Need Help Trouble Shooting Some Problems

[Gunfighter 9]

I have a BCM 14.5" Midlength rifle. I took it out to the range on Saturday for the first time, and I experienced a few issues that I need some assistance with.

First, I lubed the BCG well before shooting, but I did not break it down and clean it before hand. I found that after inserting a 30 round PMAG into the weapon and firing about 3 to 4 rounds the rifle would begin to fail to extract and cause a double feed. I am running an H2 buffer and Full auto BCM BCG. The ammo was Remington 55 grain .223. The problem seemed to stop once the magazine capacity was decreased by about 10 rounds or so.

My first guesses about the issue are that it is either a magazine problem, or that the ammo was too low powered to handle the heavy buffer/BCG and didn't generate enough recoil to extract the fired casing. Any thoughts?

My second problem involved my EO Tech XPS. I installed it per the instructions supplied. However, after about 5 or 6 rounds the device would loosen up and fall off. I did not loctite the tension screw on the sight. So I am guessing this is the problem.

[VIP3R 237]

Id say its the ammo, remington isnt up to 556 specs. Id drop an H or even try a standard carbine buffer with commercial 223, a m16 carrier, and midlength gas system. With my LMT with a m16 carrier and carbine system I have to use an H buffer when shooting umc, however you also have the softer midlength, I would try the carbine buffer first.

I dont know on the xps, but the loctite may help.

[Sgt_Gold]

I found that after inserting a 30 round PMAG into the weapon and firing about 3 to 4 rounds the rifle would begin to fail to extract and cause a double feed. I am running an H2 buffer and Full auto BCM BCG. The ammo was Remington 55 grain .223. The problem seemed to stop once the magazine capacity was decreased by about 10 rounds or so.


If the feeding\extraction problems go away after you fire enough rounds, it sounds like magazine spring is causing drag on the BCG. As you fire off the rounds, the spring extends itself and the tension lessons on the bottom of the BCG. The magazine could be sitting a little high, or the top of the magazine could be out of spec. Have you tried different magazines? If the problem goes away with a different magazine then you have your answer.

I don't think the ammunition is to blame. Under powered ammo would lead to short stroking. What you have is a round sticking in the chamber. I would also check the extractor and possibly the chamber to see if that clears up the extraction issue.

[Redhat]

I would try different ammo in 5.56mm...after you clean it.

[Tweak]

Does it lock open on the last round fired?

What kind of magazine?

[VIP3R 237]

Straight off of bcm's website http://www.bravocompanyusa.com/mobile/default.aspx#P1570 :

"These 14.5" mid length gas barreled upper receiver groups have been specifically tuned to be a very soft and fast shooting set up. They are a joy to shoot, but please feed it good ammo. With good milspec pressured ammo we have been running H buffers. We do not recommend using lower powered ammo. If using less than milspec pressured ammo, it may be best to run a standard carbine buffer."

I still say its too much buffer for the ammo.


If the feeding\extraction problems go away after you fire enough rounds, it sounds like magazine spring is causing drag on the BCG. As you fire off the rounds, the spring extends itself and the tension lessons on the bottom of the BCG. The magazine could be sitting a little high, or the top of the magazine could be out of spec. Have you tried different magazines? If the problem goes away with a different magazine then you have your answer.

I don't think the ammunition is to blame. Under powered ammo would lead to short stroking. What you have is a round sticking in the chamber. I would also check the extractor and possibly the chamber to see if that clears up the extraction issue.

[Brahmzy]

Any metal on metal screws need at least blue loctite on a firearm. Too much recoil shock to kept things tight otherwise - especially with relatively heavy optics sitting on a pic rail.

You should be able to shoot weak 223 ammo out of your factory rifle. I think if it only will shoot 5.56, you've got an issue.

[BGREID]

I would not put loctite on the EOTech just tighten it down better. I agree with others shoot the gun some more and see if the feeding problems stop, if not call BCM.

[MistWolf]

First rule of troubleshooting- Do the easiest fix first.

Let's go through the list of facts first
1- Rifle is a BCM 14.5 middy which BCM recommends be used with full power 5.56 ammo
2- Magazine is PMag, known to be generally trouble free
3- Buffer is a heavier than normal H2
4- Ammo used is 223 which does not reach full pressure in a 5.56 spec chamber

Reported Problem
1- Failure to extract
2- Double feed (Likely mis-identified. A double feed occurs when two rounds are stripped from the mag). Fresh round does not feed due to case stuck in chamber

Speculation
1- It's likely rifle has 5.56 chamber (BCM also offers barrels with SAM-R and 223 Wylde chambers)
2- It's possible 223 ammo is manufactured on the minimum side

Theories
1- If the chamber is also on the maximum side, it's possible the ammo is a loose fit which exacerbates the fact 223 ammo does not reach full pressure in a 5.56 chamber. It also means it's possible the extractor is not snapping over the rim. It it also possible the extractor is on the minimum side.

2- With the reduced velocity of the bolt resulting from lower operating pressure couple with the drag on the bolt from a fully loaded magazine, there may not be enough momentum to ensure the extractor is snapped over the rim. Once the round count in the mag is reduced, resulting in reduced drag, the momentum of the bolt is now enough to ensure the extractor is snapping over the rim.

Conclusion: Easiest fix is to use correct ammo. Next is to determine correct buffer weight

Do This Task
Note: Clean and inspect chamber for debris before testing for function. Use 5.56 ammo for testing as it is the correct ammo for the rifle.

