Mountain 50 BMG Rifle Build

[smorgousford]

Due to the enormous range that I have available to use, I decided that I "needed" a very long range caliber gun to play with (in addition to my .260 build). I know there's not usually a lot of 50's in this forum but I thought it would fit here since it's a bolt action that I plan on using for hitting long range targets "precisely". Thus, I came up with the following (nicknamed the Howitzer):

- Safety Harbor single shot 50 BMG upper with a 22" barrel
- Seekins Precision AR lower
- Magpul MOE Rifle stock
- Zel Custom Mfg billet aluminum buttstock adapter with Pachmayr pad
- Atlas V8 bipod
- TPS steel rings
- Super Sniper 10x42 scope
- Bubble level mounted to scope
- Larue Tactical Jimmy Plug magazine well filler

Total weight is just about 18lbs. I'm going to run it through my chrono soon to see how fast it's pushing things through a 22" barrel so I can come up with a ballistic table for it. I'll also provide some range targets at that time.

Here are some pictures of the rifle and the mountain range where I will be shooting it:

 

[clayne_b]

Looks good man! I like the colors scheme you got going.

 

[bm11]

18 pound .50? Better you than me!

 

[smorgousford]

18 pound .50? Better you than me!

There's actually a few videos of this same setup (barrel length, muzzle brake, weight) on YouTube and it doesn't look bad at all (just look up Safety Harbor 50). There's a lot of unburned gases coming out so velocity is considerably less than the 30"+ setups. Of course that makes a huge fireball and muzzle blast so I'll be putting on double hearing protection. The muzzle brake is also a pretty efficient design which adds to the reduction in felt recoil. My plan is to shoot this from the shoulder from time to time!

 

[din]

Looks like a nice little prairie dog set-up.

 

[TheSolitaryTraveller]

I've picked up a .50 cal once, the first thing i said was "Nope". Because my god the weight of those things, would make me drop it and leave it if I was traveling on foot with on.

but 18 pounds is pretty good, considering thats with the optics and bi-pod. But the ar-15 lower is something I always find weird looking on these .50 cal designs.

 

[kristian55]

The firing range which planned?

QUOTE=smorgousford;2519313]Due to the enormous range that I have available to use, I decided that I "needed" a very long range caliber gun to play with (in addition to my .260 build). I know there's not usually a lot of 50's in this forum but I thought it would fit here since it's a bolt action that I plan on using for hitting long range targets "precisely". Thus, I came up with the following (nicknamed the Howitzer):

- Safety Harbor single shot 50 BMG upper with a 22" barrel
- Seekins Precision AR lower
- Magpul MOE Rifle stock
- Zel Custom Mfg billet aluminum buttstock adapter with Pachmayr pad
- Atlas V8 bipod
- TPS steel rings
- Super Sniper 10x42 scope
- Bubble level mounted to scope
- Larue Tactical Jimmy Plug magazine well filler

Total weight is just about 18lbs. I'm going to run it through my chrono soon to see how fast it's pushing things through a 22" barrel so I can come up with a ballistic table for it. I'll also provide some range targets at that time.

Here are some pictures of the rifle and the mountain range where I will be shooting it:



















[/QUOTE]

 

[smorgousford]

The firing range which planned?

In the 3rd picture down you can see one of the "ranges" that I'm planning to shoot. I'm planning on shooting this from about 800 yards to about 2000 yards. I have a Swarovski laser range finder that I've had range to about 1800 yards so far (in bright sun). At my altitude (12,000+ ft), even a regular 660gr XM33 round stays supersonic for just over 2000 yards.

 

[smorgousford]

Double post

 

[smorgousford]

I've picked up a .50 cal once, the first thing i said was "Nope". Because my god the weight of those things, would make me drop it and leave it if I was traveling on foot with on.

but 18 pounds is pretty good, considering thats with the optics and bi-pod. But the ar-15 lower is something I always find weird looking on these .50 cal designs.

