Another Cycling saga…

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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dellet
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Re: Another Cycling saga…

Post by dellet »

When firing a sub, will it now pick up and chamber the next round?

That would be an improvement from the first time at range. If you’re short on subs, use a super for the second round. All you want to see is if will feed.
300 Blackout, not just for sub-sonics.
Ptrk99
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Re: Another Cycling saga…

Post by Ptrk99 »

Yeah, I knew that question was coming…lol. To be honest, I did not try that to see if it would pick up the next round. I can probably just pop one off in the back yard and test it that way but I’m guessing there is no change.

I did exchange a couple of emails with Tanner at Shield Arms about their folding lower and buffer. I’m not sure he completely understood my situation because he said they don’t recommend running their buffer without the weight inside that it comes with. He said they usually only do testing on .556 and that 300Blk is more difficult. I asked for more details about the buffer weight explaining I did not want to damage the lower and got this:

While without the weights it would be closer to the H1 weight when it comes to the 300blk round the action would be very volatile when compared to an H2 so we do not recommend it as it most likely would not solve the problem, when speaking with the gunsmiths about your direct issue they pointed me toward the gas port, spring or using different ammo.

So, their gunsmith recommends looking at anything that is NOT there lower, what a surprise. I had explained twice that this was mainly for subsonic rounds but don’t feel like that sank in. He did point me towards a company called Sprinco and said they might be able to help with my build.

I’ll update on the follow-on round as soon as I get that data. I’m still not able to get ahold of anyone at PSA and it seems that the review I submitted about the upper kit mysteriously disappeared.

More to follow on this saga…lol
Ptrk99
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Re: Another Cycling saga…

Post by Ptrk99 »

The answer is no, it does not load the next round, sadly.
GeronPG
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Re: Another Cycling saga…

Post by GeronPG »

Hey, this may be just a shot in the dark, but have you greased the recoil spring? I've seen that help a couple guns that weren't quite running right run better. .
GeronPG
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Re: Another Cycling saga…

Post by GeronPG »

But I think Dellet has given you the best perspective. You're running a pistol barrel designed for heavy subs and a suppressor. And with no suppressor.
I would think the supers would cycle and pick up the next round, though.
Ptrk99
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Re: Another Cycling saga…

Post by Ptrk99 »

Hey Geron,

Thanks for weighing in. Yes, I did grease the spring during the original build. I can see how that might get overlooked and could make a difference.

Yep, you’re spot on. It does run supers fine but subs not so much. What I really need is a super high speed camera that I can use to video the BCG and see how far back it goes. That would be a cool experiment. I don’t think any cameras I have currently will do it.

This is really just a physics question with many unknowns. First, we don’t know the force produced through the gas tube when the round goes off. That force will be used to move the mass of the BCG and expended brass countered by the weight of the buffer and the force of the spring. Maybe I will try to figure some of that out and see if math will set me free.

Some of those values would be difficult to figure out but not impossible. Who knows….

Thanks to all who have helped out. Hopefully I will find an answer at some point.
Ptrk99
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Re: Another Cycling saga…

Post by Ptrk99 »

As an update to this ongoing tale. To date I’m about another 50 rounds through the gun with all the exact same performance/issues. I reached out to Sprinco via email to ask for some help from their end and never got a response. I tried to use a buddies suppressor to see if that would increase pressure enough to get the subs to cycle but we ran into a muzzle brake issue and couldn’t get it done.

The search for a solution continues. Open to all ideas…
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dellet
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Re: Another Cycling saga…

Post by dellet »

Sadly it sounds like the manufacturer of the lower never tried 300 BLK subs, or never got it to work.

There are a lot of things that can slow down the bolt speed, most you have tried. A bad trigger or too powerful, of spring will cause the hammer to put pressure on the carrier. The Magpul BAD lever is another problem that showed up.

In the past everyone’s answer to every problem was to drill the port to .125” and be done with it. Since I shoot more supers than subs, I went against the norm. If you want to be able to shoot subs without a suppressor, you should consider enlarging the port. It shouldn’t take much. If you’re unsure, wait for the suppressor.

If you go up in drill size .001”, you can probably twist them through with your fingers. Do the math, and you will find that around .004-.005” will give you a 10% increase in area or volume. The only reason to go over .100” would be to hand load with faster powders.

