Is there a safe 50bmg AR Upper..?

[supersonic]

Ben-
So, on that Bohica- what BBL length did you get? Is .416 brass still a Barrett proprietary-only product (still only available from Mr. Ronnie)? How's the blast envelope compared to the .50's?
-Scott

[soupersnake]

Nice post tink.

Let me get this right. The bolt handle on the Bohica upper threads into the bolt body via a hole which passes through the bolt body to the firing pin channel,
in such a way that the tip of the bolt handle may impinge on the firing pin while the pin is in a forward position protruding from the bolt face (firing position) so that when the bolt is pushed forward to engage the cartridge,
the pin may contact the primer of the cartridge as it is brought forward?

Nope. I just checked last night. The channel where the bolt handle threads into the bolt goes all the way through, but the threaded section of the factory bolt handle is not long enough to actually go in far enough to contact the firing pin. You can screw the bolt handle in as far as it will go, and it doesn't protrude into the firing pin channel.

I think the warning in the manual is mainly focused on people who might try to use loctite on the bolt handle threads, as that may certainly seep down into the firing pin channel, and gum things up.

I agree that it would be better to make the bolt handle channel blind threaded so there's no chance of even loctite or anything else entering the firing pin channel. BUT, as far as torquing down the bolt handle far enough to impede the firing pin, from what I observed and tried with a Bohica bolt/bolt handle last night, it would be basically impossible to do unless you were using a bolt handle of your own design with a longer threaded section.

[a.tinkerer]

Does the forward E-Clip travel past the threaded hole that the bolt handle screws into?

If so, how much clearance is there between the bore of the bolt and the outside edge of the E-Clip?

From an earlier comment, and from images of the bolt assembly pieces, I've been getting the sense that it's bolt handle/E-Clip contact that can stick the firing pin on the bohica bolt.

Nope. I just checked last night. The channel where the bolt handle threads into the bolt goes all the way through, but the threaded section of the factory bolt handle is not long enough to actually go in far enough to contact the firing pin. You can screw the bolt handle in as far as it will go, and it doesn't protrude into the firing pin channel.

I think the warning in the manual is mainly focused on people who might try to use loctite on the bolt handle threads, as that may certainly seep down into the firing pin channel, and gum things up.

I agree that it would be better to make the bolt handle channel blind threaded so there's no chance of even loctite or anything else entering the firing pin channel. BUT, as far as torquing down the bolt handle far enough to impede the firing pin, from what I observed and tried with a Bohica bolt/bolt handle last night, it would be basically impossible to do unless you were using a bolt handle of your own design with a longer threaded section.

Cheers
Tinker

[soupersnake]

Does the forward E-Clip travel past the threaded hole that the bolt handle screws into?

If so, how much clearance is there between the bore of the bolt and the outside edge of the E-Clip?

From an earlier comment, and from images of the bolt assembly pieces, I've been getting the sense that it's bolt handle/E-Clip contact that can stick the firing pin on the bohica bolt.



Cheers
Tinker

I don't have a bolt/bolt handle with me right now, but I'll check it out. From what I recall looking at it last night, I don't remember the front E-clip traveling past the hole for the bolt handle. I pushed the firing pin through its range of motion with my finger with the bolt handle removed and I don't recall seeing the E-clip pass by the hole, but I'll have to check it specifically for that to be sure. If it does travel past that point, it could be a point of binding I guess. There's just no way the factory bolt handle can bind the firing pin itself though, from what I could see.

[a.tinkerer]

S.Snake

I don't have a bolt/bolt handle with me right now, but I'll check it out. From what I recall looking at it last night, I don't remember the front E-clip traveling past the hole for the bolt handle. I pushed the firing pin through its range of motion with my finger with the bolt handle removed and I don't recall seeing the E-clip pass by the hole, but I'll have to check it specifically for that to be sure. If it does travel past that point, it could be a point of binding I guess. There's just no way the factory bolt handle can bind the firing pin itself though, from what I could see.

That firing pin assembly with the coaxial coil spring...


SEE BELOW


If that's a telescoping assembly, judging by the photo above - and by noting the distance from the bolt handle mounting hole to the bolt face, compared to the section covered by the coil spring (if that's a telescoping assembly) -- it looks like some kind of E-Clip/bolt handle thread interference could occur -- if the tip of the threaded portion of the bolt handle were to make it into the bore of the bolt...

