6.5CM H4831SC Cortina Method Load Development Help

[MattM]

I picked up a Bergara 6.5 Creedmoor and have been working on a load for it. I’m shooting Berger 140 gr Target bullets using H4831SC. Initial results were horrible so I glass bedded the stock. Attached are the pictures of the targets from today. Temps were at 70-80 degrees with a slight right to left breeze (approx 5mph). I also attached a picture of chronograph results (Caldwell). I like the Erik Cortina method and am looking to do the seating depth next. I’m looking for opinions on what powder charge y’all would look to…thanks in advance for any input!!!

 

[Bc'z]

What distance was this shot at?
Targets G&H are sharing same horizontal plane you can load in the middle @44.3 and go to seating depth test.

 

[MattM]

What distance was this shot at?
Targets G&H are sharing same horizontal plane you can load in the middle @44.3 and go to seating depth test.

My bad…100 yards

 

[Bc'z]

My bad…100 yards

What are your plans for seating test?
As I mentioned earlier, I'd start with 44.3gr, I would look at CBTO from your charge test and start .003 deeper into the case for 1st seating depth. Load 3-4 extra for fouler rounds at this depth.
I move in .003 increments always going deeper into case, you'll find the groups will tighten up, and open back up as you progress. I usually find a good setting node within .025 of seating.

 

[MattM]

That’s how I’ve done it in the past. Moving in .003 increments deeper each time. I do 10 total groups with 3 rounds in each group. I was looking at group H as it seemed G H and I were all on the same plane.

 

[Bc'z]

That’s how I’ve done it in the past. Moving in .003 increments deeper each time. I do 10 total groups with 3 rounds in each group. I was looking at group H as it seemed G H and I were all on the same plane.

After seating test look at neck tension.
I just ran a bushing test yesterday.
I normally start all load work with a .288 bushing.
Yesterday I used a expander mandrel to set my baseline, then used a neck die to set tension and size just the neck .286-.288 bushing were used.
Initial seating test gave a .19" 3 shot group that repeated yesterday, but the .286 bushing yielded a .138" group.
Something to consider.

 

[MattM]

That is one area I have not tested yet but now I may have to! I use the Redding bushing die to full length size the brass so I would just have to get a couple more bushings. I appreciate the info!

 

[Steveb]

I have started with my first 6.5 CM and was running the same tests using H4831Sc. Is it my rifle or does the ES seem to be very high in this cartridge. I have never had ES as high as this ever, yet I am suing the same reloading practices as in my 284's which are well under 10.

Thanks

 

[243winxb]

Clean the barrel really well. Fire some factory match ammo for a base line.

 

[Bc'z]

I have started with my first 6.5 CM and was running the same tests using H4831Sc. Is it my rifle or does the ES seem to be very high in this cartridge. I have never had ES as high as this ever, yet I am suing the same reloading practices as in my 284's which are well under 10.

Thanks

During my seating test I noticed a ES of 20 and SD of 11.
I was testing 2 rifles
6.5 cm IMR4166, 123 scenar, cci200
6.5-284 RL22, 136 scenar, WLRM
Both rifles gave identical SD/ES #'s.
I'm curious to see if the final load with the higher neck tension will bring the #'s down.

 

[whatsupdoc]

H4831 is too slow for a 6.5 Creedmoor, you need to use a faster powder.
H4350 is the gold standard so find a powder close to that burn rate.
What Berger 140 are you using VLD target or Hybrid target?

 

[Fuj]

Your better off with powders in the 4350 burn range. Two
of the best are H4350 and Reloder 16 for the 140 class
bullets, 4831 is too slow for the effort.

 

[Bc'z]

H4831SC actually works rather well, it may not produce top velocities but does produce repeatable accuracy and precision.
H4350 was unobtainable when I got my 6.5 creedmoor, after trying a couple other powders including RL17, RL19, RL26, I stumbled onto this thread I posted below.
Looking at the OP's targets G&H 44-44.5gr is telling me 44.3gr is where he should start tuning his seating.

>>>>>The SECRET.... 6.5 CAROLINA LOAD<<<<<<

The 6.5 CAROLINA LOAD is the load that was given to me from the Guy in Sportsman's Warehouse in Columbia, SC last week. He was just a customer, and I've been trying to find him to thank him, but I've had no success so far. But his load has helped me so much that I thought I would pass it on...

forum.accurateshooter.com

 

[wbm]

H4831SC actually works rather well,

+1.

 

[Steveb]

I found with H4831SC (using that because can't find H4350) when using standard primers the ES was up to the 50 fps range. However, when I switched to CCI 250's the ES came down but the accuracy wasn't great.
I have also been playing with 4451 and the accuracy decent but with every primer the ES ranges around 30 fps.
Never had ES this high in the larger cartridges. With all the huppla about the 6.5 CM I had expected better so am really curious..

 

[hambone1971]

44.5 area with .2 g increments to find the node. Above and below. Testing with .5 increments is fine for finding pressure but not nodes, you will miss them, they aren't too wide. I have used H4831SC with success when others are hard to find. RL16 is my favorite.
Good luck Matt

 

[Forum Boss]

Complete WASTE of time to try to fine tune with results like that. Groups are awful, and this won’t be resolved with some small load change.

1. Let someone else shoot the gun to rule out driver error, assuming you have a decent front rest and rear bag.

2. Try another scope to rule out scope fault.

3. Check your action screws.

4. Take off the barrel and replace with a good custom barrel.

 

[Kracken McGraw]

Complete WASTE of time to try to fine tune with results like that. Groups are awful, and this won’t be resolved with some small load change.

1. Let someone else shoot the gun to rule out driver error, assuming you have a decent front rest and rear bag.

2. Try another scope to rule out scope fault.

3. Check your action screws.

4. Take off the barrel and replace with a good custom barrel.

Another option to add is to send it back to Bergara and hope they will replace the barrel.

 

[MattM]

Thanks for the replies everyone. H4350 couldn’t be found when I tried looking and I came across the thread mentioned above (South Carolina load). I’ve had results like this before that tuned up during the seating depth test so I’ll give it a try. I’m going to try 44.3 and go from there. I’ll try to remember to post results…good/bad.

 

[Forum Boss]

Thanks for the replies everyone. H4350 couldn’t be found when I tried looking and I came across the thread mentioned above (South Carolina load). I’ve had results like this before that tuned up during the seating depth test so I’ll give it a try. I’m going to try 44.3 and go from there. I’ll try to remember to post results…good/bad.

You have multiple really bad groups, but some with two touching and one WAY out. That suggests a mechanical problem, scope problem, very bad trigger pulling, or bad barrel or combination of the above. Like I said, before you waste time with seating depth changes, let someone else shoot the gun, and make sure you have a good front rest and rear bag.

I would try it with a few rounds of decent factory ammo also to rule out some significant problem with your handloads (such as very high run-out or seating faults.)