Not a super common one but we've had at least one member build one I know (fatty maybe?). I've got it in my head that I need one of these things but I'm not finding a ton of info online.

I'm thinking of using a 10:1 twist barrel around 16-18 in length. I'd prefer 1:8 but that seems to triple the cost. I'm really just building it for fun, would be shooting up my stash of fun bmg projectiles and 750 amax I think. I'd love to hear some actual experience with respect to twist rates in this caliber, or ideas on who might be cutting really short twist .510 barrels that don't cost a fortune.

The action: R700LA. I know a lot of people frown on this one for lapua sized case heads but it seems to be the easiest to obtain and I don't think I'll be seeing lapua pressures in there. Getting it to feed is really my largest concern. I've not got much experience with the magnum/ultra magnum actions but it's my understanding the rails are just different to accommodate feeding the big cartridges? It would be neat if it could feed from a mag but not sure what that would require. I haven't found much on that aspect of the build. Considering 2 options at the moment: a) buy bare LA receiver (pretty cheap) and use custom PTG bolt that already has lapua diameter bolt face and M16 extractor, or b) Dealer is finding decent prices on complete receiver, would have to open bolt face and cut/install extractor.

Right now just shopping for parts. I haven't bought anything yet. It's pretty well uncharted waters for me though so thought I'd see if anyone has already been down this road and wouldn't mind sharing..

I've not seen one in the wild as a bolt gun.   The similar wildcats I've seen usually use a form of the Savage bbl system with lock nuts.    

Might ask SSK what they recommend.  

There must not be a ton of interest in this cartridge anymore. Maybe there never was. I will give SSK a call. From what I've read they aren't too helpful to guys building them on their own, and they don't seem to offer much other than dies and brass on their website. I'm fairly certain they used to offer encore barrels chambered for it.

Seems that most of what I've read online are people recommending a larger action than the R700 but I really don't think it's going to be an issue if I don't try pushing it past subsonic. GRT is showing only around 20ksi chamber pressure to get a 750 Amax to 1000 fps so I don't expect it'll be beating up the lugs like a lapua.

I just ordered the 1:8 twist .510 barrel so I have some time to sort that out I guess. I'm thinking a regular long action will work fine. I can open up the bolt face on that to lapua size and cut it for an M16 extractor without having to solder in the sleeve (I think).

The other long lead business that needs to be attended to is getting the form 1 submitted for a can. I have a BMG suppressor but it's really, really heavy (Elite Iron). I've never submitted a form 1 and I actually haven't bought any NFA stuff since the electronic crap came about. There is a local shop with one of those kiosk deals setup in it but I have no idea if they would let me send a form 1.

I have been considering the same thing not a ton of info though.

None of the Whispers ever caught on because JDJ wanted tight control over them. Now that Kevin has basically done the 338 Whisper I hope he keeps moving up the ladder but I have my doubts. I think most recommend the bigger actions because they were built around the Lapua from the ground up. I look forward to seeing what you come up with. I really want one eventually but need to play with my 500 Encore first. I grabbed a Bowers can but have yet to put anything through it. Because it's not popular people have done other 50 variations. One of them that seems fairly straighforward is using WSM brass and cutting it off at the shoulder. Nice not to need 338 Lapua brass or bolt face. I think it's basically straight at that point which some people don't like.

We definitely need a new standard or else we'll never have an easy button. How cool would it be just order up prefits.

Well the barrel is done and should be here by next weekend.

I have the donor action now, hoping to get the bolt opened up and extractor installed this week. I have never chambered a barrel, let alone made one from a blank so this will be fun.

Still plugging away at this thing. I got the bolt opened up for the Lapua case head and the new extractor cut in & installed. The barrel blank  and expensive dies are here and the reamer and gauges are supposed to show up this week as well.

I am a little unsure of the profile for this one. I'm thinking like a heavy palma except leave it straight 1" to the muzzle, but I'm not sure how heavy that will be.

I still need to send off the Form 1. This thing is going to weight enough without a bmg can on it I'm afraid.

If I built guns for a living I'd be broke.

I think I figured out how to chamber a barrel, I think. It closes on the go gauge and doesn't close on the no-go gauge. I still need to take some weight off of it but it is actually looking like a gun now.



And one with the Alpha can attached:



I need some ammo and lighter suppressor now.

I was going to post that American Reloading had 50bmg bullets but I forgot and now they're out. Look forward to seeing you shoot it.

