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Senior Member
Originally Posted by CPM
The bolt would hang up about a half inch from seating fully. Then ,when fully closed, would get a light strike. Im ruling out the trigger, as it is a drop in Velocity 3lb, and it is hitting plenty hard. Ive got two of these btw, one a 4lb, they are built like tanks % excellent.
Vin..thank you. Ive got calipers..whats the spec on that? I did not see any drag or wear as I can now recall, but Ill check this if I can get the spec.
The obedient always think of themselves as virtuous rather than the cowards they really are.
Senior Member
Just measured a Colt and a PSA, they're both 0.3985.
Other thing could be (re: light strikes) the BCG, the part where you see the back of the firing pin when assembled, that area has a ledge inside of course. If it's not milled out to spec, the spool of the firing pin could be hitting it, keeping it from protruding through the bolt as far as it should.
Is there any corresponding "mushrooming" or witness marks on that part of the firing pin?
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It shouldn't be hard to figure out what the problem or problems are. Did you use any used parts in this build? If so, which ones?
How come your gun smith didn't test fire it?
ViniVidivici made a good call and I was about to suggest that, but he beat me to it. Just get a flashlight and look inside the receiver. If the cam pin or anything else is dragging you'll see the scarred anodizing.
I'm personally allergic to running the bolt of one brand in another brand of carrier, unless I have to. If the Young NM bolt wouldn't headspace, I would have suggested sending the entire BCG back to Young with a terse note, and get my money back. They are the ones who don't stake their carriers either, right? Snake oil I think. The chamber is much more important than the bolt for accuracy. Just run a good BCG like BCM or Daniel Defense and call it a day. Cleaning is not that hard or necessary to do after every trip to the range. Chrome is not necessary. ARs are made to run dirty.
I hate to ask this but did you try more than one magazine? Does the BCG drive home with no magazine in it? Or does it hang up? Its possible the carrier could be dragging on the magazine. The carrier should drive home with no drag if there is no magazine. Gas rings and a bolt should not be able to stop a carrier, even when the rings are new. BTW Ballistol is not a good oil for a BCG. It needs more viscosity. SLIP 2000 works very well, but there should be grease on the bearings of the carrier, the cam pin, and some grease on the gas rings and bearing. ARs like to be well lubed. Oh, and make sure the charging handle is lubed.
What buffer weight are you running? Not enough spring or buffer weight can cause problems. Minimally, if its a Carbine buffer tube it should be an H1 (says H on it), maybe run an H2. Check the length of the spring too. (look up the spec online) If its a bad spring, buy a good quality spring made by Sprinco. Its unlikely that buffer weight is the problem, but the spring? Possibly. Unless the weight is a carbine buffer weight (no mark), then, for sure, I would suggest getting an H1.
If you are running a rifle buffer tube make sure it has the correct spring and buffer, otherwise leave that alone for now. Just make sure the spring is the right length.
Ok, so a light primer strike can also be caused by a firing pin that is too short or an obstruction/goop in the bolt. Just make sure that the firing pin is extending out of the bolt to adequately strike the primer. And that it slides easily in the bolt. I don't know what the measurement is for the protrusion of the firing pin, you can look it up, but eye ball it first.
Try looking at all those possibilities before taking anymore steps.
SOTAR lubing may-be a little excessive. https://www.youtube.com/watch?v=DTpWfjVFfEU
Last edited by ScottsBad; 01-12-21 at 01:13.
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Dude BCG’s are so cheap, just toss it and buy a new one. I’m still leaning toward a light hammer spring as well. Every chintzy trigger I’ve seen, even expensive ones, do this. Throw a mil-spec trigger and BCG in there and see what happens. This is what happens when we buy products that solve problems we never had.
When you're done saying what you're saying, stop saying it.
Senior Member
Scottsbad-
I appreciate the time it took to write that. Let me quickly answer your questions, as I am pooped from work last night.
Gunsmith fired the rifle, it worked. I then fired 60 rounds myself, it hung up a couple times. Sat in a safe all year until 4JAN.
Im gonna measure to FP & Bolt cam when I get a moment.
Carrier WAS greased as you said when problems occured. I used Ballistol to clean it again, then lubed it with it cause its what I had at hand. Ballistol has fine for me for decades, but I do use better stuff otherwise.
Mags were old, proven ones of different make, some Ive used over 10 years..mags werent the issue.
Ch was greased. And my 'smith staked the carrier key before 1st round was fired.
It has a Rifle buffer. Ive been wondering if the Recoil Spring is involved in this also somehow.
Give me some time to do the measurements, Ill check back when I do.
Thanks again for the post.
Last edited by Straight Shooter; 01-12-21 at 08:56.
The obedient always think of themselves as virtuous rather than the cowards they really are.
Senior Member
Are you aware this was a new build, from parts amassed over a few years?
Where are you finding these "so cheap" bcg's? The one in my rifle was $200 a couple years ago. aint "tossing" shit.
Are you also aware this is a rifle meant for precision shooting? I wont be "throwing a mil-spec trigger in there" at all.
You are also WRONG about the Velocity trigger. If YOU havent used one-how the hell can you call it "chintzy"?
IF all this needs is a good breaking in- good, Im fine with it. Rifle wasnt ever gonna be used for SD or in life or death anyway.
IF the bcg winds up being the problem, Ill use one of the several I have in then.
The obedient always think of themselves as virtuous rather than the cowards they really are.
Senior Member
If they are 10 years old, and getting a lot of use, are the springs getting worn out?
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.400 +/- .001
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Well, I’m a master class shooter, an OIF Veteran with a B4ASI(I know a little bit about precision shooting), I own a shooting instruction company, and up until this point I’ve never heard of velocity triggers. You’d think if they were popular in any meaningful way, I would have seen a single one, somewhere. I had to google them. They’re chintzy shit. I don’t know about the BCG, but I haven’t seen a match or a fight won due to a modified BCG. It’s unneeded.
You don’t have to be a dick about it or get emotionally invested because you paid for it. More money doesn’t mean more better. Just put a normal BCG in it and any trigger that is a known quantity with a full power hammer spring in it and see what happens. All of these things are cheap.
If you’re in Texas PM me and I’ll show you that it’s possible to shoot a milspec trigger in a precision setting. There’s a million reasons why you’re going to miss before the trigger.
When you're done saying what you're saying, stop saying it.
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They’re fairly popular. If you instruct dudes that use personally owned weapons, you’ll probably encounter one at some point. I have no input on whether they are any good or not.
RLTW
“What’s New” button, but without GD: https://www.m4carbine.net/search.php...new&exclude=60 , courtesy of ST911.
Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself. I have no idea what we sell, other than CLP and training. I receive no income from sale of hard goods.
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