I just bought a rifle length MRP and it appears that when the front bolt is torqued down with the preset LMT wrench my bolt carrier will not engage, the bolt will not engage the chamber. I have been able to repeat this with multiple BCG’s and another MRP barrel. I don’t have this issue with my CQB MRP. If I just hand tighten the two bolts on the rifle length MRP the BCG will engage properly. Anyone else have this issue? I am going to call LMT next week to ask them about it.
I figured out the issue but am sending the upper back to LMT to find a solution. As the front bolt is tighten the gas tube attached to the barrel starts to bow thus when the bolt carrier goes forward the gas key on the carrier will not slide over the tube.
That is interesting. Didn’t know the upper had to be tweaked. Just thought you just slapped the lower on and had a functioning rifle. I didn’t think any adjustment was needed. Was your’s partially complete when you received it? I don’t care for bolts that are finger tight, unless thats the way it was designed. Blue lock tite perhaps?
They don’t require any tweaking. I have a couple other MRP’s and they work fine. Just slap on a lower and go. Changing barrels is simple but for some reason this upper (I am more thinking it is the barrel) is not working correctly. I’m sure LMT will find the issue.
I had a problem similar to this when I bought someone’s barrel online.
The guy I bought it from didn’t really pack it too well and I think that it bent the gas tube out of line.
Are you sure it’s the gas tube/carrier key that’s not engaging, rather than the bolt & extension? You can tell because it’ll starting peening the gas tube a bit.
I am pretty sure it is the gas tube/carrier key that’s not engaging. The barrel seems fine in my other MRP’s. You can really see the tube bow when the front bolt is torqued as required. Anyways, I am send it in for LMT to inspect. I will update the post once them let me know what is going on.
you have 2 mrps. Have you tried using different torque wrenches.
I have an MRP and the torque wrench they sent was garbage. Either way, you should confirm that the problem happens when torqued with both wrenches.
That way you’ll know that its not a bad wrench causing you to overtighten the bolts.
Don
i second the junk torque wrench. i have a matco inch pound torque wrench that worked much better than the one they sent me
I’m not in any criticizing the original poster with this opinion. Its just a general observation.
People need to get over their affection for clicker type torque wrenches. For the mechanic who uses one daily, there is nothing better.
To be accurate, they need to be well made and they need to be maintained. Its not the best tool for someone who needs a torque wrench twice a year.
For most of us, the best torque wrench is the plain old beam type torque wrench. There is no spring to take a set. There are no articulated joints to lube. Just a beam that bends and shows you how much torque you are applying. There is nothing worse than a cheaply made clicker. It gives the illusion of precision which is worse than just tightening it by feel.
Further, whereas a clicker type wrench requires special tools to calibrate, if a beam type wrenches pointer is in the middle of the gauge, its calibrated.
Yes its slower, no its not sexy, but it is completely reliable.
I’ve found that for low torque values the Park Tools 400 in lb beam type torque wrench is the best thing since sliced bread.
Don
i agree the beam type is nice and simple. But since i work inthe auto field i have access to a very nice click type torque wrench. i guess that is why i din’t like the unit they sent.
The problem is the torque values are low enogh that the clicker you use on your job is not the best thing to use.
We’re talking less than 12 ft lbs.
If you have one of those $1000 Snapon Strain Gauge digitial ones, thats different.
But a clicker thats got a max of 125 ft-lbs is going to be waaaaaayyyy offf when dialed down to 12 ft lbs.
By the way, when was the last time you had it calibrated??
I do have 2 wrenches and it happens with both. I agree they are junkie, I should have bought a good one a while ago. Hopefully it is something as simple as over torqued bolts but I am not sure that is it. If I tighten the front bolt just a little more than hand tight, the gas tube bows enough that the BCG will not engage. Anyways, LMT should have the upper now and I am sure the issue will be solved.
Where/how does one get his torque wrench calibrated?
What does it cost?
If it does it with both wrenches then its probably not the wrench.
khc3 - I got mine done by a friend who is a master machinist at Pratt & Whitney.
You can google it, and probably get lots of results.
One other option is to call the local small airport and speak with someone in the shop. They can tell you somebody local to do it. FAA certified repair shops have to get their torque wrenches calibrated every so often. I think its annually.
Don
it is an inch pound torque wrench not a big 100 ft pound wrench it is a precision wrench mainly so it works fine.