Interesting, I’d like to own one of these some day.

There seemed to be a lot better selection of pulled surplus bullets back when I bought my BMG ('08 I think). I'm a bit disappointed the blue tips seem to be all dried up. I have a few I picked up years ago but they are all loaded into BMG rounds now.

Yeah I missed the good ole days for cheap projectiles. Because I don’t shoot a lot of 50 I just figured I’d stick up on factory ammo because it’s simple but I definitely should not have passed up on $.25 projectiles.

Trimmed some weight off the barrel and polished it up a bit. It seems almost reasonable until I screw the suppressor on now. I decided to put 1x14 threads on it for the time being, so I can use the BMG can. I left an extra inch on there just in case something went horribly wrong but I think I can just re-thread it for any reasonable size thread without getting into the minor diameter of those big honkin threads.



That can is a heavy bitch, and you notice it on the end of my M96, but you really notice it when it weighs more than the rifle it's attached to.

I think I'm going to try and use the old stock but not sure what will be left by the time I carve out room for the barrel.

I did order a 338 mag from MDT. Fingers crossed the whisper round fits in there okay. They wouldn't guarantee anything but said I can always send it back if it doesn't work. Assuming that works out does anyone know if the feed rails in the receiver will get in the way of the mag? I'm guessing they normally just straddle the mag feed lips but not sure if that holds true for a 30-06 going to a lapua case.

Took a bit of work but the stock opened up for the 1” barrel okay.

MDT figured out how to ship from WA to MO via barge I guess. In the mean time I decided to see what would happen and was a bit surprised to find that the internal mag (ADL) will fit 2 cartridges and feed them. Not super smooth and it’s a bitch to load them in, but they fed, chambered and extracted.


I can’t wait to try this thing out. Temped to give it a whirl in the back yard but next weekend I’ll be able to set up a chrono and do it right when I’m out at the farm.

MDT mag showed up but I’m pretty disappointed to report that the rounds won’t fit. They jam on the fwd groove pressed into the body.


The mag is measuring about 0.465 inside those bumps, and the bullet is still about 0.500” at that point.

I’m tempted to try and remove some material to get it to work but it’s an $80 magazine so I should probably just return it and come up with a new plan.

I decided to take a chance on the MDT mag, by that I mean hack it up so the whisper will fit. I have a DBM inbound, should be here today. So I'll spend the evening cussing at the stock until it fits in there.

I had a few thoughts bouncing through my head on this one but ended up running a 1/8" end mill down the rib, hoping it would knock enough of the height off the inside to give clearance. It almost worked. I still had to spend some time with a file on the inside to get them move freely. Bonus is now I have a window mag. Downside is it's probably not quite as durable as it was. It still feels pretty stiff though. The smaller end mill was chosen to retain some of the stiffness from the groove.

In case anyone is (reading this) or wondering why the hell im using a 60 year old, beat to hell, rotten ADL stock: it’s because I’m broke I really want to shoot this stupid thing.

I just wasted 4hrs of my life inletting an ADL stock using a pocket knife, sharpened screwdriver and a 1/2 end mill chucked in a drill, among other things.

There isn’t much left of it but it really didn’t turn out any uglier than it started:





Now I’m off to load some ammo. I have quite a bit of powder I bought 20yrs ago for my Beowulf that I never used much of. I think I’m going to start with H110 since it seems pretty common for this cartridge. I can actually still buy it, and I use quite a bit for 357 currently. I’m going to try the RE7 lil’gun and 4895 at some point. For now I think I’ll start with 23, 25 & 27 grains of H110 and see what that gets me.

Sometimes you just have to settle for good enough OP.

I have been following your build from the first post and I have to say I am more than a little envious. I have wanted a 510 Whisper for a while now so please keep the updates coming.

Just out of curiosity...

What are the odds that 510 whisper is traveling slow enough that if you shoot anything steel or even rock that those AP bullets will just bounce right back at ya?

They sure as shit do not have the velocity to penetrate so I would be cautious.

I once recovered a AP core after knocking a head sized chunk out of a boulder from 200 yards away.   Core deflected down and was found laying about a foot from the boulder face still sharp.  Could see where it corkscrewed and got scratched up as it was rerouted...

I’ve had some bad experiences with thumpers and ricochets. I think you’re right, they aren’t going fast enough to splatter or fragment, and they like to keep moving. That thought is the only thing that’s kept me from giving it a go in the back yard.

