Critique My Rifle Build

[ShaneTyTrey]

I don't think a "Rifle" can legally have a barrel less than 16" long???

If you work though the proper legal process, pay some fees, it can be registered as a short barreled rifle.

Why this might make it legal, I still don’t believe you can hunt with a rifle in WA state with a barrel less than 16”.  Probably better verify that before you build it, especially if building it as a hunting rifle.

[yorketransport]

Your recommended approach to use a light bullet and getting a highest possible muzzle velocity, I can see how that makes sense. I guess what I am surprised about (and maybe this shows my ignorance) is your comment about powders being barrel length agnostic.  I just assumed faster burning powders in shorter barrels and slower in longer.

Because in my initial (and probably foolish) desire to use factory ammo I have also wondered if going the other direction with a heavy bullet and fast twist to increase the chamber pressure a bit and keep that bullet in the little short barrel a hair longer to burn as much powder as possible.  It would lose some MV this way but the rotational energy would be higher and I am assuming that also helps drive bullet expansion. I have wondered if that’s the reason the new 8.6 blackout cartridge seems to take a super fast twist in a SBR to another level.

I appreciate your thoughts, especially the bullet weight and caliber choice. I really hadn’t thought of outsourcing to custom reloaders. I like that idea and if you have any recommendations they would be greatly appreciated.

The misconception that a shorter barrel needs a faster powder is pretty common. The fastest powder in a long barrel will still be the fastest powder in a short barrel. That doesn't mean it will be the most accurate or most efficient. Sometimes performance is more important than efficiency though.

The idea of going to a medium bore, subsonic round (8.6 Blackout) is an interesting one. I had a chance to play with a 338 Whisper (338/7mm BR) for a short period of time years ago. There weren't really any hunting bullets designed for that application at the time though, so it was just a fun way to lob 300gr SMKs for target work. Now there are custom bullets designed to expand and give good terminal performance from subsonic chamberings. The addition of an extremely fast twist barrel is a game changer as well. Rotational velocity plays a big part in expansion, especially with copper bullets. Since rotational velocity doesn't diminish at the same rate as linear velocity, it can help bullets expand below what would normally be considered the minimum velocity threshold.

If you weren't looking for factory ammo, something like a fast twist 338 might be worth trying. I'd be tempted to try a 33 Nosler, 338/375 Ruger, 330 Dakota. If you're going to try something a little crazy, you may as well go all out. That's how I ended up with the 338 SnipeTac pistol, and it turned out better than I hoped. Everyone said it would be a waste to burn 140gr of H50bmg in a 20"  barrel. I think the 2890 fps with a 300gr bullet out of a 20" barrel proved a lot of "experts" wrong. Just build what you want and have fun. If it doesn't work, just take the barrel off and try again.

[dreadi]

I don't think a "Rifle" can legally have a barrel less than 16" long???

If you work though the proper legal process, pay some fees, it can be registered as a short barreled rifle.

Why this might make it legal, I still don’t believe you can hunt with a rifle in WA state with a barrel less than 16”.  Probably better verify that before you build it, especially if building it as a hunting rifle.

There are no rifle minimum barrel length stipulations in the published regs.


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[James]

Thank you for taking the time to do that, I appreciate it.

Running lots of different calibers/combos through QL, the 300WSM is your best bet with 130TTSX, other cartridges don't get the velocity, but you are only going to get about 2550fps with RL17.  With the 130TTSX at 350 yds you still have about 1750fps which should expand the bullet, how much, don't know, kind of at the limit.

Thing that I would be concerned with, and which I don't have any experience with yet, is the 5-10% of the unburned powder entering the suppressor.  How much heat will that create burning 5-8 grains of powder within the can?  Hunting situations wouldn't be a concern, one to two shots, but load development or just sighting in the rifle may be problematic.

Pipe dreams, I'll never be as cool as Steve McQueen

James, build that gun and you will be as cool as this guy.

[James]

The whole medium bore subsonic high spin angle has me thinking.  I am approaching this from the traditional copper monolith perspective, using large amounts of impact velocity so even if the bullet were to zip between the ribs there is enough impulse momentum to guarantee reasonable bullet expansion.

