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Hello,
I just put two Varminter rifles together with the heavy 24” barrels. On one of them, I put a Magpul PRS lite and on the other a Magpul PRS Gen 3. The PRS lite is asking for a carbine length buffer and the Gen 3 a rifle length. I installed both as specified. I went to the range to test them on two occasions. The first time, I had no luck with any sort of cycling. I took them apart and checked what was recommended. The other trip, it was pretty much the same thing. I’m sure I’m under gassed because it always fails to eject or it fails to feed and or lock open. Everything else like the BCG, gas tube, and ammo checks out. I just ordered two Odin works adjustable buffers and will try to set the weights to function smoothly. Have any of you done this? With one rifle length buffer, I was planning on using the weights from the carbine buffer to adjust the rifle length since I can’t find an adjustable rifle length buffer anywhere and I’m hoping they’re interchangeable. Are there any tricks you can share? This is my first time assembling an AR and I was having a good time until this.
Thanks for the help.

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ALIGN the gas blocks. Hint.............


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Stick is correct, but didn't really provide much advice.

I use a drill bit to align the gas block and gas tube holes, I simply drop it down thru the set screw hole and install the roll pin.

Secondly, most gas block journals are designed for a pinned gas block/front sight and the corresponding handguard cap that is roughly .032" thick. I use a .032" feeler gauge to set that gap. I also dimple every barrel, except for nitrided barrels, too dang hard. Then I use Loctite 242 or 620 to bed and seal the gas block to barrel. This also seals the gas block to minimize any gas pressure loss.

Thirdly, I never use a standard H1 buffer or an adjustable gas block. I start with a H3 and I go up to a Slash's Heavy Buffer or move down to a H2 depending on ejection. I am anxious to try a new A5 style buffer kit, 308 carbine spring and a slightly longer and heavier buffer than the H3.

If I could find a clamp on style gas block that would fit under a slim handguard I would go that route.

I think you are gassed fine, I think your issue is the BCG cyclic speed. Too fast and it will fail to pick up the next round and lock back. The heavier buffers will slow down the BCG and greatly improve cycling.


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Originally Posted by Darryle
Stick is correct, but didn't really provide much advice.

I use a drill bit to align the gas block and gas tube holes, I simply drop it down thru the set screw hole and install the roll pin.
Will work great if you want the GB upside down.


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Wrong, how would you get the drill bit thru the gas block and into the gas tube with the barrel in the way?

There is some common sense involved

[Linked Image from texashuntingforum.com]
[Linked Image from texashuntingforum.com]

Then I dimple the barrel if it is not already dimpled using one of these jigs:

[Linked Image from texashuntingforum.com]


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Good lord if anyone has problems lining up the gas block and gas tube, they shouldn’t be messing with mechanical objects.

Forums are a poor place to learn because everyone is an expert.

Last edited by TWR; 05/20/22.
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True, but it helps keep everything lined up and makes it easy to install the pin.

Mismatched part selection cause more problems than gas block to barrel alignment or gas leaks.

About the only things I change are barrels, handguards stocks and grips.

BCGs, buffers, buffer tubes, receivers, LPKs, triggers and muzzle brakes are generally the same, cartridge specific.


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Originally Posted by TWR
Good lord if anyone has problems lining up the gas block and gas tube, they shouldn’t be messing with mechanical objects.

Forums are a poor place to learn because everyone is an expert.

I agree.. Sorry to hear the OP is having issues with his new builds. They are "fun", but do require a little mechanical knowledge and mindset. I like his choice of stocks. I like and use the PRS quite regularly. I have some gen 2 PRS that require a rifle length buffer (or a spacer and carbine buffer) and some newer Gen 3 PRS stocks that I can use either or, depending on how I have the stock set up. Generally I just run a spikes tactical ST-T2 buffer in those (carbine length) for my rifle length gas systems with low pro gas blocks because I don't like bulky handguards. No need for an adjustable gas block either. That's just me though, as I like keeping it simple. My AR's run like sewing machines, without fail. Going back to the buffers, I have also used a captured spring system and those are smooth and quiet. One of my buddies has a pre ban Bushy that was noisy as hell, so we installed one of those and he loves it. Accuracy even improved a bit. I know I have a couple in some of my rifles, but they are not necessary. It also sounds like the op has more issues than just buffer weight. As was suggested, double check to be sure the gas block is lined up properly. This stuff isn't rocket science, but does require a little mechanical thought. Good luck with it..


