Honest results from first batches of 6.5 CM

[Bridgerland]

New to reloading.

Shooting a factory Tikka T3X in 6.5 CM. Probably 50 rounds through the barrel so far. Used an OAL to find the lands at 2.906”. All of the brass is from a factory box of eld-x. Tumbled, then trimmed all to 1.912”

Thought I’d share my group results and recipes from a range day shooting 100 yard groups.

1. 41.0 gr H4350, Hornady brass once fired, Remington large rifle primer, 143 gr ELD-X. Seated 50/1000” off the lands. Best group of the bunch:

2. Same as 1, but 80/1000” off the lands:

3. Same as 1, but 41.5 gr powder

4. Same as 2, but 41.5 gr powder


Admittedly, I’m sure there’s a fair amount of user error on these groups. For example, the 41.5 gr charges were shot immediately after the 41.0, and the barrel was hot to the touch after the 3rd shot of those groups.

Any of you use a timer between shots when grouping? Didn’t occur to me until later that a minute or two of equal time between shots could have corrected that issue.

 

[Q_Sertorius]

New to reloading.

Shooting a factory Tikka T3X in 6.5 CM. Probably 50 rounds through the barrel so far. Used an OAL to find the lands at 2.906”

Thought I’d share my group results and recipes from a range day shooting 100 yard groups.

1. 41.0 gr H4350, Hornady brass once fired, Remington large rifle primer, 143 gr ELD-X. Seated 50/1000” off the lands. Best group of the bunch, of course I’m sharing this first!
View attachment 1037593
2. Same as 1, but 80/1000” off the lands:
View attachment 1037594
3. Same as 1, but 41.5 gr powder
View attachment 1037595
4. Same as 2, but 41.5 gr powder
View attachment 1037596

Admittedly, I’m sure there’s a fair amount of user error on these groups. For example, the 41.5 gr charges were shot immediately after the 41.0, and the barrel was hot to the touch after the 3rd shot of those groups.

Any of you use a timer between shots when grouping? Didn’t occur to me until later that a minute or two of equal time between shots could have corrected that issue.

There are a lot of threads on this site you should probably read. But to summarize a couple: even a 10-round group is only about 85% accurate as a determination of how a rifle shoots. And good, modern barrels, like on a Tikka, don’t “open up” as they get warmer. A lot of the old lore about what matters in shooting is based off drawing conclusions from insufficiently large samples.

 

[Sponge]

What Q said above, look for the "Painless Load Development" thread.

As to your groups and loads, they all look good enough to move forward to me. I wouldn't get too hung up on the 'flyers'.
Of the four loads above, pick the one you like best, load 10 or 20, and shoot into one group ( or several groups and aggregate into one), if its good, load the rest of your brass with that load and go practice.

Personally, with 140-ish projectiles in 6.5 CM, I do 41.5 H4350 at 2.810" (+/- 0.005") COAL and throw charges with a Lee Perfect measure. <1.5" 10 shot groups are typical. I get similar precision with factory Precision Hunter stuff.

Hot barrel - I don't do a timer or anything fancy when doing load dev/testing. I usually have two or more rifles and rotate letting each cool enough that there isn't mirage. I do try to avoid shooting for load dev/testing when I am getting mirage as it can effect groups. ETA - I avoid shooting thru mirage as it distorts the sight picture, not because of hot barrel concerns

 

[Q_Sertorius]

Hot barrel - I don't do a timer or anything fancy when doing load dev/testing. I usually have two or more rifles and rotate letting each cool enough that there isn't mirage. I do try to avoid shooting for load dev/testing when I am getting mirage as it can effect groups.

Yes, I completely agree with avoiding mirage, especially if shooting suppressed. That's where taking a short break every ten shots or so can make a difference.

 

[MCGHeel]

There are a lot of threads on this site you should probably read. But to summarize a couple: even a 10-round group is only about 85% accurate as a determination of how a rifle shoots. And good, modern barrels, like on a Tikka, don’t “open up” as they get warmer. A lot of the old lore about what matters in shooting is based off drawing conclusions from insufficiently large samples.

Interested in your comment that barrels don’t open up as they get warmer. Defies common thinking about barrels, but common doesn’t mean correct. Could you elaborate on this or point toward a thread? Thanks

 

[nm.otter]

Thread 'Cold bore zero versus (very) Hot bore zero “test”'

Sep 9, 2023

Discussions around “cold bore shifts” and “cold bore zeroes” versus “warm or hot barrel zeroes” are constant. So is the belief that barrels “walk” when they heat up or that groups open when they heat up.

After having multiple discussions, @Ryan Avery and Jake @Unknown Munitions and I set up a day to shoot and measure what happens. Quite a bit of discussion happened with getting everyone on the same page, and explaining the limitations and resolution that would be able to be measured. Basically- the more data, the mare accurate the results will be. However, there is a...

• Formidilosus
• Replies: 611
• Forum: Firearms

• 

 

[MCGHeel]

Thread 'Cold bore zero versus (very) Hot bore zero “test”'

Sep 9, 2023

Discussions around “cold bore shifts” and “cold bore zeroes” versus “warm or hot barrel zeroes” are constant. So is the belief that barrels “walk” when they heat up or that groups open when they heat up.

After having multiple discussions, @Ryan Avery and Jake @Unknown Munitions and I set up a day to shoot and measure what happens. Quite a bit of discussion happened with getting everyone on the same page, and explaining the limitations and resolution that would be able to be measured. Basically- the more data, the mare accurate the results will be. However, there is a...

• Formidilosus
• Replies: 611
• Forum: Firearms

• 

Interesting test. Didn’t read all 31 pages of replies but my question would be whether the groups opened up, but the POI didn’t shift as demonstrated? They said they didn’t measure group sizes as part of the test. Also, I’d be interested if this holds for magnum calibers with hunting weight barrels. Looked like their biggest test caliber was 7PRC but in a competition rifle presumably with a competition taper barrel. The amount of powder burned in the magnums I would think would contribute to a good bit more heat

 

[43.6N]

1. 41.0 gr H4350, Hornady brass once fired, Remington large rifle primer, 143 gr ELD-X. Seated 50/1000” off the lands. Best group of the bunch:

You have arrived.
Stop further load dev.
Fill remainder of your brass with this load.
Start using the gun at distance until it becomes an extension of your arm.
Northern Utah? You should have plenty of PRS/NRL type events in your area. You could go shoot today with that load, and you would probably find 3-4 other people in 15min with that exact or similar combo.

 

[Sponge]

@MCGHeel in the 'Cold bore zero vs hot bore zero test' thread, OP's conclusion is this: properly made and stress relieved barrels do not see POI change or increased dispersion as the barrel heats up.

Now, there is a lot of wailing, gnashing of teeth, and whataboutism in that thread...and yes OP does not insinuate the test applies to every barrel ever made, just that good barrels don't do that (including magnums). About half of that thread is people picking gnat s--t out of black pepper on the above points instead of shooting their rifles and seeing what happens.