Need a little help

[CDH]

I’m overlooking/overthinking something. Please help clarify. Catridge is .308 Winchester. I’m attempting to load 165gr Sierra GameKing BTSP (#2145) to mimic the 168gr MatchKing, as this particular load is extremely accurate in my rifle. Load data puts COAL at 2.750” for SGK and 2.800” for SMK. Given the tip irregularities in the soft point bullet I chose to use Base To Ogive length as the measurement to load to. However, when measuring factory loaded examples of both of these I found there to be a difference of 0.096” between the two with the SMK being the longer. My thought was by setting distance to ogive the same I would be reproducing the same distance to the lands. Can I set the SGK out that far? I’ve got to be missing something here. Thanks in advance for the help.

Chris

[Jim Watson]

Well, you have the book spec and sample rounds, it might be worth trying what Sierra says and does.

I am sure you can load the soft point longer, you could try that, too.

[Hambo]

You say the GK, at whatever OAL you've chosen, is extremely accurate. Unless you need it to be more extremely accurate, I'd stop there.

[TOTS]

First, a question. How does the factory Game King shoot in your rifle? If the results are satisfactory, rock on with the factory measurements. To answer your question, try it. As long as matching the BtO keeps the OAL in spec, I’d shoot some and see what you think.

The “right” answer is to work up a load for the new bullet. I DO think you are on the right track by using the BtO measurements to start from since you know a distance from the lands that gives good enough results. But unless you work up a load you won’t know if it’s the best result possible, or even a good one, from that bullet. And if you will be reloading the ammunition, you may as well get the benefits of reloading; namely the most consistent ammunition and optimized for you and your rifle.

I would VERY much recommend the optimum charge weight method for working up a load that will be the most forgiving of temperature changes, reloading inconsistencies, etc. The second part of the process is finding the length (distance to the lands) that gives the smallest group. Seems like both, but the charge weight part especially, would be of value for a hunting load.

[CDH]

Hambo, my initial post was somewhat unclear. The SMK is extremely accurate in this particular rifle and I am trying to mimic that accuracy in a hunting bullet, the SGK.

This is classic "enemy of good is better". The SGK already is slightly less than MOA out of this rifle. I should leave well enough alone, BUT where's the fun in that. I am going to see if I can get it down a little bit just for fun. Thanks for everyone's input. We'll see what comes of this endeavor.

Chris

[TOTS]

Hambo, my initial post was somewhat unclear. The SMK is extremely accurate in this particular rifle and I am trying to mimic that accuracy in a hunting bullet, the SGK.

This is classic "enemy of good is better". The SGK already is slightly less than MOA out of this rifle. I should leave well enough alone, BUT where's the fun in that. I am going to see if I can get it down a little bit just for fun. Thanks for everyone's input. We'll see what comes of this endeavor.

Chris

If all you want is best MOA, maybe just adjust OAL in small increments in/out from factory until you get what shoots best. But it’s (probably) only best for that specific powder charge.

[CDH]

TOTS, I believe you’ve hit the nail on the head. I mocked up a SGK to the same BTO distance as the SMK and there was a little resistance when closing the bolt. I’m not sure as to why but maybe the bullet profile forward of the ogive is playing a role. I like the idea of creeping out with OAL to see if anything improves. Thanks again for help.

Chris

[okie john]

What load are you using with the SMK? What cases are you using? How are you prepping them? Adjusting OAL may help. You might also have to adjust the powder charge.

If I wanted easy accuracy, then I'd start with the Barnes TTSX and Varget with CCI 200 primers in WW or Lapua cases. 4064 and 4895 are also classic choices.

The SGK isn't a match bullet, so it may not shoot like one. Plenty of folks just shoot game with the SMK or Lapua Scenar and say that those bullets work fine.


Okie John

[CDH]

Okie John, fire-formed brass neck-sized only. Federal 210 match primers over 42.5gr IMR4064 with OAL of 2.750” +/- because the soft point varies some. That’s what led me to the idea of replicating the SMK BTO measurement. Keep in mind prior to any of my “great ideas” the worst this load has shot is one MOA and tends to be a 3/4MOA load. So all of this effort is just to see if it can be manipulated to do better. I’m going to see what happens if I gradually increase the BTO, and thereby increase the OAL, and see what happens. If we have good weather this weekend maybe we’ll be able to gather some data points. Thanks again.

Chris

[TOTS]

A general good seating depth to start from has been about .020 from the lands. Some bullets are more jump tolerant and some like to be jammed into the lands.

If you decide to work up a load, Dan Newberry’s Optimum Charge Weight method has replaced the ladder method for me.

http://optimalchargeweight.embarqspace.com