Someone earlier did note having seen someone with one of these kits at a range - who'd somehow damaged that forward E-Clip.



This shows what I'm asking about.




The blue is what appears to be the range of travel (if that firing pin assembly is telescopic) The green and red look to me to be limits of the E-Clip's travel within the bolt head (give or take something...)






Cheers
Tinker

[supersonic]

The forward E-clip doesn't even enter the bolt head (in which the threaded hole resides on the right 2:00 position when unlocked). So, no, the clip isn't even an issue here.

EDIT: I did mention before the importance of a blind threaded hole for the handle - that would just be a "fail-safe" feature. The bolt handles (both old & new) are minimally threaded/limited by handle body (respectively) in such a way that makes it impossible for them to come in contact with the FP. <THAT only happened when I removed the handle bolt from the handle on the new one and threaded it all the way in. It was without its 'limiting factor' by the handle's body. However, the bolt still needs to have thicker walls, hence more durability PLUS a blind hole. All that aside, my first choice would be a cutout @ the right rear of the upper receiver (assuming structural integrity wouldn't be comprimised) so that Bohica could produce a near-solid bolt (one-piece incl. handle) that would be able to be removed as a whole from the rear (after the action is broken open.. The constant removal of the handle + the bolt head is really a PITA, not to mention a short-cut in design/materials, IMO. In time, if the investigation is definitive, I think we will find that it was something else that caused that FP to be exposed. We'll see.......Hopefully.

[supersonic]

No, the FP assembly is not 'telescoping.' See your little blue box up around the spring area? Well, starting from the left, go about 3 spring coils to the right. EVERYTHING to the left of THAT is what you would see coming out of the rear of the bolt after the FP has been FULLY engaged.

[grammaton76]

Out of curiosity, Tinker - you mentioned shooting a lot of old guns. Are you just a collector, or do you have some kind of really neat retro-firearms job?

Re: the Bohica handle - I believe if you were to really over torque on it, you'd end up cutting threads past the normally unthreaded part?

[supersonic]

On the first (old) handle, there are only ~3 threads compared to the bolt head's ~6, plus the handle has a square shoulder about 1/8" above the threads. The shoulder is larger in diameter than the hole, so that is what stops the handle from going any further. So, to answer your question(?)......no, impossible.

[Josh3239]

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

[a.tinkerer]

grammaton-


Just a collector - although I do service my own rifles, make my own moulds/cartridge cases/dies/loading tools

On the bolt handle issues...

Out of curiosity, Tinker - you mentioned shooting a lot of old guns. Are you just a collector, or do you have some kind of really neat retro-firearms job?

Re: the Bohica handle - I believe if you were to really over torque on it, you'd end up cutting threads past the normally unthreaded part?

On the first (old) handle, there are only ~3 threads compared to the bolt head's ~6, plus the handle has a square shoulder about 1/8" above the threads. The shoulder is larger in diameter than the hole, so that is what stops the handle from going any further. So, to answer your question(?)......no, impossible.

I disagree that it's impossible to get the end of the threaded stud of the bolt handle into the bolt bore.

The bolt handle is long.
The distance from the root of the threads to the shoulder is short.
The diameter of the bolt handle at that point is the least anywhere on the bolt handle.

Leverage

Banging that bolt into/out of battery (seems these things are notoriously sticky, and the bohica handles have been getting longer as the series matures) puts a great deal of stress on the area of that small-diameter root.
That's where I'd guess we'd see the bulk of stretch on the 'threaded section' of the bolt handle.

Screw the thing in, bang it back and forth numerous times.
Notice it's loose.
Screw it in some more (tighter too for good measure)
Repeat.

This is just me guessing here (and I've replaced more handles/levers on machinery than I care to remember) but I'm thinking it's possible to lengthen that bolt handle, from the shoulder to the tip of the threaded portion, by way of said action.

It would not surprise me to hear that someone in the past has managed to break one of those bolt handles at the root of the thread, just shy of that shoulder.
There's no journal, only a spotface and shoulder, is that correct?


Still, I wonder if that would make a rat's exhaust port's difference to anything at all - and I wonder if that E-Clip passes by the bore of the threaded hole that the bolt handle screws into -- and if it does, how much clearance there is (from the factory) between that E-Clip and the tip of that bolt handle when assembled -- also wonder what the tolerance is (from the factory) on that clearance.

