Help with extra BCG sent in mail

Nickberg500 · Jan 25, 2021

I ordered a new chrome BCG from Young Manufacturing last week. There was a mess up on their end, and they possibly billed/shipped 2 BCGs. It should arrive in the next day or so.

I've seen online reviews where they measure how close a part is to mil-spec and occasionally there will be defects like a short firing pin. The review specifically found that issue with a YM BCG.

Does anyone have the tools or know how to *easily* test mill-specness? I have a caliper but that's it. I figure if they messed up and I have to ship one back, I should pick the one that's closer to mill-spec (if there's any measurable difference between the two).

JohnC · Jan 25, 2021

I think you're over thinking a number of things. Mil-Spec is one of the most useless descriptions, because it's misleading at best. If a bolt carrier group fits in your upper, fits the description of the order you placed (i.e. chromed etc) and doesn't have obvious quality issues then I wouldn't sweat it if something is more closer to mil-spec. Just because something is labeled as mil-spec, that label is not indicative of quality. Don't forget, many government contracts are awarded to the lowest bidder

Nickberg500 · Jan 25, 2021

JohnC said:
I think you're over thinking a number of things. Mil-Spec is one of the most useless descriptions, because it's misleading at best. If a bolt carrier group fits in your upper, fits the description of the order you placed (i.e. chromed etc) and doesn't have obvious quality issues then I wouldn't sweat it if something is more closer to mil-spec. Just because something is labeled as mil-spec, that label is not indicative of quality. Don't forget, many government contracts are awarded to the lowest bidder

Well, in the video I watched, the failing firing pin was described as possible inducing light primer strikes. If that's a possible scenario and I have the choice to mail the crappier BCG back (they did both arrive just now btw), might make sense to check-in here.

SkiPatrolDude · Jan 25, 2021

A long or out of spec firing pin would be just that, an out of spec firing pin. BCM sells firing pins for pretty cheap.

It's going to be very difficult to determine which one "falls within tighter spec" over the other. First you will need tools that are calibrated to great precision and accuracy. If you had headspace gauges then i suppose the best thing to do would be to check headspace for both, to the rifle it's going in... if one fails the gauges, then don't use that one. But for the AR15 platform, chances are both would easily pass.

Look over both and if one has a better fit/finish, go with that one. Check the staking - if one looks better, go with that one. Feel for the tightness of the bolt to the gas-ring-run in the carrier.... go with the tighter one (although there is such thing as too tight). Inspect the chrome lining in the gas-ring-run.. if one has any obvious imperfections, go with the other one.

Or flip a coin and chances are you will be totally fine.

Nickberg500 · Jan 25, 2021

SkiPatrolDude said:
A long or out of spec firing pin would be just that, an out of spec firing pin. BCM sells firing pins for pretty cheap.

It's going to be very difficult to determine which one "falls within tighter spec" than the other. First you will need tools that are calibrated to great precision and accuracy. If you had headspace gauges then i suppose the best thing to do would be to check headspace for both, to the rifle it's going in... if one fails the gauges, then don't use that one. But for the AR15 platform, chances are both would easily pass.

Look over both and if one has a better fit/finish, go with that one. Check the staking - if one looks better, go with that one. Feel for the tightness of the bolt to the gas-ring-run in the carrier.... go with the tighter one (although there is such thing as too tight). Inspect the chrome lining in the gas-ring-run.. if one has any obvious imperfections, go with the other one.

Or flip a coin and chances are you will be totally fine.

Gotcha, good advice. Btw YM doesn't stake their keys so they're the same in that regard

DutchV · Jan 25, 2021

Those guys are good. I doubt there will be any difference between the two BCG's.

Mule · Jan 25, 2021

As far as the firing pin goes, my understanding is that the "in-spec-ness" isn't really the bolt itself, but really more of a firing pin length issue. Meaning, how far (or not) the firing pin projects from the face of the bolt, and being under (below .028) or over (above .036) will cause issues.

As far as that goes, a firing pin protrusion gauge, or another tool that would let you measure that distance, should be all you'd need to check that aspect of things.

outrider58 · Jan 25, 2021

Mule said:
As far as the firing pin goes, my understanding is that the "in-spec-ness" isn't really the bolt itself, but really more of a firing pin length issue. Meaning, how far (or not) the firing pin projects from the face of the bolt, and being under (below .028) or over (above .036) will cause issues.

As far as that goes, a firing pin protrusion gauge, or another tool that would let you measure that distance, should be all you'd need to check that aspect of things.

