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Posted: 9/4/2005 7:35:54 PM EDT
[Last Edit: 12/26/2005 7:52:04 PM EDT by clippen]
This is a 10",new, h buffer, xm855 ammo. It is like a delayed reaction. The bolt takes a little longer than usual to cycle and sometimes will not fully feed next round. The buffer spring sounds louder than my other ar's. Any ideas?
Link Posted: 9/4/2005 8:23:49 PM EDT
Are you undergassed? This is not usually a problem with SBRs, which are usually overgassed.
What buffer and spring are you using?

Link Posted: 9/4/2005 8:32:28 PM EDT
What BCG are you using semi-auto or M16?
Link Posted: 9/5/2005 8:46:58 AM EDT
Not sure to tell whether undergassed or not. The bolt seems to be cycling back far enough to strip another round out of the mag. The buffer is standard H-buffer and carbine spring. the BCG is semi-auto RRA. Lube is clp.
Link Posted: 9/5/2005 10:31:23 AM EDT
Just cleaned and relubed w/ Breakfree CLP. Runs great for about 200 rnds then seems to get so dirty it starts slowing down the cycling rate and begins the feeding problems. Same ammo. Even tryed it on another lower of same set up. Same thing. Would it help to try a regular carbine buffer? How many rounds before cleaning is necessary to not impede functioning?
Link Posted: 9/5/2005 11:44:08 AM EDT
[Last Edit: 9/5/2005 11:52:14 AM EDT by Alpha-Romeo3]
You could try the following:

Use different brand of ammo to see if fouling in the action will improve.

Use bore cleaner inside the bolt carrier instead of CLP.

Use dry lube on the BCG instead of CLP.

Try a M16 BCG either LMT or Colt.

Try H2 buffer or the MGI rate/ recoil reducing buffer.

If any of these doesn't work, e-mail LMT on their website and request for warranty service.

Most guns are supposed to go 600 rounds minimum without FTF.

I have a stock LMT Defender 2000 M4 16" carbine with H buffer and my only upgrades are the LMT M16 BCG with Crane o-ring.

I have no problems with 600 rds. so far.

Good luck.

Maybe you could contact SMGLee, he have a tacked thread on top of this section.


ETA: SMGLee info
Link Posted: 9/5/2005 4:15:27 PM EDT
I guess I will try to use the dry lube. Any suggestions on what brand? Bore cleaner inside the carrier, too. As for the M-16 carrier, what is the purpose? Is this even legal? XM855 ammo, is this known to have heavy fouling issues? I thought xm855 was dam close to m855. I have a 16" carbine that runs great on this same ammo. What difference is the H2? Is it a lighter or heavier buffer? Thanks in advance, all help is greatly appriciated.
Link Posted: 9/5/2005 4:27:58 PM EDT
Link Posted: 9/5/2005 4:29:57 PM EDT
Link Posted: 9/5/2005 4:39:07 PM EDT

Originally Posted By C4iGrant:

Originally Posted By clippen:
This is a 10",new, h buffer, xm855 ammo. It is like a delayed reaction. The bolt takes a little longer than usual to cycle and sometimes will not fully feed next round. The buffer spring sounds louder than my other ar's. Any ideas?



OIL THE BOLT. Also check the gas key for looseness. Still don't get anything? Then change out the BCG for shits and grins.



C4


Thanks Grant.
What do you recommend for oiling the bolt, other than CLP? Do you carry the H2 buffers?
Link Posted: 9/5/2005 4:44:47 PM EDT
[Last Edit: 9/5/2005 4:46:14 PM EDT by C4iGrant]
Link Posted: 9/5/2005 4:54:56 PM EDT
[Last Edit: 9/5/2005 4:56:02 PM EDT by clippen]
Thanks -
I have doubts about the mags being suspect as I am working with about 20 different new Colt mags which work fine in the next rifle. When malfunctioning occurred I pulled mag and tested in another rifle. The key felt tight with my fingers but I did not put a wrench on it. I am really hoping it is a lube issue, and I will try your suggestions, as I have only ever used CLP. Does an M-16 BCG improve reliability that much?