1- Place a single round of 5.56 ammo in the magazine, fire and check to see if bolt locks back. If so, continue to step 2. If not, change to a carbine buffer and repeat test.
2- Fire the weapon with a fully loaded magazine of 5.56 ammo and see if condition continues. Make no other changes. Use the same magazines. If condition still exists, and H2 buffer is being used, change to a lighter buffer. If functioning is good, repeat test with 223 ammo. If condition continues with 5.56 ammo and carbine buffer, another condition, such as a tight chamber exists. Contact BCM

[Iraqgunz]

Step 1. Read what BCM posted on their website.

Step 2. Remove the H2 buffer.

Step 3. Replace with H or carbine.

Step 4. If you have an O-ring on the extractor-remove it.

Step 5. Shoot 5.56 and .223 ammo and test for function.

I can almost guarantee that this weapon will work if you follow the above.

[CLJ94104]

Tighten down the eotech screw better. Should not be an issue. I have owned a couple and never had to use loctite.

[Suwannee Tim]

I often remove optics to clean or place them on another upper. I sometimes forget to snug them down, I never tighten them, just snug. I have never had one fall off, horrible accuracy clues me in after 10 or so shots but they don't fall off. I would closely examine how you are mounting, perhaps you don't have the cross bolt in the slot or the clamping shoe may be upside down. Properly mounted but not tight you should have 1/16 or so of front to rear play.

[Gunfighter 9]

Thanks for all the replies. I will continue to investigate the problem. I intend to run primarily 5.56 mm ammo, but I was out of town and my brother likes to cheap out and use the .223 stuff. I figured it was an ammo issue but I will keep an eye on it. The magazine is a brand new PMAG. This was the first time it was used. I am leaning towards low powered ammo. In fact I purposely set up this carbine to run milspec 62 grain ammo. Again I will follow up with another range session and see what happens.

As for the XPS, I had it tightened on as far as it would go so I am going to assume that it needs some loctite to fix the problem. If that doesn't work I will contact L3 for help.

[djmorris]

I may be echoing what previous posters have said, but here's my advice since I've been in the same boat with my 16" BCM middy.


1. Break everything down and clean it spotless, focusing most of your attention on the chamber.

2. Lube the BCG inside and out. Don't just lube it, lube the **** out of it with quality lube like Slip2000 EWL. Make sure you lube the bolt itself and the bolt lugs to the point of dripping wet

3. Keep your H buffer in

4. Get some 5.56 ammo such as M193 or M855 and shoot a few hundred rounds through it before going back to any .223


Since you're running a 14.5" you MAY need to run a standard buffer, however I would at least try to stick with the H and see what happens. Can't hurt. If you're still experiencing problems after a few hundred rounds of 5.56 then throw the standard buffer in and of course, lube the hell out of the BCG again -- inside and out.


You may want to check the gas port alignment with your FSB too.

[Doc Safari]

OP: my 14.5" pinned carbine was having failures to extract on occasion with PMC Bronze .223. It was running an H buffer at the time.

I swapped out the H buffer for a carbine buffer and the problem magically went away for what amounts to several hundred additional rounds now.

Buy the eleven dollar carbine buffer from Bravo Company and at least try that before you waste hundreds more rounds of ammo and whatnot.

[JSantoro]

At one point, I "owned" 122 EOTechs...

If an individual that has owned single-digit amounts of anything has had success not using a thread-locker as a part of their mounting solution, that's great; keep on keeping on. Your experiences are not invalid. They are, however, narrow, and do not match the trend that shows up in a more representative sample size.

If the rail interface of ANY device (that is made to take and retain a zero) is a threaded one that transverses the rail slot through the short axis of the device/rail, a thread-locker is something one uses only if one wants the device to 1) retain zero, and 2) stay on the gun.

Somebody else that's seen more than a few EOTechs: http://www.kyledefoor.com/2009/12/mounting-tips-and-eotech-secret.html

Shim the rail with foil (I'd call that an option, but a smart one), and use blue Loctite or some other medium-grip thread-locker. Recommended torque on the screw is 17in-lb, if I recall correctly.

Remember to apply forward pressure to the optic prior to tightening it to the rail. If you don't, there may be empty space between the forward edge of the recoil lug on the device, and the back edge of the forward part of the rail slot. Ensure that there's no such space, or the recoil impulse can shake the optic loose...particularly if there's no thread-locker on the screw trying to keep tension under multiple linear impacts.

[Iraqgunz]

If I recall correctly all of our Model 552's had threadlocker applied to the screws from the factory. I also recall that if they didn't have it they would work loose.


At one point, I "owned" 122 EOTechs...

If an individual that has owned single-digit amounts of anything has had success not using a thread-locker as a part of their mounting solution, that's great; keep on keeping on. Your experiences are not invalid. They are, however, narrow, and do not match the trend that shows up in a more representative sample size.

If the rail interface of ANY device (that is made to take and retain a zero) is a threaded one that transverses the rail slot through the short axis of the device/rail, a thread-locker is something one uses only if one wants the device to 1) retain zero, and 2) stay on the gun.

Somebody else that's seen more than a few EOTechs: http://www.kyledefoor.com/2009/12/mounting-tips-and-eotech-secret.html

Shim the rail with foil (I'd call that an option, but a smart one), and use blue Loctite or some other medium-grip thread-locker. Recommended torque on the screw is 17in-lb, if I recall correctly.

Remember to apply forward pressure to the optic prior to tightening it to the rail. If you don't, there may be empty space between the forward edge of the recoil lug on the device, and the back edge of the forward part of the rail slot. Ensure that there's no such space, or the recoil impulse can shake the optic loose...particularly if there's no thread-locker on the screw trying to keep tension under multiple linear impacts.

[JSantoro]

It basically applies to anything with a transverse screw that either passes through, or acts as, the recoil lug. And takes a zero.....

Some of the XPS variants have an adjustable locking throw-arm that's actually quite good.