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Posted: 9/10/2010 2:20:29 PM EDT
I finally got everything to put my build together and havving an issue. I have a 20 inch BCM heavy contour SS barrel( rifle lenght gas tube) and a browells(YHM) quad rail gas block. I ordered a .750 gas block as thats what was on bravo co website spec. I did mike and everything and its .750. Issue I have is Gas block cant go far enough on barrel to be where it is supposed to be. I ordered a rifle lenght gas tube measures out to approx 13 1/2 inches. Im over an inch short on the gas tube, it wont even make into upper And where the gas block sits doesnt look right either it butts up to the the next step increase .850 in the barrel. it's way too far out from quad rail. quad rails in the Spikes BAR. My barrel and hole location look same as in their website. HELP me pull my head out rear. what am I doing or thinking worng. THANK YOU!
Link Posted: 9/10/2010 2:25:26 PM EDT
[Last Edit: 9/10/2010 2:27:00 PM EDT by RLR350]
If I understand you right, you got the gas block to line up with the hole in the barrel. If so, what is the distance from the gas hole to the end of the barrel? How long is the gas tube you have? I see you measured it t at 13.5".
Link Posted: 9/10/2010 2:35:19 PM EDT
[Last Edit: 9/10/2010 2:48:13 PM EDT by RLR350]
Forget it. Your gas tube is too short. It is longer than a mid length, but shorter than a rifle length. The gas tube should measure about 15" for a rifle length.

I think there is an intermediate length tube/system. It sounds like the tube you have may be for that since it's not for the mid or rifle.

ETA:

These are approximate lengths - I roughly measured them on rifles.

Carbine: 9.75
Mid: 11.5
Rifle: 15
Link Posted: 9/10/2010 2:51:21 PM EDT
Do you have the gas block installed in the right direction?
Link Posted: 9/10/2010 6:43:07 PM EDT
I was wondering about the 13 1/2 but I couldnt find any reference for rifle length. Only reference I found for was mid length and it was shorter than 12 and I have only built carbines in past. Well at least Im pretty sure I was sent wrong gas tube. Still dont like way gas block sits and wondering if barrel step isnt off. Hopefully thats all that it is. Hoping I can find someone to bore front 1/4 half of hole for gas block. fit will be exactly like I want it then. I miss having access to mills and lathes. at least I can put the lower together tongiht. If I ever figure out how to post pictures Ill post em. I hate way its set up here.
Link Posted: 9/10/2010 6:48:27 PM EDT
From photobucket you can copy the URL and paste it in the text.

For URL's from other places, copy the URL, hit the third button from the bottom (a map) and post the URL in the instruction box. Use "preview" to see if it posted right before submitting.

I'm interested in seeing pictures of what you are talking about. But at least you know one part of the problem is just the wrong tube. Good luck with it.
Link Posted: 9/10/2010 7:06:17 PM EDT
Post pics.

The gas block is not supposed to abut against the barrel step. Remember the space for the handguard cap. Even if you do not use it, you need to account for this "gap".
Link Posted: 9/10/2010 8:36:47 PM EDT
the gap between my quad rails and gas block is hughe. the barrel has several steps in it going from heavy, .850 to .750 I just finished lower so I'll play around with photos.
Link Posted: 9/10/2010 8:58:29 PM EDT




the gas block cannot go any closer to the rail becaise of the step. I have the tube lined up where it would be to be pinned into gas block(the hole is in .750 section of barrel). WIth everything the way it is the gas tube wouldnt even be in the gun.
Link Posted: 9/10/2010 9:00:21 PM EDT
[Last Edit: 9/10/2010 9:02:20 PM EDT by mdillon]

Link Posted: 9/11/2010 3:35:12 AM EDT


Get this tube (scroll down to about the middle of the page) and forget the one you have, it's either a middy tube, or is out of spec, either way it's a back scratcher from now on.
Before you take a rotary drill/lathe/millin machine/or kitchen knife to your gun, check the positioning of you GB. Here is how it should look like.




No way around it, ill let someone else chime in here, but if you can't get to that point with the GB (without effort) and the GB is a set screw type, you bought the wrong one.

By the way, we have the exact same barrel.

J
Link Posted: 9/11/2010 5:15:35 AM EDT
JAVO explained it. You definitely need the right gas tube. The barrel contour just has an extra step.

