Is there a safe 50bmg AR Upper..?

[supersonic]

Okay, guys, it am the A.M. and I be havin' some pictures for you to peruse on this (at least HERE) FOGGY & COLD Saturday morning (I'm going to the range tomorrow regardless!!!) In any event, let's begin: This first one shows the firing pin being pushed to it's maximum travel forward. You can see that it clearly stops BEFORE the e-clip even comes close to being in contact with the bolt. The e-clips, by the way, function as follows: the front is to retain the FP rebound spring; the rear is to prevent the FP shaft from traveling too far back during rebound (which could cause the FP to "come off its 'tracks'). It is the front FLANGE (or 'shoulder') of the FP striking the inside of the bolt FACE that actually halts further movement of the FP:

The next FIVE pictures will demonstrate the relationship between the bolt handle ("old" style) and the bolt head. You will see how the shoulder right above the threads stops (as it was designed to) against the (yet another) counter bored shelf in the side of the bolt head. I also illustrate how the handle looks (from different angles) when installed.

[supersonic]

Now, an example of the "new" style handle:

This is the new style bolt handle fastener used as an example as to WHY the bolt handle bore in the head is vulnerable & needs to be a BLIND HOLE! EDIT: for those that don't seem to 'understand' what I'm getting at here (I thought it was pretty damn simple), it is just to show the vulnerability of the FP with this "through" bolt handle hole if, say, a foreign object (or even the use of the same size, but longer fastener) gets in that hole. It could cause the FP to bind, or 'lock' (as shown in picture). I assumed no one would think I was trying to show that this is proper assembly! For those that DID 'get it (I suspect just about ALL): kindly disregard this 'edit.'

Now, I show where EXACTLY the FP rides in the bolt. In the first 2 pics, I show you (fore & then aft) the 'beefed-up' surfaces that are the 'moving parts' of the FP. In the last 2 pics, I show you (fore & aft) the holes in which the 2 surfaces ride. In front is a counter bored hole in the bolt head; in the rear is a 'reduced diameter' hole in the bolt 'sleeve' (Bohica calls it a 'carrier')




Well, that's it kiddies! Hope someone got some edumacation out of it!

[CSACANNONEER]

SS,

You know the risks. Please, be very very cautious and stay safe!

[supersonic]

SS,

You know the risks. Please, be very very cautious and stay safe!

That, I do, brother......THAT, I do. I'm taken' her out (w/ my unfired Winchester 70 Stealth II .223 WSSM & my AR-10) tomorrow to do a bunch of 'fire-forming.' I loaded my first DTC round (before I found out about surplus powders=cheap!) with a MIL ball 647g in front of 224g of H50BMG. That will be all for that load. For the rest of the case-forming, I will be using the same components (CBC/MAGTECH virgin brass/CCI #35/647g ball) with the single exception of 218g of WC860!

[rbthntr64]

Bohica Firing pin

OK guys to clear up concerns with the firing pin design, I made a drawing of it to show what it does. The step down is designed to prevent the bolt handle, or with the latest revision, bolt handle screw, for coming in contact with the FP. The flange on the old style bolt, and the countersink in the new style, prevent you from screwing it in too far. ( read safety feature) The firing pin assembly is retained when the bolt is assembled into the action.

[rbthntr64]

<snip> I loaded my first DTC round (before I found out about surplus powders=cheap!) with a MIL ball 647g in front of 224g of H50BMG. That will be all for that load.<snip>

Why are you guys using such heavy loads? These are not Benchrest rail guns. I don't post my data, but can tell you i do not exceed 215 grains.

[CSACANNONEER]

Why are you guys using such heavy loads? These are not Benchrest rail guns. I don't post my data, but can tell you i do not exceed 215 grains.

210-215 grains of just about any .50BMG powder is a starting load with a 650-750 grain bullet. So, what you are saying is that it is not safe to shoot BOHICAs with anything above a very mild starting load? I really doubt that. Any manufacturer of a 50BMG firearm should obviously take into consideration the fact that someone will shoot surplus ammo from them. I don't believe any manufacture would put themselves in a position where they are producing a firearm which will not stand up to the pressures of a "normal" surplus round of 50BMG.

[supersonic]

SS, I understand you concern, but please don't missinform. If you put the bolt through the bolt handle and screw it into the bolt and bolt body correctly, it will not lock the firing pin. The Serbu, Ultra-lite and several other AR conversions use this same set-up.

After all the pics I posted and examples of how the bolt is constructed & designed, I assumed everyone would be able to understand that was merely a demonstration to back up my theory about the bolts' needing to be blind-tapped. Maybe I was overestimating some. Maybe I WASN'T. (?) 'rbthntr64,' why don't you describe how, exactly it was that I was "missinforming?" Please.

[rbthntr64]

So, what you are saying is that it is not safe to shoot BOHICAs with anything above a very mild starting load? I really doubt that.

No I am not. Please don't put words in my mouth. I merely am saying that I do not exceed that. If you choose to, that is your caveat. Anyone that assumes that a max load from a bench rest rail gun will work their grandpa's Savage is heading for a fools paradise. That is why there is a warning in Bohica's manual about using reloads. And as far as Surplus goes, you accept a certain amount of risk using that crap also. Google Argentine 50 BMG. There was a lot that stuff that came in that blew up several rifles and injured some people. Why would someone who spends $2k+ of there hard earned money risk that and injury by using unknown quality ammo

Maybe I was overestimating some. Maybe I WASN'T. (?) 'rbthntr64,' why don't you describe how, exactly it was that I was "missinforming?" Please.

