KentG Posted May 5, 2006 Share Posted May 5, 2006 I have been going back thru posts trying to find info on lightened bolt carriers and determine if they are worth the cost. I use a Colt 16" carbine with a JP trigger group and have a F2 Comp on the way. Im kicking around replacing the bolt carrier with the JP Low mass carrier and buffer, not the full race unit but the one used with std uppers with dust cover. Is the reduction enough to notice? Thanks for any opinions! Link to comment Share on other sites More sharing options...
Zak Smith Posted May 5, 2006 Share Posted May 5, 2006 Probably a bad idea with anything other than a rifle length gas system. There are multiple different lightened carriers out there. The lower the mass, the more finicky the system will become. I am currently running the Y/M lightened carrier from MSTN and it has almost the reliability of a full weight carrier. Link to comment Share on other sites More sharing options...
George Posted May 5, 2006 Share Posted May 5, 2006 On a 16" gas system, you would be better off just using an adjustable gas block to tame some of the over-amped gas pulse the shortened gas system is delivering to the bolt. The alloy one would be bashed to shjt and the stainless one would probably make so little difference even after tuning down the gas system that it would just be an expensive way to get minimal real world results. With a 17, 18, or 20 inch AR that was running a full length gas system, this would be a good idea, but not on a 16 incher. BTW, I don't find the LMOS's to be any less reliable/finicky than a standard AR when kept clean/lubed and fed properly sized ammo from quality mags (this is the formula for making any AR reliable). Link to comment Share on other sites More sharing options...
George Posted May 5, 2006 Share Posted May 5, 2006 Yeah, it can be done. The big thing to remember is the the spring/buffer combo needs to be changed to reflect the lighter mass bolt carrier. Lighter carrier = lighter spring rate and less buffer mass needed to control bolt carrier speed and timing. This is where the adjustable gas block comes into play in the overall system. Once the carrier is lightened and the spring/buffer changed, the gas system is also tuned down so the lighter bolt isn't being hammered into the recoil system by a much larger gas pulse than is needed to drive the lightened system at the same speed as the heavier system. It is my opinion that not adjusting the LMOS system properly with the gas block actually makes a LMOS equipped rifle a more finicky system because of the excess bolt speed in play. This tightens the operating window of the overall system and is the reason for the LMOS being delivered with an adjustable gas block whenever you buy a JP rifle with the LMOS in it. The LMOS is a 3 point system (Lightened Carrier, Lighter Spring/Buffer & Adjustable Gas Block) and like a Tripod it needs all three legs to stand on it's own. Link to comment Share on other sites More sharing options...
Nick Weidhaas Posted May 5, 2006 Share Posted May 5, 2006 Yeah, it can be done. The big thing to remember is the the spring/buffer combo needs to be changed to reflect the lighter mass bolt carrier. Lighter carrier = lighter spring rate and less buffer mass needed to control bolt carrier speed and timing. This is where the adjustable gas block comes into play in the overall system. Once the carrier is lightened and the spring/buffer changed, the gas system is also tuned down so the lighter bolt isn't being hammered into the recoil system by a much larger gas pulse than is needed to drive the lightened system at the same speed as the heavier system.It is my opinion that not adjusting the LMOS system properly with the gas block actually makes a LMOS equipped rifle a more finicky system because of the excess bolt speed in play. This tightens the operating window of the overall system in my estimation and is the reason for the LMOS being delivered with an adjustable gas block whenever you buy a JP rifle with a LMOS in it. The LMOS is a 3 point system (Lightened Carrier, Lighter Spring/Buffer & Adjustable Gas Block) and like a Tripod it needs all three legs to stand on it's own. Regarding George's comments. For the most part I agree with everything he said and he has much more experience than I. However, I chose to not play with my JP adj. gas block and leave it wide open. I have had no problems and my rifle shoots great. I run a JP15 20" upper with the lightened ss JP LMOS carrier (not the aluminum carrier) and the JP buffer (standard buffer spring). Knock on wood, my rifle has NEVER failed or shown any excessive wear while running the gas block wide open with the lightened ss carrier. I keep telling myself I should experiment with the gas block adjustment, but the rifle runs and shoots so good, I don't want to screw anything up. I shot the NY State Rifle Championship at Square Deal last weekend and a guy in my squad was shooting a JP CTR02 and in the first stage his rifle was a single shot. He told me he had been playing with the gas block. After the first stage he opened it up and it ran the rest of the match. YMMV. Best, Nick- Link to comment Share on other sites More sharing options...
