View Full Version : Questions About Parts For My Next Rifle
I've assembled 3 lowers before but not ever an upper, this will be the first. With the previous rifles I bought a barreled upper, complete upper, and had a gunsmith assemble one.
Here is a list of parts I have already purchased
Geissele 15" MK16 Blem
Geissele 16" CHF barrel
LMT forged upper receiver
LMT BCG
LMT Buffer and Tube
My questions: Do I need to pin the gas block? If I just use 2 screws with locktite, do I need to put another dimple in the barrel? It only comes with one dimple. I almost got a Daniel Defense barrel because it comes pre pinned with gas block for the same price as the stripped Geissele barrel, But I like the contour on the tapered Geissele better that the DD barrel. The DD barrel looks like it has more weight out towards the muzzle.
Also I have an H buffer, any recommendations on which spring to buy?
If I get a LMT MARS stripped lower can I use a Sionics Enhanced LPK. I understand there are some proprietary parts that I think would come on the lower. Thanks in advance for any advice.
You can use the two screws and blue Loctite with just one dimple. I’d recommend finding screws that have the little teeth on the end, if not already equipped. That would be adequately attached. You can also pin it for increased peace of mind. You already have a gas block and tube, and pins?
I’d try a regular Colt spring from Brownells, or wherever.
I think you need an extra bolt release and pin with the MARS, don’t remember for sure.
You can use the two screws and blue Loctite with just one dimple. I’d recommend finding screws that have the little teeth on the end, if not already equipped. That would be adequately attached. You can also pin it for increased peace of mind. You already have a gas block and tube, and pins?
I’d try a regular Colt spring from Brownells, or wherever.
I think you need an extra bolt release and pin with the MARS, don’t remember for sure.
I don't have a gas block and tube yet. If I do pin the gas block I would have a gunsmith do it, but I would prefer to just use the screws if that's a solid connection. I think I can put another dimple myself if that would make it better than one dimple.
I don't have a gas block and tube yet. If I do pin the gas block I would have a gunsmith do it, but I would prefer to just use the screws if that's a solid connection. I think I can put another dimple myself if that would make it better than one dimple.
One dimple is best, because different brands of blocks use different spacing. Of course, if thats not important to you, you could use a dimpling jig to place a second dimple, but at that point you could pin it just as easily.
With the Mk16 rail, you’ll want a very small gas block.
One dimple is best, because different brands of blocks use different spacing. Of course, if thats not important to you, you could use a dimpling jig to place a second dimple, but at that point you could pin it just as easily.
With the Mk16 rail, you’ll want a very small gas block.
Ok thanks. Any suggestions for which brand of gas block would be good? BTW I just got the blem G rail and I am so happy. The only thing wrong with it, is the T mark numbers on the top of the rail are not white. Atleast that's the only thing I can see wrong with it. Other than that it looks perfect and paid half price for it.
Sidneyious
03-01-23, 18:49
You should be able to find a G$ gas block that is known to fit for sure.
Buffer spring? springco blue.
I dont know shite about the mars lower.
titsonritz
03-01-23, 19:01
My G handrails came with one of their gas blocks. As mentioned above, one dimple opposite the gas port is what you want to do. If you need knurled set screws PM me your shipping address, I have more than I'll ever use and can spare a few. Degrease everything and use red Loctite. I'd go with and H2 but an H will work, Colt action spring or Sprinco Blue spring, is what I use on my non-A5 guns.
The LMT-MARS lower comes with their proprietary parts including selector, magazine release and bolt catch and release, the rest of parts can be used from your LPK. I probably would not split up a LPK, but I have multiples of looses parts. I'd buy a FCG and pivot/takedown pin set, you can buy misc small parts from several places.
https://www.forwardcontrolsdesign.com/asf-small-parts-kit.html
https://www.forwardcontrolsdesign.com/AR15-detents-and-small-parts-kit_p_115.html
https://www.forwardcontrolsdesign.com/AR15-Springs-Kit_p_113.html
These are the parts in an ELPK
1- SIONICS Enhanced Trigger
1- Semi Auto Disconnect
1- SIONICS Enhanced Hammer
2- Hammer / Trigger Pin
1- Trigger Spring
1- Hammer Spring
1- Disconnector Spring
1- Ambidextrous Safety Selector Long on left side and Short on right side.
1- Safety Detent
1- Safety Detent Spring
1- Standard Bolt Catch
1- Bolt Catch Plunger
1- Bolt Catch Roll Pin
1- Bolt Catch Spring
2- Takedown / Pivot Spring
2- Takedown / Pivot Detent
1- Takedown Pin
1- Pivot Pin
1- Mag Catch
1- Mag Release Button
1- Magazine Catch Spring
1- Buffer Retainer Pin
1- Buffer Retainer Spring
You can see by crossing off the FCG, TD/pivot pin and proprietary parts not much is left.