By showing people who know nothing of the design, a bolt into the bolt of the rifle locking the firing pin. With the bolt body, and the bolt handle installed properly the firing pin will not lock. Why is it that alot of people fail to take responsibility for their actions. I can see it is a moot point to point out facts about the design. You guys have already made up your mind the design is flawed. BTW if you could even put a blind hole, tightening would distort the bottom and bind up the firing pin. The tip of the bolt act as a guide in the stepped down area of the firing pin.

I am new to your board here, but have lurked for long time without posting. I have been a gun builder for many years and an accomplished machinist. I am not a kool-aid drinker, nor am I so naive that some thing are not as they seem. The Bohica upper has had many revisions since its debut, being improved at each step of the way.

[a.tinkerer]

Thanks for your contribution to this thread.

...I am not a kool-aid drinker, nor am I so naive that some thing are not as they seem. The Bohica upper has had many revisions since its debut, being improved at each step of the way.

Do you think that the revisions to the Bohica conversion kits have made them safer for the end-user?


Also -- on powder charges and cartridge specifications -- will you please for the sake of this conversation post some factory (powder manufacturer etc) load data for the 50BMG (also for whatever 'other suffix' 50BMG surrogate cartridges you have data for...) so that we can those of us who don't shoot this class of cartridge can see what you're talking about?





Cheers
Tinker

[a.tinkerer]

Supersonic-


Thanks for the photos.




Cheers
Tinker

[a.tinkerer]

Josh-


Thanks for the comment.
I wonder if there are any other of this class of conversion kit that also have such redundant safety features.
Firing pin block = good feature!


I looked at the ferret website to see if there were any images of the works of the bolt - with no success.
I did however notice the competition track record of the ferret equipment -- looks good!!

Here is an older post on ARF written by the maker of the Ferret 50, Mr. Dave Moore. He posted this following the ALS KB

Since the mishap of a 50cal at the FCSA World Shoot I have received a lot of phone calls and emails asking if a Ferret50 will fire out of battery. I also see here that the same basic question is being asked. So I would like to post the reasons why your Ferret50 upper or rifle is safe.

The design of the Ferret50 blocks the firing pin, not just the hammer. We do this by a camming action in the bolt that retracts and blocks the firing pin from reaching the primer until the bolt is closed. How much bolt closure? The firing pin is flush with the boltface at 75% lockup. At a firing pin protrustioin of .020" the lockup is more than 80%.

The bolt lugs (3) and receiver lugs (3) can withstand approx 90,000 lbs of force - the 50BMG produces about 25,000 lbs of force on the boltface.

The bolt is also designed and vented so that in the event of a blown primer the firing pin channel does not allow pressure to build and the gasses are vented toward the inside of the receiver and away from the shooter.

It is important to me that my customers are safe, in fact it is job number 1 here. If anyone has any questions, feel free to call, email or post.

Thank you,
Dave Moore
Spider Firearms
Ferret50.com

Cheers
Tinker

[a.tinkerer]

Is it true that there is NO SAAMI SPEC for the 50BMG?

What standard is the (typical) standard by which to base one's handloading - other than factory load data?

Anyone that assumes that a max load from a bench rest rail gun will work their grandpa's Savage is heading for a fools paradise. That is why there is a warning in Bohica's manual about using reloads. And as far as Surplus goes, you accept a certain amount of risk using that crap also. Google Argentine 50 BMG. There was a lot that stuff that came in that blew up several rifles and injured some people. Why would someone who spends $2k+ of there hard earned money risk that and injury by using unknown quality ammo

Cheers
Tinker

[rbthntr64]

Do you think that the revisions to the Bohica conversion kits have made them safer for the end-user?
Also -- on powder charges and cartridge specifications -- will you please for the sake of this conversation post some factory (powder manufacturer etc) load data for the 50BMG (also for whatever 'other suffix' 50BMG surrogate cartridges you have data for...) so that we can those of us who don't shoot this class of cartridge can see what you're talking about?
Cheers
Tinker

First and foremost, I refrain from posting any load data of any sort. What works in my rifles may not in yours.

As to the revisions, I think they are more quality improvements rather than safety improvements. I have shot them all through the MkII with some MkIII upgrades. Receiver material changes, Chrome bolts, and bodies, Improved bolt handles, improved bi-pods, improved muzzle brakes, improved chamberings. Free float handguards, improved optics rails and Good customer relations considering he is a small operation.

What is that google link in your signature line? My PC identified it as a Virus.

[a.tinkerer]

Thanks for your comments

I'm just looking for published factory load data, not your specific loads.
The distinction of 'starting loads' came up around your comments, which has me wondering what we could use for comparison.
I don't run these cartridges - for the most part the BMG is much too new for my tastes!

First and foremost, I refrain from posting any load data of any sort. What works in my rifles may not in yours.

As to the revisions, I think they are more quality improvements rather than safety improvements. I have shot them all through the MkII with some MkIII upgrades. Receiver material changes, Chrome bolts, and bodies, Improved bolt handles, improved bi-pods, improved muzzle brakes, improved chamberings. Free float handguards, improved optics rails and Good customer relations considering he is a small operation.

What is that google link in your signature line? My PC identified it as a Virus.

Without any experience with the bohica or the community around it, I wonder how much attention is given to the bolt-handle mounting/firing pin channel issue (or non-issue, but it looks like an issue to me) on a daily basis.
Honestly, how often do you check for a stuck firing pin?

On the link in my signature line, I HOPE THAT'S NOT A VIRUS!
I'll explain -- this website has a notoriously crappy search feature.
Many members of the calguns community have commented on it - and one particularly creative member actually fired up a google-based Calguns specific search utility.
Clicking on that link gives you the search page, ready to go.
I quickly got tired of trying to find where it was posted here on the site (by way of using the Calguns website search...) so I just pasted it into my signature line so I can always find it.

Give it a shot.
It works great.







Cheers
Tinker