.300 "Blastout?"

[OlongJohnson]

This is a little bit LARPy, but what the heck, we do some of that from time to time around here.

I've been contemplating a defensive-use, AR-based rifle built to "Utopia spec," i.e., no evil features, for awhile. The idea would be something that can be quickly and easily taken down to travel relatively incognito in standard-size hard-sided suitcase-like luggage, and reassembled when it's time to have a long gun available. A 1301 could be an option, but once it's all set up with lights and mag extensions, etc., it's really fiddly to take it apart and put it back together. The AR paradigm of punching a couple pins is much more attractive than fiddling with mag tube springs. Utopia is a no-fly zone for the NFA, so it will have a 16-inch barrel, no flash hider or can. A blast deflector that is not a flash hider in Utopia would be in bounds.

All the talk in the PDW thread has gotten me thinking about possibly using .300 BLK instead of 5.56. The idea behind this question is just the potential reduction in hearing damage in the event that it had to be fired without ear pro, possibly indoors. Obviously, supersonic .300 BLK is not going to be hearing safe, so it's like deciding whom to vote for in a Presidential election: Which one will do less damage, more slowly than the other? Is the difference enough to matter?

Burning ~25 percent less of a faster-burning powder for more time and expanding it into ~90 percent greater volume while doing more mechanical work (taking energy out) before uncorking it seems like it should add up to something significant, at least measurable if it's measured the right way. But does it make a difference in practice?

For subsonic rounds at personal defense ranges, I figure one might as well just go with a 9mm PCC and load it up with 147gr HST or Gold Dots for all the reasons that don't need to be itemized here. Which is probably worth doing a comprehensive pros/cons analysis anyway, but for now, let's just stipulate that the superior on-target effect of .300 BLK is great enough to stay focused and stick to the original question. (It approaches the ~2300 fps threshold to do rifle stuff instead of just poking holes in things.) Also, the only current-production, OTS PCC I'm aware of that doesn't have the same evil feature problem as an AR is the Ruger, and its barrel keeps falling off. I've told Ruger in writing that I'll buy one as soon as they make it with a non-fall-offable barrel.

I've spent quite a bit of time googling and can't find much on back-to-back comparisons between unsupressed, 16-in barrel 5.56 vs .300 BLK supersonic sound levels. Anyone have data or know where to find it? Anyone have subjective impressions from their own experience?

[awp_101]

Can the barrel nut on the Ruger not be tacked/TIGged/MIGged/Rocksett/JB Welded/etc in place? Mine has seen very few rounds up to this point, but I've never felt it was an issue since it's an easy adjustment. Same for my Browning ATD.

And for a featureless AR, what about a Fightlite (IIRC) lower with a neutered 16" upper?

[RevolverRob]

Objectively - less gas escaping the muzzle, the quieter the weapon will be at the muzzle end. The less gas escaping the ejection port, the quieter the weapon will be.

I'm not an otologist so I can't say for sure what is safe. Let's just take the OSHA standard - https://oshwiki.eu/wiki/Noise#Acute_hearing_loss_.28acoustic_shock.29

Apparently, 155db peak is enough for acute hearing loss that could be permanent.

Maybe some of our suppressor guys have ideas of what non-suppressed muzzle blasts are like Hansohn Brothers kedminster

[OlongJohnson]

And for a featureless AR, what about a Fightlite (IIRC) lower with a neutered 16" upper?

You read my mind. This thread is basically me trying to decide what to put on top of a Fightlite SCR lower. I was trying to save the SCR discussion for another thread. Utopia allows a threaded barrel on a long gun, just not a flash suppressor. So worst case, a thread protector on a standard AR barrel. And no grenade launchers.

If .300 BLK, I'm basically down to the DD S2W barrel, which is pretty heavy at 2.3 lb., or the Odin Works midweight with carbine gas. I think the Odin Works, listed at 28.6 oz on Primary Arms' site, probably has about the right weight to balance well (half a pound lighter), but it ships with an adjustable gas block.

My iron sight solution for the SCR is a rail-height Pic rail front gas block (so it's fixed to the barrel) with CZ Scorpion sights. I could just get a nice stiff free-float rail, but I want to be able to run a wood or wood-look handguard to keep it more traditional looking, for which there are options if you go non-free-floating. That is also why I want to go with carbine gas, rather than pistol. That's relevant because I'm worried the Odin Works barrel is ported big to run with subs and just let the customer dial it down with the gas block to get it right on gassier loads. Haven't been able to find any discussion about using it with a fixed gas block, or anyone talking about supers only.

If I go with 5.56, it's all much easier and I can just run a mid-gas barrel of whatever weight I like.

