JP LMOS / Enhanced HP Bolt Problems

[Billiam1211]

Just picked up a JP Enterprises LMOS bolt carrier along with the High Pressure Enhanced Bolt for 308 Win. I have an Aero Precision M5E1 with a brand new Bartlein 20-inch 308 Win barrel spun up by Paul Craddock. No rounds have been fired yet through this, was just waiting on the bolt to come in and quarantine to be over.

The Problem:

The JP LMOS carrier and JP High Pressure Enhanced Bolt came in today and I assembled them and tried dropping it into my upper. Problem is the BCG wont go in all the way. It seems that the bolt lugs are contacting part of the chamber or feed ramps which is not allowing to continue forward. I have an old Toolcraft BCG and decided to try the bolt from that. Dropped it in the JP LMOS carrier and it closed just fine.

You can also see in the photo below that the JP Enhanced Bolt will go into the chamber just fine, but not when installed into either the Toolcraft or JP carrier.

What could be wrong with the bolt? Tight tolerances on the chamber and the bolt stacking up?

Thanks for input!

Bill

 

[MontanaMan]

When you say the JP bolt won't close, are you talking about with a round chambered or with an empty chamber?

If it's with a round chambered, likely short on headspace.

MM

 

[Billiam1211]

When you say the JP bolt won't close, are you talking about with a round chambered or with an empty chamber?

If it's with a round chambered, likely short on headspace.

MM

Empty chamber. I updated my original post and threw up some photos

 

[_Windrider_]

Did Paul know which bolt you were using when he chambered it? Can I see the entire assembled BCG?

 

[Ravenworks]

If it were me I'd oil that bolt heavily,it's more than likely stiff.
Headspace is important

 

[Billiam1211]

Did Paul know which bolt you were using when he chambered it? Can I see the entire assembled BCG?

Paul had the Toolcraft bolt when he made the barrel for me. I decided last minute to upgrade to the JP bolt. You want a picture of the completed JP Bolt/Carrier?

 

[_Windrider_]

Paul had the Toolcraft bolt when he made the barrel for me. I decided last minute to upgrade to the JP bolt. You want a picture of the completed JP Bolt/Carrier?

Just want see it’s assembled properly. I’m sure it is. Just trying to help.

so you didn’t tell Paul you changed bolts?

 

[whatsupdoc]

The JP bolt without the carrier will it enter the extension and rotate engaging the lugs?

 

[Billiam1211]

The JP bolt without the carrier will it enter the extension and rotate engaging the lugs?

Yes it will. I tested that several times to be sure

 

[Billiam1211]

Just want see it’s assembled properly. I’m sure it is. Just trying to help.

so you didn’t tell Paul you changed bolts?

Unfortunately no, I didn't tell him I changed. I've had the barrel mounted in the upper for some time but haven't gotten the chance to shoot due to quarantine. I was originally planning on running the Toolcraft but in my quarantine driven anxiety I decided to try a JP LMOS system. I didn't realize the tolerances would be so tight that it wouldn't accept other bolts.

 

[_Windrider_]

Unfortunately no, I didn't tell him I changed. I've had the barrel mounted in the upper for some time but haven't gotten the chance to shoot due to quarantine. I was originally planning on running the Toolcraft but in my quarantine driven anxiety I decided to try a JP LMOS system. I didn't realize the tolerances would be so tight that it wouldn't accept other bolts.

Yeah man. JP is extremely tight. You might have to send the barrel back so Paul can tweak it.

 

[whatsupdoc]

That is strange, take a caliper and measure both bolts from the front of the locking lugs to the back.

 

[whatsupdoc]

Also, maybe its the photos but the extension looks like it is not indexed correctly.

 

[Billiam1211]

Yeah man. JP is extremely tight. You might have to send the barrel back so Paul can tweak it.

I actually got in touch with Paul last night and ran the issue past him. I was surprised to find out that he used to use the JP bolts when customers asked for head-spaced bolts but he stopped due to inconsistencies. Not sure who he uses now, but he told me to keep the LMOS carrier and return the JP Enhanced bolt. I took the calipers out and measured the bolt lugs out of curiousity and noticed that there was a few thousands of wiggle room from lug to lug. Very surprising experience. Thankfully JP customer service is top notch.

 

[_Windrider_]

I actually got in touch with Paul last night and ran the issue past him. I was surprised to find out that he used to use the JP bolts when customers asked for head-spaced bolts but he stopped due to inconsistencies. Not sure who he uses now, but he told me to keep the LMOS carrier and return the JP Enhanced bolt. I took the calipers out and measured the bolt lugs out of curiousity and noticed that there was a few thousands of wiggle room from lug to lug. Very surprising experience. Thankfully JP customer service is top notch.

Interesting. I only run JP bolts and Paul does all my AR barrels. Never had an issue.

 

[MontanaMan]

Here's a dimensioned drawing of the bolt to measure against..............keep in mind some important dimension are resultant.

