Thread: Seating depth adjustment after 600 rnds down barrel 6.5PRC

I found that my 6.5PRC wasn't shooting nice little sub-half moa groups anymore with the load i'd been using.
As i was about to load up a new batch after firing off all of the last batch, with new lots of powder, bullets and the cases are up to their 7th cycle. I thought i'd adjust the seating depth to try get the accuracy back.
143ELDX, RL26 56.6gr, Hornady brass, Fed210m
You can see my old load dev here: https://www.nzhuntingandshooting.co....66/#post976066

Old groups which were indicating it wasn't where it used to be, now at about 0.75moa:
CBTO of 2.264"





So after watching Erik Cortina YouTube clips where he reckons the groups change in windows/nodes of about 0.003" of seating adjustment. I decided to load four 3 round groups increasing at 0.003" adjustments.

I shot starting at the longest COAL. CBTO 2.276" and then 2.272" (yeah i know that's 0.004" diff but that's what the die pushed out also ended up being a 4 shot group because i had a spare empty case).



These groups were good enough for me so initial 'test' was over! Two consecutive 'tight enough' groups indicate to me a better seating depth to use.
I didn't fire the 2.267" or 2.270" as components are bloody scarce.
I know they aren't the compulsory '5 shot' groups, however this is a lightweight hunting rifle and has proven it cant handle anymore than 3-4shot groups.
The load will prove it self over the next few follow up groups and give me a clearer idea of its actual accuracy in time.

What a difference a few 'thou' can make!

Originally Posted by Roarless20

I found that my 6.5PRC wasn't shooting nice little sub-half moa groups anymore with the load i'd been using.
As i was about to load up a new batch after firing off all of the last batch, with new lots of powder, bullets and the cases are up to their 7th cycle. I thought i'd adjust the seating depth to try get the accuracy back.
143ELDX, RL26 56.6gr, Hornady brass, Fed210m
You can see my old load dev here: https://www.nzhuntingandshooting.co....66/#post976066

Old groups which were indicating it wasn't where it used to be, now at about 0.75moa:
CBTO of 2.264"

Attachment 184692
Attachment 184699


So after watching Erik Cortina YouTube clips where he reckons the groups change in windows/nodes of about 0.003" of seating adjustment. I decided to load four 3 round groups increasing at 0.003" adjustments.

I shot starting at the longest COAL. CBTO 2.276" and then 2.272" (yeah i know that's 0.004" diff but that's what the die pushed out also ended up being a 4 shot group because i had a spare empty case).

Attachment 184702

These groups were good enough for me so initial 'test' was over! Two consecutive 'tight enough' groups indicate to me a better seating depth to use.
I didn't fire the 2.267" or 2.270" as components are bloody scarce.
I know they aren't the compulsory '5 shot' groups, however this is a lightweight hunting rifle and has proven it cant handle anymore than 3-4shot groups.
The load will prove it self over the next few follow up groups and give me a clearer idea of its actual accuracy in time.

What a difference a few 'thou' can make!

Seen and done some amazing things with seating depths!

Sent from my SM-A025F using Tapatalk

What velocity are you getting with that load? Barrel length?

2850+fps with 18" barrel.
It was shooting 2900+ in the early days until I realised It was carbon ringing in the barrel.

Do you think you have enough data to make those conclusions and why?
I've been reading reading these with great interest, https://precisionrifleblog.com/2020/...-for-shooters/
I'm a scientist and a novice shooter, this series of articles make a lot of sense to the scientist in me. But the novice likes to listen to as many points of view as possible....so yeah hence the questions.

I think fiscal caution limits many of us to semi dependence on indicative trends" rather than extra expenditure attaining statistical absolutes. Using a load that indicates possibilities in a 20-30 shot club shoot can confirm or deny a load theory whilst actually enjoying what you can afford to blow away. Same thing justifies "refining or confirming the feal world test" at the club shoot and within rhe fiscal limitations .
With more availae funds we tend to buy a second etc rifle and extend the discipline F class anyone?

Originally Posted by Woody

I think fiscal caution limits many of us to semi dependence on indicative trends" rather than extra expenditure attaining statistical absolutes. Using a load that indicates possibilities in a 20-30 shot club shoot can confirm or deny a load theory whilst actually enjoying what you can afford to blow away. Same thing justifies "refining or confirming the feal world test" at the club shoot and within rhe fiscal limitations .
With more availae funds we tend to buy a second etc rifle and extend the discipline F class anyone?

Huh?

Well, perhaps some might throw in the towel and go buy a red lycra outfit and a "sitting down walming machine" I suppose.

Originally Posted by tnankie

Do you think you have enough data to make those conclusions and why?
I've been reading reading these with great interest, https://precisionrifleblog.com/2020/...-for-shooters/
I'm a scientist and a novice shooter, this series of articles make a lot of sense to the scientist in me. But the novice likes to listen to as many points of view as possible....so yeah hence the questions.

Im not after what the "actual statistical accuracy" of the load is. I was after 'some' amount of improvement in group size over what the last of my load batch was now shooting.
I shot 4 similar looking groups after checking new powder lot, bullet lot and also checking zero after falling with the rifle after a weekend of hunting . They all shot similar shaped and sized groups. After changing seating depth you can see two obviously better groups.
Now after loading up a batch at that longest seating depth I will find out if it stays 0.5moa or better. If I find it trends to be the same as the last lots at approx 0.7moa then I'll be pissed at my hard work & time wasted , but it will still be more than accurate enough for my hunting needs

ah I think I understand, qualitative not quantitative. Follow up question, how often/do you ever end up chasing an adjustment with three shot tests? As in adjust something one way get a worse response adjust it the other way and get no improvement?


Or is 0.003" a relatively coarse adjustment?


Actually ignore that I re-read your first post and I see your really comparing 2.276-2.272" to 2.264", so its more like is 0.010" a relatively coarse adjustment?

Originally Posted by tnankie

ah I think I understand, qualitative not quantitative. Follow up question, how often/do you ever end up chasing an adjustment with three shot tests? As in adjust something one way get a worse response adjust it the other way and get no improvement?


Or is 0.003" a relatively coarse adjustment?


Actually ignore that I re-read your first post and I see your really comparing 2.276-2.272" to 2.264", so its more like is 0.010" a relatively coarse adjustment?

Mate i'm only just starting to advance my reloading skill/experience in the last few years so dont really "know" much on the subject, just what i've seen on the net.
I haven't made such small adjustments before. If a load shoots roughly 0.5moa i stop tinkering. However i haven't stayed with the same load and fired that many rounds out of a rifle to need to re-adjust the seating depth before either.
0.003" is a very fine adjustment. I have only just started playing with seating depth adjustments in the last 2 years initially with the Berger 0.030" adjustment sort of method.

While i was out testing some other rifles (.243 87gr vmax load and a CZ .223 i bedded the action for) the other day, I shot another 3 shot group to continue to verify the 2.276" cbto seating depth i have settled on:


Looks like it is still shooting well Pretty sure it will shoot sub-half moa for me pretty well!
Looks like my extra effort is paying off too .
I know it wont shoot those small groups all the time but it is clearly an improvement over the initial load depth.