LMT MRP Barrels

[underwoodbitsandspurs]

I have a CQB and I want a different barrel for it. It was sent to me with the wrong barrel, I talked to the dealer and LMT and in the end it's not getting replaced. Anyways, I am going to have a barrel made for it. I did some searching and could not find the answer. So basically I need to know if the parts off the MRP barrel can be swapped with a standard barrel? Compass Lake is going to turn my blank for me, so if the dimensions are different I will have to let them know.

So does anybody know details about the MRP barrels? What is the inside diameter of the gas block? Is the MRP straight gas tubes the same length as the bent standard gas tubes? Does the MRP barrel extension fit on a standard barrel without modifications? Will the straight gas tube work with gas blocks other then the MRP gas blocks? What contour does the SS MRP barrels have?

I could just buy a 16" SS MRP barrel and have it cut back to 14.5", but I already have a 1.25" diameter 20" SS Blank with 1 in 8 twist. Thanks, any help would be greatly appreciated.

[Duffy]

https://dbmg-llc.3dcartstores.com/MWS-conversion_p_33.html

;)

[ICANHITHIMMAN]

What barrel do you have what do you want?

[underwoodbitsandspurs]

https://dbmg-llc.3dcartstores.com/MWS-conversion_p_33.html
;)

Thanks for the info, I have looked at there website before.



What barrel do you have what do you want?

They sent me the CL 16" and I ordered the CL 14.5". What I would like to do now is take all the parts off the 16" and install them on a different barrel. I want a 14.5" SS barrel for it too, that is why I was looking at making the 16" a parts donor.

I took a closer look at the MRP barrel and it looks like the area where the extension goes is different. I thought just the barrel extension was different.

[SomeOtherGuy]

If your original barrel is not used much you should be able to resell it for nearly the cost of a new barrel, if that's an interest.

[ALCOAR]

Your crazy if you don't take advantage of the Rock barrels imho, however DBMG seems to be doing a good job with their conversion work on traditional barrels and that is the only option I would consider outside of a traditional Rock MRP barrel.

Not all the SS barrels are the same contour, for instance my Rock 18" SS has a larger contour behind the GB than the Rock 16" SS does that is pictured below. Beyond having the barrels being made by Mike Rock which I think is more than enough, the MRP barrels have several proprietary features or specs like angled drilled gas ports that make them a touch above every other traditional barrel imho. The MRP GB design is impeccable and the perfectly indexed and straight gas tubes never hurt anybody;)

Rock 16" 5R SS...

behind the GB
http://i888.photobucket.com/albums/ac81/trident1982/DSC00579-1.jpg

in front of the GB
http://i888.photobucket.com/albums/ac81/trident1982/DSC00576-1.jpg

[Shotdown]

The Rock Creek barrel website doesn't show any MRP barrels. Where did you find it and what price?

[ALCOAR]

That's correct as Mike produces the MRP/MWS barrel lineup under contract exclusively for LMT. He incorporates the LMT proprietary MRP specs into them, and then ultimately LMT sells them to their dealers and individual customers. That said, the Rock Creek site still has the MRP barrels essentially listed(just gotta know what to look for), as the MRP barrels lie within his two types of barrels he produces and the overall specs are described as noted below...just not the LMT MRP specific barrel specs.

So if we look on the Rock creek site, the MRP CL lineup of barrels falls directly under the following description....

"Rock Creek Barrels offers a line of 5 and 6 groove OEM production grade barrels in both stainless and chrome moly. These barrels are pull buttoned with leader bar equipped machines, stress relieved and inspected for uniformity. Available in quantity. Please call for pricing information"

And these barrels can be found in the LMT store or LMT dealer for $346 regardless of length or caliber...all MRP CL barrels are the same msrp. All my CL MRP barrels in the past and present have been no more then 1.5moa (10rd groups) shooters with quality ammo including my little 10.5".
http://www.lmtstore.com/bolts-carriers-groups/barrels/556-16-17-chrome-lined-threaded-muzzle-for-mrp.html

Looking at the Rock creek site, the LMT MRP SS models fall directly under his second mfg'ing category which is as follows...

"The flagship of Rock Creek Barrels' product line is the single point cut rifled barrel. These barrels are manufactured on twin spindle hydraulic Pratt & Whitney rifling machines and are available in 5R or 7R rifling profiles. All barrels are hand lapped to superb interior finishes. By the very nature of the way we modified these Pratt and Whitney machines, twist rates from 1:5 to 1:35+ are available."

