AR in x39?

[DW357]

In a regular trigger setup the hammer spring strength doesn't affect trigger pull weight.
For an x39 AR the usual recommendation is a heavier hammer spring and an enhanced firing pin. To avoid light primer strikes.

For other issues like FTE, FTF you would need to tune the gun to the cartridge with buffer spring, buffer weight, gas system adjustments.

For those reasons I would not try to use that lower for multi cal uppers.

Magazines and gas tunes can be finicky and hang up bolt engagement if not aligned.

The x39 upper (10.5") along with the 4 oz spike tactical tungsten buffer and carbine spring works great. All of the cases land at the 4 o'clock position and no FTFs and FTEs.
I use this same buffer and spring with my 10.5" BCA 5.56 upper which works great too - all brass lands at 3-4 o'clock.

It's just a light strike issue at this point. I thought the hammer spring does increase the trigger pull no? I could be wrong as I'm far from an AR expert.

 

[240Geezer]

Trigger spring is the main factor in trigger pull weight. After that the engagement surfaces. That's why trigger polish jobs/ enhanced triggers. Lastly hammer spring weight.
Have you lubed the trigger and pins?

 

[DW357]

Trigger spring is the main factor in trigger pull weight. After that the engagement surfaces. That's why trigger polish jobs/ enhanced triggers. Lastly hammer spring weight.
Have you lubed the trigger and pins?

Gotcha. Well that's good news.
I haven't touched the trigger, springs or pins since I first installed it. The pins and springs relatively dirty but not horrible.

 

[240Geezer]

Douche it out then lube it up. See if you feel a difference.

 

[Tweed]

What trigger? stock milspec trigger or a lightened drop in trigger?

Rock River Arms 2 stage 4.5-5 lb pull weight. same lower on a few different uppers.

L-R standard pin, pin I tried filing and still had problems, Windham x39 pin.

 

[Tweed]

x39 firing pin protrusion

 

[paul73]

It is odd people have so many problems with x39 primers - it is difficult to assume cheap steel Tula.223 uses a different primer, yet, both .308 and .223 fires fine.

 

[DW357]

Rock River Arms 2 stage 4.5-5 lb pull weight. same lower on a few different uppers.

L-R standard pin, pin I tried filing and still had problems, Windham x39 pin.

Thanks. I’ll try the heavier spring first before grabbing one of those Windham firing pins.

 

[DW357]

It is odd people have so many problems with x39 primers - it is difficult to assume cheap steel Tula.223 uses a different primer, yet, both .308 and .223 fires fine.

I have no issues using this trigger with Tula and Silver Bear 223/5.56. Large rifle primers have a thicker and taller cup than small rifle primers. I think that’s part of the problem.

 

[Uzi2]

I have no issues using this trigger with Tula and Silver Bear 223/5.56. Large rifle primers have a thicker and taller cup than small rifle primers. I think that’s part of the problem.

Have you checked or had checked the headspace on the gun?

 

[drgrant]

Yup you’re right. Still getting light strikes. I tried it with a 3lb velocity trigger and same issue. I guess the only strange thing is it always fires the first round that’s chambered but the second round always gets a light strike.
Really annoying. I don’t want to swap out springs every time I want to shoot this x39 upper.
I think I’ll have to just stick with the AK/SKS and not bother with x39 AR uppers. Definitely was a $233 gamble…

I wonder how a Larure MBT 2S with the heavy spring would fare. Still gets you a nice trigger.

 

[paul73]

I wonder how a Larure MBT 2S with the heavy spring would fare. Still gets you a nice trigger.

the optional heavy #6 spring there is on trigger only - the striker spring is same.

it fires all tula on my builds on .223 and .308 just fine. i do not have any interest in making a 7.62x39 upper, especially now after the bidens embargo - so cannot comment on that.
i didn`t have a single dud yet on my mbt 2s triggers - and i have 4 of them now - 2 ar15 and 2 ar10s. but they are a bit heavier at #4.5 pull.

 

[drgrant]

the optional heavy #6 spring there is on trigger only - the striker spring is same.

it fires all tula on my builds on .223 and .308 just fine. i do not have any interest in making a 7.62x39 upper, especially now after the bidens embargo - so cannot comment on that.
i didn`t have a single dud yet on my mbt 2s triggers - and i have 4 of them now - 2 ar15 and 2 ar10s. but they are a bit heavier at #4.5 pull.

I could have sworn the spring is the hammer spring..... hammer spring will influence the trigger pull slightly.

ETA: you're right, it's different. Too much bourbon... lol

 

[paul73]

I could have sworn the spring is the hammer spring..... hammer spring will influence the trigger pull slightly.

ETA: you're right, it's different. Too much bourbon... lol

 

[DW357]

Have you checked or had checked the headspace on the gun?