I don’t really have any plans to shoot the black tips out of this one, it was just handy when I was needing to make a dummy round. i have a bunch of blue tip and some spotter-tracer that should be fun though. The blue tips really need sizing (reason I got them cheap).

The only mechanical detail I have left to address is the bolt release. It came to me with a broken bolt release spring and the tab busted off of the trigger as well. I just got the side bolt release from PTG yesterday but I’m more interested test firing right now.

Tomorrow I’ll hopefully get to try it out. I borrowed the scope and rings from my BMG. I’m eying the fixed power SWFA scope that has 140 MOA of adjustment. May be optimistic of my gunsmithing and marksmanship abilities but I think it would be fun to push it out towards 1000.

If it doesn’t blow my face off I’m planning on parkerizing it just as soon as I get that bolt release machined. Oh and the stock. I think I may just bed it and refinish it and see how it works. It’s growing on me a little. I even have a little swivel/rail/bipod adapter I just picked up for it.

I made it out here, about a 3 hr drive and forgot the box with the damn chrono. All of these sounded like they had a bit of a crack, 23, 25 & 27 grains of H110 all sounded the same.

It was ejecting full rounds just fine earlier but was struggling with the empties for some reason. It’s like the ejector is too weak to kick them out.

It’s got no recoil and was very pleasant to shoot without ears. I think I can improve a bit with some load development and a purpose built can.

What length is your barrel? I couldn’t find anyone advertising the fast twist in .510 but when I called pac-nor they said it was no problem. I haven’t got it finished up to the point I can really see how it shoots.

From that last video you can probably see it still needed a couple tweaks. I chambered it too tight. A couple turns by hand and it’s really smooth now. Also had to replace the ejector spring and got a new firing pin spring as well. They were both rusted up bad when I took the donor rifle apart. I picked a real turd to build this one on.

Right now I’ve got it all taken apart waiting to get it parkerized. I did get the side bolt release milled into it. Also glued the pillars in and bedded the stock to the action and bottom metal. Not sure if that old stock will ever shoot worth a damn but it looks pretty nice now.

My alpha can is probably similar to the cyclops. I was getting tired of holding the thing up by time I got done test firing. I can’t stand the thought of another year + wait right now so I think I’m going to build one myself. Maybe I’ll get lucky and it will work well, maybe not. I guess it’s only a $200 tax stamp I’ll be out. Which reminds me, I need to get that Form 1 submitted.

Do you ever shoot any old surplus bullets in that, or just the amax’s? I haven’t found a ton of load data for it and so far I’ve failed to generate any of my own. Hoping next weekend I can do some real shooting.

Hopefully in another week or so I can post a pic of the turd all polished up.

I had a midnight parkerizing party last night and got that part taken care of. I gave up on getting it put together before I left town this morning though. The bolt, trigger and side bolt release need to be installed yet.

The damn recoil lug was supposed to be carbon steel but didn’t take a bit of the coating, I gave up on it after an hour. Not sure if not being affected by parkerizing is an indicator it isn’t going to rust? Probably wishful thinking.

Got it back together tonight but not without inventing some new cuss words. I buggered it up bad enough installing the side bolt release I ended up having to refinish the receiver. Turns out I didn't quite mill the through depth slot quite far enough aft and it was binding. Stupid f*(king thing is installed now though.

Finished (still slathered in oil):



Here is the damn side bolt release that gave me so much trouble:


And probably of most interest is the bolt work. This is the bulk of the work aside from the barrel. The nose needs to be opened up a bit but that also requires installation of a M-16 style extractor. I tried to get a picture that shows:

In case anyone is wondering:

Barrel blank: $300 (Pac-Nor 510 bore, 8 twist)
Reamer and gauges: $350 (PTG) could be rented I'm sure.
Dies: $250 (CH4D)
Bottom metal: $130 (Stocky's)
Mag: $80 (MDT)
M-16 extractor: $40

Donor gun: $400
Bolt release: $25 (PTG)
Recoil lug: $30 (Badger)

Of course a few other bits. Pins, springs, park solution, etc.

Someone not wanting or able to do the machine work would need to send the bolt out to be modified or buy a $300 bolt from PTG that's ready to go. The barrel could probably be sourced chambered and threaded for a savage type barrel nut.