I completely agree with the AR-15 lower looking weird on the 50. However, I wanted to keep the weight as low as possible and I already had a spare AR lower so this is what became of it. I used some paint and the Jimmy Plug to try to make it look a bit more acceptable. I have to hike in about 3/4 of a mile to shoot so there was no way I could deal with a 30+ lb gun and enjoy it.

 

[kristian55]

Interesting, I compare it to .510AM
but the length of the barrel at 510AM-30",Twist 1-15.
What loss of speed per inch barrel?

The firing range which planned?

In the 3rd picture down you can see one of the "ranges" that I'm planning to shoot. I'm planning on shooting this from about 800 yards to about 2000 yards. I have a Swarovski laser range finder that I've had range to about 1800 yards so far (in bright sun). At my altitude (12,000+ ft), even a regular 660gr XM33 round stays supersonic for just over 2000 yards.

 

[smorgousford]

Interesting, I compare it to .510AM
but the length of the barrel at 510AM-30",Twist 1-15.
What loss of speed per inch barrel?

According to the manufacturer, Safety Harbor Firearms, they measured the following from one example of each barrel length on one day (so not a very large data sample):

18" Barrel: 2283.57 fps
22" Barrel: 2385.89 fps
29" Barrel: 2561.91 fps

Average of 3 shots
Temperature was 90+ F
Humidity was 85%
Ammo: Summit/French Reloaded M33 Ball
Distance from muzzle to chronograph: 20 Feet

 

[yellowXJ]

Man, that looks like it will be a bitch to get targets set up at those locations you have pictured. Where is this?

 

[smorgousford]

Man, that looks like it will be a bitch to get targets set up at those locations you have pictured. Where is this?

You're definitely right. I'm going to be shooting at rocks in that picture on the side of the mountains. I think the round should be carrying enough energy to make make a good dust puff. According to my calculations, the 750gr AMAX will be carrying around 4000 lbft of energy at one mile...

I have another area that's a little more level where I can actually setup targets.

This is in the middle of Colorado

 

[yellowXJ]

You're definitely right. I'm going to be shooting at rocks in that picture on the side of the mountains. I think the round should be carrying enough energy to make make a good dust puff. According to my calculations, the 750gr AMAX will be carrying around 4000 lbft of energy at one mile...

I have another area that's a little more level where I can actually setup targets.

This is in the middle of Colorado

Colorado was my guess but I know a lot of the area around here looks similar. I'm just north of Denver.

 

[Cascade_Sherpa]

Sweet project! Would that be legal to hunt with in CO? It would be badass to see the results of a 750 gr amax on a mulie or elk!

 

[TheSolitaryTraveller]

I completely agree with the AR-15 lower looking weird on the 50. However, I wanted to keep the weight as low as possible and I already had a spare AR lower so this is what became of it. I used some paint and the Jimmy Plug to try to make it look a bit more acceptable. I have to hike in about 3/4 of a mile to shoot so there was no way I could deal with a 30+ lb gun and enjoy it.

Isn't possible to get a .50 cal bmg ar-15 lower milled out for you or an ar-15 lower without a mag well, that way it's more flush as a design and you save a few ounces. Because i would think there would be such option out there, considering designing such a lower would be rather simple.

 

[smorgousford]

Sweet project! Would that be legal to hunt with in CO? It would be badass to see the results of a 750 gr amax on a mulie or elk!

According to the regulations that I see in my Colorado Big Game Guide (Official Colorado Parks and Wildlife Publication) there is only a minimum rifle limit (6mm, 16" barrel, 26" long, 1000lbft at 100 yards). So it looks like all the big game is possible with the big 50!

 

[smorgousford]

Isn't possible to get a .50 cal bmg ar-15 lower milled out for you or an ar-15 lower without a mag well, that way it's more flush as a design and you save a few ounces. Because i would think there would be such option out there, considering designing such a lower would be rather simple.

