Rock Creek barrel and huge change in coal

[BigRso]

So I got my new bisley 308 rock creek yesterday. I used forster 308 win go and no go gauges for install and torqued nut to 35 lbs. (Savage SA)

I had a few cartridges loaded 175 smk in lc brass coal of 2.850" and 165 game kings 2.750"

I chamber each one as they did chamber they where very tight and heavy bolt lift to extract. So I used the wooding rod method to find out max oal with each.

175 smk 2.806" and 165 game king 2.708"

Is that chamber suppose to be so short

It seems by measurements that it is consistent with about 42-44 thousandths difference then my mcgowen barrel chamber in 308 win.

So am I good to go or is something wrong I really don't care about the cartridges being seated shorter more pressure so will have to work up loads but had to do that with this new barrel anyway.

 

[Niles Coyote]

The proper thing to do is just that, work up a load.

Now what I did...

My latest 308 has a much shorter OAL too. 175 smk’s are touching the lands at 2.79 so what I did is use a load that I know is not loaded to near the max and also works well in all my other 308’s (varget at 43.0) and Tried that with the bullet adjusted to jump .015”. It shot well but needed a little adjusting to get the best accuracy out of it, IIRC it ended up being at 43.3grains and the higher velocity load for my other rifles is 44.5-44.6 so I tried the 44.5 with the bullet jumping .015 again. while that load did not show any pressure problems I needed to adjust it down to 44.3 for best accuracy.

 

[BigRso]

The proper thing to do is just that, work up a load.

Now what I did...

My latest 308 has a much shorter OAL too. 175 smk’s are touching the lands at 2.79 so what I did is use a load that I know is not loaded to near the max and also works well in all my other 308’s (varget at 43.0) and Tried that with the bullet adjusted to jump .015”. It shot well but needed a little adjusting to get the best accuracy out of it, IIRC it ended up being at 43.3grains and the higher velocity load for my other rifles is 44.5-44.6 so I tried the 44.5 with the bullet jumping .015 again. while that load did not show any pressure problems I needed to adjust it down to 44.3 for best accuracy.

So the shorter coal was to be expected with bisley chamber?

 

[buffybuster]

Are you saying the chamber for the new and old barrel were cut with the SAME reamer and they have different throat dimensions?

 

[BigRso]

Are you saying the chamber for the new and old barrel were cut with the SAME reamer and they have different throat dimensions?

No not at all different reamers I just did not expect such a drastic change in coal from 308 win to 308 bisley and wanted to confirm that the loss of .042-.044 is ok and expected

 

[tomme boy]

McGowen uses a standard 308 win reamer. The Bisley has a shorter throat. Seat about 100 a little shorter and then go shoot them up. Check your throat after that.

 

[BigRso]

McGowen uses a standard 308 win reamer. The Bisley has a shorter throat. Seat about 100 a little shorter and then go shoot them up. Check your throat after that.

simple but yet perfect answer thank you very much. that is all I was after

 

[turbo54]

Are you saying the chamber for the new and old barrel were cut with the SAME reamer and they have different throat dimensions?

FYI, this is totally possible. Different land/groove diameters (even slight) can and will create very real differences in where a bullet kisses the lands.

OP: Bisley chambers are short throated. They generally shoot fantastic. Good luck with your new barrel, I hope it works great for you.

 

[Al_Ski]

FYI, this is totally possible. Different land/groove diameters (even slight) can and will create very real differences in where a bullet kisses the lands.

Are you sure about that?

My O.A.L is the same length when touching the lands when using either a .300" groove diameter or a .299" diameter. The throat is slightly longer with the tighter bore, the bullet contacts the lands just forward of the free bore not on the tip...

 

[BigRso]

FYI, this is totally possible. Different land/groove diameters (even slight) can and will create very real differences in where a bullet kisses the lands.

OP: Bisley chambers are short throated. They generally shoot fantastic. Good luck with your new barrel, I hope it works great for you.

Thank you and I am sure it will.