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Posted: 10/18/2022 12:46:15 PM EDT
I've only shot 50 BMG in the past from an AR-50, so my familiarity of semi-auto 50 BMG guns is new. I have a new M107A1, and have been using some 2021 CBC M33 ball to get it sighted in. I was having charging and firing issues, and the root cause seems to be pierced primers. Typically in other small arms munitions that usually tells me ammo is too hot. I chrono'd these out of the 29" barrel at 2,849 avg. That certainly is higher than any other M33 ball I've tested. I don't see anything indicating this design is known for popping primers, or could I possibly be dealing with 2020+ supply chain issues, and a material quality issue with CBC's primers? It's rather annoying to have to whack the charging handle, and then field strip the gun to get the primer piece out of the firing pin channel... 50 BMG, M33 Ball, CBC Pierced Primer by Buffman RANGE, on Flickr |
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Originally Posted By Pair0dimes: What a bummer man. Hope you get it squared away. I don't really have anything to add, but that sucks. ETA - tried any Lake City M33? Might have better luck. |
| Have you run it through the AR50 as well? Be a good way to remove the gun as a variable. I was always told CBC was good to go. I think they loaded a bunch of the Barrett branded ammo. |
BikerNut:
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Normal people like motorcycles. Real people like motorcycles.
People who don't like motorcycles are just... weird.
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Originally Posted By ALASKANFIRE: Have you run it through the AR50 as well? Be a good way to remove the gun as a variable. I was always told CBC was good to go. I think they loaded a bunch of the Barrett branded ammo. |
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Remove your bolt from the carrier and let's see the firing pin tip. The firing pins are through hardened, not case hardened. Piercing the primers on a .50 will etch the hell out of the firing pin tip and cause nothing but pierced primers on known good ammo after the tip gets gas cut from pierced primers. If you have a way to check the headspace on the ammo, do it. I would bet dollars to doughnuts the shoulder is set back too far. You're more than likely going to need a new firing pin if the tip isn't good and rounded. Any sharp ess to it and you will need a new firing pin. Changing it is super easy. Don't get the whole firing pin assembly unless you just want a spare. The firing spring can be a bitch to change out if you aren't familiar with it. It is very much like an M2 firing pin assembly. As a matter of fact, the bolt carrier assembly in the 82A1 family of rifles is very much like an upside down bolt from the M2HB MG. That's where the idea came from. The cocking lever is very similar also. Where the cocking lever faces up on the M2, the 82A1/M107 cocking lever cams off of the rear pocket in the trigger housing. Hope it works out okay for you. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
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Originally Posted By 50cal: Remove your bolt from the carrier and let's see the firing pin tip. The firing pins are through hardened, not case hardened. Piercing the primers on a .50 will etch the hell out of the firing pin tip and cause nothing but pierced primers on known good ammo after the tip gets gas cut from pierced primers. If you have a way to check the headspace on the ammo, do it. I would bet dollars to doughnuts the shoulder is set back too far. You're more than likely going to need a new firing pin if the tip isn't good and rounded. Any sharp ess to it and you will need a new firing pin. Changing it is super easy. Don't get the whole firing pin assembly unless you just want a spare. The firing spring can be a bitch to change out if you aren't familiar with it. It is very much like an M2 firing pin assembly. As a matter of fact, the bolt carrier assembly in the 82A1 family of rifles is very much like an upside down bolt from the M2HB MG. That's where the idea came from. The cocking lever is very similar also. Where the cocking lever faces up on the M2, the 82A1/M107 cocking lever cams off of the rear pocket in the trigger housing. Hope it works out okay for you. |
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I'm not so sure about them replacing it. Things have changed there. I got in trouble for a few times for going out of my way to help civilian customers. A firing pin is really cheap to make. It would be a good gesture to send one out. But it's all about the $$$, no matter how small the amount is coming in. I stayed in trouble being helpful. Quite a bit of trouble. 
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I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
CBC is the left, LC 2020 middle, PMC Right 107A1 FP issues by Buffman RANGE, on FlickrOld 1940s brass, PMC, CBC, Hornady  107A1 FP issues by Buffman RANGE, on FlickrI detect a little anomaly on the firing pin, but it's well below how far the firing pin would detent in primer. There are no sharp edges  107A1 FP issues by Buffman RANGE, on Flickr 107A1 FP issues by Buffman RANGE, on Flickr 107A1 FP issues by Buffman RANGE, on Flickr
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Originally Posted By Kalashnikov762: FWIW, I had the same problem with Magtech/CBC ammo a long time ago albeit in 243. Never used it again. I wouldn't use their primers if I got them for free. Vendor offered to swap out out the 120rds I have left with LC so I may just go that route and see if it continues. PMC brass showed good primer indentation, where as this CBC stuff on the ones that didn't pierced showed the primer cratering/fllowing a bit. SO maybe it's just soft primers.. |
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The firing pin looks good. There are no problems there. It is most likely the shoulder of the cartridge datum line is set back a few thousandths below minimum . Try a few rounds of something else if possible. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
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That little nick on the side of your firing pin is from a piece of primer cup that flowed into the face of the bolt. Usually see that on pierced primers. After that, if it continues, you will see gas cutting of the firing pin and eventually a sharp point to the pin and continued pierced primers. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
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Originally Posted By Buffman_LT1: It's entirely possible that it's a QC/Manufacturing issue with CBC. I have that with some Fioochi 4.6 that was old stock. If the primers are silver, the gun I'm using them in are getting pierced. If they're the black ones no problem.. Vendor offered to swap out out the 120rds I have left with LC so I may just go that route and see if it continues. PMC brass showed good primer indentation, where as this CBC stuff on the ones that didn't pierced showed the primer cratering/fllowing a bit. SO maybe it's just soft primers.. I'd just take the swap offer. No need to keep putting your firing pin in jeopardy. Sure sounds like bad primers if other ammo is performing normally. |