I'd consider changing that railed gas block to a low profile like JAVO has. YHM makes a decent one for a good price or a Vltor silver one would work well, too.

Good luck with the rest of the build. That is a nice looking barrel.
Link Posted: 9/11/2010 5:21:37 AM EDT
Originally Posted By RLR350:
JAVO explained it. You definitely need the right gas tube. The barrel contour just has an extra step.

I'd consider changing that railed gas block to a low profile like JAVO has. YHM makes a decent one for a good price or a Vltor silver one would work well, too.

Good luck with the rest of the build. That is a nice looking barrel.


That GB is the YHM Lo pro set screw. They can be had for around 20 bucks. No frills solid unit.

Got it from BCM with the SS410, they are currently out of stock. PK firearms got em' (here)

GET THE .750

J
Link Posted: 9/11/2010 5:51:33 AM EDT
Those are pretty hard to beat for simplicity, function and price. I'v used several and even sacrificed one for a dimpling jig.

I'm assuming those are 11" rails. If you want to close the gap, a 12" raill will go up to tha GB. It will take a 13.5" or so to cover the GB. Here is a silver Vltor GB (basically the same design as the YHM) on a SS barrel with a 12" tube.

Link Posted: 9/11/2010 5:58:05 AM EDT
Originally Posted By RLR350:
Those are pretty hard to beat for simplicity, function and price. I'v used several and even sacrificed one for a dimpling jig.

I'm assuming those are 11" rails. If you want to close the gap, a 12" raill will go up to tha GB. It will take a 13.5" or so to cover the GB. Here is a silver Vltor GB (basically the same design as the YHM) on a SS barrel with a 12" tube.

http://i369.photobucket.com/albums/oo134/rlr350/IMG_2301.jpg


In my case, i like having the gap, FWIW gives me mental peace that should something happen with the GB, i can check what it is quickly. Also the second i see a KAC Flip-up/GB SAM-R sight im jumping on it.

J
Link Posted: 9/11/2010 6:27:02 AM EDT
Agreed. The low profile one looks good that way and is easier to get to should the need arise. The set screwed, railed one doesn't look right and just asks for something to smack it out of alignment, especially if a front sight is installed on it. I guess I'm not a big fan of the railed ones, gap or no gap, when there are better options. But, in the end, they all will work.
Link Posted: 9/11/2010 6:41:14 AM EDT
[Last Edit: 9/11/2010 6:46:38 AM EDT by mdillon]
Where did you get gas tube? only thing I can find is some maufactures do make differet length rife length gas tubes but no one lists sizes. Somewhere between 13 1/2 to 15 1/2 on spec charts is what I have found, but charts didnt list manufactures. Theres nothing wrong with the gas block I have. I'd just like to bore out about the front quarter of it and put an .850 step so it sits closer to quad. Three screw hold it in place and barrel is dimpled for screws. I went with it because I have a piece that screws into bottom of block and locks the gas block/barrel screw screws into place. I dont have any intention of using gas block for sight. I saw design and figured with my luck and murpheys law one less thing I have to worry about backing out. Otherwise it would have been exactly what's sitting on yours. what kind of accuracy are you getting out of the barco co barrel and fav bullets yet?. Thanks,
Link Posted: 9/11/2010 7:06:03 AM EDT
Your gas port is already drilled in the barrel. The gas block has to sit over it in order for the weapon to function. Simply drilling out the bore of the gas block and moving it back would require you to drill a new gas port and covering the old one - which is not even practical. Basically, you are stuck with the position the barrel was designed for, which in your case is rifle length.

Gas blocks are mostly a personal preference. What you are doing is fine, you just need to order a rifle length gas tube. Here is one in stock. Here is another. Don't let the 12" measurement on the GTS site confuse you - they are using the common length of a rifle hand guard, not the actual length of the tube. That rifle tube will be about 15 3/16" long.

Unfortunately, you got an oddball gas tube which screwed up the process from the start. Do what you were doing, just get the proper tube.
Link Posted: 9/11/2010 9:04:33 AM EDT
I called Rguns they said had em n stock and they were over 15 inches, Guna stop on way to work and grab one. Thanks for help, Just annoying thought I had everything squared away before I started.
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