What constitutes reliable cycling? 300BLK

[The Gump]

I have read over and over that 175 SMK sub's will not cycle reliably in the 300BLK platform. Being the non-beliver that I can be from time to time I gave it a shot, or rather 100 today. My gun ran just like it does with 208 AMAX's and 220 SMK's. With the exception of a few rounds for zeroing and about 10 rounds at 300 yards, all rounds were fired from the shoulder as fast as my friend and I could pull the trigger. Not one problem.

Set-up:
AR 15
8" Noveske
AAC 762 SDN-6
Standard Buffer
175 SMK Blem's
11.2gr AA1680 +/- .1
CCI 400 Primers

Am I missing something here?
Does this round need to be run in full auto to not cycle reliably?
I do not own/plan on owning a FA lower (at least in the foreseeable future) and you won't catch me with a slide stock on any of my guns (kind of gehey IMO).

 

[Munson]

Re: What constitutes reliable cycling? 300BLK

everyone is going to have their own opinion, but I say 2K rounds without cleaning for pistols and carbines.

 

[The Gump]

Re: What constitutes reliable cycling? 300BLK

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Munson</div><div class="ubbcode-body">everyone is going to have their own opinion, but I say 2K rounds without cleaning for pistols and carbines. </div></div>

I'm not speaking of cycling in general. I'm speaking of a suppressed 300BLK AR cycling subsonic 175 SMK's specifically.

 

[mscott]

Re: What constitutes reliable cycling? 300BLK

I think a lot of shooters having trouble getting subs to cycle are not using A1680.

 

[southpaw68]

Re: What constitutes reliable cycling? 300BLK

I haven't had the chance to load up any of my own subs, but the factory Remington subs I have shot will not cycle in my gun. they were 220gn...So maybe there is some credance to different powder used making a difference in cylcling reliability. Are you shooting suppressed? What sort of gas block are you using? Have you opened up the gas port on the barrel at all? These are things I have considered if I decide I need mine to cycle unsuppressed. I'm fairly certain I'll have no problems running suppressed.

 

[The Gump]

Re: What constitutes reliable cycling? 300BLK

I'm shooting suppressed with an unmodified Noveske barrel and gas block.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: southpaw68</div><div class="ubbcode-body">I haven't had the chance to load up any of my own subs, but the factory Remington subs I have shot will not cycle in my gun. they were 220gn...So maybe there is some credance to different powder used making a difference in cylcling reliability. Are you shooting suppressed? What sort of gas block are you using? Have you opened up the gas port on the barrel at all? These are things I have considered if I decide I need mine to cycle unsuppressed. I'm fairly certain I'll have no problems running suppressed.
</div></div>

 

[country888]

Re: What constitutes reliable cycling? 300BLK

I have not had any problems suppressed or unsuppressed with any bullet in my Noveske or Saturn barrels. I do load my own sub and supers. 1680 in the subs & H110 in my supers. No mods to eather barrel.

 

[MitchInOR]

Re: What constitutes reliable cycling? 300BLK

I'll have to give that a try. You're using 11.2 grains 1680 and they are staying subsonic?

 

[Jeepocabra]

Re: What constitutes reliable cycling? 300BLK

Depends on the gas system. with 175 SMK's I can get my 16" pistol gas upper to cycle subs at only 975 FPS. Fairly acurate too. I was only experimenting to see if I could get a cheaper subsonic option when I loaded them.

 

[dlklamfo]

Re: What constitutes reliable cycling? 300BLK

If you got them to cycle then I don't see what you're worried about. What velocity are you getting? Thanks for sharing your experience.

 

[i_rep]

Re: What constitutes reliable cycling? 300BLK

You must be lucky if your getting those to stay subsonic....There is a difference in getting them to cycle and to cycle and still be subsonic. I believe if they are still subsonic it is due to you only having an 8" bbl.

Most that have troubles would not be running an SBR. Its more picky keeping lighter loads to stay subsonic and still cycle.

There are many ways to fix the problems.....larger gas ports...lighter buffer...modified spring(you said std buffer,but did not mention the spring).

 

[50APIT]

Re: What constitutes reliable cycling? 300BLK

I found that gas port size was the biggest factor in getting reliable function for subsonic loadings.

I am using a delta company arms 10" barrel with pistol length gas system that I have opened the gas port to .125" and it cycles 147gr subsonic w/suppressor every time. I have an adjustable gas block that allows me to use it for supersonic loads as well.

Prior to opening the gas port, I tried both semi & full-auto carriers, taking weights out of the buffer and a lighter spring. None of those would cycle the low weight subsonics and even if they did, I wouldn't use use supersonic ammo in that configuration. Now I am able to use a spikes T2 buffer in the lower which means no parts swapping even when going back to 556.

My dad's noveske 10" barrel will not cycle them using my lower and his barrel which has a .08" gas port.

 

[The Gump]

Re: What constitutes reliable cycling? 300BLK

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchinOR</div><div class="ubbcode-body">I'll have to give that a try. You're using 11.2 grains 1680 and they are staying subsonic? </div></div>

At 90 degrees and 70% humidity they are subsonic. There is no sonic crack what so ever. I have run them at 11.0gr too and they cycled.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: phearkno1</div><div class="ubbcode-body">If you got them to cycle then I don't see what you're worried about. What velocity are you getting? Thanks for sharing your experience. </div></div>

It's not that I'm worried about anything so much. I just want to understand why people say it can not be done. If I wasn't hard headed I would not have tried it and would still be spending buku on 208's and 220's or modifying ports and such. Now I can use cheep 175 blems and no mods. I was also wandering if the gun needs to cycle in FA to be considered cycling reliably.

I haven't run them over a chronograph, but again, no sonic crack. Once it get cooler and dryer things may change, but until then...

 

[Cornholeo]

I will be loading some of these up this week and try them out. Th only difference in builds is I have an H2 buffer as per Noveske's build on their full rifle. It has fed and cycled flawlessly suppressed so I am looking forward to using some of the blem 175SMKs I got on here.