That measurement can also be taken by using the 'tail' end of a caliper. Simply measure from the rim of the bolt down to the bolt face with the tail of the caliper and write it down. Next, using the same method, use the tail of the caliper and measure the from the rim of the bolt down the the tip of the protruding firing pin. Subtract that figure from the first figure and you will get your "protrusion" length. :thumbsup:

Nickberg500 · Jan 25, 2021

outrider58 said:
That measurement can also be taken by using the 'tail' end of a caliper. Simply measure from the rim of the bolt down to the bolt face with the tail of the caliper and write it down. Next, using the same method, use the tail of the caliper and measure the from the rim of the bolt down the the tip of the protruding firing pin. Subtract that figure from the first figure and you will get your "protrusion" length.

Ding ding! We have a winner!

I'll have to try this out when I get a moment to test it. +1 cookie point for a tip using my existing equipment.

Russ D · Jan 25, 2021

If you didn’t overpay, I’m sure someone here would save you the trouble of returning it and but it from you. BCG’s are hard to come by these days. I’d be interested.

babalou · Jan 25, 2021

light primer strikes

Nickberg500 said:
Well, in the video I watched, the failing firing pin was described as possible inducing light primer strikes. If that's a possible scenario and I have the choice to mail the crappier BCG back (they did both arrive just now btw), might make sense to check-in here.

reminds me of a joke I heard when I was in 6th grade in the late 70's.

What is red and has seven dents... Snow White's cherry. Like strikes lolol

Sorry, sigh back into the corner I go. Bad babalou, bad babalou

Magnumite · Jan 25, 2021

babalou said:
reminds me of a joke I heard when I was in 6th grade in the late 70's.

What is red and has seven dents... Snow White's cherry. Like strikes lolol

Sorry, sigh back into the corner I go. Bad babalou, bad babalou

You’re a bad boy, Johnny...but I hadn’t head that one so carry on....+1 for delivery

Nickberg500 · Jan 25, 2021

Russ D said:
If you didn’t overpay, I’m sure someone here would save you the trouble of returning it and but it from you. BCG’s are hard to come by these days. I’d be interested.

I think I paid $190 if you include shipping. It's an all chrome M16 BCG, got it on recommendation from inRange when discussing the what-would-stoner-do rifle. I'm in the Finksburg area north of Baltimore county if you want to buy or trade for it.

GunBum · Jan 25, 2021

“Milspec”

A window so wide, even the lowest bidder can get through. :lol2:

Nickberg500 · Jan 26, 2021

outrider58 said:
That measurement can also be taken by using the 'tail' end of a caliper. Simply measure from the rim of the bolt down to the bolt face with the tail of the caliper and write it down. Next, using the same method, use the tail of the caliper and measure the from the rim of the bolt down the the tip of the protruding firing pin. Subtract that figure from the first figure and you will get your "protrusion" length.

I don't know if this M16 BCG is special, but my caliper is giving me an average of 0.75 mm protrusion using the tail method. Is that bad? Looking online that seems to be too long.

outrider58 · Jan 26, 2021

Nickberg500 said:
I don't know if this M16 BCG is special, but my caliper is giving me an average of 0.75 mm protrusion using the tail method. Is that bad? Looking online that seems to be too long.

EAT: Just converted mine to mm. Anything between 0.72mm and 0.91mm is fine. If anything, you are on the short side of the spec, but you are within the good range.

Ed Anger · Jan 26, 2021

Russ D said:
If you didn’t overpay, I’m sure someone here would save you the trouble of returning it and but it from you. BCG’s are hard to come by these days. I’d be interested.

They're so hard to come by, I thought you meant BCG, or bacille Calmette-Guerin, a (lousy) vaccine for tuberculosis (TB) disease.

Nickberg500 · Jan 26, 2021

outrider58 said:
EAT: Just converted mine to mm. Anything between 0.72mm and 0.91mm is fine. If anything, you are on the short side of the spec, but you are within the good range.

Thanks Outrider! I owe you a beer after all the times you've given me advice

outrider58 · Jan 26, 2021

Nickberg500 said:
Thanks Outrider! I owe you a beer after all the times you've given me advice

I like vodka.

blipper · Jan 26, 2021

Ed Anger said:
They're so hard to come by, I thought you meant BCG, or bacille Calmette-Guerin, a (lousy) vaccine for tuberculosis (TB) disease.

It's used to treat bladder cancer too.

Help with extra BCG sent in mail

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