ETA. I will swap a BCG in I know functions as well.
Link Posted: 9/5/2005 4:59:24 PM EDT
[Last Edit: 9/5/2005 4:59:46 PM EDT by fq1234]
Are you using an LMT Enhanced Bolt Carrier? If so, that could be the problem, they aren't made to be used with the shorties.
Link Posted: 9/5/2005 5:08:00 PM EDT
Link Posted: 9/5/2005 5:09:42 PM EDT
Link Posted: 9/5/2005 5:15:29 PM EDT
Yes, this is all new rifle and regular RRA BCG.(not enhanced carrier or bolt).
Link Posted: 9/5/2005 5:21:26 PM EDT
Link Posted: 9/5/2005 5:58:06 PM EDT
Roger that. I did check those (barrel retension screws) and will test all other items tomorrow. Thanks again for your expertise.
clippen
Link Posted: 9/5/2005 7:04:40 PM EDT

Originally Posted By clippen:
I guess I will try to use the dry lube. Any suggestions on what brand? Bore cleaner inside the carrier, too. As for the M-16 carrier, what is the purpose? Is this even legal? XM855 ammo, is this known to have heavy fouling issues? I thought xm855 was dam close to m855. I have a 16" carbine that runs great on this same ammo. What difference is the H2? Is it a lighter or heavier buffer? Thanks in advance, all help is greatly appriciated.


Using bore cleaner inside the gas chamber of the bolt carrier makes the fouling a little less and this is from years of experience.

I recommended dry lube because that's what I use here where I live in the desert.

It helps prevent dust fouling of the internal parts. Use different lube products, some will have more or less fouling.

Even if your current ammo is clean, I'm just suggesting to try something else just to try to eliminate the ammo issue.

The M16 BCG and the heavy buffers are always the way to go for carbines and shorties. I'm only using a LMT BCG with Crane O-ring and standard H buffer and it works for me but shorter carbines have to do more mods just to make it work more reliably.

The only last thing I would suggest and it's up to you if you want to. I also have some new pre-ban Colt magazines and I replaced the followers with Magpul enhanced followers. It will even make a slightly bad magazine work fine. The next level of magazine upgrade is replacing the springs with Wolff extra power springs.

Here's a reference big MRP thread: MRP Goodness thread link

C4iGrant of G&R tactical is a pretty good guy to deal with. I have been a loyal customer since my first order from him and they're one of my reliable supplier. He's great with communications and fast shipping.
Link Posted: 9/6/2005 4:27:14 AM EDT
[Last Edit: 9/6/2005 4:30:22 AM EDT by MSTN]
Link Posted: 9/6/2005 4:53:16 AM EDT
tag-
Link Posted: 10/30/2005 7:05:56 PM EDT
Well- I am still having problems. I have 2 identical set- ups now. 1 runs fine the other does not. I used different lubes, carriers, ammo, and mags, which all work in one carbine and not the other. I did not swap out lowers which will be my next step (ran out of range time). Has anyone ever had a bad buffer spring? When I pull the charging handle back slowly and release it slowly it acts as if it almost hangs up about midway back forward. I'm thinking bad spring or bur in tube. It feels different than other carbine

Wes- Extraction is perfect, feeding is the problem. Even with a fresh mag using the bolt release. The ammo is LC 03 xm855pd now, but it runs flawless in the other 10.5 mrp. The bore looks fine, but the round only moves forward about a quarter inch before stopping, so I think that is not the issue either.

