Having an issue with my new BCM upper - help appreciated

AR/M4 AR Technical Discussion
1

Brand new BMC mid-length upper, 14.5", with Battlecomp 1.5 brake.

Lower has a CS blue-end spring and Spikes T2 tungsten buffer weight.

Started off shooting Wolf 62 grn poly ammo - everything worked great. Switched over to Federal American Eagle 55 grain and everything worked great. Went back to Wolf and suddenly it wouldn’t strip off the next round out of the mag. Fired fine, ejected fine, but 50% of the time would not strip the next round off the mag. On the last round it wouldn’t push the bolt back far enough to lock the bolt open on the empty mag. But when I went back to the Federal ammo everything worked just right.

Am I correct in assuming that perhaps the Wolf ammo is not as powerful as the Federal and is therefore not giving the bolt enough “oomph” to push it back far enough over the rear of the next round in the magazine to allow for chambering?

Could it be the muzzle brake causing this?

Would I be advised to perhaps try a lighter, shorter buffer spring, or a carbine weight buffer instead of the T2 buffer?

2

Wolf is weak and inconsistent ammo; if you are going to run cheap Russian stuff, I’d stick with Brown/Silver Bear and/or the newer Wolf ‘WPA’. But yes, in order to give yourself the best chance with weak ammo, a switch to a carbine buffer may help.

3

your assumptions are correct.

Where did the blue ended spring come from? Sounds like a sprinco enhanced spring. Your middy would be best served by a standard CS spring. I would also ditch the spikes buffer and get a mil-spec H buffer.

4

Bingo - it is a Sprinco Enhanced spring. I’m going to get a regular old Brownell’s 3-pack of carbine springs ($5.85!) and a regular carbine buffer (or do I need the H buffer?) I’m reading that most people just recommend a normal weight carbine buffer and not the H buffer.

Thanks for the help, guys!

5

  1. GET RID OF THAT RETARDED CS Bullshit immediately. (I’m not shittin on you… I made the same foolish purchase ONCE too.)

  2. GET RID OF THAT RETARDED Spikes T2 Bullshit immediately.

  3. Get an H buffer and Mil spec carbine spring put into that gun.

The 14.5 middy can be a little finnicky. Messing around with aftermarket garbage will definitely screw it up. Some of the carbine gas systems will tollerate that junk, but the 14.5 middy not so much.

6

I agree with markm. I have found the best combo for the two 14.5 BCM middys that I have is an H buffer and a standard mil-spec carbine spring. Tried an H2 buffer and it worked fine in one gun, but the other was finicky with it. Go get a mil-spec spring and an H buffer and run with it.

7

Both 14.5" BCM mid-lengths I’ve run have worked well with H buffers and GI springs. I have 432 rounds of almost exclusively Wolf & Brown Bear through one, and 770 rounds of all Wolf and Brown Bear through another. No malfunctions in either except for 3 stuck cases with Wolf in the first carbine and one failure to feed from the first magazine in the second.

8

I’ve used the Sprinco blue spring in a number of midlengths with zero issues. I’ve even used their rifle spring and 6oz buffer in a Vltor A5 extension w/ a DD 14.5" mid.
When Mike Pannone did his “why doesn’t my AR jam” test that the DI-minati always refer to, he used a Sprinco spring. They’re not aftermarket garbage.

9

It ma be an importation distinction that this is a 14.5" midlength, and that Pannone’s tests used carbine-length gas systems.

If the use of a GI spring in the OP’s gun gives him a reliable gun then the Springco is to blame.

10

It can be the buffer or the spring…it’s a “recipe” as they mention below. The permutations of gas port, spring, buffer, and ammo are endless…I don’t use Wolf, Silver Bear, or other steel case ammo in my 5.56 ARs so I don’t have experience with it.

[i]
STANDARD Power Buffer Spring,“WHITE Spring” Equivalent spring load to a “fresh” Mil-Spec M4 Carbine Spring. This spring will perform reliably in any properly configured and maintained 5.56 Carbine, if you wish to maintain the performance of a “fresh” Mil-Spec load spring without concern for replacement. This is the best choice for shooters and purists that wish to maintain the performance of most factory supplied Mil-Spec springs, but do not wish to be concerned with frequent replacement of same or do not have the time or inclination to seek enhanced performce options. The WHITE spring is recommended for 1st Gen M&P’s, most RRA’s, most Colt 6920 LE’s, 6.8 Shortie Piston Guns, and when training with SRTA and other low power and light charged “budget” rounds. Color Coded WHITE.

ENHANCED Power Buffer Spring, “BLUE Spring” Offers improved performance with most non-suppressed 7.5"-12.5" shorties, middies, and all mid-length uppers with adjustable gas blocks. Best performance is usually achieved using buffers ranging from ST-2T, H2, DPMS Extra Heavy . Will run in some RRA’S and some Colt 6920 LE’s, but use of heavier buffers may not be possible with the aforementioned as well as most uppers with light weight carrier groups (VTAC, etc.) Color Coded BLUE.

