AR 10 bolt lock position

[greg1147]

6.5 CM AERO parts, 18" barrel, Superlative Gas Block, cycles as it should except for not locking back on last round. Buffer and spring are correct
changed bolt catch to correct actually looks the same as a AR15. Manually locks back, but with mag inserted and mag release depressed bolt goes into battery. Also bolt doesn't lock back as far as AR 15. Figure it's not a battle rifle and it runs as it should except for this one small item. Any input or tech
appreciated.
Little clarification on what is going on, or what's not going on.
Mag inserted, bolt catch enabled

Bolt being held open by charging handle

Bolt held open by bolt catch manually engaged

Empty mag will not hold the bolt open when inserted and manually charged

 

[mtrmn]

"Also bolt doesn't lock back as far as AR 15"

Bolt catch should catch the front face of the bolt locking lugs--NOT the front edge of the bolt carrier. If it is trying to catch the CARRIER, the bolt is not coming back far enough. When you manually pull the charging handle all the way rearward, the front face of the locking lugs should be about 1/8" behind the bolt catch.

 

[PinesAndProjectiles]

Open up your gas port another half a turn. Keep going until the bolt locks back on the empty mag.

 

[bfoosh006]

Open up your gas port another half a turn. Keep going until the bolt locks back on the empty mag.

I will add .... do the single mag loaded round trick. Load and fire a single round ( via the mag ) ... adjust the gas block until you have lock back on the then empty mag.
BTW, what mag are you using ? And what ammo ?

 

[r.tenorio671]

....if your not using the Aero AR10 bolt catch, that could also be the problem. I found that various "DPMS" pattern AR10 bolt catches have a very thin finger to catch the back of the magazine follower and can actually slip off the edge. Check out the attached pics and notes on each, might provide some useful info in resolving your issue.

 

[greg1147]

I will add .... do the single mag loaded round trick. Load and fire a single round ( via the mag ) ... adjust the gas block until you have lock back on the then empty mag.
BTW, what mag are you using ? And what ammo ?

Hornady 147 gr ELD and a combination of Magpul and C products

 

[greg1147]

....if your not using the Aero AR10 bolt catch, that could also be the problem. I found that various "DPMS" pattern AR10 bolt catches have a very thin finger to catch the back of the magazine follower and can actually slip off the edge. Check out the attached pics and notes on each, might provide some useful info in resolving your issue.

I actually replaced the bolt catch with an AERO which was the exact same that was installed. Now I have an extra LOL

 

[greg1147]

Last and easiest to replace, I received the AERO specific buffer spring and installed it, fuckin works, a carbine spring is a carbine spring
right apparently not. At least with AERO.

 

[hlee]

Just to close the loop, count the coils on the new and old springs. I’d bet there is a difference, and that the new spring has fewer. Your pic of the bolt locked open sure looked like the latch was catching on the carrier and not the bolt face. This can happen if your spring is too long.

 

[r.tenorio671]

Just to close the loop, count the coils on the new and old springs. I’d bet there is a difference, and that the new spring has fewer. Your pic of the bolt locked open sure looked like the latch was catching on the carrier and not the bolt face. This can happen if your spring is too long.

....just to add, the amount of coils can be misleading, depending on the manufacturer of the spring. The overall length of the spring at rest and fully compressed can be influenced by the amount of individual coils, distance between each coil and the diameter of the wire used to make the spring. Also, the spring rate will also be influenced by these parameters. But...you got it working, that's all that matters..