Photos My self designed/built 50BMG

jwSubMOA

jwSubMOA

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Minuteman
May 13, 2010
506
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Mississippi
#1
Thought yall might like this.I built this a couple of years ago and enjoyed every moment of it.It has a 30" barrel and uses a barrel nut like a Savage.The telescoping action allows the use of any caliber from 12.7mm Russian all the way down to any Magnum or standard cartridge through the use of interchangable bolt faces and firing pin tips.Currently I have the 50BMG,8mm Remington magnum,8mm Mauser and 308 Winchester.Barrel changes below .338 Lapua require the use of a barrel adapter that the barrels screw into and then use a barrel nut to set headspace.The trigger is a Remington 700 set to 4 lbs.Every part except the pistol grip and original barrel blank is handmade.Currently it has a 20X Super Sniper in Burris Extreme rings and the scope base is cut at 20MOA.I'm planning to go to Quantico over Labor Day weekend to compete in the 1000yrd FCSA match.Let me know what you think.
 
#8
Re: My self designed/built 50BMG

very simplified system. I really like it. Almost takes the bolt out of the system, just a the bolt face left. How does it cycle? Looks like it has potential to bind up being the bolt slides on the rails below it.
 
#9
Re: My self designed/built 50BMG

Nice work!!!

Looks scary. I would be too afraid to pull the trigger

I would love to see the muzzle blast on that thing
smile.gif


Kudos mate
 
#14
Re: My self designed/built 50BMG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">Nice work!!!

Looks scary. I would be too afraid to pull the trigger

I would love to see the muzzle blast on that thing
smile.gif


Kudos mate </div></div>

Thanks!I designed it with a 600% safety margin in 50 bmg so there would be no concern of structural failure.The snaller calibers approach 2000%,the bolt thrust being to low to be of any concern. I intended it primarily for 50bmg but realized it would be great for other calibers and load development.The brake is very effective but yes,the blast is awe inspiring.
 
#16
Re: My self designed/built 50BMG

I haven't been able to shoot since my motorcycle accident,but I'm hoping to go and fire it with some friends in the next couple of weeks.When we go I'll get some video.
 
#17
Re: My self designed/built 50BMG

That is verrry cool! It's always great to see what individuals are able to build. Looks like a M21 EBR from the grip back. It is definitely a unique design and very cool that you're able to swap different calibers relatively easily.
 
#18
Re: My self designed/built 50BMG

Thanks!You can swap calibers in less than 2 minutes if you hurry.When I recover and get my prosthetic arm and leg I plan on building a smaller version for .338lapua down,maybe 12-17 lbs.
 
#20
Re: My self designed/built 50BMG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwSubMOA</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: vman</div><div class="ubbcode-body">Nice work!!!

Looks scary. I would be too afraid to pull the trigger

I would love to see the muzzle blast on that thing
smile.gif


Kudos mate </div></div>

Thanks!I designed it with a 600% safety margin in 50 bmg so there would be no concern of structural failure.The snaller calibers approach 2000%,the bolt thrust being to low to be of any concern. I intended it primarily for 50bmg but realized it would be great for other calibers and load development.The brake is very effective but yes,the blast is awe inspiring. </div></div>

Being a stress/structural analyst when people quote safety margins I feel compelled to ask how they arrived at it.

Would you mind sharing how you calculated the margins on this?
 
#21
Re: My self designed/built 50BMG

I used the calculations for bolt thrust,Area of the case headXChamber Pressure.I then took that figure multiplied by 6 to determine the parameters for the bolt lugs and abutments.Using calculations for area in shear and the shear and yield strengths of the reciever and bolt materials(4140) to determine sizing and heat treatment required.The finished parts were fluidized bed heat treated to my specs to minimize distortion.The calculations for the smaller calibers showed loads that brought the safety margin to 2000% in some calibers.I assure you I wouldn't build something that would allow myself or someone else to get hurt.That is why it is heavily overbuilt.As a note the lug area is about 175% of the McMillan 50bmg action and near 300% in shear.
 
#22
Re: My self designed/built 50BMG

Thanks for answering it. Definitely a conservative approach, if you didn't take into effect the geometry factors they're easily covered in the 6x factor. I like the sanity check on the end as well, "what does the big toy use and how far off am I from that?"

Pretty nifty setup all in all.
 
#25
Re: My self designed/built 50BMG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwSubMOA</div><div class="ubbcode-body">Thanks!You can swap calibers in less than 2 minutes if you hurry.When I recover and get my prosthetic arm and leg I plan on building a smaller version for .338lapua down,maybe 12-17 lbs. </div></div>


Man I gotta give you a lot of respect for losing an arm and leg and continuing to pursue shooting.
smile.gif


BTW is that the JP tank break?
 
#26
Re: My self designed/built 50BMG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GIC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: jwSubMOA</div><div class="ubbcode-body">Thanks!You can swap calibers in less than 2 minutes if you hurry.When I recover and get my prosthetic arm and leg I plan on building a smaller version for .338lapua down,maybe 12-17 lbs. </div></div>


Man I gotta give you a lot of respect for losing an arm and leg and continuing to pursue shooting.
smile.gif


BTW is that the JP tank break? </div></div>


Man I appreciate the support!I love to shoot and work with guns and can't imagine not shooting.That brake is custom and works amazingly well.I have some recent video if I can post it.
grin.gif
 
#28
Re: My self designed/built 50BMG

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TOP PREDATOR</div><div class="ubbcode-body">definately on the same lines of a jp brake, i got one, works great.

is there a serial #000002 coming soon? </div></div>

One of these days.I am being fitted for my leg now and should get my arm soon.I hope within the next year to be able to do some new projects including upgrading this rifle.
 
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