Very custom big bore whisper rifle. 700 long action?

[fastline]

I am getting ready to sort through a big bore whisper project. I own a machine shop and wish to do much of the work myself or as much as is cost effective. I may use the 500 SW brass and custom machined bullets. Stay subsonic, with suppression. Very high grain slugs only or until I find a point of too much length to stabilize flight.

I was originally going to chop up a 700 short action I have but now not sure if I can really make that work. Bullet length may be over 3" and the bottom opening on the short is about 2.8". I am not above machining out what I need within reason. The long might be a better way to go but I am now questioning the 700 platform all together.

I would like to buy a bulk length barrel rifled to my spec and I will crown, chamber, and thread it. Barrel availability may dictate which direction this goes.

here is a short list of requirements. Please advise if you can.

1. Bolt action
2. Removable mag feed
3. Handle up to roughly 3.25" round length
4. Easy platform to work with and customize to new round.
5. Possibly barrel availability.

This will be used out to 300-400M, full floating.

If anyone can provide any type of drawings comparing the long and short 700 actions, that would be just super. I am still not sure if cutting up this short is a great idea.

 

[Scorch]

.500 S&W is a rimmed case. Choose a rimless case or consider another cartridge for your Whisper project. .458X2" anyone?

Magazine length for a Remington 700 short action is 3.080".

Buy a barrel from a reputable barrel maker, that way you'll reduce the amount of work you'll do if you have accuracy issues.

 

[darkgael]

Whisper

I love the idea. It does seem to me, however, that you are reinventing the wheel kinda. Heavy subsonic bullets and cartridges are readily available from J.D. Jones at SSK.
I wanted the same kind of set up, albeit a single shot, some years ago. I picked up one of Jones' fast twist barrels chambered for the 50 Gov't (50-70) case. 750 grain bullets at about 850 fps. Great and accurate shooter. At 300 yards, it has a retained velocity of 817 fps (so my ballistics program tells me).
Pete

 

[fastline]

I will have to machine the S&W brass, no biggy. I also plan to mod the short action to work with longer rounds. The frustrating part might be the detach mag. Mag kits are WAY high for what they are. I was considering brazing a simple toggle on the bottom of the receiver to work with a readily available mag.

However, with a few more numbers run, I might be able to run my target ammo and still stay right at 3" OAL round length. If that radically simplifies the build, that is probably a way to go. If I like it, I might do another with a long action which seems better suited.

 

[Slopemeno]

.458 x2, exactly. And what's the drop at 400 yards?

 

[darkgael]

Drop

.458 x2, exactly. And what's the drop at 400 yards?

I was unable to find velocity data for the 458X2 for heavy bullets of the type that the OP seems to want. Using velocity data for the .458 Whisper, assuming that 950 fps can be achieved, my ballistic program tells me that a 400 yard zero will have a midrange trajectory of +81.4" and a retained velocity of 892 fps at 400 .
With 100 yard zero, drop at 400 yds is 239 inches. Increase velocity to 1044 fps and drop is 200 inches.
One should expect similar velocity from any case used since the goal is to stay subsonic.

 

[Slopemeno]

I kinda figures the drop would be extreme.

 

[mapsjanhere]

As you're obviously going for something like a 50 BMG bullet in a 50 SW case (probably trimmed down to .532 to get rid of the half rim) you're better off with a long action. A P17 would be a great starting point, strong action, large opening; unfortunately these are getting scarce. If you can afford it, go for a CZ magnum system, all the space you want with an action build from modern steel.

 

[Clark]

I looked at the 50 SW case last month and passed.
I wanted a larger rim.
I went for the 50/70 or [56-50 centerfire ] case.
I made a lathe fixtures for shortened the case to 1/2".
I use a 186 gr .500" round lead ball from Track the Wolf for $12.50/100
I made a seater die that screws into two presses at the same time that swages the bullet when seating.



It is quiet with 1 gr Red dot 400 fps with 1.6 cu in gas expansion before bullet escapement [26" barrel].

It is quiet with 2.8 gr Red dot 800 fps with 3.75 cu in gas expansion before bullet escapement [60" barrel].

 

[darkgael]

Ha!

Clark: great little wildcat. It reminds me of larger version of the .44 Bulldog loads that I put together.
Pete

 

[Clark]

Pete,
1) In the middle of the night when they attacked, I was shooting raccoons with the 12 ga when they came out of the chicken coop. The next day the wife and neighbors complained.

2) To make less noise, I was shooting 22 and CB shorts. This required a brain shot, and I could only do that if they held still.

3) To stay quiet but get more power, I put a 26" 22 cal barrel liner on the end of the 22 rifle barrel [ making a very long gun] and shot sub sonic quick shock bullets. I still needed multiple body shots to stop one.

4) To stay quiet and have even more power, I have been getting body shots with a 45/70 and a steel case filler. With a 20" barrel I can only use 1 gr of powder and sound like a BB gun [will not wake up the wife in the middle of the night]. The threshold of super sonic gas escapement from the barrel is one atmosphere above ambient. I need a tiny charge and long barrel to get the muzzle pressure that low. That gives 400 fps on a 150 gr bullet. That is ok for side shots through the ribs and lungs, but I cannot get through the shoulder when shooting head on with the big ones.

5) To stay quiet and have even more power, I came up with the 50 cal. It has about the same ballistics as a 45/70 20" with a CB50 with a 26" barrel, marginal improvement. But with a 48" tube barrel extender with 1/2" inside diameter, I can use 2.8 gr of powder and get 800 fps and sound like a BB gun [making a very long gun again]. 800 fps is quiet on soft targets, but very noisy if it hits plywood. I have not shot any game with the extender on yet. The pic I showed above with ball still round makes all kinds of noise, as the gas can leak around a ball, reach supersonic speeds, and send a sound wave down the barrel like a wave guide.
I have to seat the bullet without deforming it so bad that it will not chamber.
I made a bullet swager / bullet seater die that takes two presses at the same time and a ram between them. This forms a meplat on the bullet, the cartridge fits in the chamber, and the bullet has .5" cylindrical sides so gas cannot get around it if jammed into the lands. The die is shaped much like the 50CB chamber, so that the squished Lead ball will fit in the chamber, but also seal gas.

 

[fastline]

These will run through a clip feed and I believe I have everything accounted for now including my max ammo length staying under 3" to work in the 700 short action. Should not be an issue. Still looking at high twist barrel blank options though. Only found one so far with a 1:9 twist. That is technically a little faster than I need. My calcs are looking at a 1:10 twist worst case and 1:14 for the lighter stuff.

I would have to work on different slug designs to achieve an accurate slug for the barrel I use I guess. I would use 750-1000+ gr.