Springfield XD Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
1,678 Posts
Discussion Starter #1
What kind of milage do you expect from a mil-spec BCG? I have hands on experience with three Bcg's. BCM , Spikes Tactical , and Palmetto State Armory premium. All have basically the same specs but are quite different in pricing.
 

·
Registered
Joined
·
7,003 Posts
It's the bolt itself - and the cam pin - that's going to be the primary wear item(s). Add to it the firing pin and the firing pin retaining pin (this is likely the part that will most incur damage during re-assembly), for completeness' sake.

Of the bolt itself, the lugs are an obvious wear area, along with the part of the gun that they mate with. Small components such as the gas rings, extractor and its sub-components as well as the ejector/ejector spring are items that will wear, too.

There are reasonably agreed-upon preventative maintenance milestones for each of these small components that a conscientious shooter/user can follow. :)

The carrier itself?

That's a much, much more durable component, and for as much as I searched in the past, no-one was able to give a solid number or even reason a guess, and that includes guys like the late William Larsen.

It's possible that the gas key will incur damage from handling (i.e. dropped during cleaning) or pre-existing failures in installation (including bolt failures, but problems with various "premium" coatings causing assembly issues can also manifest, witness the SOTAR PSA bolt autopsy) can manifest over time and with use, but that carrier body is a robust item, and even in threads like the ARFCOM/Battlefield LV, shows less concern is on the BCG versus the bolt itself.

I purchased several spare BCGs not for the fear that the BCG itself will "break," but rather to help expedite my being able to get the gun back on-line during a training class, in case it goes down during. Having headspace-checked bolts w/BCGs ready to just slap into the gun means that I can get back into the game relatively fast and not have to depend solely on my backup gun. :)
 

·
Premium Member
Joined
·
3,819 Posts
20,000 or so rds for a military spec BCG. Check exact head space upon delivery/assembly/build. Check again at 1000 rds. Then check every 5000 rounds. Please understand that after a certain fairly high but variable round count the bolt head and barrel extension will take a liking to each other. Metal will slightly move. The will lap.

What this means is that if you have a high round count bolt and it becomes non usable it might be a safe idea to change out the barrel along with the new bolt. You can swap out bolts back and forth but you have to work at it. Changing bolts every 1000 rds will make everybody happy. They wear evenly. Cam pins have finite lives.

Same with firing pins and retainer cotter pins. Firing pins can become peened at both ends. Sometimes a cheap bolt will scour a groove in the cam pin. Not good. Ejectors last a long time. Sometimes a cheap spring will compress or set. Ejection moves aft. The AR15 is a very forgiving platform if certain things are done correctly.

hundreds of builds.
 

·
Registered
Joined
·
7,036 Posts
Well, I have experience with five manufacturers. BCM, SOLGW, DPMS, Del-Ton and PSA premium.
Del-Ton had a failure and was replaced by them. Bcg basically locked up. PSA kept burning up gas rings and idk if the key was leaking but kept short stroking. Could have been the gas port undersized.
BCM, SOLGW and DPMS incurred no problems. For the money I think SOLGW is gtg especially if you get them on sale at Primary Arms.
 

·
Registered
Joined
·
7,003 Posts
^ You didn't by-chance tear down either your Del-Ton or your PSA to see if you could find a root-cause? :)

Currently, in terms of complete BCGs, I would be willing to spend my own money on (in no particular order) -

SOLGW (I'm right there with you on this one!)
Sionics
BCM
Daniel Defense

That said, we should all understand that these items are still mass-produced, with tolerances, and that despite care used in every step from raw materials sourcing to the selected manufacturer (i.e. SOLGW looks to Microbest) to assembly to final QC/QA, weirdness can still happen, and also that every once in a while, one can just slip through the cracks.

Proof? Look at the SOTAR "autopsy" of a customer-provided Knight's Sandcutter BCG.

Issues can happen, even with what's ostensibly regarded as "the best."

And I think that this rolls well into the advice that HB of CJ posted above.....

