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New member, new build


Stubbie68
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Hi all. Glad to be here. Retired military and former armorer so I know my way around an AR platform. I'm not a gunsmith so I'm a bit ignorant when it comes to building from scratch and troubleshooting failures but I know the parts and functions of each. I decided it was time so I bought a bunch of parts. Got too excited and bought everything already but no worries, if I need to swap something to make it work it's fine. 

What I was hoping for was to list the parts I got and get opinions as well as heads up on potential problems or issues.

Here goes, .308 build:

Aero M5 forged upper and lower, JP enterprises bcg nitrided, ballistic advantage 20" heavy bull barrel stainless, Odin works tunable gas block and rifle length gas tube, rise armament RA 535 trigger, Guntec AR10/.308 buffer tube and spring assembly, don't know any details about buffer weight or spring. And a few other parts but these are the main ones.

Any and all comments welcome. Thanks in advance!!

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Welcome to the forum and thank you for your service.

It looks like you have a list of good parts.  I do have a couple of questions though.  Is this the buffer kit you have?  Is it a carbine extension or rifle extension?  What is the diameter of your gas port?  I assume it is rifle gas length since that is what gas tube you purchased.

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Mods/Admins - Let's get this moved to the Build Section, and out of here.  

Let's get all the other questions about random parts or guns out of here, too.  That's not what this section is about.  It's about INFORMATION of these things, that makes them run. 

308 AR - What You Need To Know

Compatibility, Troubleshooting and Frequently Asked Questions. This Board is "Read Only"

Edited by 98Z5V
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1 hour ago, Armed Eye Doc said:

Welcome to the forum and thank you for your service.

It looks like you have a list of good parts.  I do have a couple of questions though.  Is this the buffer kit you have?  Is it a carbine extension or rifle extension?  What is the diameter of your gas port?  I assume it is rifle gas length since that is what gas tube you purchased.

This is the buffer assembly I purchased. https://www.opticsplanet.com/guntec-usa-ar-10-lr-308-rifle-stock-tube-kit.html

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2 minutes ago, Stubbie68 said:

I guess I need to bump this up to get some attention???

It'll catch on - you'll be alright. 

The recoil system is the most concerning set of parts that you've listed.  When they come in, spec them out and post the details.  That's gonna tell us if your gun will run, or be a jam-o-matic. 

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4 minutes ago, 98Z5V said:

It'll catch on - you'll be alright. 

The recoil system is the most concerning set of parts that you've listed.  When they come in, spec them out and post the details.  That's gonna tell us if your gun will run, or be a jam-o-matic. 

Thank you!! That's the stuff I am looking for. Will do. Jam-o-matic is no bueno.

 

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Welcome stubbie. Once you have this thing built, unless you just bench shoot or shoot from the prone at long distances at your local range, you may get tired of this thing’s weight with a 20 inch bull barrel. I went with a 16”modified (little less girth in areas) bull barrel on my .260 rem and that is the only change I wish I would have done. I would have gone with a much lighter barrel, maybe not a pencil barrel, but probably a step up. 
 

I am sure yours will shoot great and if it works for you and you are happy with it, that’s all that matters.

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On 12/10/2021 at 7:01 PM, ARTrooper said:

Welcome stubbie. Once you have this thing built, unless you just bench shoot or shoot from the prone at long distances at your local range, you may get tired of this thing’s weight with a 20 inch bull barrel. I went with a 16”modified (little less girth in areas) bull barrel on my .260 rem and that is the only change I wish I would have done. I would have gone with a much lighter barrel, maybe not a pencil barrel, but probably a step up. 
 

I am sure yours will shoot great and if it works for you and you are happy with it, that’s all that matters.

I very much appreciate the comment. Transporting it will be the only weight concern. I'll be shooting from a bench or bi-pod. I want the extra length to squeeze as much velocity as I can get. Long distance accuracy is what I want most. From my experience it's about 70 to 80 FPS per inch of length. At least that is what the average seems to be with a traditional bolt action. Not sure if it is the same for the AR platform. Either way it's already purchased. Thanks for your comment!!!

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Welcome and thanks for your service.  I'm also retired, small arms instructor for 20 years and ran the Armory/trained all active duty and Reserve personnel attached to my units, etc.  In addition I shot on a rifle and pistol team for several years so know my away around the accuracy end of the shooting deal pretty good.

Typically a heavier profile longer barrel provides improved accuracy and increased velocity so a win-win there.  The problem I see with 308 AR platforms with longer barrels is weight.  The very first one I built quite a few years ago had a heavy profile 18" barrel and it was HEAVY.  With the added weight it also felt awkward as a hunting rifle so I never used it as such and built a 14.7" rifle with a light profile barrel instead.  It shredded a couple of pounds from the build but also completely changed balance and "feel" of the rifle at the same time.  It still crosses the scales at exactly 10 pounds but doesn't feel barrel end heavy/unbalanced for carrying all day as a hunting rifle.  