UGGGGGGGG! Has anyone ever had a bad buffer, buffer spring, or buffer tube that produced these FTF.
Link Posted: 10/31/2005 2:52:06 AM EDT

Originally Posted By clippen:
Well- I am still having problems. I have 2 identical set- ups now. 1 runs fine the other does not. I used different lubes, carriers, ammo, and mags, which all work in one carbine and not the other. I did not swap out lowers which will be my next step (ran out of range time). Has anyone ever had a bad buffer spring? When I pull the charging handle back slowly and release it slowly it acts as if it almost hangs up about midway back forward. I'm thinking bad spring or bur in tube. It feels different than other carbine



Did you re-check the gas tube carrier key alignment?
Link Posted: 10/31/2005 3:29:51 AM EDT
Link Posted: 10/31/2005 12:43:07 PM EDT
[Last Edit: 10/31/2005 12:54:34 PM EDT by clippen]

Originally Posted By Tweak:

Originally Posted By clippen:
When I pull the charging handle back slowly and release it slowly it acts as if it almost hangs up about midway back forward.



Drop a round in the chamber, drop the bolt, press in on the bolt catch and fire. What happened?

Bolt cycles back to chamber

Pull the trigger and hold it to the rear. Fully retract the bolt and slowly let it go into battery, does the snag go away?

Yes, what does that mean?

Remove the bolt carrier and stip out the bolt. Slowly slide the carrier into the upper and see if it binds, Compare the fit of that bolt carrier and upper to that of the other carbine.



Seems the same.

There is a chunk that seems to be missing on the inside of the reciever, near the high wear area, which is not on the other carbine. see pics





This bolt action upper has less than 200 rounds
Link Posted: 10/31/2005 3:00:13 PM EDT
first of all, XM885PD is one of the dirtiest ammo I have shot so far...have you tried other ammo??

two.. send it back to LMT to get the bugs worked out.

Link Posted: 10/31/2005 3:09:26 PM EDT
Link Posted: 10/31/2005 3:15:56 PM EDT

Originally Posted By SMGLee:
first of all, XM885PD is one of the dirtiest ammo I have shot so far...have you tried other ammo??

two.. send it back to LMT to get the bugs worked out.




I have tried different ammo, but the other identical upper runs on xm855pd just fine. no problems at all. I know you have experience with these uppers, have you ever noticed the extreme wear as in the pics.

After seeing this problem, I supposed it will have to go back to LMT. I had this upper for a while waiting on a tax stamp. Also, it came from a dealer. Does it need to go back through the dealer or can it go directly to LMT from me. Is it warrantied? Thanks for the input.
Link Posted: 10/31/2005 3:25:20 PM EDT
[Last Edit: 10/31/2005 4:48:47 PM EDT by clippen]

Originally Posted By Tweak:

Originally Posted By clippen:
Bolt cycles back to chamber



It doesn't lock open on the bolt catch?


Yes, what does that mean?


That the hammer is dragging on the bolt carrier. Is the bottom of the carrier cut away so that you can see the firing pin?


There is a chunk that seems to be missing on the inside of the reciever, near the high wear area, which is not on the other carbine.


common wear



I misunderstood you. Yes, it locks open on the bolt catch. I'm not sure what you are asking regarding the carrier. see pic



I just looked at another carrier in another upper and it is cut away with exposed firing pin. Which do I need in this weapon. Why the difference? I have RRA 2 stage trigger in all of these weapons if that matters.
Link Posted: 10/31/2005 9:32:35 PM EDT
[Last Edit: 10/31/2005 9:34:28 PM EDT by Painter]
I am curious about this also. I have the other MRP mentioned, which is at about 600 rounds. I am using a Colt bolt and half circle carrier. I just looked at my buffer. It doesn't have an H stamped on it, but feels pretty close to same weight as another H I have. I am also running mags with magpul followers.

Clippens upper seems to have a tight spot when you manually cycle it. Also, there are a few spots that seem to be wearing quickly, considering his round count is low. If you look up inside the upper, with the bolt pulled back out of the way, you can see the gas tube, and also the scallop that is milled allowing the bolt cam pin to move, as the bolt rotates. On his, it seems like the rear side of the scallop is wearing hard.
The other day, we swapped bolts, and his upper was still acting up. Next time, we will bring more test parts.

Also, break in time is understood. Just trying to get a few more rounds between failure.