Extra Power Buffer Spring, “RED Spring” Best option for 16"+ barrels with carbine length gas system platforms with standard front sight towers and H buffers, gas piston guns, some suppressed shorties, and 9mm. Color Coded RED.

7.62 X 51 , 6.8, ETC. Applications: Several of our OEM clients are utilizing the “RED Spring” in both their fixed and collapsible stock platforms. Please call us to discuss successful “recipes”.

In addition to use in 5.56 Fixed Stock Rifles, our “GREEN Spring” is just the ticket for use in the VLTOR A-5 Stock System using their standard weight (5.3 Oz.) buffer for maximum versatility with almost any 5.56 upper BBL configuration, both with or without a “can”.[/i]

11

I built my 14.5PA midlength approximately 8 weeks ago. At the time, I had a brand new H2 buffer and carbine spring still in the wrapper. I used the combo out of shear convenience, and have had nothing but great results with it.

I broke the rifle in with 300 rounds of Remington 62gr FMJ, then transitioned to Wolf 62gr HP for the next 1000 rounds (I was at a course). Then shot another 700 rounds of XM193A, 60gr Hornady TAP, and a little more of the Remington.

2000 rounds total to date, zero malfunctions, and it locked back on an empty magazine everytime. Rifle was not officially cleaned until the 2K round mark, I just kept a moderate amount of Slip2000 on it.

12

Yes, and in addition, Pannone was using a “Red” extra power spring and a H3 buffer…so direct relevance is somewhat limited.

That said, (and I’m feeling the deja vu here from last weeks very similar thread), as per Boss Hogg I like my Sprinco springs so I’d be swapping the buffer out first to a carbine one and trying that out before I moved onto the the spring. I have a middy (but a 16") that did the same thing with cheap’n’nasty ammo - when I swapped my H2 buffer out for a Car one, it started working fine with Bear, but when I swapped the blue sprinco for a “mil spec” spring and kept the H2 buffer, it still short stroked on occasion.

I know the stock recommendation in these circumstances seems to be a Mil Spec spring and a H buffer - but we are not talking Mil Spec ammo here, we’re trying to get it to run 100% with weak crap, so I think dropping in a H buffer is probably a bit of a waste of time and not light enough, considering the OP is already using what is effectively a H 1.5+ in the Spikes ST-T2. Use of a car buffer over an H would give the max possible wiggle room for those “even weaker than usual” rounds that you often encounter with Wolf.

13

Thanks to everyone for the assistance.

Question - is it possible to open up my T2 tungsten powder buffer and remove the extra weight to make it into a carbine-weight buffer?

14

Possible? Hmm, well, everything is possible, I guess :wink: …however, for the measly $10-$11 a carbine buffer costs…I’d strongly advise against it.

15

AGREED!! There’s no telling what inner diameter of that Spike thing might be.

16

The baseline is the H buffer and the GI spring. Everything should start there to avoid these kinds of shenanigans. I don’t understand how people jump off the 10th floor without any understanding of the floors below.

As a reverence to others reading this, as a general rule for guns 1.45"-16" with carbine or mid-length gas systems, start out with an H buffer and a GI spring. All uppers within these parameters should work with this combination of buffer/spring over the widest variety of ammo.

It may very well be that the OP has an obstructed gas port, a kinked gas tube, an offset FSB, or a whole host of other problems, but with the non-standard parts installed it is impossible to gauge this.

17

Yes, it is, see above.

However it is only becoming the “stock answer” because so many people choose to deviate from it and then complain about problems.

Put the stock parts back in and report back.

In fact, that should be the answer for 99% of the “my shit don’t work” threads here.

18

MP does not use the red spring for anything. At all. Ever.

He uses both the blue and the white springs in carbines. I don’t think he uses the blue spring in midlengths.

The white spring was something that he developed.

A BCM 14.5 midlength with an H buffer and a BCM stock action spring should be able to function with any commercially available ammunition - that has been my experience.

19

If not and for know for sure then fair enough, and times and equipment may well have changed since 08 but this quote from the oft-quoted article:

“On my rifle, I use a Sprinco Super Duty M4 buffer spring as well as a DPMS Extra-Heavy Buffer (it is .2oz lighter than an H3 buffer)”

  • sounds like what is now known as a “Red” to me. Sprinco’s own wording is that red is best for some carbine length gas guns.

The “white” is brand new, only been around a month or so - I do think its a good thing they released that.

20

Actually that I very much do agree with. If everyone started with than baseline…and then did a bit of meddlin’ one piece at a time…then they’d know for sure what did what.

  • ETA - but in this particular case as we are talking about trying to make a rifle (that is otherwise already running perfectly with decent ammo) run with shitty weak ammo, I still say go with Car buffer over H :wink: