LMT Enhanced carrier again - where to get Cam Pin ?

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Dr.Phil
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Re: LMT Enhanced carrier again - where to get Cam Pin ?

Post by Dr.Phil »

Just to help anyone who stumbles upon this thread and was wondering what the deal is with the LMT Enhanced Bolt Carrier Group, I thought that I would repost this quote from Bill Alexander:
Taken From: http://www.m4carbine.net/showthread.php?t=3379
Bill Alexander wrote:Let us perhaps be a little more precise with regard to the details of the LMT enhanced bolt and carrier system. As shown the details are very often misinterpreted.

In the first instance one must understand why the system exists, more particulaly in the context that the design is brilliant in its execution, but as reported frequently on the errornet is not always reliable. The design basis for the assembly is specifically to enhance the durability of the M4 configuration as currently issued. This gun is to some extent unbalanced. Port pressures running military grade ammunition are well in excess of the design levels which leads to very high carrier acceleration rates (+22 f/s/s). this combined with chamber pressure drop often creates the undesirable condition that the bolt commences to unlock while still subject to a degree of head thrust from the cartridge case. The result is that the lugs are subject to a biaxial loading of both shear and bending.

The LMT system being both the carrier and the bolt seeks to operate directly in this gun and elleviate symptoms. The carrier is set up with a longer delay during the initial portion of its movement. To facilitate this longer cam path and movement of the bolt forwards in the carrier, the front edge of the carrier is extended such that it still continues to retain the extractor pivot pin. Additional exhaust vents act to drop the piston pressure faster and to relieve any blowby at the tail of the bolt.

The bolt itself is of particular interest. The function of the dual spring extractor is frequently misinterpreted as an attempt to add spring force to the extractor claw. Rather it reduces the fatigue that the extractor spring(s) undergo by allowing the use of longer springs with lower K values; the % relative compression during the movement of the extractor is reduced. Remember that additional extractor force is not required now that the carrier is slowing the extraction cycle. The mitigation of stress in the bolt is accomplished in several ways. Material is the least visible change but is important to the design. The traditional Carpenter 158 is abandoned, being replaced by a significantly tougher grade from a different manufacturer. The lugs themselves are generously radiused between lugs and at the rear the diameter is actually reduced to allow a larger transition radius to be machined. The incorrectly identified sand cuts on the lugs are stress relief cuts. These allow any individual lug to elastically deform and give a smoother load over the contact patch. While this type of feature is very difficult to calculate and even more difficult to implement it helps to place the lug in a true shear load rather than amplify the bending moment. As noted the lug opposite the extractor is relieved. This feature prevents the unequal transfer of load to the two opposite lugs but I would argue that the stress relief groove already in place largely accomplishes this purpose. This is a academic quibble so I will bow to LMT in this respect. There is one additional feature that can be found in the bolt, but I am not at liberty to disclose the detail.

When considering wether to use the LMT parts one must consider the weapon. Correctly ported guns will derive little or no benefit from a carrier that is specifically set up to absorb excessive port pressures and some degree of residual case pressure. If not sufficiently gassed the reliability will suffer. This is not a fault of the carrier rather a mistake made in the application so be careful with simple substitutions. The bolt itself is exemplary. If not constrained by a $ value the bolt is a worthy addition to any rifle and will do nothing but enhance the durability of this part of the system.

Bill Alexander
"Don't tell fish stories where the people know you; but particularly,
don't tell them where they know the fish."
--Mark Twain
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Dr.Phil
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Re: LMT Enhanced carrier again - where to get Cam Pin ?

Post by Dr.Phil »

UPDATE!!!

I just happened to do a quick search this morning and found the LWRCI Enhanced Cam Pins...
Image
https://leitner-wise.com/store/Precisio ... p200617391

I don't have confirmation of this, but since LWRCI is a spin off of the original company created by Paul Leitner-Wise, he likely told LWRCI that his Enhance Cam pin was not part of the original sale of the company.

If you are a fan of "Enhanced" AR parts like I am, you might also like his heavy duty buffer retainer pin.
Image
https://leitner-wise.com/store/G2-Heavy ... p141104163

Here is a link to one of my previous thread that goes over my Enhanced BCG experiences.
viewtopic.php?f=128&t=96365
"Don't tell fish stories where the people know you; but particularly,
don't tell them where they know the fish."
--Mark Twain
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dellet
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Re: LMT Enhanced carrier again - where to get Cam Pin ?

Post by dellet »

Dr.Phil wrote: Wed Jun 03, 2020 9:51 am UPDATE!!!

I just happened to do a quick search this morning and found the LWRCI Enhanced Cam Pins...
Image
https://leitner-wise.com/store/Precisio ... p200617391

I don't have confirmation of this, but since LWRCI is a spin off of the original company created by Paul Leitner-Wise, he likely told LWRCI that his Enhance Cam pin was not part of the original sale of the company.

If you are a fan of "Enhanced" AR parts like I am, you might also like his heavy duty buffer retainer pin.
Image
https://leitner-wise.com/store/G2-Heavy ... p141104163

Here is a link to one of my previous thread that goes over my Enhanced BCG experiences.
viewtopic.php?f=128&t=96365
I'm skeptical Doc.

Spend all this time and money tuning the gas, carrier and buffer systems, then the same guys try and sell me an "enhanced" buffer retainer that you only need if you're beating the crud out of it with an over gassed, high speed hard hitting buffer.

Thinking maybe they haven't seen your credit card come through their bank lately and know you like gadgets :mrgreen:
300 Blackout, not just for sub-sonics.
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Dr.Phil
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Re: LMT Enhanced carrier again - where to get Cam Pin ?

Post by Dr.Phil »

LOL!!!

Yes, it is totally unnecessary, but it is almost identical to the one on the HK-416, so it has to be awesome. ;)
Image
Actually, my interest in the the heavy duty retainer is pretty novel, it prevents the buffer from getting dinged up by the retainer.
The better fix for that is to actually removed the retainer or use the JP Captured system though.
"Don't tell fish stories where the people know you; but particularly,
don't tell them where they know the fish."
--Mark Twain
laid_back
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Re: LMT Enhanced carrier again - where to get Cam Pin ?

Post by laid_back »

I am chasing some lightweight parts for a build I am doing.
Ordered 2 Titanium cam pins from ironcityrifleworks.com. One Black Diamond coated and one CV4. $15 each.
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