A 20" bull barrel rifle build may want to make you hire someone to carry it around for you at the range, but since you mentioned weight isn't a concern I'll bet it will shoot very well once you find a load that it likes.  There are some really good bullets out there these days and with careful attention to detail I'm sure you'll quickly get that rifle to or better than I MOA without much trouble. Let us know how it goes?........Cliff

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On 12/12/2021 at 6:20 PM, Stubbie68 said:

I very much appreciate the comment. Transporting it will be the only weight concern. I'll be shooting from a bench or bi-pod. I want the extra length to squeeze as much velocity as I can get. Long distance accuracy is what I want most. From my experience it's about 70 to 80 FPS per inch of length. At least that is what the average seems to be with a traditional bolt action. Not sure if it is the same for the AR platform. Either way it's already purchased. Thanks for your comment!!!

Anytime! Guess if you decide you need something lighter you can always build another rifle 😉

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  • 2 weeks later...

So I thought I would update the post. I finished putting everything together. I had to fabricate a wrench to fit the ballistic advantage heavy barrel nut so I could torque it to spec. The hand guard I ordered is too short and the gas block sticks out. Not a huge deal and I'll order a longer one from the same manufacturer at a later date. For now  it's together and ready to test at the range. Just need to find the time. 

AR Trooper and Cliff R, you guys were spot on. This pig is heavy. I don't mind it much as I won't be walking around with it much but I wanted to give you props for warning me.

Anyway, more to follow once I get to the range and tune the gas system and sight in the scope. 

Happy holidays everyone!! And a safe Blessed New Year!!

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@Stubbie68that rifle looks beautiful. Glad you don’t mind the weight, I am sure that thing will make some nice groups from the prone or a bench. Even with that shorter rail it doesn’t take away from it at all, makes it easier to adjust your gas block. I have 3 rifles with 15 inch handguards and SLR adjustable gas blocks that are a pain to reach when trying to adjust them. Probably next builds I will go shorter with the rails for that reason. 
 

That’s a damn fine build though and half the fun is playing around with new parts later. 

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3 hours ago, Stubbie68 said:

The hand guard I ordered is too short and the gas block sticks out. Not a huge deal and I'll order a longer one from the same manufacturer at a later date.

 

Not a big deal - every single military Mk 12 is like that, for a reason, and it's never a hindrance in any way.  I wouldn't change that gun you have, man, for anything. 

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  • 2 weeks later...

So I finally made it out to the range today. Didn't go well. I will try to give as much information as I can. 

Bottom line is, in my best guess, it is either one of 2 things. Buffer is too heavy (mass) or spring is too stiff or something is wrong with the gas system.

I have an adjustable gas block and it functioned exactly the same from when I started (first round) to when I adjusted it all the way out. The bolt is not going all the way to the rear. Not cycling correctly. I tried one round at a time to make sure it was ejecting at 3 o'clock and the bolt was locking to the rear after the last round. The bolt does not travel back far enough to lock and while it does strip the next round from the magazine (sometimes) it does not have enough force forward to lock the bolt onto the back of the round. In other words it will not go into battery. With multiple rounds loaded in the magazine I had to drop the magazine, pull the bolt all the way to the rear (the round that was stripped remained in the chamber) and let it slam forward from the full open position to lock the bolt into battery. I am guessing the buffer is too heavy and/or spring too stiff. At least that is what I hope it is since it's an easy fix. Hope it's not the gas system.

Any suggestions on a better way to trouble shoot or how to narrow it down? Thanks in advance.

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Just measured the spring and weighed the buffer. Buffer is 157 Grams or 5.5 ounces. Spring is pretty stiff and has 36 loops. I checked the travel in the tube and pulling the charging handle all the way back the bolt face is not in contact with the bolt catch. There is a short distance between the bolt face and the catch when fully to the rear so nothing physical is impeding travel to the rear and it goes physically back far enough to work properly.

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1 hour ago, Stubbie68 said:

Any suggestions on a better way to trouble shoot or how to narrow it down? Thanks in advance.

How many rounds fired? Was the BCG dripping with oil? Gas block wide open? 

These things take a little break-in sometimes, metal mates up, carbon needs to seal up the gas system, stuff like that. Don't be to worried it didn't take off running the first trip out.

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41 minutes ago, jtallen83 said:

How many rounds fired? Was the BCG dripping with oil? Gas block wide open? 

These things take a little break-in sometimes, metal mates up, carbon needs to seal up the gas system, stuff like that. Don't be to worried it didn't take off running the first trip out.

Only fired 20 rounds. Have to admit was a little frustrated. Had to pull the charging handle back on every round.

BCG was oiled up well. Gas block was wide open at the end after I tried adjusting with no change.

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Your buffer weight is ok but I still think we need measurements of the entire recoil system. Please post pictures of the buffer length, internal depth of you tube and spring length. 
 

Also, if these are correct in dimensions it very well could be your gas system, which is an easy fix with some basic tools.

 

please start with the above

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