View Full Version : Bolt over base ftf issue
So I took my 14.5 (pinned with a2x) out to break it in on Saturday. Lower has had about 200 rounds threw it, upper was brand new.
St-t2 buffer with standard carbine spring
unknown buffer tube, mil spec
15.4 standard BCM barrel w/carbine gas system
First 150 was a mix of my old Norinco (which was all flawless) and HSM .223 55gn plinking ammo. Everything past the 150 was HSM (couldn't resist 180 for 500 rounds).
My first 150 rounds were good to go, no malfunctions of any kind. I let a couple of my buddies try my carbine and they were getting lots of Bolt over base malfunctions. 1 out of 3 or 4 rounds. This was all with a fairly new PMAG that has maybe 100 rounds through it before Saturday. I loaded 1 round in all 4 of my mags (other 3 are old USGI with magpul followers). The bolt wouldn't lock back on any of them. I had no issues at all if I manually cycled the bolt.
I had cleaned the hell out of the rifle the day before And lubed everything with EWL 30w. Once I started to get malfunctions I noticed the bolt itself no longer seemed wet and I had left my lube at home.
Should I just chalk it up to being an idiot and under lubing a new upper. Or might I need to take a lighter buffer to shoot that .223 55gn ammo?
At least I had 0 extraction problems, and I was hitting a barrel at 275yards with just 2 clicks of windage adjustment.
vicious_cb
03-26-12, 12:41
Im guessing its a 14.5" middy? If so why are you running a ST-T2? The buffer weight is close to a H2 and BCM ported the gun to run an H-buffer with 5.56 pressured ammo. Junk the ST-T2 and use an H or carbine buffer.
Ditch the shit S2-T2 buffer....Install a mil spec H1 buffer from BCM.
TangoSauce
03-26-12, 12:47
I had major bolt-over-base issues with a carbine before. After a few thousand rounds and controlled testing, it was a combination of ammo and spring. Remington brass was a no-go, but Lake City ran fine. A Sprinco spring is now a must in all my rifles too. Give it some more time to determine you problems, otherwise maybe check to ensure your gas block is properly aligned. The buffer is def the first place to start though.
A cure for your ails.
1. Get rid of the shit ammo.
2. Get rid of the Spike's buffer and stick with a real H buffer. I would only use an H2 if you are going to shoot real stuff like Federal M193, M855 or similar.
OK, so solid H buffer.
I could have sworn Grant said that HSM practice ammo was GTG for plinking ammo.
Well I will try a H or Carbine buffer, if that doesn't cycle I can just give it to my dad, his contender will have no problems I am sure. Plus I already owe him some .223 ammo.
OK, so solid H buffer.
I could have sworn Grant said that HSM practice ammo was GTG for plinking ammo.
Well I will try a H or Carbine buffer, if that doesn't cycle I can just give it to my dad, his contender will have no problems I am sure. Plus I already owe him some .223 ammo.
I have limited experience with HSM and cannot say that I would recommend it.
C4
Thanks Grant, I guess I am not that good at reading anymore.:p
I will try and get an order of XM855, and a H and maybe a Carbine buffer. The wife should have no problem with me getting my self a birthday present 1 day early :alcoholic:
I ran through a little over 1k rounds of HSM 55gr fmj through a RRA 16" middy a few years ago during a 3 day EAG class without a failure.
However, that was a few years ago, and I was running a CAR buffer on a more generously ported 16" gun.
I'm certainly no Grant or Iraqgunz but I concur the tighter gas port and heavier buffer are your probable issue. Pickup a good H buffer and some mil-spec. 5.56 pressure ammo and try again.
GunTotinRedneck
03-26-12, 19:01
Or you could try one of those new AR-Restor hydraulic buffers.
http://www.brownells.com/.aspx/pid=22351/Product/AR-RESTOR-trade-
Or you could try one of those new AR-Restor hydraulic buffers.
http://www.brownells.com/.aspx/pid=22351/Product/AR-RESTOR-trade-
Might be nice for a while, but mine broke in under 1000 rounds.