[757_Magnum]

The muzzle blast and pressure are a huge part of my reasons for jumping deep into 300 BLK and making 223/5.56 my secondary caliber for training and ammo availability. I'm still in the middle of my current ultimate 300 BLK build with 10.5" DD S2W barrel, and still haven't shot my Rattler, but my first pistol build with a Hanson 10.3" barrel seemed to be less jarring with 110 gr Hornady Black V-Max factory loads. I searched forums high and low for other observations, and the majority had the same results. I think the 5.5" Rattler has been reported to be similar to a 16" 5.56 with a different muzzle device. I'm going with a linear comp or blast can on mine.

As far as a Utopia long gun, my pick would be a Marlin 1894C in 357, especially now that they're back in production and reported to be even better than the sought after JM stamped ones. That caliber in a rifle barrel approaches 30-30, which is often compared to 7.62x39, which is compared to 300 BLK supersonic. Add an optic rail and/or a Midwest Industries fore end if you want a light, and you're good. I didn't have the optic and light, but I chose that over the neutered ARs when I lived in L.A. for a year during the recession back in 2009. Get the 1894CST if you have any cans.

[OlongJohnson]

1894 would be the gear train for this mission if I was permanently stuck in Utopia, but it doesn't as easily take down to a length that fits in normal, CTRL-SHIFT-n, suitcase-shape luggage. I know it's just one screw, but it's a pretty fiddly one that I'd rather only mess with when necessary. Not like the AR pins. And with an SCR, you can still use detachable 10-round mags for reloads.

[757_Magnum]

Ah, I missed the part about fitting into luggage. Well, it's sleek enough to fit into golf club bag if that's your thing :D.

[Spartan1980]

GJM would know if anyone does but there was a gunsmith in AK that built Guide Guns before Marlin did. Only they were betterer and were take down for stowage in the float planes up there. You could probably cobble 3 AR platform guns together for what one cost though. They weren’t cheap but they were cool!


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[OlongJohnson]

This one was discussed in the lever gun thread a few months ago.

https://www.chiappafirearms.com/product.php?id=107

There was a demo model on GB recently where the chrome had pealed off some notable locations.

[BobM]

GJM would know if anyone does but there was a gunsmith in AK that built Guide Guns before Marlin did. Only they were betterer and were take down for stowage in the float planes up there. You could probably cobble 3 AR platform guns together for what one cost though. They weren’t cheap but they were cool!


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Wild West Guns I think.

[mmc45414]

Much of this is what has me starting down the 300BO slippery slope, 16" in 5.56 just seems like ten pounds of shit in a five pound bag. This first occurred to me when a friend was beside me shooting his 26" R700, and while neither one was hearing safe you didn't feel the blast when the bolt gun was fired. I will always have both, but 300BO seems like it might be better for the things short barrel guns are good for.

I have also had one lower setup with the YHM pull pins, sure is a simple, $18 way to make something fit in a common duffle bag.

[Hansohn Brothers]

Objectively - less gas escaping the muzzle, the quieter the weapon will be at the muzzle end. The less gas escaping the ejection port, the quieter the weapon will be.

I'm not an otologist so I can't say for sure what is safe. Let's just take the OSHA standard - https://oshwiki.eu/wiki/Noise#Acute_hearing_loss_.28acoustic_shock.29

Apparently, 155db peak is enough for acute hearing loss that could be permanent.

Maybe some of our suppressor guys have ideas of what non-suppressed muzzle blasts are like Hansohn Brothers kedminster
For 300 BLK subsonic on an 8" AR platform, we are looking at 160+db at muzzle and 155+db at ear. 5.56 on an AR platform will be 165+db at muzzle and same at ear (155+db). .308 on a bolt action is at 170+db at the muzzle. Adding a silencer (YHM Resonator K) will bring down the noise level to 137ish db at ear and 145db at the muzzle.

Here is a good video showing measurements.
https://www.youtube.com/watch?v=DxEwobrBgpY

All things equal, the 300BLK subs will be quieter than 9mm subs due to the smaller diameter bullet.

[awp_101]

For 300 BLK subsonic on an 8" AR platform, we are looking at 160+db at muzzle and 155+db at ear.
Just for giggles, do you have the db for supers out of the same set up?

[OlongJohnson]

Do you have any idea where to find numbers for a 16-in barrel .300 blk unsuppressed? Ideally, with comparison using same equipment to a 16-in barrel 5.56 unsuppressed?

[Hansohn Brothers]

Just for giggles, do you have the db for supers out of the same set up?

Sure don't, but I imagine it would be closer to the 5.56mm numbers.

[Hansohn Brothers]

Do you have any idea where to find numbers for a 16-in barrel .300 blk unsuppressed? Ideally, with comparison using same equipment to a 16-in barrel 5.56 unsuppressed?

I'm sorry, we don't have a 16" 300 BLK AR style rifle, only 16" bolt actions.