The next time, we will bring a few extra complete lowers, extra BCGs, different mags, and different ammo.

And a clean and light lube in between.
I wasn't thinking about putting an O-ring on the extractor yet, but maybe use a bolt with one to see if that does anything.

Anything else
Thanks for the help
Link Posted: 11/1/2005 12:34:53 AM EDT
Link Posted: 11/1/2005 11:33:31 AM EDT

Clippens upper seems to have a tight spot when you manually cycle it. Also, there are a few spots that seem to be wearing quickly


Can you guys get a clear, evenly lit pic of the inside of the upper?

Link Posted: 11/2/2005 4:45:51 AM EDT
I will try to get a better pic of the upper.
Link Posted: 11/20/2005 6:19:12 PM EDT
This upper went back to LMT, I will update when I get it back.
Link Posted: 11/28/2005 7:44:40 AM EDT
Wow, LMT customer service is awsome. They sent me back a new upper in about a week. I can't wait to test it this weekend. They said they put several hundred rounds through this new one and even tested it with the new bolt group (enhanced bolt) I ordered.
Link Posted: 11/28/2005 1:31:36 PM EDT

Originally Posted By clippen:
Wow, LMT customer service is awsome. They sent me back a new upper in about a week. I can't wait to test it this weekend. They said they put several hundred rounds through this new one and even tested it with the new bolt group (enhanced bolt) I ordered.



I agree. LMT's customer service is top notch. They take great care of their customers. Let us know how it works out for you.
Link Posted: 12/26/2005 7:32:54 PM EDT
I finaly got some range time with the new upper. Right off the bat, 2 rounds, then fail to feed. Round stopped just starting up the feed ramps. This continued through two mags. I swapped lowers with another rifle. 8-30 rd. mags no problems at all. Tryed the other upper with the lower that would not work with the MRP and it worked fine with a different upper. So, I put the MRP back on this lower, again FTF again and again. I am stumped. The lower that won't work with the 10.5 MRP is my SBR lower. It is a Olympic lower with RRA parts kit. RRA two stage trigger. Which parts in the lower should I start replacing? The H-Buffers and springs are identical.
Clippen
Link Posted: 12/26/2005 8:44:09 PM EDT

Originally Posted By clippen:
I finaly got some range time with the new upper. Right off the bat, 2 rounds, then fail to feed. Round stopped just starting up the feed ramps. This continued through two mags. I swapped lowers with another rifle. 8-30 rd. mags no problems at all. Tryed the other upper with the lower that would not work with the MRP and it worked fine with a different upper. So, I put the MRP back on this lower, again FTF again and again. I am stumped. The lower that won't work with the 10.5 MRP is my SBR lower. It is a Olympic lower with RRA parts kit. RRA two stage trigger. Which parts in the lower should I start replacing? The H-Buffers and springs are identical.
Clippen

you know, i had this exact problem with my 16" LMT upper. I gave up and sold it.
Link Posted: 12/27/2005 8:11:09 AM EDT
So what kind of carrier DO I want for my 16" rifle length MRP? Shrouded firing pin or exposed? Grant, I think the pics on your website for standard and M16 BCGs are the same pic so I can't tell the difference.

My problem is that it occasionally has problems chambering a round using the bolt release. Similar description as the above -- round is just starting up the feed ramp. Using the fwd assist chambers the round and all is well. Mags all have Magpul followers. Once the round is chambered it tends to run, although I recall one time when I had a slight hangup before chambering the next round. I have been using the MGI buffer. Chambering seems to be a little more "sure" when I use the standard buffer, but I can't be sure.

There is slight hammer drag when cycling the bolt with the trigger forward. "Slight" meaning if the trigger is forward and my finger is touching the trigger I can barely feel slight contact when the bolt is retracted. Isn't that normal? FWIW it is an Accuracy Speaks single-stage trigger in an early PWA lower.

I ordered a new chrome-silicone M4 buffer spring from Brownells, hopefully it will be here this week for my match on 1/1. I don't know the age of old the one I'm currently using.
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