These barrels can be found in the LMT store or LMT dealer, and the msrp is $466 regardless of barrel length or caliber just like for the CL models above. All my MRP SS barrels have been well below 1moa and they are really lights out!
http://www.lmtstore.com/bolts-carriers-groups/barrels/556-16-17-stainless-steel-threaded-muzzle-for-mrp.html

[MikeCLeonard]

the MRP barrels have several proprietary features or specs like angled drilled gas ports that make them a touch above every other traditional barrel imho.

Trident...I've been through a lot of AR15 configs...and keep coming back to the MRP...I love the damn things, and they fit my needs better than anything else I've ever used...But one question I've contemplated lately has been about the angled gas port and what benefit it serves. I originally thought it was designed to reduce gas-port erosion, but I can't get it to make sense in my mind.

Maybe that's not the reason at all for the design, but if it is, wouldn't the steel on the inside angle be more prone to erosion since there just isn't as much steel there as on both sides of the port at a 90 degree angle? Just seems like the acute angle could get burned out faster...see super technical illustration below.

and sorry for the hijack!

http://i95.photobucket.com/albums/l154/mikecleonard/GB.png

[careboy]

What barrel do you have what do you want?
http://www.primeaffiliate.com/track/images/22.gif

[ALCOAR]

Hey Mike, AR15Barrels has posted lots of great info on this topic, here is some of what he has posted over time...

"Reduced gas port erosion over the life of the barrel.
Since the port does not erode nearly as much, you don't need to "buffer up" over the life of the barrel like you should with regular barrels."

"If you look at how gas ports erode, you can see that it's NOT from the gas going around the corner from the breech, but from the muzzle.

http://ar15barrels.com/tech/gas-port-erosion.jpg

My reasoning for this is that the gasses and burning powder that are pushing the bullet down bore are all moving in a forward motion.
When the gas port appears, the expansion of the gas that feeds the port has to change directions.
If the majority of the gasses feeding the port were really from the breech end, I would think that the wear would be on the trailing edge of the port, not the leading edge.

I believe that LMT is smart for drilling the port at an angle as that's the natural tendency of how the gas wants to flow.
That should dramatically reduce port erosion through the usable life of the barrel, reducing the need for heavier buffers as the port wears oversized like most carbines."

MRP gas port...
http://ar15barrels.com/tech/mrp-gas-port.jpg

[MikeCLeonard]

Interesting and cool info...Thanks Trident! I had never seen that explained...and appreciate it!

-Mike :)

[ALCOAR]

My pleasure friend-0:)

Here are a few last quotes from AR15barrels regarding this topic that might be of some further interest or further help clarify...

"I can tell you this:
Every carbine barrel I have looked down with a borescope that had a shot-out throat also exhibited a lot of port erosion to the muzzle side of the gas port.

That tells me that the majority of the gas was flowing into the port from PAST the gas port, not before it.
That alone is my reasoning that a rearward slanted gas port is the superior design."

"They(MRP) drill the gas port at an angle which happens to co-incide with the direction that naturally occurs during erosion.

A normal gas port is drilled straight down into the bore.
When it erodes, the 90 degree corner is heavily notched off towards the front of the hole.

LMT simply drills the port at 45 degrees angle towards the front of the barrel.

When the gas flows back through the port, there is much less tendency for the port to erode because the port is already at the natural angle the gas wants to flow."

Thanks AR15barrels for the above sourced info:)

[underwoodbitsandspurs]

Thanks for all the info.

Thanks Trident for the info, I have always liked Mike Rock barrels too. The most accurate rifle I have ever owned was a Rem 700 .308 with a Mike Rock M24 profile barrel. I sold it in 2004, I still regret selling that rifle.

The barrel blank I have right now that I want to use for my MRP is a Mike Rock SS 5R 1 in 8 twist. I was going to use the MRP SS 16" and have it cut back to 14.5", but it has the mid length gas. I would prefer carbine gas because I might be cutting it back to 12" if I end up moving to Oregon this winter, and I also would prefer the 1 in 8 twist too. That's why I wanted to know if I could just take the MRP parts and put them on a standard barrel. But I looked at the MRP barrel closer and it looks like where the barrel extension goes on is different then a standard AR15 barrel. I guess I will have to call Compass Lake and see if he will turn my blank just like the MRP barrel.

Thanks again for all the info.