MM

 

[Bigjake83]

The only time I've ever seen this is when the upper receiver is out of spec or someone is trying to mix DPMS and Armalite parts.

Let this be a lesson to all, always use the bolt the barrel was headspaced to. Once headspace has been set especially in a Large frame AR the mix and match game never goes well.

 

[Billiam1211]

The only time I've ever seen this is when the upper receiver is out of spec or someone is trying to mix DPMS and Armalite parts.

Let this be a lesson to all, always use the bolt the barrel was headspaced to. Once headspace has been set especially in a Large frame AR the mix and match game never goes well.

I'm learning that the hard way

 

[Bigjake83]

I'm learning that the hard way

Trust me, we all have done something similar at one point or another.

 

[MSTN]

whatsupdoc nailed it.

The problem isn't the bolt.

 

[Billiam1211]

whatsupdoc nailed it.

The problem isn't the bolt.

That the barrel extension isn't perfectly centered?

 

[ajwcotton]

Look at the barrel extension the lugs/feed ramps are clearly rotated too far clockwise in the reciever. Loosen the barrel nut and center the barrel extension before tightening. Also make sure the index pin and pin recess in the upper are not damaged due to overtightening.

 

[2aBaC̶a̶]

If you look at where the receiver feed ramps and barrel feed ramps meet, it looks like the barrel extension is rotated off center.

Now look at the thickness of the lugs on the JP bolt vs the toolcraft lugs. The toolcraft are probably small enough to slide through the off center lug slots while the JP isnt.

 

[Billiam1211]

If you look at where the receiver feed ramps and barrel feed ramps meet, it looks like the barrel extension is rotated off center.

Now look at the thickness of the lugs on the JP bolt vs the toolcraft lugs. The toolcraft are probably small enough to slide through the off center lug slots while the JP isnt.

So I'm in the shop right now and took the whole upper apart. Without the barrel torqued on, I rotated the extension so that it was perfectly centered and the JP Bolt slid right in and chambered... FML

You all are saints. Thank you.

 

[whatsupdoc]

For what its worth, I see many bolts that the rear edge of the bolt lugs get shaved due to barrel extension indexing.
I shim all my barrel extension indexing pins to the upper. I make a small " U" or "J" out of hardened shim stock and adjust the barrel indexing so the bolt does not swipe the extension.

 

[Billiam1211]

For what its worth, I see many bolts that the rear edge of the bolt lugs get shaved due to barrel extension indexing.
I shim all my barrel extension indexing pins to the upper. I make a small " U" or "J" out of hardened shim stock and adjust the barrel indexing so the bolt does not swipe the extension.

this is exactly what the issue is after taking everything apart. When I torque the barrel nut down the JP bolt catches the extension. Before applying torque, the bolt closes no problem. I noticed that there is some wiggle room with the indexing pin to the upper.

is there any online content or tutorial on how to shim the pin?

 

[_Windrider_]

this is exactly what the issue is after taking everything apart. When I torque the barrel nut down the JP bolt catches the extension. Before applying torque, the bolt closes no problem. I noticed that there is some wiggle room with the indexing pin to the upper.

is there any online content or tutorial on how to shim the pin?

What u need to do is call aero and tell them their tolerances suck. The last AR10 I built was on a zev receiver set and it fit like a glove.

 

[whatsupdoc]

What u need to do is call aero and tell them their tolerances suck. The last AR10 I built was on a second receiver set and it fit like a glove.

That is possible, but the JP seems to have wider lugs than the toolcraft and being there is no standard its the wild west.

 

[whatsupdoc]

this is exactly what the issue is after taking everything apart. When I torque the barrel nut down the JP bolt catches the extension. Before applying torque, the bolt closes no problem. I noticed that there is some wiggle room with the indexing pin to the upper.

is there any online content or tutorial on how to shim the pin?

Not that I know of, its not that difficult.

Cut a piece of shim stock to the height of the indexing pin and around one inch long.
Use a drill bit about the same diameter as the indexing pin and bend the shim around the rod, now you have a long "U".
Trim the ends so that the "U" will fit around the indexing pin just short of making contact with the extension shoulder.
Use some grease to hold the shim in place while you slide the barrel into the upper. (I usually just bend the shim around the pin)
Seat the barrel into the upper without the nut and twist the barrel back and forth to feel how much play you have.

You need to find the correct shim thickness by trial and error on your setup. If you dont have shims available you can get a feeler gage set from auto parts store and use them.

 

[2aBaC̶a̶]

Small nail. Hammer to the thickness you need, file the edges. It really just needs to hold until you torque the thing down.

 

[Billiam1211]

I got stimulus parts in the mail! Ordered a new M5 upper from Armorally.com, if that one doesn't index correctly I'm going to try out the shim stock around the indexing pin until it lines up.

At this point I should have just bought a GA Precision GAP-10 with the amount of money I've dumped into this damn rifle

 

[_Windrider_]

I got stimulus parts in the mail! Ordered a new M5 upper from Armorally.com, if that one doesn't index correctly I'm going to try out the shim stock around the indexing pin until it lines up.

