New AR, FTFs

[jscwerve]

So, finally got the rifle together and took it to the range for the first time. Since I had to sight my hunting rifle, I only had time to run a 100 rounds down the pipe. In that 100 rounds, I had 6!!!!!!! FTFs!!!!!!! What should I be looking for? I re-magazined the 6 rounds and 2 of them fired, they are also the 2 that I used the foreward assist to make sure the bolt was all the way foreward because on all the FTFs the hammer drop didn't feel quite right (light).

-buffer spring not strong enough?
-new parts not broken in yet, machine markings causing fully feeding problems?
-crap ammo?
-action gummed up (although I don't think possible)?
-FSB gas hole misaligned? (NO failure to feeds though)

The rifle is a Spikes lower that I put a DPMS LPK into. Upper is a Del-Ton 16" this is it:http://www.del-ton.com/Del_Ton_AR_15_Barrel_Assembly_p/dt2003.htm Using Magpul Pmags, tried several.
Didn't use crap ammo because I was sighting my cheap red dot. Used Federal 55grn (walmart box)(I know 55grn isn't optimum for a 1-7 barrel, but it shoots fine and no keyholing, yes, 62grn+ would be better). When plinking, the steel cased ammo didn't have an FTF, but only shot 30 (fired after the brass, so polymer coating not the cause). Upper and lower were cleaned to a point of sterile (delton uppers have a ton of crap all over them) and then lubricated lightly on wear points with Hopps lubricant. Gas rings all perfect, new and intact.

Anything else I should be looking for? Any and all ideas are apprecieated. I am not too worried, I am figuring it is new gun break in stuff, but this is my first AR, so want ideas. Thanks!
J.C.

[BadShot]

Could be gas, but that would more likely be a Failure to Eject not FTF. Could be any number of springs related issues, or even a short firing pin. You might could try a new firing pin. Doubt that's it though.

On a side note, what kind of stock are we talking about? I've seen folks use carbine length springs and buffers in A2 stocks and suffer FTE. Again you're having FTF... also don't lightly lube.. AR's prefer to run wet, don't be stingy. Again first thing coming to my mind is the firing pin being a smidge short. Trigger control group springs could be light too. While I doubt the firing pin is actually short, it's one possibility.

Were it me, I'd replace the trigger control group springs and firing pin.

[RARGUNS]

Did you check to see if it was leaving a dimple in the primer before you reloaded the FTF rounds?

[BPTactical]

On a new rifle a few hiccups MAY occur.
FTF usually signifies Failure To Feed.
Sounds like you are suffering from FTI- Failure To Ignite.
BadShot brings out good points to check. Double check your assembly. Is the hammer spring backwards? Make sure the parts are correct for the application!
As RAR mentioned check for light primer strikes.
As it is an infrequent occurrence it is a bit harder to track down.
Was the headspace checked?
Your description of the hammer fall feeling odd makes me suspicious of incomplete bolt lock up or a hanging firing pin.
Clean it well and either use the swabs or a pressurized cleaner to clean the chamber recesses/lug recesses well.
If the bolt is not closing completely do not fire the weapon!
I would disassemble the bolt and carrier and look carefully for any burrs or errant machining marks. Look for shiny points of contact or anything that looks unusual. Pay attention to the lugs of the bolt and the recesses in the barrel extension for burrs etc.
When reassembled check the firing pin for free travel. When dry and the bolt seated in the carrier all the way shake the BCG. You should hear the firing pin rattle back and forth. Firing pin protrusion should be .028 to .036 IIRC. Roll the firing pin on a flat surface-if it is bent it will be apparent.
Throw your Hoppes oil in the trash can- it is too light. Go get a good full synthetic oil like Tetra or Mobil 1 30wt and lube the gas rings, a drop or two down the Gas Key and firing pin and then on the contact points of the carrier and receiver. It should spray oil for the first few rounds.

You can rule out a gas issue(unless you ate Santiagos), if it was a gas issue it would not be causing FTI's rather it would short stroke and cause Failure To Extract/Eject or FTE's.

If it still gives you fits touch base with me- we will get her rolling for you!

[BPTactical]

"Do no put oil inside your gas system as it will carbon up and make a mess"

With normal petroleum based oil I will agree, as it burns away. I have found that the synthetics will actually help the carbon issue. Ever since I started wiping the back of the bolt (gas side) and the interior of the bolt carrier with Tetra the carbon build up in these two problem areas virtually wipes away.

Good shakedown of the operating cycles BTW....




[Beer]

[jscwerve]

Thanks all for the replies! Now I have some things to look for. Sorry for the misuse of terms, should have said FTI I guess. I will check on all the things that were mentioned. Also, learned a few things, this is my first AR, so I didn't know they liked it that wet to operate, I lubed it the same as any of my other guns.

Yes, the FTI's were light primer strikes, as if the bolt was not foreward quite enough (a few thousanths I am guessing) as far as "knowing" if it was seated properly, I am unsure as to how to check that after I just fired a round. The rounds that I rechambered only went off after I made sure the bolt was seated with the foreward assist, is that not why it is there? .

As far as checking headspace, I will get a hold of some guages and check, guess it is my bad for not checking first, del-ton states that they have headspaced and test fired all their uppers, and I have heard nothing bad about them. Thanks BP tactical, I will also check the pin protrusion. It is a
very infrequent failure. And after I put the failed rounds back into a magazine, the first 4 failed the same as they had before, and the last 2 fired after I bumped the assist to make sure everything was seated properly. As far as metal burrs and such, I will check again. That was one of the first things I looked for when I got home. Also, the bolt carrier is chrome lined, so pretty obvious if something is wrong inside of it. I am sure it is not a gas system issue as it had no feedin problems whatsoever or shortstroking, etc.

Stock- it is a carbine length spring, buffer, and tube. All measured to be proper lengths. ( Had another thread on that!!)

Thanks all so much for the advice! I will check those things and report back as to my findings!