Getting FSP pins tight enough

[SteadyUp]

So as the title says, I'm having some issues getting the front sight post pins tight enough on a new barrel I installed on a Colt 6920 upper.

Details:

Upper: Colt upper, with Daniel Defense 16" lightweight carbine barrel. Colt BCG (A new gas tube, and gas tube roll pin were used during installation. Additionally, the FSB from the Colt barrel was NOT used on the DD barrel. The DD barrel came with its own FSB and pins.)

Lower: Colt LE6920 w/ Vltor A5 buffer system (standard A5 buffer weight)
No other bells or whistles or fiddle ****ery

Ammo used: IMI M193 and PMC 223 Rem. 55gr
Magazines: Brownells, Okay, D&H, Magpul

Reason I think front sight post pins aren't tight enough is because before I installed the new barrel, the carbine ran without any issues, always locked back the BCG after emptying a magazine, and never had issues with short stroking.

After I installed the new barrel, and tested the gun at the range today, I was getting short stroking every 5 or 6 rounds, and failure to lock back on an empty mag, with multiple mags.

So are there any tips for getting FSP pins tighter? I thought I pounded the ever-loving jeebus out of them, but apparently not so. Or should I just send the damn thing off the ADCO or someone who has bigger muscles than me?

Here's a picture of the front sight post pins. As you can see in the picture, the pins don't even come close to being flush with the front sight post.

http://i1124.photobucket.com/albums/l564/BME5101982/AR-15/Troubleshooting%20Photos/IMG_1708.jpg

[seb5]

So you switched out a factory Colt barrel for a DD? Is the FSB from the original barrel? FSB are drilled and pinned to each barrel and are unique to that barrel. Is the gas tube properly indexed? Did you have the A-5 stock on before the change?

As far as the pins go I put Kroil on them, install with a gunsmith hammer and punch and then transition to a shop hammer and larger punch on a supported surface. Did you put them in the right direction?

[Ramone]

I cannot cite my source- it was a USMC armorer at Quantico- but I was told, once upon a time, that several shots were required to seal the joints on the FSB with carbon.

Which may or may not be true, and may or may not have any bearing on your issue.

[SteadyUp]

So you switched out a factory Colt barrel for a DD? Is the FSB from the original barrel? FSB are drilled and pinned to each barrel and are unique to that barrel. Is the gas tube properly indexed? Did you have the A-5 stock on before the change?

As far as the pins go I put Kroil on them, install with a gunsmith hammer and punch and then transition to a shop hammer and larger punch on a supported surface. Did you put them in the right direction?

Correct, I switched out the factory Colt barrel for the DD barrel. The DD barrel came with its own FSB and pins, which I used (I'm aware that FSBs are barrel specific once drilled). Gas tube is properly indexed, and A5 system has been on the gun for a while (it had at least 3000 rounds through it with the Colt barrel).

I installed them the same way you do, starting off with a front sight pin punch and 2 lb hammer, then switching over to a larger punch and a big ass hammer. I use the Brownells front sight block (the orange one, meant for FSBs) to support the FSB. I hammer the pins on a concrete floor (using the Brownells block), as my work bench isn't stable enough for my liking.

[BJV]

I've had the same issue with a DD barrel. It seemed to me that the holes for the taper pins had not been sufficiently reamed. This could have been a mistake, or perhaps DD reams the holes this way on purpose to leave extra material for custom fitting by the end user (which is exactly what I did), or perhaps to allow for an extremely tight fit through the use of a press.

You can purchase or borrow a 2/0 taper reamer and finish ream the holes by hand to achieve the fit that you want. Go slowly and check fit often. Remember that you don't want to ream too far, since you're going to be driving the pins in for a tight fit.

If you're not comfortable doing this, you can always send it off to your 'smith of choice.

[SteadyUp]

I've had the same issue with a DD barrel. It seemed to me that the holes for the taper pins had not been sufficiently reamed. This could have been a mistake, or perhaps DD reams the holes this way on purpose to leave extra material for custom fitting by the end user (which is exactly what I did), or perhaps to allow for an extremely tight fit through the use of a press.

You can purchase or borrow a 2/0 taper reamer and finish ream the holes by hand to achieve the fit that you want. Go slowly and check fit often. Remember that you don't want to ream too far, since you're going to be driving the pins in for a tight fit.

If you're not comfortable doing this, you can always send it off to your 'smith of choice.

I thought that might be a possibility, but I didn't want to just grab a reamer and start opening up the FSB holes. Thanks for your input.

[Iraqgunz]

You may have to open the holes up.

[SteadyUp]

You may have to open the holes up.

Roger that.

When reaming, do you ream the entire barrel and FSB as one, or do you just ream the FSB? This is new territory for me, and I'm considering sending the barrel out if I feel it is too much for me to do.

[BJV]

You'd ream the holes with the FSB on the barrel and in the correct position.

They're not cheap barrels - send it out for the work and be done with it.

[SteadyUp]

You'd ream the holes with the FSB on the barrel and in the correct position.

They're not cheap barrels - send it out for the work and be done with it.

Already making arrangements to do so.