It seemed like the old mag would actually fit 2 rounds and chamber them okay. I had always heard the feed rails would need to be opened up for a lapua case so that surprised me. I think I would still recommend using the bottom metal system of your choice. Feeding from a single stack mag like that eliminates all the headache.

Jumping in here kinda late, but I have a 510 whipser too and am just getting into it.

I actually love the look of the old wood stock on it.  I had a old Remington 700 converted into a integrally suppressed one, with the original adl wood stock!


I bought my 510 from a member on SH, but its a surgeon action, built by LRI.  Its actually a 7 twist barrel.



I havent gotten it out to shoot it yet, but I'm gettin ready to get it sighted in and get my form1 sent off for it.  I have built quite a few and already have some ideas in mind.  

I think I remember seeing that rifle when I was googling 510 Whisper stuff. That is a really nice looking setup.

What kind of mags did it come with? Curious if there’s an off the shelf option that will fit these oddballs.

they are made by accurate mag... based upon the 300RUM (3.715)  and engraved with 510 whisper on the bottom.  I'm gonna assume they were custom made.

ACCURATE-MAG

Its an amazing rifle.. way more than I needed, but when i looked into custom building one it would have been more than this one cost me for all the stuff I got.

Interesting. Yours don’t appear to have that groove pressed into the front that I was dealing with, but I see it on the pics of their website. That was a part of the build/conversion I hadn’t seen mentioned much.

I would like to see what you come up with for the suppressor. I have a few ideas there as well. I’m not enjoying having that 5# can on the front of it.

I’ve been collecting material and making sketches but haven’t nailed down a design. A bunch of cones is probably the most practical but k’s (done right) sound really nice IME. I have a 1.75 x 12” ti tube and a bunch of 17-4 and 7075 round stock sitting in the shop waiting on me.

ETA: I just realized I was following a thread elsewhere on your suppressor. Small world for sure when it comes to the big whispers. The spacing question never really got answered did it? I've been wondering about that as well, these are some long bullets and I'm not able to wrap my head around how a 2.5"+ bullet might relate to spacing.

It does not have the groove in them, so you might just reach out to them becasue its obvious that these were made for the build because they are stamped 510 Whisper.

As for the suppressor, if you look at the sales thread, that guy used 20 MJ-r mushrooms, and he said it sounded incredible.  I wanted to buy it from him but the freaking transfer would have been terrible.


My plan is to do what you said.  1.75" x 12-14".   I've thought about using 60 degree cones spaced like this

.81, .81, .81, .73, .73, .73, .65, .65, .65, .65, .56, .56, .56, .56

That is total stack length of 8.9"  I may put one more of each in there to pick up another couple inches plus 2.5"ish of blast chamber.



Current thoughts.  

Yeah that's about where I am right now. I may only go 11" or so in length but 60's spaced just about like that seem to be working well for others.

Those mushroom baffles are pretty intriguing. I do have to wonder how much all of those would weigh though.

I had solicited some ideas in the silencer building subforum a while back: https://www.ar15.com/forums/armory/Big-bore-subsonic-suppressors/55-542962/

One of the more knowledgeable sounding guys posted this example:


I think he's active on the form 1 forum as well. I'm not sure I understand the "SD" & "RSC".

50 is 50 degree
SD is code for Super Dupers ( i believe they were 50s)
RSC is below




I'm basing my design and thoughts off of just super sizing a known top tier 300 BLK suppressor.  I'd love to do a large volume "Flo" like WTT did, but the amount of milling wouldn't make it feasible for me!

I finally got around to getting some loads through the chrono:
M33 ball, 650 grns, H110, large pistol mag primer, 17" barrel
23gr  886 fps
25gr 990 fps
27gr 1082 fps

I realized when I went to grab some large rifle mag primers that I did not have any. So I must have been using reg rifle primers in the last batch. I had some blue tips left from that batch so I shot them too:
25gr  735.8 fps with a ES of 97.4 (5 shots).

They all blew when they hit the berm which kind of surprised me.

I think the mag primers must be important. Probably more so with these loads aren't making much pressure in a big empty case. I have always heard to use them with H110 but I guess I blanked that when loading the last batch.

Hopefully I can find some N110 to try for the next round.

Oh and still waiting on the stamp for the suppressor so no updates there.

ETA: Just to keep everything tied up nicely here is the link to the suppressor that is finally in work:
https://www.ar15.com/forums/armory/Big-bore-subsonic-suppressors/55-542962/?r=-1&page=1&anc=5993655#i5993655