Totally shitcan the spikes buffer. It brought me nothing but headache.
Regular buffers work fine just fine. You might need to experiment between car through h-2, maybe play with the springs.
Nothing good comes easy. The reason I stay with mil spec is simple... You can diagnose problems quicker with them than other parts. Simple. I need that.
GunTotinRedneck
03-26-12, 20:15
Might be nice for a while, but mine broke in under 1000 rounds.
Totally shitcan the spikes buffer. It brought me nothing but headache.
Regular buffers work fine just fine. You might need to experiment between car through h-2, maybe play with the springs.
Nothing good comes easy. The reason I stay with mil spec is simple... You can diagnose problems quicker with them than other parts. Simple. I need that.
You sir just saved me $95! Much thanks!!! :dance3:
You might want to consider changing the title of this thread, since the BCM upper would be the last part to cause the failures you are experiencing.
Or you could try one of those new AR-Restor hydraulic buffers.
...
...
Might be nice for a while, but mine broke in under 1000 rounds.
......
You sir just saved me $95! Much thanks!!! :dance3:
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GunTotinRedneck,
Just curious, how could you "recommend" a hydraulic buffer to a member here when you have absolutely no experience with one what-so-ever!!
This site has standards about having hands-on experience when making recommendations and doesn't tolerate posters acting like they know what they're talking about, when in fact they're simply "talking through their buttocks".
This isn't your first "incident" in your 24-hour posting frenzy...Know what I mean?
Please "read more and post way, way, way, way less" and if that is disagreeable, then just go be a blowhard somewhere else.
But maybe it's just me...
.
I know that I am going to get spanked for this post but I don't think I need to prove myself here.....
I have found that the Spike's St-T2 buffer and a Wolf XP spring shoots the smoothest in my BCM 14.5 Middy. I have a pinned AAC Breakout on the muzzle. Granted, my rifle will not lock back on most Wolf, Remington and other lighter shooting ammo. I try to use the IMI 193 or other hotter 5.56 loads.
This all goes back to using good ammo in good guns.
Or you could try one of those new AR-Restor hydraulic buffers.
http://www.brownells.com/.aspx/pid=22351/Product/AR-RESTOR-trade-
Or just use a normal buffer (H) that the gun was meant to be used with. The mindset at M4C is that you don't recommend products you don't have experience with.
Makes sense, doesn't it?
GunTotinRedneck
03-26-12, 23:07
=========================================
GunTotinRedneck,
Just curious, how could you "recommend" a hydraulic buffer to a member here when you have absolutely no experience with one what-so-ever!!
This site has standards about having hands-on experience when making recommendations and doesn't tolerate posters acting like they know what they're talking about, when in fact they're simply "talking through their buttocks".
This isn't your first "incident" in your 24-hour posting frenzy...Know what I mean?
Please "read more and post way, way, way, way less" and if that is disagreeable, then just go be a blowhard somewhere else.
But maybe it's just me...
.
The Enidine/Brownells hydraulic buffer was recommended to me by two guys I know at the range I go to. I'll shut my yap now.
The Enidine/Brownells hydraulic buffer was recommended to me by two guys I know at the range I go to. I'll shut my yap now.
Then your range needs to shoot more or I need a good one from the company. My experience is one of one(witch is none).
So I'm going to say, again, is what I said in the first place((check post I posted before).
TangoSauce
03-27-12, 01:27
Why add another moving part to your rifle that can break when all you need to do is change the buffer weight?
I know that I am going to get spanked for this post but I don't think I need to prove myself here.....
I have found that the Spike's St-T2 buffer and a Wolf XP spring shoots the smoothest in my BCM 14.5 Middy. I have a pinned AAC Breakout on the muzzle. Granted, my rifle will not lock back on most Wolf, Remington and other lighter shooting ammo. I try to use the IMI 193 or other hotter 5.56 loads.
This all goes back to using good ammo in good guns.
In semi, maybe. I like to give most things the benefit of the doubt.
In semi, maybe. I like to give most things the benefit of the doubt.
