Troubleshooting at the range...things not always as they seem

[rxer311]

I posted this on one of the other forums as well. I figure it may be of help to somebody else here down the road.

I finished my Spikes "Crusader" build and finally got it out to the range today.

The important specs are as follows:
- 14.5" Voodoo mid length barrel with pinned Manimal Flash hider
- Black Rain ordnance clamp on gas block
- Aim Surplus Nitride BCG
- Standard Carbine Spring
- Standard Carbine Buffer
- Independence 5.56 x193 ammo

So I set up and started shooting from a rest to get my irons dialed in first. I always just run 3 rounds at a time through a magazine just to check function. The first 3 rounds cycled fine, but the bolt did not lock back on the final round. Loaded 3 more rounds. Same result. So I just continued with this cycle until I got my sites locked in. Sometimes the bolt would lock back, sometimes not. So I started dialing in my Meprolight RDS. Kept having the same results. All rounds were cycling fine but the bolt would not lock back. After I got my RDS locked in I loaded a 20 round mag and did a mag dump. All rounds cycled just fine, but the bolt did not lock back on the final round. I checked out my shell deflector and it seemed to be getting dinged up.

I started thinking to myself that this rifle has to be short stroking. I checked my has system visually for leaks, but everything looked fine from a visual standpoint. I thought I would try some cheap fixes and see what I came up with. I headed to my local guns store for some supplies. I already had the lightest buffer so I purchased a Wolf low power spring. I also picked up 2 boxes of Tulammo .223 which is known to be terribly under powered and a box of Hornaday TAP 55gr (my preferred home defense ammo).

I headed back to the range. I field stripped the rifle and did a cleaning then reassembled everything with the Wolf low power spring. Loaded 3 rounds of the mil spec ammo into the mag and started shooting again. The problem got worse. Where as before the bolt would lock back on the last round about 1/2 the time, now it was never locking back. So I removed the wolf spring and installed the standard buffer spring.

This time I loaded the mag with the under powered Tula with 3 rounds. I shot 3 rounds and each of the 3 rounds ejected perfectly at the 3 o'clock position and threw the spent cases halfway across the range! Bolt locked back after the 3rd round. I continued with this process until all 40 rounds of Tula were spent. Everything cycled perfectly and the bolt locked back after every last round.

Loaded the mag with 3 rounds of TAP ammo and was getting results similar to the mil spec ammo.

Keep in mind that this entire range session of about 250 rounds to this point, I never had a single failure to feed or failure to eject. Weird, I thought.

Ah hah! This rifle is overgassed! It cycles Tula just fine which is terribly under powered! Back to the gun store. I purchased a Spikes ST-2 buffer. to slow down my carrier.

Guess what happened?

Consistent ejection and consistent lock back of my bolt after the last round of the mag. This rifle was so over gassed that I was getting bolt carrier bounce and the carrier was rebounding faster than the magazine spring could push my bolt catch into position. The heavier buffer slowed down the carrier allowing the rifle to continue cycling properly while now also locking the bolt back after the final round of the magazine.

Sometimes things aren't always as they seem...

If you are having problems, make sure to check all options before you give up and tear your rifle apart.

[JGifford]

I use slow motion video to diagnose issues.

[JGifford]

Ps. Try a Sprinco blue and h buffer, too. It's snappy but flat, or go vltor a5. Both are good solutions I've found.

[RogerRonas]

I posted this on one of the other forums as well. I figure it may be of help to somebody else here down the road.

I finished my Spikes "Crusader" build and finally got it out to the range today.

The important specs are as follows:
- 14.5" Voodoo mid length barrel with pinned Manimal Flash hider
- Black Rain ordnance clamp on gas block
- Aim Surplus Nitride BCG
- Standard Carbine Spring
- Standard Carbine Buffer
- Independence 5.56 x193 ammo

So I set up and started shooting from a rest to get my irons dialed in first. I always just run 3 rounds at a time through a magazine just to check function. The first 3 rounds cycled fine, but the bolt did not lock back on the final round. Loaded 3 more rounds. Same result. So I just continued with this cycle until I got my sites locked in. Sometimes the bolt would lock back, sometimes not. So I started dialing in my Meprolight RDS. Kept having the same results. All rounds were cycling fine but the bolt would not lock back. After I got my RDS locked in I loaded a 20 round mag and did a mag dump. All rounds cycled just fine, but the bolt did not lock back on the final round. I checked out my shell deflector and it seemed to be getting dinged up.

I started thinking to myself that this rifle has to be short stroking. I checked my has system visually for leaks, but everything looked fine from a visual standpoint. I thought I would try some cheap fixes and see what I came up with. I headed to my local guns store for some supplies. I already had the lightest buffer so I purchased a Wolf low power spring. I also picked up 2 boxes of Tulammo .223 which is known to be terribly under powered and a box of Hornaday TAP 55gr (my preferred home defense ammo).

I headed back to the range. I field stripped the rifle and did a cleaning then reassembled everything with the Wolf low power spring. Loaded 3 rounds of the mil spec ammo into the mag and started shooting again. The problem got worse. Where as before the bolt would lock back on the last round about 1/2 the time, now it was never locking back. So I removed the wolf spring and installed the standard buffer spring.

This time I loaded the mag with the under powered Tula with 3 rounds. I shot 3 rounds and each of the 3 rounds ejected perfectly at the 3 o'clock position and threw the spent cases halfway across the range! Bolt locked back after the 3rd round. I continued with this process until all 40 rounds of Tula were spent. Everything cycled perfectly and the bolt locked back after every last round.

Loaded the mag with 3 rounds of TAP ammo and was getting results similar to the mil spec ammo.

Keep in mind that this entire range session of about 250 rounds to this point, I never had a single failure to feed or failure to eject. Weird, I thought.

Ah hah! This rifle is overgassed! It cycles Tula just fine which is terribly under powered! Back to the gun store. I purchased a Spikes ST-2 buffer. to slow down my carrier.

Guess what happened?

Consistent ejection and consistent lock back of my bolt after the last round of the mag. This rifle was so over gassed that I was getting bolt carrier bounce and the carrier was rebounding faster than the magazine spring could push my bolt catch into position. The heavier buffer slowed down the carrier allowing the rifle to continue cycling properly while now also locking the bolt back after the final round of the magazine.

Sometimes things aren't always as they seem...

If you are having problems, make sure to check all options before you give up and tear your rifle apart.

Verey informative.
Thank you,
Roger