20,000 or so rds for a military spec BCG. Check exact head space upon delivery/assembly/build. Check again at 1000 rds. Then check every 5000 rounds. Please understand that after a certain fairly high but variable round count the bolt head and barrel extension will take a liking to each other. Metal will slightly move. The will lap.

What this means is that if you have a high round count bolt and it becomes non usable it might be a safe idea to change out the barrel along with the new bolt. You can swap out bolts back and forth but you have to work at it. Changing bolts every 1000 rds will make everybody happy. They wear evenly. Cam pins have finite lives.

Same with firing pins and retainer cotter pins. Firing pins can become peened at both ends. Sometimes a cheap bolt will scour a groove in the cam pin. Not good. Ejectors last a long time. Sometimes a cheap spring will compress or set. Ejection moves aft. The AR15 is a very forgiving platform if certain things are done correctly.
And overall, while I agree with much of what you wrote, I think it's worth pointing out that none of these issues are directly cairrer-related: instead, they are related to the bolt itself and/or the wear components that are a part of the carrier (i.e. firing pin retaining pin, firing pin, and cam pin).

Also, as an addition to HB of CJ's post, remember that cam pin orientation should be noted and kept the same, if at all possible. You don't need to buy the SOTAR/FCD component, but it's worth it to mark the orientation for yourself.

Additionally, for those rolling their own, the M-Guns Optimized Carrier Key Screws (OCKS) are worth the spend.
 

·
Registered
Joined
·
7,036 Posts
The upper was sent back to Del-Ton.
They replaced the bcg saying it was out of spec lol. Something happened within 300rds and changed because it was fine when I bought it new. Ammo was federal and didn't experience any malfunctions till I got home and tried to retract the bcg with a magazine inserted. Wouldn't budge till I removed the mag and dropped the hammer forward. PSA was just returned and supposevely repaired. When I received it back I didn't bother with it and quickly sold it off to another sucker.
 

·
Registered
Joined
·
698 Posts
You know, I've been shooting piston guns for so long, I forgot gas ring wear was even a thing...

I'm not sure how many tens of thousands of rounds my Osprey defense OPS-416 has seen over the past decade, but the bolt carrier itself is pretty much rock solid, and since it doesn't use gas rings, I've not even thought about the bolt... I haven't had any signs on the brass though. I should probably check it with a go/no-go gauge. I've got one laying around somewhere...

I imagine for me, of the BCG, I might worry about cracking the strike face of the bolt carrier and bolt lugs failing over time. When I bought the piston kit, Osprey Defense (I think) claimed something like over 1,000,000 cycles before breakage, but I'm not sure I can shoot that much right now to test it out...
 
  • Like
Reactions: TSiWRX

·
Premium Member
Joined
·
3,819 Posts
I forgot to add, (old age is a bummer, let me tell you!) that the gas rings should be considered other bolt parts that can be routinely changed out. They can go quite a distance if intact and free. Your mileage will vary. Gas rings that seem loose but still work OK can be left alone.

Try to even the gaps between rings if you remove such. Easy to rotate each ring slightly.

Inspecting the bolt head includes looking for any abbe normal wear on the lugs. Polishing on the back side is normal and good. Gouging or visual metal movement is not good. Use a dental mirror to eye ball the barrel extension lugs. A little lapping and polishing is again normal.

Do not forget to do the occasional head space check. The AR15 platform is forgiving on head space. Some tack drivers will close bolts with the field gauge but still shoot fine. Be sure to inspect the fired brass. A "field gage" head space gage is nice but not absolutely necessary.

Grab the bolt and try to break it in half visually inspecting the cam pin hole. Look for small cracks. These usually start at either edge on both ends. Turn a pair of binoculars around to use as very good magnifiers. The bolt should NOT wear grooves in the cam pin. Just even polishing.

If in specification the cam pin will NOT fit either way into the bolt head. Only one way. Use lots of lube.

When cleaning the barrel be sure to use a cleaning rod muzzle or crown protector. Be sure to remember to twirl the chamber brush around some to get the chamber clean. I ran the bcg quite wet. Just used LSA. Blue lock tite on the key screws. Do not stake. Have fun.

