Your thoughts on a load development?

[ShtrRdy]

I wanted to use a different muzzle brake on a 308 Win rifle and have been having a heck of a time finding a load it likes. Prior to doing this I was using a brake from another rifle and found a load that would give me a quarter moa 3-shot group.

If you have a little time would you please have a look at the attached picture and follow along with my description.

Leading up to this target I ran a series of powder charge weights using Varget behind a 175 gr SMK and kicked off with a CCI primer. I used powder charges of 41.1 gr to 42.3 gr in 0.3 grain steps. I was getting close to a velocity that I thought was a safe upper limit for the 175 gr SMK in the 308. Next I loaded and fired the two groups in the upper left hand part of the target surrounded by a green line. Fired from 100 yards.

What got my attention on these two targets is 4 of the eight shots were virtually on top of each other. Also, two of the other shots were close to each other, and the remaining two were off on their own. Another interesting result is the average velocity was close to each other.

At this point I decided to try some different seating depths while using a powder charge of 42.6 grains.. The touch point, (TP), for this combination was a CBTO = 3.226". This is a relative number since I was using a Sinclair bullet Comparitor to make the measurement. The seating depth I had been using is 0.010" off the lands from TP for a CBTO = 3.216". First i stepped toward the lands in steps of 0.003". Those are the other three targets on the top row. The bottom row is stepping away from the lands in 0.003" steps. Nothing looks special for all those seating depths. One curious thing I noticed from the target in the lower right is two of the shots were in the same neighborhood as the 4 shots on the two upper left targets.

What do you think I should try next? Go back to trying more powder charge weights? Continue seating depth testing while making steps of 0.005" or 0.010"? Abandon this muzzle brake and borrow the one from the other rifle?

For those who want to know more about the equipment:
Stiller TAC 30 action
Krieger 4 groove barrel in a heavy Palma contour. 12 twist. 24" long.
Trigger Tech Special trigger
AICS chassis
Atlas bipod
TAB gear rear bag
Stiller scope rail pinned and screwed
Nightforce rings
S&B PM-II scope

 

[Jeff Porter]

if you listen to the Hornady podcast #50 and -# 52 …. Your would try a different powder or a different bullet.
A quick glance at all of those groups say they are all the same , grouping about 1 moa from 12-3 on the target.

 

[deep south]

Using crush washer to attach brake?

 

[Doom]

If you are using calibers you need to zero the caliper with Sinclair Comparator attached. If using a micrometer then subtract the Comparator dimension. It makes reading things much easier.

Ignore the chronograph data.

Before I could recommend your next step it would be helpful to know what you are planning to do with this load. Based on your bipod I am assuming you are shooting F-T/R? If so, what group sizes can you consistently shoot with this equipment?

 

[FeMan]

IME, seating depth nodes can be as far apart as 0.030" or more. Your span of 24k might have missed one, so I would try a few groups going in from 3.198 just to be sure.

The 308 w/175 SMKs and Varget is a pretty shootable combination, but something there isn't working. Since you changed brakes and seem to now have an issue, I would suspect the brake. What about a repeat without the brake to see? Also, do you have enough neck clearance?

 

[Benchrest Braxton]

if you listen to the Hornady podcast #50 and -# 52 …. Your would try a different powder or a different bullet.
A quick glance at all of those groups say they are all the same , grouping about 1 moa from 12-3 on the target.

you have to take what they say with a grain of salt, since they don't believe a sub 1/2 moa rifle exists, but in general they have good advice.

my loading theory from now on will be minimum 2 powders and 2 bullets to try out. optimally 3/4 of each. just load up some moderate/near max loads off the lands and see which combo it wants. no need to try and force precision by dumping hundreds of rounds of ammo in search of finding a good shooting load.

my buddies full blown custom shotgunned with ramshot magnum powder (2-3" groups at 100y), tried the 153 a tips and 150 smk's, same result.

switched over to n565 and was printing sub 1/2 moa with ease. crazy the difference a powder swap can make

 

[Sandstorm]

Get rid of the brake.

 

[bozo699]

I for the life of me can’t figure out why people shoot over 2 times?… if the first two don’t go in the same hole of close why trip a third?… I usually load one at a time but never more than two!… if two go in the same hole I’ll load another
Wayne

 

[ShtrRdy]

I for the life of me can’t figure out why people shoot over 2 times?… if the first two don’t go in the same hole of close why trip a third?… I usually load one at a time but never more than two!… if two go in the same hole I’ll load another
Wayne

Because I load at home and then go to the range. Is that a fair reason?

 

[bozo699]

Because I load at home and then go to the range. Is that a fair reason?

No, load at the range
Wayne

 

[ShtrRdy]

Using crush washer to attach brake?

No, the brake is a Blast Tamer. Please see picture below.

If you are using calibers you need to zero the caliper with Sinclair Comparator attached. If using a micrometer then subtract the Comparator dimension. It makes reading things much easier.

Ignore the chronograph data.

Before I could recommend your next step it would be helpful to know what you are planning to do with this load. Based on your bipod I am assuming you are shooting F-T/R? If so, what group sizes can you consistently shoot with this equipment?

Thanks for you suggestion for the Sinclair bullet Comparitor.

The rifle will be used for general long range fun. No competition planned.

IME, seating depth nodes can be as far apart as 0.030" or more. Your span of 24k might have missed one, so I would try a few groups going in from 3.198 just to be sure.

The 308 w/175 SMKs and Varget is a pretty shootable combination, but something there isn't working. Since you changed brakes and seem to now have an issue, I would suspect the brake. What about a repeat without the brake to see? Also, do you have enough neck clearance?

Yes, to the neck clearance question.
I had good results when using a different brake I borrowed from a different rifle.
What size steps do you like to use when doing seating depth testing?

 

[DLT]

No, load at the range
Wayne

I suspect many don’t have that option

 

[bozo699]

I suspect many don’t have that option

Why?….. I am lucky my reloading room sets on my range but I have tested at my 1000 yard club at a thousand , just take my range boxes with me….. so why wouldn’t that be a option for anyone?…. Just asking……
Wayne

 

[bozo699]

I mean people complain all the time about component costs and unobtainable components….. why waste them?… bring a press and your stuff to the range .
Wayne

 

[quest450]

Lol.....you can lead a horse to water

 

[Bill Norris]

I for the life of me can’t figure out why people shoot over 2 times?… if the first two don’t go in the same hole of close why trip a third?… I usually load one at a time but never more than two!… if two go in the same hole I’ll load another
Wayne

Agree. 3 shots can be a waste when developing loads. If two don't look promising why bother with the third one.

 

[FeMan]

I shoot at 0.003” increments like you are usually. I’ll get down to 2 or 1 if it’s a match rifle.

I also start with 3 rounds. I go to 4 or more when fine tuning. As far as firing the “third” shot, it all depends. If I have a rifle that is really behaving predictably, I’ll shoot them all. You can watch the satellite orbit of the “flyer “ come around and the drop into the group after several 0.003” increments. When I can see it coming and it drops in, I have real confidence. When it’s all random, I also skip and jump ahead hoping for something better.