At this point I should have just bought a GA Precision GAP-10 with the amount of money I've dumped into this damn rifle

I’ve said it a million times, you can save money in certain places but the receiver set is no place to skimp. Aero makes a good product but I’d rather spend a little more and never have to worry about sloppy tolerances.

 

[B_w.]

I had the same issue on a upper and used locktite slip fit compound to hold the barrel and receiver in place while I tightened it otherwise it would twist like yours.

 

[Billiam1211]

So the latest in the this saga...

As of the last post I have now received a replacement Aero Precision M5E1 upper receiver. I also picked up a Rubber City Armory 308 HP Bolt just to test as an alternative. The verdict is that the new upper is a super tight fit, no wiggle from the indexing pin. I torqued the barrel on and started testing the bolts all using the JP LMOS carrier. SAME EXACT RESULTS. Neither the JP or the Rubber City Armory bolts fully insert into the upper on an empty chamber. I put the Toolcraft bolt in the carrier, drops right in... I'm assuming when Paul Craddock head-spaced it to the Toolcraft bolt it was an unbelievably tight fit. I'm just going to roll with the Toolcraft bolt and call it a day. I'm sure the accuracy won't disappoint.

Anyone want to buy a High Pressure bolt? I have 2

 

[357Max]

Yes I do want a HP bolt actually. I just got a return authorization from Toolcraft, for a dual ejector small pin bolt that's going back to them for replacement.

Just pm me with what you want for one, preferably with the small firing pin since that's what I have.

Also can you confirm the Rubber city bolt has the small pin? I called them before buying the Toolcraft & they told me it had the large pin (about 9 months ago).

 

[MontanaMan]

So the latest in the this saga...

As of the last post I have now received a replacement Aero Precision M5E1 upper receiver. I also picked up a Rubber City Armory 308 HP Bolt just to test as an alternative. The verdict is that the new upper is a super tight fit, no wiggle from the indexing pin. I torqued the barrel on and started testing the bolts all using the JP LMOS carrier. SAME EXACT RESULTS. Neither the JP or the Rubber City Armory bolts fully insert into the upper on an empty chamber. I put the Toolcraft bolt in the carrier, drops right in... I'm assuming when Paul Craddock head-spaced it to the Toolcraft bolt it was an unbelievably tight fit. I'm just going to roll with the Toolcraft bolt and call it a day. I'm sure the accuracy won't disappoint.

Anyone want to buy a High Pressure bolt? I have 2

Did you ever measure the difference in the bolt lug length's on the various bolts?

Save the bolts...............they'll work on other extensions.

I just tested a JP bolt that I have (new) on 3 different barrels...........a Craddock, a WOA & a BA.

Fits all 3 to about a +.002 - .003" headspace.

MM

MM

 

[Billiam1211]

Did you ever measure the difference in the bolt lug length's on the various bolts?

Save the bolts...............they'll work on other extensions.

I just tested a JP bolt that I have (new) on 3 different barrels...........a Craddock, a WOA & a BA.

Fits all 3 to about a +.002 - .003" headspace.

MM

I did but don't remember the difference. Everything is still laid out on my work bench so I can definitely measure the lugs and post that up here for reference. I'm assuming its just a fitment issue. Had I sent Paul one of the other bolts, I'm sure he would have fit them properly as well.

 

[whatsupdoc]

Yes I do want a HP bolt actually. I just got a return authorization from Toolcraft, for a dual ejector small pin bolt that's going back to them for replacement.

Just pm me with what you want for one, preferably with the small firing pin since that's what I have.

Also can you confirm the Rubber city bolt has the small pin? I called them before buying the Toolcraft & they told me it had the large pin (about 9 months ago).

What was the issue with the Toolcraft dual ejector bolt?

 

[Billiam1211]

Yes I do want a HP bolt actually. I just got a return authorization from Toolcraft, for a dual ejector small pin bolt that's going back to them for replacement.

Just pm me with what you want for one, preferably with the small firing pin since that's what I have.

Also can you confirm the Rubber city bolt has the small pin? I called them before buying the Toolcraft & they told me it had the large pin (about 9 months ago).

Both bolts are small pin high pressure bolts. I'll pm you with the info once I'm done working. I'm going to probably hold on to 1 of the extra bolts for a 260/6.5 upper build.

 

[357Max]

What was the issue with the Toolcraft dual ejector bolt?

I don't want to hijack Billiam1211's thread. I'll post a separate thread for this and tag you in it.

 

[Billiam1211]

Well I finally got a chance to hit the range with the new Craddock Barrel today. Ran with the JP LMOS carrier and the Toolcraft bolt that Paul head-spaced and shot about 40 rounds while doing a break-in. Shot 5-shot groups with cleanings in between. After dialing in the gas system, the rifle cycled flawlessly so I think it's safe to just leave it be.

 

[sheepdog697]

Also, maybe its the photos but the extension looks like it is not indexed correctly.

well played.