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
Originally Posted by Pharmseller
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Originally Posted by PaintedDesert
Hello,
I just put two Varminter rifles together with the heavy 24” barrels. On one of them, I put a Magpul PRS lite and on the other a Magpul PRS Gen 3. The PRS lite is asking for a carbine length buffer and the Gen 3 a rifle length. I installed both as specified. I went to the range to test them on two occasions. The first time, I had no luck with any sort of cycling. I took them apart and checked what was recommended. The other trip, it was pretty much the same thing. I’m sure I’m under gassed because it always fails to eject or it fails to feed and or lock open. Everything else like the BCG, gas tube, and ammo checks out. I just ordered two Odin works adjustable buffers and will try to set the weights to function smoothly. Have any of you done this? With one rifle length buffer, I was planning on using the weights from the carbine buffer to adjust the rifle length since I can’t find an adjustable rifle length buffer anywhere and I’m hoping they’re interchangeable. Are there any tricks you can share? This is my first time assembling an AR and I was having a good time until this.
Thanks for the help.

With a gen 3 PRS, you use can use either buffer length. That all depends on what buffer tube you went with. Whether it is the rifle length or carbine buffer tube. Which did you use on your builds? Do not use a rifle length buffer in a carbine tube and don't use a carbine buffer in a rifle length tube! I realized you are a new member, but pictures of your build would be good/helpful. Here's an example of a gen 2 PRS:
[Linked Image from i.imgur.com]
Those require the use of a rifle length buffer only, or you can use a spacer and carbine buffer. This is similar to your set up and has a 24" barrel, but older PRS stock.

Here's an example of a rifle length buffer tube:
[Linked Image from i.imgur.com]
I just run an H2 buffer in this one and it works just fine...


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
Originally Posted by Pharmseller
You want to see an animal drop right now? Shoot him in the ear hole.

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Thanks for the replies. Pictures are going to be hard for me to do. I’m not a total idiot, I have no trouble posting in the other forums I take part in, just here it seems to be trouble. Maybe its my age and understanding sizes in electronic format. While I am no expert, I do good with my hands and such and feel like I do the right things and look for answers when I don’t know something. I’m not afraid to ask in a forum either, chances are there will be a few people that will like to help. I have a few videos from Sinclair International on the ar 15, and have done all sorts of work to the others I own like triggers and barrels and all that connects to barrels. It seems like the only thing I never explored is buffers in all of the work I’ve done to these things. Since I can’t post pictures, at least not without sending them to someone that can, I will post the specs.

Lowers
Stag with Timney and one with a Timney Calvin elite. CMMG Ambi safety. Magpul enhanced trigger guard. Hogue grips. Standard pins and hardware from stag. One with a PRS lite and one Gen 3 PRS stocks. PRS lite has carbine length tube and buffer, Gen 3 has rifle length tube and buffer, both from Stag.

Uppers
Left hand stag 24” barrel with m loc hand guard. One has a black rain ordinance nickel boron and the other is a stag nickel boron BGG. Stag upper receivers. Ambi Charging handles from Raptor. I bought the uppers from Brownells and they were a unit with the barrel, hand guards, gas block, tube and upper receiver already built without the BCG or handle.

