act between dwell time, gas pressure, buffer weight, recoil spring tension. The 605 having the shortest dwell time combined with lower gas pressure is the reason it is the most difficult to run reliably.

With the 10" carbine length, gas pressure in the barrel is still very high...but dwell time is short. Add another 5.5" to the barrel length with the 605 and gas pressure is reduced by 50% (in theory). The dwell time will be even less in the 605 because bullet velocity has increased with the longer barrel length.

Dwell time is better for reliability than gas pressure. The optimum setup for reliability is the 20" barrel with the gas port at the 15" mark. This give a gas-burst dwell time 500% greater or more over the 605 gas setup, with a low gas pressure that does not over accelerate the bolt.

The 10" and 605 systems can work well..but only if everything is in perfect balance. Start throwing in different ammo mixes, lower temperatures, and dirty field conditions, the setup is now out of balance and reliability will suffer.

I'm extremely pleased that 45Bravo has been able to get the two barrels I sent him to run reasonably well. I'm anxious to get everything together and do a review as soon as possible.

Link Posted: 12/1/2007 3:28:21 PM EDT
Great, now I'm starting to think I should have went ahead and bought the CAR or Midlength instead of the rifle system for my upper.
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