COL for maximized accuracy?

[toxic]

So I've been doing a lot of reading but I'm a little confused. Looking for some wisdom from the seasoned reloaders. What I'm loading for is an AR with a 5.56 chamber but I think my questions are more general in nature - and will apply for my bolt guns too. I've always used safe published loads and lengths but I'm looking to squeeze accuracy out of my guns...safely.

Is it advantageous to load with such a long COL that the bullet engages the rifling? Can this cause a high pressure situation from either larger case volume or even resistance from the "stuck" bullet? If so is loading.10 short of the rifling the acceptable thing to do?

I have been trimming cases to published lengths. Should I be trimming cases based on the length of the chamber of the individual firearm? If so how far from the edge of the chamber to allow stretch and how do I even measure my chamber effectively?

Thanks in advance for any elightenment...

 

[kevguy]

So I've been doing a lot of reading but I'm a little confused. Looking for some wisdom from the seasoned reloaders. What I'm loading for is an AR with a 5.56 chamber but I think my questions are more general in nature - and will apply for my bolt guns too. I've always used safe published loads and lengths but I'm looking to squeeze accuracy out of my guns...safely.

Is it advantageous to load with such a long COL that the bullet engages the rifling? Can this cause a high pressure situation from either larger case volume or even resistance from the "stuck" bullet? If so is loading.10 short of the rifling the acceptable thing to do?

I have been trimming cases to published lengths. Should I be trimming cases based on the length of the chamber of the individual firearm? If so how far from the edge of the chamber to allow stretch and how do I even measure my chamber effectively?

Thanks in advance for any elightenment...

Yes, trim to the SAAMI length. COL to 10 -15 thou just off the lands.

 

[toxic]

Thanks for that. It sounds like I have this most ways right.

Any opinions on the the Sinclair Seating Depth Tool? I don't think it's an essential tool but it looks like would make things easier.

I think I have just rationalized that the limiting factor for "perfect" length is limited in my AR because of the length of my mags. I can see loading my bolt actions as single shot but it would just feel wrong in an AR.

 

[Suputin]

Just to be clear COAL has nothing to do with the length of the case. For accuracy you want all your cases trimmed to the same length. The actual length makes little difference. There is no benefit to trying to fit the case length to the chamber.

The big limitation to working with an AR is the magazine. You will need to load bullets short enough to feed through the mag reliably. Even if it were possible, seating bullets long enough to hit the lands is not a good idea in an AR. In the event you need to eject a live round, you will discover that having the bullet jammed into the lands will make that very difficult. It can also result in a stuck bullet and powder spilled all inside the guts of the rifle and the locking lugs, which is a serious pain to resolve.

 

[sunray]

As mentioned, the mag is the limiting factory. However, the bullet shouldn't touch the lands. Just off 'em is what you want. And it's not the same for every rifle either. You have to experiment with different OAL's that'll fit the mag.

 

[toxic]

Got it. Trim all cases to the same published length.

With the AR it will be load to about as long as I can still reliably mag feed. Start with an extra light charge and work my way up.

For the bolt actions I will do more playing with the length (at least 10 thou away from the rifling) and see if I can tighten up my groups with a "magic" length.

I think I'm going to need a better sandbag rest.