Problem with my Spikes SBR

[Cizzolicious]

Hello all, I've been a longtime lurker but joined up so I could post a question about my 11.5" AR, I'll try to follow the format about technical issues as much as possible:

What make and manufacture is your AR? Spikes lower with CMMG 2 stage trigger, spikes 11.5 ST-15 upper (carbine length gas system). AIM Surplus NiB BCG and PRI gas buster CH.

2. What modifications were made prior to actually shooting it: Only major mod other than listed above is the Spikes ST-T2 heavy buffer

3. What type of ammunition did you use? This is the part that gets weird. It only cycles the crappy steel cased Tula .223. It has been 100% with over 500 rounds, not a single malfunction. I tried shooting some CBC 77 gr OTM 5.56, and it was about 75% reliable, literally every 4th round would FTE (see pic). With winchester 5.56 it would FTE about every 6th or 7th round.

5. Were modifications made to the gas port? None that I know of

6. Take a good picture of the part or problem in question. Sometimes a picture is worth a thousand words. See below

Just wondering if anyone has heard of a rifle not cycling brass cased 5.56, but will cycle steel .223? Thanks for any info!

[VIP3R 237]

Take out the ST-T2 and try a real buffer before anything else and see how it runs. The ST-T2 is known to cause issues. Also check your gas key and see it it loose, check your gas rings, and your gas block as well unless it's a FSB style.

[Cizzolicious]

Take out the ST-T2 and try a real buffer before anything else and see how it runs. The ST-T2 is known to cause issues. Also check your gas key and see it it loose, check your gas rings, and your gas block as well unless it's a FSB style.

Thanks! Yeah I took out the ST-T2 but haven't been back to the range yet. Gas key doesn't appear to be loose, and I have a FSB gas block.

[CoryCop25]

I concur. Try an H2 or H3 buffer. It sounds like you have an over gas issue with the standard pressure 5.56 rounds.

[fixit69]

I'll echo the same thing on the spikes T2. It caused me no end of problems including the same thing in your pic. The H2 solved my issues.

[sinlessorrow]

Try a H2.
Could be oovergassed.
What extractor assembly is in the bolt?

[Cizzolicious]

Try a H2.
Could be oovergassed.
What extractor assembly is in the bolt?

Sorry haven't been able to test it with the carbine buffer yet. To answer you extractor question, it's an AIM Surplus NiB BCG and they have this to say about their extractor:

"When installing the extractor to the bolt, a crane-o-ring is inserted with the spring to insure proper ejection."

[stitch702]

Yes I had the same thing happen with my spikes stt2 on my 7.5 pistol. H2 solved my problems.


Sent via pony express

[Cizzolicious]

Well I don't have an H2 buffer, anyone recommend a good place to get one that won't break the bank? A regular carbine buffer on my last range trip had the same result, lots of FTE. I emailed Spikes and they weren't much help, I'd expect that a factory spikes upper would run 5.56 but I guess having it only run .223 is acceptable to them.

[SteveL]

Well I don't have an H2 buffer, anyone recommend a good place to get one that won't break the bank? A regular carbine buffer on my last range trip had the same result, lots of FTE. I emailed Spikes and they weren't much help, I'd expect that a factory spikes upper would run 5.56 but I guess having it only run .223 is acceptable to them.

I would just get one from BCM. As the weight of the buffer goes up so does the price because of the use of Tungsten weights in heavier buffers (or that's my understanding anyway).