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POF Roller Cam Pin

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Replied by OleCowboy on topic POF Roller Cam Pin

You are correct.

A good friend of mine built an offroad suspension system for Jeeps. It was the BEST, yes the best, he was a mech engineer automotive suspensions his speciality and the head of suspension at a major auto company. He broke away, started his own company and initially was a success. I visited with him out in LA at the OffRoad Expo. I made the comment (lightly) thats it outperformed EVERYTHING out there, but was VERY complex, loaded with parts and complexity, requiring you to go to a course just to install it. But he replied NOTHING outperforms it. Time and mechanical components are not friends, he company finally went out of business several years later. Yes, complex parts array, lack of common repair parts and the inability for the system to be dialed-in by the end user.

Fine line between simple and complex systems in overall results...
10 years 2 months ago #34577

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Replied by SEMPERFIDOC on topic POF Roller Cam Pin

Keep it simple!
10 years 2 months ago #34582

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Replied by SOC on topic POF Roller Cam Pin


A few less complex ways to solve what is called "cam pin drag".

1. Profiled cam pin head shaped to reduce ware VS standard cam pin shape.

2. Cam pin head with a low friction coating or pressed on static bushing with similar qualities. (lower friction and softer than the upper receiver would be ideal moving any ware to a part that is easier to replace and less expensive.)

3. Low friction high durability coating applied to the upper receiver.

4. A spring placed between the bolt and carrier over the bolt tail.

All the above could be applied and only one requires a moving part added.

I like coating all metal on metal parts in diamondblack specifically.
10 years 2 months ago #34584

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Replied by SEMPERFIDOC on topic POF Roller Cam Pin


Diamondback??? Im not familiar with that coating, how is it compared to NP3? Is it a permanent coating or a temporary spray on aerosol?

Doc Jr
10 years 2 months ago #34585

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Replied by SOC on topic POF Roller Cam Pin


www.springerprecision.com/ionbond.php

IMHO Diamond black is to NP3 what NP3 is to chrome.

NP3 is basically just nickle with teflon in it.

Also DB is only a few microns thick when applied so it can be used in a precision barrel bore without effecting accuracy.

DB is also bonded to the surface in such a way that you can only remove it by removing the underlying metal.
10 years 2 months ago #34588

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Replied by gunner312 on topic POF Roller Cam Pin

I've been reading this and as someone who has been involved with the AR15 system since the very beginning of issue to the military. (1966 in RVN) I only have this to say about roller cam pins in the bolt carrier of the AR.

First, the head of the Cam pin only keeps the pin from falling through the bolt carrier.

Second, it keeps it in place on the top of the carrier, the hole perpendicular to the long axis of the pin gives clearance for the firing pin and clocks the square for retention/removal of the pin. The movement of the pin keeps the square properly clocked (timed)if the pin turns wrong, it will drag on the firing pin reducing pin strike and lock time.

I feel that having a round head on the pin gives this a chance to happen.

In 23 years in the service and over 30 years since, I have never seen a stoppage of failure to fire caused by the cam pin. The only problems faintly in that area were due to poor maintenance and a lack of operator headspace and timing.

Roller Cam pin? not necessary, and just another place for carbon top build up and be difficult to clean out of.

Semper Fidelis

Gunner312
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9 years 3 months ago #43843

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Replied by OleCowboy on topic POF Roller Cam Pin

Like you I have carried one since '67 and with 26 years of service never saw this as an issue.

NOW lets compare ROLLER vs FLAT Tappets (lifters). Are they in search of a solution to a non problem or just neater, keener or is their measurable performance gains and lifecycle improvements?

We already know the answer and its Roller all the way, its OEM at FOMOCO, GM and Chrysler in many engines.

How about this?

Balanced Bolt Carrier

With a long history of innovation Sharps Rifle Company (SRC) has done it again!
After developing the most technologically advanced AR-15/M16/M4 bolt in the world Sharps felt compelled to develop a bolt carrier unit to complement it.

We began by identifying what the shortcomings were with the traditional AR-15/M16/M4 bolt carrier. We identified two primary issues. The first being the rotational camming of the carrier during the unlocking portion of the operational cycle. The second being the canting of the bolt carrier group upon firing due to the gas pressure exerted to the gas key which naturally causes the front of the bolt carrier group to rise and the rear of the bolt carrier group to be pressed downward during its rearward travel.

