Throat length Vs. Cartridge Overall Length questions.

[Punisher29073]

I have recently acquired a fine Remington 700 5r 308. I was preparing to load my first loads for this rifle with SMK 175s and measuring the throat length. By my measurements I have a very long throat, 2.938". My book says maximum COL for 308 is 2.875". Normally I would back off the lands .005" and start loading. My Wyatt's detachable box magazine will only accept a cartridge 2.881".

1) Is it surprising to have a throat this long? I realize it is a factory gun, not a custom.
2) If I load to the 2.880 so the magazine will work, is the .058" too far for the bullet to be jumping?
3) Is .216" of bearing surface between case neck and bullet enough?

Any suggestions are appreciated.

Ryan

 

[Boomholzer]

Hi Ryan,

1) Is it surprising to have a throat this long? I realize it is a factory gun, not a custom.
Nope. Especially the Rem700
2) If I load to the 2.880 so the magazine will work, is the .058" too far for the bullet to be jumping?
Nope.
3) Is .216" of bearing surface between case neck and bullet enough?
It is but consider that your going to get nowhere near touching the lands so alittle extra jump won't matter. Point being, don't go compromising your neck seat trying to minimize the jump, it will NOT help. In fact it might hurt performance.

 

[dumbbell]

Trade u throats. Mine is 3.110 on my aac sd until I hit lands on 208 amax

 

[turbo54]

First response was golden, but I'll add this:

Not only is .058" jump ok with 168 and 175 sierras, but so is .158" and .258" jump.

These bullets are very tolerant to this.

Not to say it's not worthwhile to play with seating depth when tweaking a load. I suggest you read about "optimal barrel time".

Federal Gold Medal 175gr is loaded to ~2.810". I'd suggest you start there.

Have fun.

 

[Punisher29073]

You guys have made feel much better. Thanks for the help.

Ryan

 

[melloyello]

If memory serves me correctly my aac-sd is 2.933"
I load my 175smk to 2.86", I also have a Wyatts detacable magazine.

 

[Punisher29073]

My goal is to achieve 1/2 MOA with this gun. Is anyone achieving that being that far off the lands? Maybe I am reading too much in to it, I hope. I am very excited about this rifle. I am going to use the ladder method for the first time as well.

Ryan

 

[Boomholzer]

My goal is to achieve 1/2 MOA with this gun. Is anyone achieving that being that far off the lands? Maybe I am reading too much in to it, I hope. I am very excited about this rifle. I am going to use the ladder method for the first time as well.

Ryan

Sure.
Don’t fear the jump. For the majority of shooters it is inevitable.

As far as loading to the lands, understand that in the tiny slices of time upon primer ignition, the bullet can start to “squirt” out the case, changing the case volume. The case volume or powder chamber is dynamic in this sense. One of the things that ‘loading-to-the-lands’ provides is more consistency in the pressures developed or pressure profile (pressure vs. time) during the initial ignition.
With that said; there are a few simple things that are often overlooked and all without initially worrying about bushing dies. Before seating the clean bullet, clean the neck interior to remove all residual tumbling wax, resizing, lube, etc. This variance in lube can affect the friction or traction between the neck and bullet, much like large variances in neck tension.

And as always, change one variable at a time. Best wishes.