George Posted May 5, 2006 Share Posted May 5, 2006 The SS carrier is hefty enough and hard enough (compared to the alloy carriers) that it will not peen the plating off (what plating? it's stainless) like an alloy LMOS carrier will. This plating loss is what eventually kills the alloy carriers. The worst area is where the gas rings scrub the inside of the bolt carrier and next in line is the face of the carrier where it slams into the bbl extension. The "alloy" carriers have a noticeably reduced service life when fed full gas. My last one ran almost 10k before I replaced it. John Paul asked for it back to inspect because he had never seen one that ran reliably for that long ;-) Link to comment Share on other sites More sharing options...
Nick Weidhaas Posted May 5, 2006 Share Posted May 5, 2006 George that makes sense. Thanks for pointing out the differences. I've never tried the aluminum carrier. I bet it makes a big difference, especially with the gas system tuned. Nick- Link to comment Share on other sites More sharing options...
rpmwfo Posted May 6, 2006 Share Posted May 6, 2006 I plan on milling one of my carriers to lighten it once I get some time off from work. All it would take is a mill. I have wanted to play around with one to see how big of a difference it makes, but don't feel like shelling out the cash for a lightened carrier for a proof of concept. OTOH, I don't mind cutting up one of the carriers I have laying around in the parts box. I don't have a lathe so I can't duplicate the cuts on the JP. A mill will work for setting up one like the YM. Take a look at a few of the pictures of the YM lightened carriers and you will get an idea of where to make the cuts. Link to comment Share on other sites More sharing options...
MCFooter Posted May 7, 2006 Share Posted May 7, 2006 .... Take a look at a few of the pictures of the YM lightened carriers and you will get an idea of where to make the cuts. Where might I find some of these pictures? Link to comment Share on other sites More sharing options...
MyBoyElroy Posted May 8, 2006 Share Posted May 8, 2006 Link to comment Share on other sites More sharing options...
MCFooter Posted May 8, 2006 Share Posted May 8, 2006 Thanks, MyBoyElroy Two of the three Look the same is that the case or are there small differences between them? Link to comment Share on other sites More sharing options...
John Dunn Posted May 8, 2006 Share Posted May 8, 2006 Are those keys staked at all? Link to comment Share on other sites More sharing options...
MyBoyElroy Posted May 8, 2006 Share Posted May 8, 2006 Are those keys staked at all? Not as you see them pictured. The heavy carrier has functioned for years without problem but I do check it. Link to comment Share on other sites More sharing options...
George Posted May 8, 2006 Share Posted May 8, 2006 Are those keys staked at all? My eyes say they aren't I wouldn't leave home without a staked carrier key in any of my AR's! Link to comment Share on other sites More sharing options...
MyBoyElroy Posted May 8, 2006 Share Posted May 8, 2006 (edited) Thanks, MyBoyElroyTwo of the three Look the same is that the case or are there small differences between them? Two of the carriers are "lightweight" and the other is an original heavy National Match carrier I've had for years. The lightweights are identical. One is going into Sluggo's new rifle and one is in mine already. Edited May 8, 2006 by MyBoyElroy Link to comment Share on other sites More sharing options...
