Gunsmithing New AR build issues

[Islas82]

Hey guys so about a month ago I decided to put my first AR together and for the most part am pretty happy with it. Only issue I have now is that I think the buffer (Armspec SRS 3.8oz) might be too heavy so bolt is not locking on the last round but gun is cycling fine with the 3 different types of ammo I have ran thru it. Just got back from the range and noticed something strange and was wondering if I could pick y’alls brains. Picked up my brass to inspect and I notice a dent on all of them (see pictures) any idea what could be causing this or if I should even worry about it? I shot .223 norma 77s and frontier 68s today the dents are only on the frontier casings, norma brass looks fine.

shooting a 18” aero precision .223 wylde barrel with a rifle length gas system.

thanks

 

[Slab74]

Bolt lock has a better chance of being mag related than buffer tube. AR’s are tough on brass. If it is cycling fine, but not locking, try different mags. 90% of semi automatic issues are mag related.

 

[Islas82]

Bolt lock has a better chance of being mag related than buffer tube. AR’s are tough on brass. If it is cycling fine, but not locking, try different mags. 90% of semi automatic issues are mag related.

Will try that next time am out, thx

 

[Slab74]

Will try that next time am out, thx

I number all mags for all my semi autos, rifles and pistols. I keep notes on any malfunctions. New mags need a breaking in period for some platforms. I only hunt or carry mags that have 300+ malfunction free mags.

 

[FisherT&C]

The dent is probably caused by the case deflector behind the ejection port. The lapua brass probably doesn't have it because the pressure is different so therefore it has a different ejection trajectory. The lock open malfunction could be the mags, or the recoil spring could be too heavy. Test all your mags to determine if they will trip the bolt catch manually. If the bolt catch binds on the magazine just trim the mags with a knife or needle file. You can test the magazines by removing the upper and inserting empty magazine to see if the mag trips the bolt catch or insert empty mags in the rifle and charge it to see if the bolt catch captures the bolt.

 

[mmlj]

I had the same problem on my AR pistol build. I believe you are under gassed. Check to see where the cases are being ejected. If they are, using the face of a clock, at the 4-5 o'clock position, you are under gassed. Check the gas key on the bolt carrier group. Mine was loose after only 50 rounds on a newly purchase one. Next, I would try a lighter buffer. Let us know if your problem gets resolved.

 

[Islas82]

The dent is probably caused by the case deflector behind the ejection port. The lapua brass probably doesn't have it because the pressure is different so therefore it has a different ejection trajectory. The lock open malfunction could be the mags, or the recoil spring could be too heavy. Test all your mags to determine if they will trip the bolt catch manually. If the bolt catch binds on the magazine just trim the mags with a knife or needle file. You can test the magazines by removing the upper and inserting empty magazine to see if the mag trips the bolt catch or insert empty mags in the rifle and charge it to see if the bolt catch captures the bolt.

Tried all my mags and they all lock the bolt.

 

[Islas82]

I had the same problem on my AR pistol build. I believe you are under gassed. Check to see where the cases are being ejected. If they are, using the face of a clock, at the 4-5 o'clock position, you are under gassed. Check the gas key on the bolt carrier group. Mine was loose after only 50 rounds on a newly purchase one. Next, I would try a lighter buffer. Let us know if your problem gets resolved.

Will check gas key. Am also leaning towards the heavy buffer issue. Brass seems to be ejecting at the 3-4 o’clock position. My gas block is opened all the way so if its an under gas issue I could only lighten the buffer.

 

[loveha]

What gas block? Did you start closed and open it a little after each shot with one round in the mag?
There is such a thing as to much gas. 18" with rifle gas I don't see why it wouldn't work with an H1 buffer. If it was an H2 or H3 then I would suspect a buffer weight issue.
If this was my rifle, I would be looking at gas block alignment or buffer spring. Would get a Sprinco white spring.

 

[Islas82]

What gas block? Did you start closed and open it a little after each shot with one round in the mag?
There is such a thing as to much gas. 18" with rifle gas I don't see why it wouldn't work with an H1 buffer. If it was an H2 or H3 then I would suspect a buffer weight issue.
If this was my rifle, I would be looking at gas block alignment or buffer spring. Would get a Sprinco white spring.

Got a Odin works block. No I didn’t do that closed 1 shot because I thought there shouldn’t be a problem with my gas set up like you said.

 

[mmlj]

As I have experienced, this can be frustrating and expensive with purchasing additional parts. As suggested above, isolate and focus on one issue at a time:
1. Gas block alignment, gas key, adjustable gas block range of openings.
2. Buffer weight.
3. Buffer spring.
You should solve the problem with adjustments to one or more of the above suggestions.
Lastly, it may be necessary to have the gas hole in your barrel enlarged by your gunsmith. This should give you a wide range of adjustments on the gas block to work with the lightest to heaviest bullets in your caliber.

 

[Drvred]

Buy some self adhesive Velcro. Cut a piece of the fuzzy side the size of the deflector, and stick it on the deflector.
It cushions the case when the mouth bangs off it.

 

[Strykervet]

Try going down one on your buffer. If you have an H1, try an H. And of course a spring, that's an easy fix and if it doesn't do anything then a spare never hurts.

I'm guessing the BCG is a full mass setup?

 

[Islas82]

Try going down one on your buffer. If you have an H1, try an H. And of course a spring, that's an easy fix and if it doesn't do anything then a spare never hurts.

I'm guessing the BCG is a full mass setup?

Yes its a full mass BCG. The buffer is a armaspec SRS-H the equivalent to a H weight buffer and sprig. The SRS is a recoil spring similar to the JP silent capture.

 

[Islas82]

Ok so I replaced the buffer spring kit to a lighter one (3.3oz from 3.8oz) and messed around with my adjustable block a bit today and same result. Bolt just wont lock and experienced some FTF maybe 8 rounds out of 60 that I shot today. Also I removed my gas block when I got home to check alignment and noticed that my barrel and block were quite dirty, don’t know if its a leak or because of me adjusting the block to try to find the sweet spot. Even when its open all the way bolt won’t lock back. Am considering moving to a low mass BCG. Any suggestions?

 

[loveha]

Looks very leaky. I would buy a clamp on to try after cleaning the area up. Can you mic the barrel and block by chance? How does it fit? Does it go on easy, or is it fairly precise and takes a bit to slide on?

 

[Islas82]

Looks very leaky. I would buy a clamp on to try after cleaning the area up. Can you mic the barrel and block by chance? How does it fit? Does it go on easy, or is it fairly precise and takes a bit to slide on?

Fits easy. I just plugged my barrel (chamber side) and pumped some air in. I can feel air coming out of the gas tube fine, didnt feel any air leaking out.

 

[Islas82]

Looks very leaky. I would buy a clamp on to try after cleaning the area up. Can you mic the barrel and block by chance? How does it fit? Does it go on easy, or is it fairly precise and takes a bit to slide on?

What do you mean by mic the barrel and block?

 

[loveha]

What do you mean by mic the barrel and block?

Micrometers or calipers. Just to see what the tolerance is between the two.

 

[Islas82]

Micrometers or calipers. Just to see what the tolerance is between the two.

My calipers are reading .75 on my barrel and .73 on my block. Which makes no sense but is not state of the art calipers. There is some wiggle though and slides on easily

 

[GH41]

If your measurements are accurate you couldn't get the GB on the barrel. They are NOT accurate! You have a set screw GB. Don't worry about the leak. If you shoot it enough it will seal itself. Things like this happen when you put unproven game gun shit in a rifle.