My G handrails came with one of their gas blocks. As mentioned above, one dimple opposite the gas port is what you want to do. If you need knurled set screws PM me your shipping address, I have more than I'll ever use and can spare a few. Degrease everything and use red Loctite. I'd go with and H2 but an H will work, Colt action spring or Sprinco Blue spring, is what I use on my non-A5 guns.
The LMT-MARS lower comes with their proprietary parts including selector, magazine release and bolt catch and release, the rest of parts can be used from your LPK. I probably would not split up a LPK, but I have multiples of looses parts. I'd buy a FCG and pivot/takedown pin set, you can buy misc small parts from several places.
https://www.forwardcontrolsdesign.com/asf-small-parts-kit.html
https://www.forwardcontrolsdesign.com/AR15-detents-and-small-parts-kit_p_115.html
https://www.forwardcontrolsdesign.com/AR15-Springs-Kit_p_113.html
These are the parts in an ELPK
1- SIONICS Enhanced Trigger
1- Semi Auto Disconnect
1- SIONICS Enhanced Hammer
2- Hammer / Trigger Pin
1- Trigger Spring
1- Hammer Spring
1- Disconnector Spring
1- Ambidextrous Safety Selector Long on left side and Short on right side.
1- Safety Detent
1- Safety Detent Spring
1- Standard Bolt Catch
1- Bolt Catch Plunger
1- Bolt Catch Roll Pin
1- Bolt Catch Spring
2- Takedown / Pivot Spring
2- Takedown / Pivot Detent
1- Takedown Pin
1- Pivot Pin
1- Mag Catch
1- Mag Release Button
1- Magazine Catch Spring
1- Buffer Retainer Pin
1- Buffer Retainer Spring
You can see by crossing off the FCG, TD/pivot pin and proprietary parts not much is left.
Thanks for the offer on the screws. I will let you know if I need them.
I have a BCM gas block under a MK8 and a Geissele under a MK4, and they both leave plenty of clearance. Once a gas block is installed, I see absolutely no reason to replace it with another brand's block...so any barrel that uses set screws has 2 dimples.
If you're mechanically inclined and buy a block with BCM spacing, I'll let you borrow my BRD dimple jig.
Ok thanks. Any suggestions for which brand of gas block would be good? BTW I just got the blem G rail and I am so happy. The only thing wrong with it, is the T mark numbers on the top of the rail are not white. Atleast that's the only thing I can see wrong with it. Other than that it looks perfect and paid half price for it.
Myself, I'm sold on these: https://geissele.com/super-gas-block-black.html
I agree that $80.00 might be a little steep, but they are foolproof to install.
Back when ALGDefense had a separate site, she sold a carbon steel Super Gas Block for less and that is what I have always used. (ALG stands for Alice L. Geissele in case you didn't know)
Here are the instructions so you can see how simply it is:
https://geissele.com/amfile/file/download/file/9317aa42f90e53a906015028af61719d/product/42/
Spikes, of all people, sell a nice dimple jig that is set up to take set screw spacing from any variation out there. It has come in handy on more than one occasion. Only complaint is the bit that comes with it dies a quick death
Ok thanks. Any suggestions for which brand of gas block would be good?
I’ve only used a handful of brands gas blocks, but BRT is the smallest, and IIRC, Ballistic Advantage is small, too. The G model is fairly large, but I’d imagine it works. BRT and G pin easily with a drill press, although I haven’t tried the nitrided G version, only the stainless. If the barrel comes with a gas block, I’d test fit it with the rail before buying or drilling anything.
Is the barrel nitrided?
One More Time
03-02-23, 10:14
One dimple with knurled screws will be sufficient, it's under the rail so it's not likely to get bumped.
Not sure what a smith would charge to pin it.
If you get a BCM gas block you could do it yourself for $145
https://brdengineering.com/products/gas-block-pro-drilling-jig-a-0750-vltorbcmranier
Universal gas block jig is $185
https://brdengineering.com/products/2aumk4-universal-gas-block-drilling-jig
Sell it off after you use it a couple of times and it's sorta like renting it.
Hammer_Man
03-02-23, 10:23
Double post
Hammer_Man
03-02-23, 10:31
If you buy the BRD jig to pin your own gas block, you’ll also need to buy a taper reamer to fit the taper pins. I believe the correct size is a number 2 taper reamer.