Putting your upper on a different lower would certainly narrow down the problem.

Some things to consider.
300 Blackout, not just for sub-sonics.
Sfbeninati
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Re: Another Cycling saga…

Post by Sfbeninati »

dellet wrote: Sun Jan 01, 2023 12:33 pm I’m assuming you were shooting without the suppressor, it will make a difference.

First in theory, it should work fine with the info you provided. Pistol gas, H2 buffer weight, FA carrier. Port is on the small side, but should work with factory ammo.

First thing I would question is the lube. Is it rated to at least 30* less than the temp you were shooting?
Lubes like Frog lube will stop an AR in its tracks in cold weather.

Next is how many rounds through the rifle, if it’s less than 2-300, either go shoot that many supers, or hand cycle it. I prefer live fire.

You need to have a rock solid shoulder mount. Like limp writing a pistol, allowing the rifle to move instead of the buffer will cause light loads to not cycle.

Leave drilling the port as a last resort. When you pulled it apart to check, there should have been a perfect carbon circle centered around the port. If there was not a circle, there is a leak. Also a good way to check if the block is aligned properly.

You might try some Remington UMC subs. If they won’t cycle those, it’s not an ammo issue.

I wouldn’t change anything drastic until you have the suppressor in hand.


Have you ever used frog lube? I live in Alaska and almost only use it for my firearms (2 ARs, 1 PCC, 4 Pistols). In the past 6 years I’ve only had issues when I didn’t follow the instructions the first time around. It’s not like your traditional petroleum lubes so it is less intuitive thus most make the mistake initially without following the instructions. Takes a bit to get use to but several 1000 rounds about ⅓ in the winter well below 30 and no issues (other than what I stated before). I also use their extreme frog lube more in the winter versus the paste.
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dellet
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Re: Another Cycling saga…

Post by dellet »

Sfbeninati wrote: Sat Jun 03, 2023 3:16 am
dellet wrote: Sun Jan 01, 2023 12:33 pm I’m assuming you were shooting without the suppressor, it will make a difference.

First in theory, it should work fine with the info you provided. Pistol gas, H2 buffer weight, FA carrier. Port is on the small side, but should work with factory ammo.

First thing I would question is the lube. Is it rated to at least 30* less than the temp you were shooting?
Lubes like Frog lube will stop an AR in its tracks in cold weather.

Next is how many rounds through the rifle, if it’s less than 2-300, either go shoot that many supers, or hand cycle it. I prefer live fire.

You need to have a rock solid shoulder mount. Like limp writing a pistol, allowing the rifle to move instead of the buffer will cause light loads to not cycle.

Leave drilling the port as a last resort. When you pulled it apart to check, there should have been a perfect carbon circle centered around the port. If there was not a circle, there is a leak. Also a good way to check if the block is aligned properly.

You might try some Remington UMC subs. If they won’t cycle those, it’s not an ammo issue.

I wouldn’t change anything drastic until you have the suppressor in hand.


Have you ever used frog lube? I live in Alaska and almost only use it for my firearms (2 ARs, 1 PCC, 4 Pistols). In the past 6 years I’ve only had issues when I didn’t follow the instructions the first time around. It’s not like your traditional petroleum lubes so it is less intuitive thus most make the mistake initially without following the instructions. Takes a bit to get use to but several 1000 rounds about ⅓ in the winter well below 30 and no issues (other than what I stated before). I also use their extreme frog lube more in the winter versus the paste.
Used it, rejected it years ago when it first came out.

I know they have changed the formula since, but I’ll never trust the product for two reasons.

No matter how careful you are applying the lube, it gets where you don’t want it. That’s just the nature of any lube.since frog lube is designed to get into the pores of the metal and leach back out when warm, it by definition and design re-applies itself incorrectly. This was a huge problem in temps of mid teens and impossible to work with in sub zero temps and worse when snow turned to water and mixed with the lube. This was my fault because I did not research the product well enough, as the companies own literature hinted at this problem and when contacted, pointed it out.

Then there was the issue of mold growing during storage. They completely missed the mark on that one. Again, organic compounds just doing what organic compounds do.

Too many other quality lubes out there that are easier to apply, with the worse side effect being an oil stain, instead of a stoppage when you need it the least. Second shot.
300 Blackout, not just for sub-sonics.
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