I have not. Though since the whole entire upper with BCG cost me $233 I wouldn’t be surprised if the headspace is off
I thought I had a mil spec hammer spring kicking around but apparently not. I’m going to try a heavier spring and if that doesn’t work I could bring it to Northeast Arms to check the headspace

 

[jpm]

I have not. Though since the whole entire upper with BCG cost me $233 I wouldn’t be surprised if the headspace is off
I thought I had a mil spec hammer spring kicking around but apparently not. I’m going to try a heavier spring and if that doesn’t work I could bring it to Northeast Arms to check the headspace

All the issues I had with light strikes on x39 were solved with a stronger hammer spring.

 

[Atlantis]

I wonder how a Larure MBT 2S with the heavy spring would fare. Still gets you a nice trigger.

I run the MBT 2S with light spring on a 16" 7.62, mid length gas, carbine buffer. Zero issues, fwiw.

 

[DW357]

I run the MBT 2S with light spring on a 16" 7.62, mid length gas, carbine buffer. Zero issues, fwiw.

Thanks

 

[Uzi2]

I have not. Though since the whole entire upper with BCG cost me $233 I wouldn’t be surprised if the headspace is off
I thought I had a mil spec hammer spring kicking around but apparently not. I’m going to try a heavier spring and if that doesn’t work I could bring it to Northeast Arms to check the headspace

Cost of the upper really has little to do with it. BLEMS with critical functional issues like headspace are not usually sold.....cosmetic issues yes but not something like way out of spec headspace......that's a set up for a liability suit.

I've got several BLEM uppers that cost sub $300 and all are in spec headspace wise. I've got gauges and check every one I buy.
I can't even find the cosmetic blem on them except for one. It needed a corner radius touched up, so two minutes with a diamond burr saved me about $250.00

 

[DW357]

Cost of the upper really has little to do with it. BLEMS with critical functional issues like headspace are not usually sold.....cosmetic issues yes but not something like way out of spec headspace......that's a set up for a liability suit.

I've got several BLEM uppers that cost sub $300 and all are in spec headspace wise. I've got gauges and check every one I buy.
I can't even find the cosmetic blem on them except for one. It needed a corner radius touched up, so two minutes with a diamond burr saved me about $250.00

Update.
Received the heavier hammer springs from Rise Armament today as well as a new firing pin from bear creek Arsenal.
Was lazy and pulled a few bullets and just test fired the empty cases in my basement. All went bang so I’m back in business!
And it didn’t appear to increase the trigger pull. If it did it’s basically not noticeable. Will be blasting off some rounds tomorrow morning.

 

[92G]

Update.
Received the heavier hammer springs from Rise Armament today as well as a new firing pin from bear creek Arsenal.
Was lazy and pulled a few bullets and just test fired the empty cases in my basement. All went bang so I’m back in business!
And it didn’t appear to increase the trigger pull. If it did it’s basically not noticeable. Will be blasting off some rounds tomorrow morning.

great. now we’ll see how long the bolt lugs last!

 

[DW357]

great. now we’ll see how long the bolt lugs last!

Haha oh boy. I’m known to break things around here so it will be interesting to see.
I heard the lugs and extractor are weak points. For $233 for the entire upper and BCG, I can’t say I’d be surprised if the bolt lugs shear off down the road
So far bear creek arsenals customer service seems to be good. I’d imagine they would replace the bolt if the lugs shear off? We shall see.

 

[Fixxah]

Yeah I looked into those as well. Stay away from AR15s chambered in x39, magazine feed issues abound. However, I recently picked up an AR that takes AK magazines, which solved my concerns. Very hard for me to obtain, but so far shoots like a dream.
View attachment 374894

Looks awfully killy.

 

[DW357]

Took it to the range today and had 1 FTF out of 60 rounds. But I don’t think it was a light strike I think it was just a shit primer as it didn’t go off after a second strike. Had a good solid hit.

Fun range toy for sure. The muzzle blast with a 10.5" barrel is awesome

 

[jpm]

Haha oh boy. I’m known to break things around here so it will be interesting to see.
I heard the lugs and extractor are weak points. For $233 for the entire upper and BCG, I can’t say I’d be surprised if the bolt lugs shear off down the road
So far bear creek arsenals customer service seems to be good. I’d imagine they would replace the bolt if the lugs shear off? We shall see.

They probably would, I complained about a dust cover on an upper I bought recently, looks like it had been used before, and they sent me a brand new one with spring no charge.

 

[paul73]

Took it to the range today and had 1 FTF out of 60 rounds. But I don’t think it was a light strike I think it was just a shit primer as it didn’t go off after a second strike. Had a good solid hit.

Fun range toy for sure. The muzzle blast with a 10.5" barrel is awesome

What groups it does at 100yds?

 

[DW357]

What groups it does at 100yds?

I haven’t put it on paper yet but no issues ringing my 8" steel at 100. Good enough for my needs.
I just have a primary arms red dot on it.

 

[DW357]

Had my first malfunction with the Bear Creek Arsenal 10.5" upper today. Using C-Product mags. First malfunction ever and I got at least 600 rounds through it. Not bad

 

[btnh6668]

Should be interesting to see how it does with higher round count. 1 out of 600 is good odds though considering.

 

[Lefty38-55]

Added a JP Ent adjustable gas block, zero stoppages …