I wonder what the percentage of energy of a bullet is in linear motion vs rotational.  I could make some calculations and get in the ballpark, but it’s going to be almost all linear. The real question is how much of bullet expansion is from impulse momentum of impact from the linear motion vs the rotational, that would be very hard to rough out, but I bet rotational impulse momentums contribution is higher than one would expect.  If I knew that, I could find the sweet spot of bullet expansion balancing spin and MV for a given limited amount of overall bullet energy.

The copper bullets I use in my muzzy expand nicely at very low velocities, much to the surprise of a deer and bear last year😊 But there are reliefs in the bullet and that I am pretty sure are there to initiate the expansion.
I know there are brands of copper bullets that fragment to offer effectiveness at lower impact velocities and some people swear by them, but if I am honest I am hesitant in that direction.

I guess to sum up this rambling, optimizing the bullet design and spin could be a path forward for a short barreled hunting rifle with non lead ammo. I just need a lot more data...

The misconception that a shorter barrel needs a faster powder is pretty common. The fastest powder in a long barrel will still be the fastest powder in a short barrel. That doesn't mean it will be the most accurate or most efficient. Sometimes performance is more important than efficiency though.

The idea of going to a medium bore, subsonic round (8.6 Blackout) is an interesting one. I had a chance to play with a 338 Whisper (338/7mm BR) for a short period of time years ago. There weren't really any hunting bullets designed for that application at the time though, so it was just a fun way to lob 300gr SMKs for target work. Now there are custom bullets designed to expand and give good terminal performance from subsonic chamberings. The addition of an extremely fast twist barrel is a game changer as well. Rotational velocity plays a big part in expansion, especially with copper bullets. Since rotational velocity doesn't diminish at the same rate as linear velocity, it can help bullets expand below what would normally be considered the minimum velocity threshold.

If you weren't looking for factory ammo, something like a fast twist 338 might be worth trying. I'd be tempted to try a 33 Nosler, 338/375 Ruger, 330 Dakota. If you're going to try something a little crazy, you may as well go all out. That's how I ended up with the 338 SnipeTac pistol, and it turned out better than I hoped. Everyone said it would be a waste to burn 140gr of H50bmg in a 20"  barrel. I think the 2890 fps with a 300gr bullet out of a 20" barrel proved a lot of "experts" wrong. Just build what you want and have fun. If it doesn't work, just take the barrel off and try again.

[Stein]

If I were a betting man, I would bet that rotational energy has next to no impact on energy delivered or bullet expansion.  When bullets open, I don't recall ever seeing any evidence they were spinning, there is no bending of the petals as you would expect if they kept spinning.  The force on the petals I have seen is always perfectly linear back the direction they came from. 

The coppers I hunt with won't open below 1500 reliably, I do agree you have valid concerns there.

I didn't read every reply, did you consider some version of a bullpup?  Seems it might be easier to deal with the barrel being too short than finding a bullet that will work.

[kselkhunter]

The criteria you've set have created a tradeoff of picking a cartridge/bullet combination that has enough velocity out of 10" barrel with high enough BC to deliver enough impact energy to harvest a 800-1000lb Roosevelt elk at 350 yards.   In factory ammunition.  And you prefer copper bullets.   That is a challenging goal.

If you could change the 350 yard requirement to something closer and/or the bullet selection, it would open up alot more options of cartridge and factory ammo.   

As of right now the only factory ammo that comes to mind would be something in a magnum caliber with high BC bullets at high velocities that is regularly loaded by factory ammo suppliers.  6.5 PRC, 26 Nosler, up through the 27/28/30/etc. to the 338 RUM and 33 Nosler are what come to mind.  The hard part is finding one that is available as factory ammo in the right bullet/cartridge combination and something you could acquire at a store or online realistically.  The 130gr TTSX in 300WSM suggested from the Quickload data doesn't exist as a factory round from anybody. 

[hunter399]

My biggest question is the supper high BC bullet gonna stabilize enough for 350 yards out of such a short barrel.

[ShaneTyTrey]

I don't think a "Rifle" can legally have a barrel less than 16" long???

If you work though the proper legal process, pay some fees, it can be registered as a short barreled rifle.

Why this might make it legal, I still don’t believe you can hunt with a rifle in WA state with a barrel less than 16”.  Probably better verify that before you build it, especially if building it as a hunting rifle.