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I also have never had a problem aligning the gas block/gas tube on an AR15 or AR10, but YMMV. It may be a gas issue, but this thread reminded me of a customer that brought 2 AR15s (5.56NATO) he recently assembled, and neither would cycle. I took his uppers off, and tried them one at a time on one of our lowers at the shop, and they ran fine. Turns out "Mr Assembler" ordered .308/AR10 Buffer springs & weights.....no bueno. Not saying that's the case here, but one more thing to check if it's not the gas part of the operation. -Tom T


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Originally Posted by PaintedDesert
Thanks for the replies. Pictures are going to be hard for me to do. I’m not a total idiot, I have no trouble posting in the other forums I take part in, just here it seems to be trouble. Maybe its my age and understanding sizes in electronic format. While I am no expert, I do good with my hands and such and feel like I do the right things and look for answers when I don’t know something. I’m not afraid to ask in a forum either, chances are there will be a few people that will like to help. I have a few videos from Sinclair International on the ar 15, and have done all sorts of work to the others I own like triggers and barrels and all that connects to barrels. It seems like the only thing I never explored is buffers in all of the work I’ve done to these things. Since I can’t post pictures, at least not without sending them to someone that can, I will post the specs.

Lowers
Stag with Timney and one with a Timney Calvin elite. CMMG Ambi safety. Magpul enhanced trigger guard. Hogue grips. Standard pins and hardware from stag. One with a PRS lite and one Gen 3 PRS stocks. PRS lite has carbine length tube and buffer, Gen 3 has rifle length tube and buffer, both from Stag.

Uppers
Left hand stag 24” barrel with m loc hand guard. One has a black rain ordinance nickel boron and the other is a stag nickel boron BGG. Stag upper receivers. Ambi Charging handles from Raptor. I bought the uppers from Brownells and they were a unit with the barrel, hand guards, gas block, tube and upper receiver already built without the BCG or handle.
Good description. It sounds like they did not install the gas block right. An easy way to check is get a piece of small vacuum line and put it on the end of the gas tube, then blow in to it and see if there is a blockage. That is a quick and simple way to see if anything is plugged or if it is not in alignment. It shouldn't be a buffer problem, especially if they were supplied by the manufacture. Yours sound a lot like the rifle I posted a pic of earlier. One of them is a left hand stag with 24" barrel. I was using a black rain ordinance BCG and Raptor as well. Good combo. Now, I don't have my lefty anymore. I see no need in having a left handed AR personally, but I'm assuming you bought a left hand BCG for both uppers?? I know it sounds like a dumb question, but just making sure..


Originally Posted by raybass
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style.
Originally Posted by Pharmseller
You want to see an animal drop right now? Shoot him in the ear hole.

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Yes, definitely. I checked and triple checked when ordering and upon delivery.

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Email pictures to:

xxx**[email protected]**xxx

Everything between the asterisks and xxxs


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I doubt a factory Stag would have gas block issues.

If you’ve got a rifle length receiver extension, use a rifle buffer and spring. You’re cheating yourself if you don’t.

24” barrels can have issues with carbine receiver extensions, buffers and springs. Different gas system than a rifle on a 20” due to 4” extra dwell time. Hard to say but I’d guess heavier might be better just nothing but guesses without seeing it. I’d start with the rifle lower, get it sorted out first with both uppers. That way you’re not chasing your tail with so many variables.

I suspect the BCG’s are your hiccup. But again, I’m just guessing from this point.

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Here are the pictures sent by the OP, let him know and he can send me more for upload.

I still say an H3 buffer will fix the issues.

[Linked Image from texashuntingforum.com]
[Linked Image from texashuntingforum.com]


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Well the rifle carrier weighs more than the H3 so let’s try to get the rifle running first.

Have you tried the BCG from the carbine in the rifle?

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Originally Posted by TWR
Well the rifle carrier weighs more than the H3 so let’s try to get the rifle running first.

Have you tried the BCG from the carbine in the rifle?

Yes. I tried both out in each rifle. Same results. I thought it might be the rubber o ring in the BCG extractor providing too much outward force thus keeping it from cycling 100%. Only minor improvement was made.

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What ammo?

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Federal American Eagle
Lake City
Herters
All 55 grain FMJ all factory.

I tried handloads of 69 grain Sierra HPBT match with TAC and BLC-2.

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