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New member, new build


Stubbie68
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17 minutes ago, Stubbie68 said:

Only fired 20 rounds.

That's just test fire one, no worries, post up those measurements. Gas port size may need to be checked, that's gonna slow up getting that carbon seal on the gas block, might wanna just get it measured and have it though. Field strip and look everything over for odd wear marks. If everything looks fine send another box or two with the gas wide open. It can be frustrating when they don't take right off but it's always good to get some malfunction training in on a new weapon. :thumbup:

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2 hours ago, Stubbie68 said:

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.

Don't worry about ejection pattern, until this thing is broken in.  That isn't the end-all/be-all anyway.  I don't care where my brass goes, as long as it gets out of the gun, and the gun functions.  I don't set any rifle up, ever, based on any ejection pattern.

Next, always start an adjustable gas block wide open.  All the way.  You save ammo that way, if you want to hear my version of the story.  Always, Wide Fukkin Open to start.

On 12/7/2021 at 7:51 PM, Stubbie68 said:

Guntec AR10/.308 buffer tube and spring assembly, don't know any details about buffer weight or spring.

You need to spec these out, and find out what the details on the recoil system are.  And post the results.  You listed the weight of the buffer at 5.5oz, and that's a good weight.  What's the length of the buffer?  What's the internal depth of the receiver extension?  I'd shiitcan the spring, just because it's an unknown.  Unless you can give a relaxed length, wire diameter, and coil count, it's an unknown.  Beyond that, we'll never know if it's chrome silicon, or what the material is that it's made of.  Those details are super important.

After the recoil system is solved, we'll move to the gas system - unless you want to get to that now.  Pull the gas block, and measure the gas port diameter with numbers drill bits, use the shank of the bit to measure. 

Edited by 98Z5V
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Okay, here is what I have so far.

Buffer weight 5.5 oz.

Buffer tube depth 9 5/8"

Spring wire diameter .081"

Spring relaxed length (as soon as I took it out of the rifle) 12" meaning it might relax more after sitting a while. Don't know.20220108_094127.thumb.jpg.f0aee93027690d1f7ad8bf2a08fc15c0.jpg20220108_094045.thumb.jpg.187717785d45ca22f8bb4f079d3dd784.jpg

Spring coil count 38

Spring is polished or stainless, don't know which, I am guessing stainless

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This is the exact buffer, tube and spring combo I purchased from Guntec. Unfortunately none of the specs are listed on their website.

https://guntecusa.com/product/ar10-lr-308-rifle-stock-tube-kit-308-cal/

My dies, and bullets are in the mail on the way here. If I am going to burn ammo trying to get this thing "broken in" I will do it with cheap stuff. I will reload a few hundred and use them. 150 gr. Hornady FMJ should do the trick. I have primers and powder already so I will load them up to average velocities. I could try a couple hot loads to see if that helps.

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Relaxed spring length is off, should be 13.75”. Coil count should be 34 at that length. So bye bye spring. Need the length of the buffer please………..

 

your buffer tube seems correct enough, should be 9 5/8”… your buffer length should be 5 3/16

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I know exactly what your issue is because I've had it and corrected it myself. Your buffer is too long. Take the rubber pad off the back, reassemble the rifle and do a manual function check. You'll find that it will lock back and function correctly because your buffer is now shorter and therefore has more rearward travel. You need a shorter buffer of the appropriate weight.

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Posted (edited)

The buffer itself is just a hare shy of 5 5/16. So almost 1/8 longer than was stated it should be. What about the spring? Replace both? Anyone have a link to the correct combination?

I should also note that I can manually lock the bolt to the rear with the current length buffer and there is additional travel beyond the locking point. Not much but it is there.

Edited by Stubbie68
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7 hours ago, 98Z5V said:

Yep, that's an AR15 rifle buffer.  It should be 5.900" long, if it was made right.  .308AR rifle buffers need to be 5.200" long. 

Wrong buffer.

No disrespect intended and maybe I am reading this wrong. Actual length of the buffer was 5 5/16. That is a lot closer to 5.2 than it is 5.9. The latter would be like 5 13/16. Is that not correct? At 5 5/16 that is 1/16 greater than 5 1/4 or 5.25. 

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On 1/9/2022 at 7:04 PM, Stubbie68 said:

No disrespect intended and maybe I am reading this wrong. Actual length of the buffer was 5 5/16. That is a lot closer to 5.2 than it is 5.9. The latter would be like 5 13/16. Is that not correct? At 5 5/16 that is 1/16 greater than 5 1/4 or 5.25. 

You could trim the delrin pad down and it’ll be fine. Replace the spring and now move on to your gas port…

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22 hours ago, edgecrusher said:

You could trim the delrin pad down and it’ll be fine. Replace the spring and now move on to your gas port…

I understand. Trimming the pad won't be a problem. I have been searching for a spring that matches the specs mentioned but I'm having a lot of trouble. Most sites I looked at just say what it's for but don't list the specs. Any suggestions?

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4 minutes ago, Stubbie68 said:

Any suggestions?

Armalite;

https://dsgarms.com/lower-receiver-parts-armea1095

They don't list it seperate on the Armalite site any longer but they might help you out if you called and asked nice. Try searching for that part number and you might find it.

I have used these Tubbs springs in both rifle and carbine builds without issue, they are a GOOD bit higher now.

https://www.larue.com/products/tubbs-buffer-spring-ar10-sr-25-buffer-springs/#reviews-tab

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On 1/9/2022 at 5:04 PM, Stubbie68 said:

No disrespect intended and maybe I am reading this wrong. Actual length of the buffer was 5 5/16. That is a lot closer to 5.2 than it is 5.9. The latter would be like 5 13/16. Is that not correct? At 5 5/16 that is 1/16 greater than 5 1/4 or 5.25. 

Sure looks long as fuk in the pic you posted, and not close to what it should be - Maybe you should have layed that thing down flat, on a table, next to a tape measure (not standing up on a bench), - like we asked in the first place.

Bottom line - it's too long, and won't work in your gun like that, ever.  :thumbup:

You smell what I'm spreading, here?...

 

Edited by 98Z5V
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On 1/10/2022 at 9:30 PM, jtallen83 said:

I have used these Tubbs springs in both rifle and carbine builds without issue, they are a GOOD bit higher now.

https://www.larue.com/products/tubbs-buffer-spring-ar10-sr-25-buffer-springs/#reviews-tab

Ordered!!

And the buffer has been shortened by 1/16"

I also pulled the gas block and verified the distance from the shoulder to the gas port on the barrel and the distance from the edge of the gas block to the hole for the gas tube. They line up perfectly now. They were not perfectly aligned before.

On 1/10/2022 at 9:54 PM, 98Z5V said:

You smell what I'm spreading, here?...

 

I'm smellin' somethin'!!

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  • 1 month later...

Just thought I would check back in. Like I mentioned previously, replaced the spring with the heavier flat spring that was recommended by jtallen83. Also, shortened the buffer by a sixteenth. Double checked the gas block and put it all back together. Took me a while to get back to the range. After some minor adjustment to the gas block screw it seems to be running perfectly. Locks on the last round and chambers consistently. Put another 50 rounds down range with no jams or failures. Shot groups weren't bad but not great either. I'm sure there will be a breaking in period and the ammo I was using was cheap brass reloads so it's to be expected. One more trip to burn up my last 50 of reloads then I'll work on load development with some better brass and a few different powders. 

Does anyone have a "pet" load that seems to work well? 

Anyway, I would be remiss if I didn't say thank you to all the folks that provided input and guidance. I really do appreciate it.

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