Armed with this knowledge our team of innovative engineers set about to correct those shortcomings. We used computer design technology coupled with real world testing to address both of these issues. When the process was completed we sent the resulting prototypes to a broad spectrum of professionals who use their rifles hard for their personal evaluation and feedback. Their observations were then incorporated into the final design resulting in the new SRC Balanced Bolt Carrier (BBC).

The Sharps BBC is precisely machined from S7 steel which then undergoes our proprietary heat treatment process. Finally the BBC is finished inside and out with NP3 to minimize the need for lubricants, to aid in smooth operation and to make clean up a breeze. The BBC has the SRC logo machine cut on the side of the carrier which is visible when the ejection port door is open. It fits standard AR-15/M16/M4 rifles chambered in .223/5.56mm, 25-45 Sharps and 300 Blackout calibers.

srcarms.com/wordpress/bolt-carrier/balance-bolt-carrier/
9 years 3 months ago #43844

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Replied by gunner312 on topic POF Roller Cam Pin

Well,

In the case of a roller cam in an engine, the movement imparted by the cam moves the roller lifter in an entirely different direction (vertical) from a roller pin which imparts a rotational un-locking movement to the bolt caused by the rear-word movement of the bolt carrier. Oranges and apples in other words.

It seems that from what I read that the main changes are to the bolt and that the bolt carrier is more or less unchanged.

From what I see, the main changes are in that they have re-profiled the locking lugs and use S7 steel rather than the 9310 or S2 used in older bolts.

Now, if the re-profiled bolt lugs do in fact reduce the incidence of bolt lug shear, I think that it would reduce the amount of torque in recoil pulse which would enable the shooter to retain sight alignment and sight picture and get back on target quicker which speaking as a trigger puller, would be a good thing.

Getting back to bolt lug shear, I have read of this happening but only in arms that were either badly maintained or which had fired a large number of rounds. I think I remember numbers above 20000 and in one case estimated at 60000 plus. From photos I've seen it appeared to me that the failures could be attributed to under lubrication, poor maintenance/cleaning and possibly to the machining methods in use at the time of manufacture which would/could cause/allow stress risers at the point of shear. OR any combination of the previous.

If in fact the re-profiled bolt lugs do in fact do what they say, it's a good thing.

I'd go for those but a roller cam in my AR? - Nah.

Semper Fidelis

Gunner312
9 years 3 months ago #43850

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Replied by OleCowboy on topic POF Roller Cam Pin

It was not meant to be a compare between the two systems but rather I was addressing the question of results. Is there a performance gain (measurable) in going to the roller set up in the AR. We know doing that in auto engines produced measurable results, point being that if you cannot identify a positive result of some kind and at a level that is meaningful then not likely it makes for a need to modify. Its my guess that switching to the roller has to provide a positive at an early rd count, say prevent failures occurring at 10,000 rds...just guessing. Just based upon personal experience neither of us have seen identifiable and consistent failures at the point or even well beyond. Therefore I see no NEED (keyword) for the mod.

All that said there is another factor that comes up. Its the roller itself. In order for it to function there has to be space between it and its arbor. Since the roller is not removable, there is a gap all the way around then junk can creep in which may detriment it usefulness and results and create a negative where there was not one.

Pass.

As for the balanced bolt by Sharps, I am hoping to connect with them at NRA Nashville, hopefully one of their engineers...till then I will reserve judgement.
Last edit: 9 years 3 months ago by OleCowboy.
9 years 3 months ago #43851

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Replied by funfred on topic POF Roller Cam Pin

If someone were to put a roller on the cam pin, wouldn't it make more sense to put it on the same plane as the contact surface of the carrier. That's where it would be of any value, just like a roller lifter.
Puttin' it out in the air in case it hits the upper is kinda like curb feelers on a Jeep.

SRC's carrier, what were they able to address as far as camming of the carrier?
The only areas I can see being addressed are the carrier to upper interface - by tightening up the clearances, the bolt's inertia - by lightening the bolt, reduced friction between the cam pin and carrier, reduced friction between the bolt and carrier and reduced friction between the locking lugs.

Given any number of carriers and uppers that get thrown together for a nice fit, there's also those with the slick finishes.
I smell snake oil being used in SRC's marketing, at least as it has to do with camming of the carrier.

As far as balancing, no mention of how they manage that. Yeah, yeah...proprietary secrets.
Again, make the same mods for clearance and friction reduction that you made to allegedly address camming and, voila', your BCG amazingly runs smoother.
The forces acting on the gas key can't be mitigated to a "balance". If they did that, there would be two gas keys each on opposite sides of the carrier.
More marketing, me thinks.
9 years 3 months ago #43852

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