New AR Problems

[dfinan]

Ok looking for help from all the black gun experts out there. Finally got to go to the range and tune the gas system test the rifle and work on zeroing it in. We ran into a problem with the gun failing to go into battery

We looked at and tried the following

1. 3 different magazines (all 2nd gen magpull 30 round mags with 3-5 rounds loaded)
2. Two different bullets, a 55 grain hornady soft point (exposed lead) and a Ultramax 55 grain fmj (fmj ones appeared top go into battery consistently to start with but started having problems after about 10 rounds.
3. If the bolt was release with the paddle while empty it was pretty consistent and went into battery (though it failed a few times).
4. The gas system was tuned to one click more then needed to lock the bolt back on an empty magazine.

One additional note on the soft point bullets two of them showed gouges or grooves in the the jacket towards the base of the bullet prior to where the case starts, and the case had no marks or scoring. In all cases all rounds fired correctly when manually dropped in and the bolt was allowed to close while the gun barrel was pointed down.

I have pictures below and a vidoe of the issue if anyone has any suggestions. Aside form this issue, the gun was fun to shoot had zero rise and felt like I was shooting a .22 but sounded like something much larger .

 

[jtischauser]

When you manually rack the bolt is it smooth or tight? Reason I ask is that Boomfab had a few carriers awhile back that had the can pin race out of spec on the right side. Might be part of your problem???

Might try another carrier with that bolt and see if it changes.

 

[dfinan]

Manually racking it and releasing it it feels smooth, I suspect it may just need a heavier duty buffer spring, but am looking at several possibilities on whats causing the issue.
that intially was an issue, the guys that helped with the build ran into but replaced that part with one that was in spec, after they contacted boomfab and talked with them about the issue. Definitely happy with the gun just have to do a little more work tunning it, amazed at how little recoil and muzzle climb there was on the rounds I did fire. Of course it make a ton more noise then normal.

 

[jtischauser]

Manually racking it and releasing it it feels smooth, I suspect it may just need a heavier duty buffer spring, but am looking at several possibilities on whats causing the issue.
that intially was an issue, the guys that helped with the build ran into but replaced that part with one that was in spec, after they contacted boomfab and talked with them about the issue. Definitely happy with the gun just have to do a little more work tunning it, amazed at how little recoil and muzzle climb there was on the rounds I did fire. Of course it make a ton more noise then normal.

You shouldn't need any special buffer spring.

What buffer/spring setup are you using?

 

[dfinan]

Jp Low mass buffer and I cant remember the spring will have to look up the email I ordered it with

 

[jtischauser]

Jp Low mass buffer and I cant remember the spring will have to look up the email I ordered it with

I run the JP spring with their buffers. I can't speak for anything else but any old rifle length buffer during should work.

Might make sure you don't have a carbine spring in it,

 

[benny hill]

I would take the barrel out and run a reamer in the chamber to make sure it is good and check headspace. If headface is tight it may be that some ammo fit and some don't and will not lockup.

Also clean-up and blend feed ramps.

 

[dfinan]

Im leaning towards checking the headspace first and then the buffer spring, I had to make a last minute change in the stock and I dont think I changed the spring, but these are the two things I have seen mentioned the most to check first

To elaborate, I initially got the entry level skeleton stock, it was way shorter then I expected and while I could shoulder the rifle it messed up the ergonomics for my arm length, I replaced it with the same style skeleton stock in fixed length but I dont think I got a different spring when I reordered. I ordered it with the buffer tube and stock only, so i think I am going to replace that first. If thats the only thing I messed up in this build I can live with that spring is an easy fix.

 

[benny hill]

there is a big difference in rifle springs and buffers. short spring in a long stock may be yout problem as it will not close

 

[dfinan]

there is a big difference in rifle springs and buffers. short spring in a long stock may be yout problem as it will not close

Yup going to stop by a shop and get the correct A1/A2 length spring and swap it out I bet that does it.

 

[Brandon Deem]

One additional note on the soft point bullets two of them showed gouges or grooves in the the jacket towards the base of the bullet prior to where the case starts.

I had something extremely similar except the jacket had gouges almost the full length.

The gun had several hundred rounds through it before it started. I didn't take enough notes to know if it was a different ammo or not. After research I found the gouges were from the locking lugs at the top of the feed ramps on the barrel. I used a diamond hone on the dremel and rounded over all the edges on the feed ramps. Problem solved.

Before the fix I found even the rounds that did chamber had gouges on the jacket. Afterwards no gouges what so ever and super smooth feeding.