| Fired 15 rounds of PPU Match and 8 rds of LC M33 ball today, and no pierced primers. Primers are showing a very normal dimple vs the cratering the CBC was exhibiting when it wasn't piercing. I think I'll just get this swapped out and have the vendor note that they may have soft primers :D |
It may be hard to see from pics, but on the CBC stuff the primer is very close to flush with the head of the brass.  50BMG-M33-CBC (2) by Buffman RANGE, on FlickrWhere as the LC, and the PPU, the primer was recessed into it's pocket..  50 BMG (12.7x99mm), 725gr Brass Solid, PPU Match by Buffman RANGE, on Flickr
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US made ammo, the primer can be recessed a maximum of.010", or up to flush with the base. All the LC and Olin we had used for test firing was below flush. The firing pin protrusion is between .057" to .064" |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
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Originally Posted By skullbox: I stumbled upon this thread after realizing I bought a ton of this stuff from SGAMMO. I've fired around 15 rds of it from the first batch I got, but after de-linking a few 100 others from a different shipment I hope I don't run into this issue. |
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Originally Posted By skullbox: I checked that first batch of ammo that I fired and I don't have any pierced primers. I won't know about the other 2 batches until I have a chance to fire them. Could this be specific to the M107? I have the M82 The M107 and the 82a1 series bolt carrier parts share a lot of the same parts. The bolt and firing pin\firing pin extension being big ones that are the same part. The interior of the bolt and the shoulder depth, and firing pin length being the parts that set the firing pin protrusion of between .057"- .063". Ammo having a primer that sits flush to .010" below flush keep there from being pierced primers. Ammo having the correct headspace being a big factor also. Somewhere around here I have a gauge I made up by parting off the chamber end of a barrel and threading the chamber face end. Then made a threaded cap that you screwed onto the chamber end. I made witness marks for where a "go gauge" "no go" and "field/reject" gauges screwed down onto the chamber end. You inserted a loaded round into the gauge then screwed on the threaded cap onto the end until it bottomed out on the round and it showed you what the ammo was headspace as. Used it to segregate ammo by the rear of the loaded round to the datum line of the shoulder of the cartridge. You could also use it as a sizing gauge to tell you how far you had to screw your sizing die down until you were at minimum headspace. I really need to hunt up that gauge. It's been awhile since I've seen it. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
I commented earlier that i had some of the same lot as the op. Finally went out and shot some more. This was fired from a M107 (not a1). No pierced primers. Ammo is definitely warm but I have seen much worse ejector swipes from XM33 ball. It was 40 degrees F at the range when I shot. |
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Primers look like they might be a little soft but as long as none pierced, you're good. Surplus is gonna be hotter than handloads, those are meant to cycle the action of an M2. That and militaries don't care about reloaders, they just want their gun to go bang everytime the trigger is pulled. Save the brass, reload, repeat. |
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Those pics indicate that your firing pin hole is excessively large and you are getting primer flow. It exacerbates primer piercing and you might see the hole egg shaped if gas cutting has occurred from pierced primers. It can be fixed, but generally it easier to replace the part. |
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Originally Posted By Sandlewood_3: I commented earlier that i had some of the same lot as the op. Finally went out and shot some more. This was fired from a M107 (not a1). No pierced primers. Ammo is definitely warm but I have seen much worse ejector swipes from XM33 ball. It was 40 degrees F at the range when I shot. I just checked mine. Same lot... From my M82A1 I have a few cratered primers but none that are pierced: 
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Interesting observation. I should have more fire cases I just grabbed a quick few out of the bag with all my spent rounds. I'll have to take a better at this. I'll pose this question... Is blowing primers "worse" than pierced ones? I've had some blown out primers from the 77gr razor core stuff in my 18" ARs. It was obviously HOT ammo but didn't seem to be an issue other making sure a lose primer didn't cause a malfunction. |
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If you start getting gas cutting, there will be a black ring start that corresponds with the diameter of the primer. As it worsens, the bolt material will will start getting a pitted look. A pierced primers will etch the rounded point of the firing pin. It will start looking like a sharp point instead of a rounded ball shape. I forget the actual radius of the firing pin point. The cratered look of some of the primers is from slightly higher chamber pressure. We use to see it on older WW2 era ammo. |
I hated going to weddings. All the grandmas would poke me and say "You're next". They stopped that when I started doing it to them at funerals.
Sic semper evello mortem tyrannis
Sic semper evello mortem tyrannis
| Not directly related, but in the past there was some CBC (75?) 308 that was blowing stuff up. I had some and pulled it down to look at the powder. All the rounds had black sealant in the neck, and I could not pull 2 projectiles at all- pretty much glued in. Glad I didn't shoot it.... |
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Bought a batch of this cbc magtech ammo from sgammo for my brand new Barrett M82A1 and the 4th round blew out the primer and the flake jammed up my firing pin. Had to completely tear down the rifle and bolt. Brand new gun, no experience doing so before. 0 out of 10 would not recommend this garbage ammo. Not worth its weight in gold. Have had plenty of primers about to blow out. Sgammo says this is not a common issue, i call bs, its all over the internet.
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Originally Posted By DieHardBarrett: Bought a batch of this cbc magtech ammo from sgammo for my brand new Barrett M82A1 and the 4th round blew out the primer and the flake jammed up my firing pin. Had to completely tear down the rifle and bolt. Brand new gun, no experience doing so before. 0 out of 10 would not recommend this garbage ammo. Not worth its weight in gold. Have had plenty of primers about to blow out. Sgammo says this is not a common issue, i call bs, its all over the internet. https://imgur.com/a/VXwVlRg |
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