My son got a new MSR recently and it is sometimes failing to fire when the trigger is pulled.

When the rifle fails to fire, It takes some force to extract the cartridge from the chamber. The extracted round will have no or very, very little sign of a primer strike. If i take those rounds that failed to fire and put them in either one of two other MSR's, they fire for sure.

I've compared the firing pin dimensions and bolt dimensions with the same parts from my rifle. They are the same within .001".

All the ammo is my own reloads. But my reloads always fire in other rifles.

I checked headspace on reloads (.223) and i think it was around 1.456 where my cartridge drawing shows a headspace of 1.467.

Any ideas or suggestions?

What brand is it? I had a bear creek upper do that, but the same cartridge would fire out of my aero or spikes just fine

I'd tear it down and make sure everything is installed correctly.

It's an Anderson. I dont think I'd know what to check in the upper. Might need to cast the chamber of something. But I'd be inclined to send it back to Anderson for evaluation before I'd take it apart myself

clean it good and shoot a hundred rounds through it. probably needs broke in

I would clean the chamber and BCG good and try it. Look in the chamber with a light.

Try factory loads before tearing it down. Not an ar but I’ve seen guns that only shoot factory loads
Sounds like bolt not closing. Does firing pin snap ?

Firing pin in an AR "floats". No spring. A little cosmoline or whatever they are shipped with now can keep the bolt from closing. Keep the firing pin from striking hard enough. Also just like in any self loading fire arm, when its new parts may need to wear together a bit before it runs smooth.

"Tearing one down" is very simple also. Can be done just using a bullet for a tool. Better videos than this but this shows how simple they are.

Take the BCG apart and spray it inside and out with brake and parts cleaner. Blow out with air. Very light oil on the parts. If that doesn’t work then it’s time todo an inspection on the chamber. I would also try some factory loads.

The hammer definitely drops. BCG has been cleaned twice. It was fully disassembled and thoroughly cleaned before first time fired. Weve also cleaned the chamber with a wire AR chamber brush. I don't believe it's dirty enough to prevent firing. We keep our weapons CLEAN and we'll lubed. I might want to disassemble the bolt by taking the extractor out and clean that. We haven't done that yet.

I do wonder if the bolt is not going far enough forward. But if the hammer drops, you would think the bolt would be fully into battery.

I'm also not sure why the round is difficult to extract when the round fails to fire. That would make me think the cartridge was not sized well enough. But I've checked head space on the the brass and the loads cycle and fire in two other rifles. Maybe just a rough finish in the chamber? JB bore paste to polish it up?

I wondered if the extractor was not riding over the rim and that's keeping the brass from meeting the bolt face. But if that were the case I'd think the bolt wouldn't close enough for the hammer to drop. And the hammer is definitely dripping.

I need to try factory ammo. I also need to try swapping BCGs between rifles to see if the problem follows the upper or follows the BCG.

If the problem is the ammo, i don't know what it could be about my reloads that would make it flawless in two rifles but unreliable in a third rifle.

Throw a different bcg out of a different rifle in there and see if it shoots. The bear creek that gave me problems ended up having a blemish on the bcg that kept it from locking up. Ordered a whole new carrier group from sharps, no issues since. I actually really like that barrel for how cheap the upper was, it's very accurate.

This is the first thing I'd try.

Had AR that had same problem, problem with mine was when it was built, ream was worn out. Brass wasn't fitting chamber complete. Had a gun smith and I watched reream it, use dab of vaseline, on ream, he removed 2 very small pcs. in chamber rifle has fired everytime . I'd try another firing pin, also. As stated above might have some brass that isn't sized right, guessing your using a SB die, as stated different BCG

try another BCG, if thats not it, check headspace.

if it doesn't run factory ammo 100% I would suspect firing pin protrusion to be the issue

you can have a firing pin the right length but if it bottoms out inside the bolt before protruding enough that can cause the issue as well.

it may also be a tighter chamber than your others if it runs factory great I would be looking to see if you might need to bump your shoulders back a couple more thousandths


always think , if the tool wears what gets tighter
they will start the tool in budget work as large as it can go and when they hit minimum spec retire the tool

but simple test works or doesn't with a few boxes of factory.
it gives you a place to start looking know in the correct direction

given the hard to eject un-fired round I would suspect tighter chamber
but try some factory

my dad ordered the same 300blk upper as mine a few months after I got mine , his chamber is noticeably tighter
I can rack a mag full of rounds through my gun and they will hang up in his
his shoots factory fine.
300 is a little different beast as the thickness of the cut down 223 brass makes a difference
I don't recall it off the top of my head but we found a very specific no go size for his gun
I am going to switch him off my reloads at some point but , for now I measure find all under that size then rack all those rounds through his gun making sure they chamber and eject easily.

if you find it un-reliable with factory , call the manufacturer an have them check it

When you say hard to eject the misfire is it hard to pull back the bolt? If so it’s your reloads. I know reloading is fun but at today’s dirt cheap sales on 223 is factory ammunition not cheaper? Components are still high
Please people don’t quote cost per round based on pre Covid components prices. Human nature is to emphasize in the direction that you lean. Based on type of course around here you can get 223 ammo cheaper than buying just the powder. Primers bullets plus paying fir your time no way reloading is cheaper. I’m talking plinking rounds I know reloading is only way to achieve certain results for accuracy and hunting situations

I would buy two hundred rounds for the price of a pound of powder but its not that cheap here.

might not be fully returning to battery so a different BCG might show either it is that or not that. Try your BCG on another rifle too.

Well I just priced 8lbs of 8208xbr 2k mid south varmit nightmare 55gr sp, 2 k cci small rifle primers and came up with $6.20 c per 20 rounds at current prices. I add brass since I have thousands of that. but that's an extra .12c per piece for processed military brass so $8.20 a box of 20 if your not reusing your brass.

so .43c per shot roughly and the same price as fmj bulk ammo. But this is not crap bulk fmj ammo it's nickel size groups with soft points good for game at the crap 2" grouping fmj junk price ammo.

now I rounded down on my pricing as well that 8 lb jug of powder would lond 235 rounds more than I figured. Brass would be able to be used 6 to 10 times and primers are 20$ per 1000 than I figured.

I MYSELF never bother shooting plinking ammo. I prefer to not have sight my guns in back and forth and I like to hit what I'm shooting at. So I always shoot my hunting loads the gins are set up for. And why not when it cost me less than shooting the inaccurate crap ammo. yes it's less when figuring using brass over and over, getting more rounds per jug of powder than I figured and getting good hunting ammo vs junk.



Now figured some of us buy things on sale in large amounts and still have thousands of primers , lbs of powder, and thousands of bullets on hand bought over a decade ago so that's less than 13c per shot for me. Now a lot of those that get mad and say I'm hoarding probably are just jealous they didn't stock up.
Should be a trump slump again so their chance will be comming.