Seating depth issues with 6.5 CM AR-10

[Kjclark45]

I recently built a 6.5 creedmoor AR10. I don’t want to mention any barrel manufacturers names but I ordered a custom one and not sure if there are any issues (using with aero upper and lower and toolcraft 6.5 BCG). After shooting some factory ammo I Loaded up test ammo with 130 eld-m’s to 2.776” for mag length. Couple shot well then one wouldn’t go in to battery. Saw marks of hitting the lands. Now I’m in the gun room seating them deeper and I had to sweat to 2.668” for them to cycle freely without forcing the bolt open. I feel like this is too short. Am I right in the feeling this or just keep with that seating or switch bullets. Note: was hoping to go with the 130gr to help gain some velocity. Also going to attach the reamer blueprint that was provided by the barrel manufacturer.

 

[straightshooter1]

I recently built a 6.5 creedmoor AR10. I don’t want to mention any barrel manufacturers names but I ordered a custom one and not sure if there are any issues (using with aero upper and lower and toolcraft 6.5 BCG). After shooting some factory ammo I Loaded up test ammo with 130 eld-m’s to 2.776” for mag length. Couple shot well then one wouldn’t go in to battery. Saw marks of hitting the lands. Now I’m in the gun room seating them deeper and I had to sweat to 2.668” for them to cycle freely without forcing the bolt open. I feel like this is too short. Am I right in the feeling this or just keep with that seating or switch bullets. Note: was hoping to go with the 130gr to help gain some velocity. Also going to attach the reamer blueprint that was provided by the barrel manufacturer.View attachment 7461874

What's your CBTO measurement on your loads?

 

[Kjclark45]

What's your CBTO measurement on your loads?

I do not have the tool to measure

 

[TheOfficeT-Rex]

No issues on the factory rounds? Do those hit the lands too? That sounds way too short, since most factory match rounds come in around 2.8"

How many rounds down the tube? Is it possible that you've started to get some carbon ring?

 

[Kjclark45]

No issues on the factory rounds? Do those hit the lands too? That sounds way too short, since most factory match rounds come in around 2.8"

How many rounds down the tube? Is it possible that you've started to get some carbon ring?

Only 82 rounds down the pipe so far. Need to get some factory match rounds to try. I was shooting Nosler ballistic tips for the first 80 and they cycled perfectly. Also have some hornady American hunters that cycle perfect

 

[TheOfficeT-Rex]

I feel like there is something else at play here. What are your other measurements? Headspace compared to fired, case diameter at the base, length of factory ammo, etc.

 

[Nimothy]

This might be a crimp issue too. They might be getting a little longer in the mag during recoil. I def get some Hornady factory loads. If it won’t shoot those reasonably well, I’d say there is something wrong

 

[giumau1]

check your neck tension. As Nimothy said, they might be getting longer. I would not recommend a crimp but make sure you have at least 3 thou or more NT.

 

[Kjclark45]

I was crimpping the rounds so i dont think they would be moving out in the mag but wont do that any more since i have 5 thou of NT. I did manage go and get a Hornady OAL gauge on the way back from deer camp and was able to measure the OAL to the lands for 130gr ELD-M's. The measurement came out to 2.606' at the lands.

Edit: I did try to get some factory match ammo to test but they were all out.