If you want to pin your gas block, I would recommend the Geissele gas block. It uses a straight coil pin, and is pretty simple to do, you just need a decent drill press.
gunnerblue
03-02-23, 10:33
As others have said, one set screw in a dimple with adhesive is sufficient. I wouldn't use blue loctite, though, as it is not heat resistant. Red loctite handles heat better but can be difficult to remove. Rockett has been my preference because it's resistant to heat but can still be easily removed.
One More Time
03-02-23, 10:40
From BRD
"5/32" is the standard pin for the Geissele gas block. #31 provides a base hole to ream to fit 1/8" diameter coiled roll pins, 1/8" dowel pins or 2/0 taper pins"
The BCM block comes with a #31 bit and bushing for an 1/8" coil pin
The universal comes with both bits and bushings.
Both will need to be reamed to size, straight and tapered.
BRD has those as well.
One More Time
03-02-23, 10:53
BRD Universal demonstration, using a cordless drill.
Looks like the end mill bit he mentions at the start will be needed also.
Some simple math and a steady hand gets it done, looks easy enough.
https://youtu.be/E2n5wrc73fQ
I’ve only used a handful of brands gas blocks, but BRT is the smallest, and IIRC, Ballistic Advantage is small, too. The G model is fairly large, but I’d imagine it works. BRT and G pin easily with a drill press, although I haven’t tried the nitrided G version, only the stainless. If the barrel comes with a gas block, I’d test fit it with the rail before buying or drilling anything.
Is the barrel nitrided?
Primary Arms where I got it says manganese phosphate CHF 1/7. It did not come with a gas block. I still need to purchase one. I really am so happy with the G rail blem. No dings or scratches at all.
I have a BCM gas block under a MK8 and a Geissele under a MK4, and they both leave plenty of clearance. Once a gas block is installed, I see absolutely no reason to replace it with another brand's block...so any barrel that uses set screws has 2 dimples.
If you're mechanically inclined and buy a block with BCM spacing, I'll let you borrow my BRD dimple jig.
Thank you for the offer. I will let you know if I need it.
BCM uses Loctite 272 and 10-14 in-lbs on the gas block set screws.
BCM uses Loctite 272 and 10-14 in-lbs on the gas block set screws.
Do their factory rifles have 2 dimples and no pin?
I could put the gas block on with one screw and then use a transfer punch to locate where to drill the second dimple. Don't think I really need a jig. I was a millwright for years. I would not attempt to pin the barrel with the tools that I have.
Do their factory rifles have 2 dimples and no pin?
1 dimple opposite the gas port and no pin.
titsonritz
03-02-23, 19:44
I could put the gas block on with one screw and then use a transfer punch to locate where to drill the second dimple. Don't think I really need a jig. I was a millwright for years. I would not attempt to pin the barrel with the tools that I have.
Use two screws, one in the dimple and one w/o a dimple.
Use two screws, one in the dimple and one w/o a dimple.
Sounds like that is the way to go.
I could put the gas block on with one screw and then use a transfer punch to locate where to drill the second dimple. Don't think I really need a jig. I was a millwright for years. I would not attempt to pin the barrel with the tools that I have.
I have a jig but never use it. Just get the correct bit. From Geissele instructions:
Spot drill barrel. Using a 135 deg split point #25 drill such
as McMaster-Carr PN: 28765A75 spot drill the barrel
through the open setscrew hole. A hand drill works well
for this step. All that is needed is a dimple so that the
setscrew enters into the dimple and does not pull up
proud bumps when tightened. It also keeps the setscrew
in shear from any axial or radial loads applied to the gas
block in service. Blow out chips from drilling and install
and tighten the 2nd set screw. Now remove the 1st set
screw and dimple the barrel through that hole. Re-install
the 1st setscrew. Re-check gas tube alignment. It is
permissible to use a locking compound such as Loctite
Blue on the setscrews
I drill and pin using a Grizzly drill press and an Irwin drill press vise. The coil pin Geissele furnishes is nice.
As far as gas blocks go, these are excellent https://www.midwayusa.com/product/1022268021
Thanks everyone for all the advice. When it comes time to assemble this rifle, I will get a lot of useful information from this thread. BTW I bought a stripped LMT MARS lower today.
I recognize a man of class.
I recognize a man of class.
I don't know about that but I just want rifle parts atleast the quality of the Colt and FN rifles that I used in the Army. Also I don't need to worry about SBR or pistol braces. 16" barrel is just right for me. I've heard it said that 16" is too long to do anything with. So many people now days want the shortest barrel they can get and all their powder to burn on the outside of their barrel. I was kicking in doors and clearing rooms in Iraq with 20" muskets and a flashlight before we got M4. I really really like 16" and will probably put an ACOG on this rifle.
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