Paule Posted May 8, 2006 Share Posted May 8, 2006 Dan Young, who designed all of his current carriers and the patented one he sold to Les Baer (and still makes), will tell you that more carriers have problems due to improper staking than due to lack of staking. His preferred method is to polish the mating surfaces to perfection and coat with red loctite prior to torqueing the bolts to spec (snug but not overly tight). He does many thousands every year with few failures. Plus, 600 deg. of heat and you can take them apart of you need to replace a key. YMMV Link to comment Share on other sites More sharing options...
MCFooter Posted May 9, 2006 Share Posted May 9, 2006 OK you guys are begging TWO Questions. 1) Where can you buy the Dan Young Carriers? (I can't seem to find them with a search) 2) How do they compare with the JP's on Quality, Price and Service? Thanks Link to comment Share on other sites More sharing options...
George Posted May 9, 2006 Share Posted May 9, 2006 "Red" loctite on clean smooth parts IS as good, or better than staking, but just torque on them bolts alone ain't gonna cut it for the long haul. Link to comment Share on other sites More sharing options...
uscbigdawg Posted May 9, 2006 Share Posted May 9, 2006 And have any of y'all tried JP's stainless lightened carrier? I have the aluminum, but would like a comparison, as sometimes I don't feel like being so finicky and clean with everything. Rich Link to comment Share on other sites More sharing options...
Paule Posted May 9, 2006 Share Posted May 9, 2006 The lightened SS JP carrier runs well, but does not have forward assist notches. If that does not trouble you then it's a nice carrier. As is the case with any non-standard carriers, if you only change one piece you get little benefit, and maybe something less. The couple of ounces between a full weight and a milled carrier is usually not enough to cause any problems, but without tuning the other components there is little benefit either. Torqueing key screws alone will result in sheared screws, usually in short order. Link to comment Share on other sites More sharing options...
George Posted May 9, 2006 Share Posted May 9, 2006 Torqueing key screws alone will result in sheared screws, usually in short order. Learned the reason for that type of thing the hard way working on fast motorcycles in the 70's. High speed gettoff's because of a 10 cent part failure that should not have been allowed to happen aren't much fun ;-/ Luckily I walked away from that spill with everything but my ego as a top wrench intact ;-) Link to comment Share on other sites More sharing options...
D.Hayden Posted May 9, 2006 Share Posted May 9, 2006 Are those keys staked at all? Newbie quesiton.. what's 'staking'? Link to comment Share on other sites More sharing options...
George Posted May 9, 2006 Share Posted May 9, 2006 Staking = Chiseling a dent into the bolt head and the surrounding metal of the carrier so that the deformed metal locks the bolt head to the carrier key. This acts like a cotter key in a castle nut and keeps the bolt from turning back out on it's own under the beating the carriers take. There is a special punch for this that will dimple the bolt and surrounding metal in three places. Staking means that the torque applied to the bolts can be kept under the amount that stretches them and causes the bolts to shear as Paul mentioned. http://www.tpub.com/content/gunsandammo/TM...-249-23P_91.htm Link to comment Share on other sites More sharing options...
uscbigdawg Posted May 14, 2006 Share Posted May 14, 2006 Okay so I've resolved that I'm not going to run my aluminum LMOS at the US3GN. Just don't want to. I'm going to pick up either a JP lightened stainless carrier, MSTN lightened carrier or a Les Baer Slickside carrier (which I think is the same as the YM carrier). Basically, it'll be who I can get my hands on first. My uppers all run the JP gas block, so that's no worries. Are the stainless/reduced weight carriers going to need the JP Low Mass Buffer (like my aluminum one)? Thanks in advance. Rich Link to comment Share on other sites More sharing options...
Larry White Posted May 14, 2006 Share Posted May 14, 2006 (edited) Cant speak for the others but the JP comes with a buffer(red) for use with a standard spring or you can use the buffer/spring for your alum carrier.-------Larry Edited May 14, 2006 by lkytx Link to comment Share on other sites More sharing options...
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