By way of mensuration, that would take some things into account:
-Tolerance on the bore diameter of the bolt
-Tolerance on the 'wall thickness' of the bolt head at the threaded feature
-Tolerance of the depth of the spot-face where the bolt handle's shoulder registers when screwed in tight
-Torque spec on that bolt handle
-Tolerance of Length of the bolt handle, from face of the shoulder to the tip of the threaded feature
-Tolerance of the groove that the E-Clip registers in when properly installed
-Diameters of the E-Clip, Inner and Outer, and tolerance of their coaxial relationship


Ever hear of the concept of 'Stacking Tolerance'?


Still I don't know what relationship that E-Clip has to the bolt handle's threaded portion...

...but if they cross paths, those are the kinds of things one would take into account in design and manufacture of some of the features associated with their build and fit.






Cheers
Tinker

[supersonic]

.Screw the thing in, bang it back and forth numerous times.Notice it's loose.
Screw it in some more (tighter too for good measure)
Repeat.
This is just me guessing here (and I've replaced more handles/levers on machinery than I care to remember) but I'm thinking it's possible to lengthen that bolt handle, from the shoulder to the tip of the threaded portion, by way of said action.

You can 'guess' until the cows come home. However, that oversized-diameter shoulder STOPS any further downward movement of the threaded portion. It would take many, many 'whacks' of a heavy hammer to even cause the bolt handle to move in ANY direction. At most, the handle would be stripped & simply wobble side-to-side. I guess if one were to add intense heat to the shoulder and hammer it against an anvil, the diameter could be reduced. But that is a bit far-fetched, don't you think?

Still I don't know what relationship that E-Clip has to the bolt handle's threaded portion...

Then obviously you didn't read or understand my earlier post on my thorough inspection of MY Bohica MKIII bolt/handle assembly. It references your color diagrams to get the point across. Go back and read it again.

[a.tinkerer]

You mean your 4:00pm or so edit that was written after the post you reference?

Then obviously you didn't read or understand my earlier post on my thorough inspection of MY Bohica MKIII bolt/handle assembly. It references your color diagrams to get the point across. Go back and read it again.

Just saw that and thanks for answering.



I get the sense you don't appreciate my persistent question and inquiry on the safety features (and not so safety features) of AR-15 50bmg(or whatever suffix) conversion kits.

If you're sold on the notion that they are all perfectly safe and that it takes *error* outside the function and design of these conversion kits - good for you!

With this thread I'm exploring the questions that come up along the way as to which one(s) might be the solid choice.
It was noted earlier in this thread by someone else that they felt the recent southern california incident may well have been caused by a stuck firing pin.
Some things came up along the way noting issues with the firing pin and associated E-Clips.
I'm still wondering what could contribute (by way of the bohica design) to a stuck firing pin condition.

I think it's great that you are persistently contributing to this discussion.
Like I said above, I have a sense you don't like the challenge to the perceived integrity of the products.




Cheers
Tinker

[a.tinkerer]

Aaaand...


Went back and read the post following my colorful illustration (funny that the linked image above it has been scrubbed...)


If you can get the time together, can you photograph the rear of your bolt head?
I'm guessing (just checked outside, cows not home yet) now from what you've said that there'll be a bore in the bolt head roughly similar to the outside diameter of the firing pin body and spring, and that the E-Clip ends up touching off to the back face of the bolt head..?





Cheers
Tinker

[supersonic]

You mean your 4:00pm or so edit that was written after the post you reference

You seem to be reaching for what isn't there. Wrong post. Look down one more. There ya' go.

A (funny that the linked image above it has been scrubbed...)

"Scrubbed" because of its irrelevance to this discussion, that's all. I only include what is relevant.

By the way, it's nothing against you. It's just that it seems as though you are posting your observations before reading the entire thread and making assumptions after overlooking important facts that have been posted prior (and your posts are a little 'long-winded' for my taste, but that's just me) Anyhoo, NO, the bore is not 'roughly' the same as the FP, and NO, the e-clip doesn't stop against the housing. The front flange of the FP stops against the inside of the bolt face. I will post detailed pics in the A.M.
-Scott

EDIT: My bad, the bolt head is counter bored, so YES the bore IS roughly the same as the FP. My apologies.