There are no rifle minimum barrel length stipulations in the published regs.


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I believe 16” is the law from back when all the kids took hunters Ed, I just checked and it says that.

[James]

Hopefully its just that hunters Ed needs to update there info, because i don’t see it in the current regs.

How silly would that be if you could hunt elk with a 9mm that has a 4” barrel but not a 300 WM with a 15” barrel?

I believe 16” is the law from back when all the kids took hunters Ed, I just checked and it says that.

If the appropriate twist rate is chosen I can’t think of a reason it wouldn’t.

My biggest question is the supper high BC bullet gonna stabilize enough for 350 yards out of such a short barrel.

[emac]

.  I don't think i would want to shoot a 10" .300 WSM even with a can on it, without at least wearing earplugs under my muffs.

My 10" AR in 223 is hell.on the ears with no can .

I have a 6.8 spc with a 7.5" barrel and talk about hell on the ears. 

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[dreadi]

I don't think a "Rifle" can legally have a barrel less than 16" long???

If you work though the proper legal process, pay some fees, it can be registered as a short barreled rifle.

Why this might make it legal, I still don’t believe you can hunt with a rifle in WA state with a barrel less than 16”.  Probably better verify that before you build it, especially if building it as a hunting rifle.

There are no rifle minimum barrel length stipulations in the published regs.


BLACK HAMMER ARMS
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I believe 16” is the law from back when all the kids took hunters Ed, I just checked and it says that.

It looks like they need to update their publication for Hunter's Ed because it's not in the published regs and it's not in the WAC WAC 220-414-020

WAC 220-414-020
Unlawful methods for hunting—Firearms.
(1) It is unlawful to hunt any big game with:
(a) A fully automatic firearm.
(b) A centerfire cartridge less than 22 caliber for cougar.
(c) A centerfire cartridge less than 24 caliber for any other big game.
(d) A shotgun, provided that a 20 gauge, or larger shotgun, using shells loaded with slugs or buckshot size #1 or larger, may be used to hunt deer, bear, and cougar.
(e) A shotgun for any other big game, except that a 12 gauge or 10 gauge shotgun using slugs may be used.
(f) A handgun during a modern firearm season that does not meet the following criteria: Have a minimum barrel length of four inches, per manufacturer's specification, and fire a centerfire cartridge.
(g) Any rimfire cartridge.
(2) It is unlawful to hunt game birds with a shotgun capable of holding more than three shells.
(3) It is unlawful to hunt game birds or game animals, except bullfrogs, in a manner other than with a firearm, a bow and arrow, a crossbow, or by falconry.
(4) It is unlawful to hunt game animals or game birds with a shotgun larger than 10 gauge.
(5) It is unlawful to hunt game birds with a rifle or handgun, with the exception of blue grouse, spruce grouse and ruffed grouse.
(6) It is unlawful to hunt turkey with a weapon other than shotgun shooting #4 or smaller shot, bow and arrow, crossbow, or muzzleloading shotgun shooting #4 or smaller shot.
(7) A violation of this section is punishable under RCW 77.15.400, 77.15.410, or 77.15.430, depending on the species hunted.

[dreadi]

Hopefully its just that hunters Ed needs to update there info, because i don’t see it in the current regs.

How silly would that be if you could hunt elk with a 9mm that has a 4” barrel but not a 300 WM with a 15” barrel?

I believe 16” is the law from back when all the kids took hunters Ed, I just checked and it says that.

If the appropriate twist rate is chosen I can’t think of a reason it wouldn’t.

My biggest question is the supper high BC bullet gonna stabilize enough for 350 yards out of such a short barrel.

It's about as silly as the regs telling you that you can hunt Tiger Mountain during modern season with a 458 SOCOM AR pistol but not a 300 Blackout AR pistol.

[dreadi]

.  I don't think i would want to shoot a 10" .300 WSM even with a can on it, without at least wearing earplugs under my muffs.

My 10" AR in 223 is hell.on the ears with no can .

I have a 6.8 spc with a 7.5" barrel and talk about hell on the ears. 

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I can imagine. That's why I suppressed my 18"

[emac]

My 20" 6.8 rifle barks it is almost as bad as the pistol

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