6.5CM H4831SC Cortina Method Load Development Help

[davidjoe]

OP, I was curious whether that barrel twist is intended for the bullet you are using. In a quick search, I found another 6.5 Bergara user who wrote that everything BUT a Berger 140 groups sub moa, including other 140’s. It makes me think the Berger bullet you are shooting is long for the twist and on the cusp of instability where severe flyers occur.

I have shot groups like that when my twist rate is too slow. If a shorter, lighter bullet groups well, then twist might be the problem, even though I think you have an 8 twist, and that’s the minimum rate Berger prints.

 

[gme]

like the boss says, it looks like you have a mechanical problem, the 6.5 CM is an easy cartridge to get to shoot, just came back from test firing a 6.5 CM rifle I just finished for a customer this morning, this is the first five rounds out of the gun with a common "bread and butter" load (41 gr. H4350, Hornady 140 eldm 2.810 C.O.A.L.) yep it was windy

 

[SCL]

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!!!

Try this load-
H4350, 41.5gr, 140gr Hornady ELDM, 2.81 COL, Hornady brass , CCI BR 4 primers.
This load is very popular on the web and works quite well for my 1/8 twist RPR. Attached pic is from yesterday @ 100 yrds with 12mph tail wind, around 85 degrees @ 1pm. 3 shots.

 

[std7mag]

I'm still wondering when people started shooting ladder group tests?

Shoot your ladder test using your target, or a chrono to find your powder charge nodes.

THEN shoot groups adjusting your seating depth.

From what i'm seeing of your groups, your testing is giving you zero useful information.

 

[6.5PRC123]

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!!!

Bergara had to send me a new muzzle break as the one that came on my PRC had too small of an opening. May want to try to shoot it w/o the break on if it has one.

 

[newbieshooter]

I'm still wondering when people started shooting ladder group tests?

Shoot your ladder test using your target, or a chrono to find your powder charge nodes.

THEN shoot groups adjusting your seating depth.

From what i'm seeing of your groups, your testing is giving you zero useful information.

isn't it the method Erik uses/promotes here?

Long range load development at 100 yards.

I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly. This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder. At plain sight, 38.5 gr...

forum.accurateshooter.com

 

[std7mag]

isn't it the method Erik uses/promotes here?

Long range load development at 100 yards.

I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly. This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder. At plain sight, 38.5 gr...

forum.accurateshooter.com

The first sentence says it all.

Your trying to do 2 things at once.
Do only 1 thing at a time. That way you can read & identify what is actually going on.

Ladder test, or velocity test over a chrono, is going to tell you what powder charge your barrel likes.

Seating depth test will then tell you what the bullet likes by group size.

If your bullet doesn't like the seating depth, how are you gonna have good groups regardless of what powder charge the barrel likes?