It is possible and is offered by some manufacturers (Safety Harbor actually offers one). I just had an extra lower around and it's a pain for me to get new firearms due to the distance to the nearest FFL from me.

Also, a few extra ounces behind the balance point is fine with me. The balance point of the rifle is actually where the tan action meets the black forearm. I actually added the billet aluminum adapter at the rear of the rifle to help mostly with balance.

 

[hognuts]

Sweet project! Would that be legal to hunt with in CO? It would be badass to see the results of a 750 gr amax on a mulie or elk!

Here is what a 750 grain AMAX does to a LITTLE mulie....poor bambi!

650 yards with 750 Grain AMAX, damn near decapitated him!

 

[S12A]

damn i love that Barret setup

 

[mzvarner]

God I wish I had access to a range like that. That weapon is pretty amazing too. Post a range report!

 

[smorgousford]

Here is what a 750 grain AMAX does to a LITTLE mulie....poor bambi!

650 yards with 750 Grain AMAX, damn near decapitated him!

That is great! You nearly made a mount with your single shot. Did he take a step after being hit?

 

[hognuts]

I really like the look of your weapon, that thing just looks mean! Negative on him taking a step. He literally flipped over backwards. He was facing down hill grazing when I shot. He was laying with his head up hill on his back in a pile when he dropped. The grass was "painted red" in a 3' perimeter around where he dropped! Enjoy the new rifle!

 

[kristian55]

From our conversation with Kirby Allen:

Chambering(510 AM), Min barrel length(30"),Recommended barrel length(30"-45"),Twist rate(1-15).

Loaded correctly out of a 30" barrel length, the 50 BMG should drive a 750 gr A-Max bullet to 2600 fps give or take 50 fps depending on specific barrel. Loaded to the same pressure in same barrel length, the 510 AM will get you a solid 2750 fps.

Now, if you load the 50 BMG up to where you JUST start to see an ejector rings on the case head, this is not dangerous at all but not the proper way to load the 50 BMG. Still if you do load to this level, the 50 BMG will get to around 2700 fps again plus or minus 50 fps. Loaded to the same level, the 510 AM will get over 2900 fps, again, plus or minus 50 fps depending on specific barrel.

According to the manufacturer, Safety Harbor Firearms, they measured the following from one example of each barrel length on one day (so not a very large data sample):

18" Barrel: 2283.57 fps
22" Barrel: 2385.89 fps
29" Barrel: 2561.91 fps

Average of 3 shots
Temperature was 90+ F
Humidity was 85%
Ammo: Summit/French Reloaded M33 Ball
Distance from muzzle to chronograph: 20 Feet

 

[smorgousford]

I really like the look of your weapon, that thing just looks mean! Negative on him taking a step. He literally flipped over backwards. He was facing down hill grazing when I shot. He was laying with his head up hill on his back in a pile when he dropped. The grass was "painted red" in a 3' perimeter around where he dropped! Enjoy the new rifle!

Great story! If I ever draw a moose tag up here, this is the rifle that I'm seriously thinking about using. Ever see a moose do a backflip?

 

[smorgousford]

I was able to get the Howitzer out to the range today for a zeroing/chronograph session. Here's the data I came up with:

Load: PMC Bronze 660gr FMJ-BT
Ave Velocity: 2610 fps
Std Deviation: 11.25 fps
Energy at the Muzzle: 10,003 ft-lbs
Energy at One Mile: 2,829 ft-lbs
Time of flight for one mile shot: 2.78 seconds
Velocity at one mile: 1390 fps

This data is for my shooting conditions today (19.55 inHg absolute barometric pressure).

I think an average velocity of 2610 out of a 22" barrel is pretty good!

Here's a video of me shooting one shot:
IMG_1742_zpsebc7b6d9.mp4 Video by smorgousford | Photobucket

Fun times!