My full autos are standard spring and an H2.
Hydraulic buffers are trash and will eventually cause issues. Stick with the standard H, H2, H3 or Vltor buffers and life will be good.
The Enidine/Brownells hydraulic buffer was recommended to me by two guys I know at the range I go to. I'll shut my yap now.
My full autos are standard spring and an H2.
H2or T2? Because if you got it to run on a 3 pin or especially a DIAS I would go to where ever to see it and have you tell me how you did it.
If you meant H2 then I copy. That's what we did.
Or you could try one of those new AR-Restor hydraulic buffers.
http://www.brownells.com/.aspx/pid=22351/Product/AR-RESTOR-trade-
Please don't post second hand, BS information, especially about a piece of junk like a hydraulic buffer. Stick to what you have personally had experience with. And for charity's sake, 1-2 mags doesn't qualify as useful experience.
To the OP, is your 14.5" a midlength or carbine gas gun? I suspect the ST buffer and ammo as your issue.
Bolt over is universally a magazine problem. If it were a buffer/action spring issue, you should be able to induce simply through a bad combination of parts.
Bolt over is universally a magazine problem. If it were a buffer/action spring issue, you should be able to induce simply through a bad combination of parts.
That's what I was thinking. But he was failing to get the bolt to lock back on the last shots. ZIn the first post, he mentioned four mags loaded with single rounds to test this, and none locked back. But he manually pulled the bolt back, it locked.
It's got to be a shit buffer or shit spring, right?
But still, if none of that works, last come to last, he might have a gouge or burr or something inside the receiver extension hanging it up/slowing it down. very last resort though.
H2or T2? Because if you got it to run on a 3 pin or especially a DIAS I would go to where ever to see it and have you tell me how you did it.
If you meant H2 then I copy. That's what we did.
H2.
I am aware that there are bolt bounce issues with the T2 and that is a no go in full auto.
sinlessorrow
03-28-12, 00:04
I know that I am going to get spanked for this post but I don't think I need to prove myself here.....
I have found that the Spike's St-T2 buffer and a Wolf XP spring shoots the smoothest in my BCM 14.5 Middy. I have a pinned AAC Breakout on the muzzle. Granted, my rifle will not lock back on most Wolf, Remington and other lighter shooting ammo. I try to use the IMI 193 or other hotter 5.56 loads.
This all goes back to using good ammo in good guns.
the ST-T2 is a crap buffer.
spikes claims its the best thing since sliced bread but the issue is having tungsten powder does nothing to help bolt bounce.
a good H2 with proper sliding weights is the best option.
Alright so I got some Bday money and am going to put and order in for a case of XM855 and a new buffer.
So if I want to mess around with lighter .223 commercial ammo should I just go with a carbine buffer, or should I get an H as well?
Alright so I got some Bday money and am going to put and order in for a case of XM855 and a new buffer.
So if I want to mess around with lighter .223 commercial ammo should I just go with a carbine buffer, or should I get an H as well?
Is your gun a midlength or carbine length gas system?
Carbine
H buffer should be good to go, assuming there's not something else going on.
So I figured I would update this. I took my mom shooting for mothers day :) ar functioned perfectly. All I did was put in an H buffer and put 200 rounds of 55gn 5.56 ammo through it. I also used up 150 rounds of that hsm stuff, tword the end of the day (around 380 total rounds) I had 1 failure to lock the bolt. Last 70 rounds or so were fine. I can't wait to do some more shooting this summer!
sinlessorrow
05-14-12, 20:52
So I figured I would update this. I took my mom shooting for mothers day :) ar functioned perfectly. All I did was put in an H buffer and put 200 rounds of 55gn 5.56 ammo through it. I also used up 150 rounds of that hsm stuff, tword the end of the day (around 380 total rounds) I had 1 failure to lock the bolt. Last 70 rounds or so were fine. I can't wait to do some more shooting this summer!
good to hear, its always fun bringing the fam to shoot.
I take my mom occasionally as well and she loves it
She had a blast, I think I might be building her an ar in the future.
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