That is all. :)
 

·
Registered
Joined
·
7,003 Posts
Try to even the gaps between rings if you remove such. Easy to rotate each ring slightly.
Why?

The rings will simply rotate during use, anyway.

I thought this was old myth that's now gone the way of the do-do?

The bolt should NOT wear grooves in the cam pin. Just even polishing.

If in specification the cam pin will NOT fit either way into the bolt head. Only one way. Use lots of lube.
The SOTAR cam pin video - regardless of whether one wishes to buy this product - explains this pretty nicely:


Blue lock tite on the key screws. Do not stake.
This is completely opposite everything I've ever heard or been taught by various industry SMEs, with key hardware, torque, and staking being crucial.
 

·
Registered
Joined
·
7,003 Posts
For those of you who are interested, School of the American Rifle has been doing "physicals" and "autopsies" on several popular makes of BCGs.

There's lots to be learned in those videos. :)
 

·
Premium Member
Joined
·
21,647 Posts
I have never owned one long enough to fail other than the gas rings. I currently own a piston set up so who knows now.
 

·
Registered
Joined
·
7,003 Posts
Can those be found online?
I'm assuming you were responding to me, about the SOTAR physicals/autopsies?

Yes!

I think you may not have been able to search them up because his YouTube account got hacked and was down for much of last week. Here's a direct link for your troubles (I also apologize for the late reply, I decided to take a Forum break for a few days). :)

Instructor Chad

He's just re-uploaded much of his old material, as well as came back with some excellent new stuff as well.
 

·
Registered
Joined
·
1,678 Posts
Discussion Starter #17
I'm assuming you were responding to me, about the SOTAR physicals/autopsies?

Yes!

I think you may not have been able to search them up because his YouTube account got hacked and was down for much of last week. Here's a direct link for your troubles (I also apologize for the late reply, I decided to take a Forum break for a few days). :)

Instructor Chad

He's just re-uploaded much of his old material, as well as came back with some excellent new stuff as well.
I really enjoyed this, Thanks!
 

·
Registered
Joined
·
7,003 Posts
No problem! Glad to be of-service.

He's always updating with new and interesting stuff - so stay-tuned or subscribe to that Channel. :)

I've learned so much in the last few months from watching his Channel, reading his (currently only) Blog post, and reading the back-and-forth in his FB Group.

For example, I'd always thought that a good Mil-Spec bolt should have both the O-ring "doughnut" *_and_* the insert in-place. I have even added the doughnut to the bolts that came without or came without it installed. I've never experienced a spontaneous FTE in the tens of thousands of 5.56 that I've put through my beaters, so I automatically thought that I was doing things right.....come to learn that, instead, it was probably just a matter of luck and likely a testament to the excellent nature of the guns that I've bought that I hadn't made more trouble for myself with this improper setup!

"The More You Know!" :)

 

·
Registered
Joined
·
1,678 Posts
Discussion Starter #19
No problem! Glad to be of-service.

He's always updating with new and interesting stuff - so stay-tuned or subscribe to that Channel. :)

I've learned so much in the last few months from watching his Channel, reading his (currently only) Blog post, and reading the back-and-forth in his FB Group.

For example, I'd always thought that a good Mil-Spec bolt should have both the O-ring "doughnut" *_and_* the insert in-place. I have even added the doughnut to the bolts that came without or came without it installed. I've never experienced a spontaneous FTE in the tens of thousands of 5.56 that I've put through my beaters, so I automatically thought that I was doing things right.....come to learn that, instead, it was probably just a matter of luck and likely a testament to the excellent nature of the guns that I've bought that I hadn't made more trouble for myself with this improper setup!

"The More You Know!" :)

Absolutely. He covered two BCGs that taught me lots. One was the Fail Zero NIB and the other was the AO precision. I need to join his FB group . I would like to read his blogs also. Can you direct me to those?
 
1 - 19 of 19 Posts
Top