[MistWolf]

...If .300 BLK...
See if you can't get someone to make you a 16 inch pistol gas, Dissipater type barrel in 300 BLK. Use a BRT Covert Comp. Since you're using drop in handguards, an adjustable gas block will work.

[Caballoflaco]

See if you can't get someone to make you a 16 inch pistol gas, Dissipater type barrel in 300 BLK. Use a BRT Covert Comp. Since you're using drop in handguards, an adjustable gas block will work.

An AR height sight post would make for a shitty cheek weld on an scr fight light reciever.

The other option OlongJohnson might consider since he wants a 16” barrel and would be limited to 10rd mags if traveling in a ban state would be an upper in 7.62x39 or 6.8 spc, although the latter would still be blastier all centerfire supersonic rifle cartridges fired indoors will be capable of causing permanent hearing damage.

[MistWolf]

An AR height sight post would make for a shitty cheek weld on an scr fight light receiver...

Worse than the ultra tall AR optics mounts that are currently popular?

[OlongJohnson]

Already addressed the sight issue in post #4:


My iron sight solution for the SCR is a rail-height Pic rail front gas block (so it's fixed to the barrel) with CZ Scorpion sights.


But this Dissipator concept is interesting. Would love to set the rail-height Pic mount at mid length rather than carbine. Been searching for a little while and can't find anyone who's done it in .300 BLK so far. Sometimes, being first is cool. Usually, being first is a PITA. Dahmek, another rabbit hole.


See if you can't get someone to make you a 16 inch pistol gas, Dissipater type barrel in 300 BLK. Use a BRT Covert Comp. Since you're using drop in handguards, an adjustable gas block will work.

My desire to avoid an adjustable on this build is partly for reliability; I'd rather not use it even if it could work.

[RevolverRob]

How about a 12" barrel with a KVP XL Linear Comp pinned and welded: https://www.kawvalleyprecision.com/KVP-XL-Linear-Comp-p/kvp-slim-xl-comp-blk.htm

Recoil would be reduced and what sound is there would be thrown forward, probably getting close to the 155 threshold, if not maybe a bit below it. The Linear Comp is a compensator, not a flash hider.

[MistWolf]

...My desire to avoid an adjustable on this build is partly for reliability; I'd rather not use it even if it could work.
I was looking at adjustability for super/sub, suppressed/unsuppressed, forgetting you want something for a jurisdiction where suppressors are illegal.

[OlongJohnson]

Did some googling on what is a flash hider and what is not in Utopia. The people on "Utoguns.com" basically focus on the language in the advertising versus the language in the law of what is prohibited, as the law provides no metrics for determining what is or is not. The principle seems to be that if the mfr. says it does any of the prohibited functions to any extent, then it is a no-go. So I also have a project to go dig up the actual code and itemize the language of each muzzle device's manufacturer against the language in the law, to figure out exactly what's likely to be GTG. Of course, the safest is a thread protector.

The BRT Covert comp web site page (https://blackrivertactical.com/WP/BRT-Covert-Comp-7-62-p7674675)states, "It provides low light performance nearly as good as the common A2 style muzzle device." Which people on Utoguns.com mostly agree is the manufacturer stating that it functions as a flash suppressor.

[OlongJohnson]

I was looking at adjustability for super/sub, suppressed/unsuppressed, forgetting you want something for a jurisdiction where suppressors are illegal.

That's what the pistol upper (an AW in Utopia) and single shot (cheap, handy length, takes down into three pieces that will fit in a backpack in seconds, nice trigger, accurate, 16.5-in barrel threaded from the mfr. and no action noise) are for.

Scout .300 AAC Blackout Stainless Steel with Black Stocks (https://cva.com/product/scout-35-whelen-stainless-steel-with-black-stocks-copy/)

Also available in .350 Legend, apparently.

54693

[mmc45414]

My 300BO plunge also includes this:
54692

[Borderland]

My 300BO plunge also includes this:
54692

That would be a super cheap way to get into 300 BLK. I'm not sure what purpose it would have for me because I have several .223 rifles. I seriously considered the Ruger American Ranch when I was exploring 300 BLK. Still interested but not a huge fan of Ruger bolt rifles, my only hangup. What MOA could one expect from a rifle set up like that?

[mmc45414]

What MOA could one expect from a rifle set up like that?
Dunno yet, I have had it for a while but not shot it much. Had a Sig Romeo5 on it, just mounted the 2.5x Tasco this morning. Also added the flash hider, I have no can and couldn't stand having threads with nothing, so I stuck a $10 flash hider on it.

One thing about the Rugers, they have three lug bolts, so they are good for a DBM.

[OlongJohnson]

I do like the AR mags on the RARR. Just to note, the earlier RARRs that used Ruger's rotary mag cannot be converted just by changing bottom metal. There are apparently some machining differences (feed ramps would be obvious) between old and new.