6 BRA 12 twist testing (update 3-4-18)

[JamesnTN]

Since I was unable to make the 600 yard Nationals I decided to twist on a new Brux 12 Twist chambered in a 6 BRA with a .270 neck and .075 FB. (Barrel work done by Tim Claunch)

Gathering info from Jim O’Hara and a couple others including the gentleman that took his very own 12 twist BRA and won in his class fireforming brass at a UBR match (Mr Larry Moore) I began testing using XBR 8208 and started out with the Federal 205 primers and further did testing with various other primers I settled in on using CCI 450. Then I began testing with bushings and at the time I was using the Berger 80 that were HBN coated and settle on the .265 bushing.
Later I changed over to the Bart’s 80 FB naked as the HBN was giving me eratic velocity readings. Once I changed my ES and SD numbers equalized out and I was more satisfied with the results. Although at 100 yards in the pics posted on testing bushings, primers and Powder charges the groups were very promising, but I knew they never hold up out farther.

Here are the Powder tests groups











As you can see as Powder went up the groups began to do the same. All these were 3 shot groups.
Next post will be primer testing.

 

[JamesnTN]

Here is the primer testing reaults.








Not very promising to say the least but again these were using the Berger HBN coated bullets.

 

[JamesnTN]

Now here’s the bushing test results

 

[JamesnTN]

This morning early I got up and I wanted to test the Bart’s 80 FB and see what results I would have gotten based on a late test yesterday and changing the bushing from a .265 to the .266 since I am now using non coated bullets.

Here are the results using the Bart 80 FB this am



So needless to say I chose the 450 primer based on the test results.

Now next I tested the BART 80 grain BT and here are the results as well.

 

[JamesnTN]

So based on the test results I loaded five each of the Bart 80 BT at 31.4 and 31.6 grains and took them to 500 yards this afternoon.
For those who say the 80’s fall apart after 300 yards shouldn’t be so negative. These shot well and after running the numbers on a ballistic app. They actually perform better to 500 yards over the 108 BT not by much but they do and at 600 yards the 108 BT slightly edges the 80’s but just slightly. The difference where the 80 makes up over the 108 is velocity 3250 fps vs 2950 fps.

Here are the 500 yard testing results of today.




A closeup of the group measured.







All this testing done in 2 days screwed the barrel on Friday morning and fire formed and load developed and fine tuned.

 

[pacificman]

All good info...looks like you may have found what your rifle likes for sure! I enjoy seeing tests like
what you have posted as many of these makes me think of things I can try with my own rifles and loads.
Accuracy being what most of us want for sure! Good stuff man!!!

 

[kvd]

Thank you for posting this. Good information. How long is your Brux 12 twist barrel?

 

[Grimstod]

Good info. I wish I had this kind of time to do this much testing in a singe week.

 

[X-Caveman]

@JamesnTN what BC are you using for Bart's 80 boat tail in your ballistic ap?

Also, are you loading into the lands or off? Thanks!

 

[boltfluter]

James,

Nice write up and shooting, as usual. Always enjoy your posts.

Paul

www.proprecisionrifles.com

 

[WyleWD]

Great post James. 8208 is a much overlooked powder in the BR's with the bullet weight range you're using. Thanks for the pictures too. WD

 

[JamesnTN]

@JamesnTN what BC are you using for Bart's 80 boat tail in your ballistic ap?

Also, are you loading into the lands or off? Thanks!

I used a .183 BC that’s probably low but I looked around at the BC of bullets alike and came up with this number.

I am loading into the lands I’ll have to look and see but it’s somewhere around .012 in.

Also the barrel used is a Brux at 30”

 

[WyleWD]

James, What type of crown was put on the barrel for this rifle? And is there any type crown you prefer for short or long range? WD

 

[JamesnTN]

James, What type of crown was put on the barrel for this rifle? And is there any type crown you prefer for short or long range? WD

I have a recessed 11* crown on it. I prefer the 11* over any other crown to be honest.

 

[birdog]

Very nice work up. Took a lot of time. Thanks for sharing

 

[JamesnTN]

Very nice work up. Took a lot of time. Thanks for sharing

Thanks Randy.

It came together quiet well even though there were a few hiccups with USPS on delivery of the barrel. I’m hoping it’ll stay tuned much easier using 8208.

 

[JamesnTN]

Today I decided to screw on the 12 Twiat BRA barrel and do a little testing in the cooler weather. After a couple sighted shots and starting at 31.5 grains of 8208 (new lot) and seemed to have found its happy spot once again at about 1/2 grain more than when I tested this last fall at 85*
Today’s test was shot at 100 yards at 55* with the Bart BT 80’s and CCI 450 Primers
Tomorrow I’ll go to 500 and see what tweaks I need from the last time I shot it at 500.

These are 5 shot groups.

 

[johara1]

James, looks like a keeper..... jim

 

[KenOath]

Some nice small groups there James, I’ll be curious to see how the flat base 80s do at 500, that’s the distance I shoot my BR at with the 105s but often wondered how the lighter bullets would do on a good day...

Cheers Rushty

 

[JamesnTN]

Some nice small groups there James, I’ll be curious to see how the flat base 80s do at 500, that’s the distance I shoot my BR at with the 105s but often wondered how the lighter bullets would do on a good day...

Cheers Rushty

I haven’t tested his FB at 500 yet but the BT seems to do well out to 500. I’m going to see if they’ll fall apart at 600 when the weather gets a bit nicer.