I'm stumped??

R

riverratt

New member
I'm working up a load using 162gr bullets, starline brass, CCI BR primers and AA 4064 in my 7mm-08 with a 22", 1:9.5 twist barrel.

The gun itself has proven to be able to shoot the 120gr ballistic tip bullets consistently at or under .75" but I personally want a heavier bullet for my style of hunting. It doesn't like any loading that I've tried in the 140gr range and haven't been able to get ahold of anything in the 150gr range.

Ok so now here's my issues. Using 3 shot groups I've been able to isolate an apparent accuracy node between 38.5gr and 39.5gr based on group location (POI). I then picked a middle charge weight of 39gr and started adjusting seating depth. I was already as close as I want to be to the lands with a .010" jump so I started working back with 3 shot groups. .025 seemed to do ok but .020" and .030" strung vertical with about 1.5-2" groups. .070"-.085 jump all had the same POI with just a shade over 1" of vertical stringing. Once again pick the middle of this node at .080" jump and carefully load 20 rounds.

Now at the range I intend to run 4, 5 shot groups to verify this load before loading a few hundred. What I found is usually 3 shots would land right around .5"-.6" and 2 of them would string vertical some as much as 2" always high and it isn't consistent, as in it isn't the 1st 3 are good then the last 2 are flyers so not caused by a hot barrel. I know this would usually indicate velocity changes but this isn't reflected through my chrono. I'm getting 2647fps average, 11fps SD and 18fps ES over the 20 shots.

This is the same method I've used for years to get good quality loads with multiple component combinations for every rifle I have. For whatever reason this is different. At this point I'm personally thinking it has something to do with the added recoil on the plastic stock but I'm not sure. It's just a factory savage 110 that I've relieved some of the stock from to prevent barrel contact.
 
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Have you tried adjusting seating depths in .003 increments instead of .01 increments.

If you haven’t watched Erik Cortina’s “Chasing the Lands” on youtube check it out helped me a bunch

Your ES/SD are good you are on the correct path it is your seating depth .
 
A 162gr Hornady is a long bullet for the 7mm-08 if the chamber isn't throated out.
Lots of bullet pushed into the case.
Add to that a medium fast powder.

I still don't know how you DIDN'T get a 140gr bullet to work!

Personally, i do a 10 shot ladder test going up 0.3gr per shot.
After charge found, i start at 0.005" off the lands. (Hunting rifles)
I'll go in 0.010" increments till i get something that settles in. Then go 0.005 up or down to fine tune.

Also, being a Savage, don't forget to tune the torque on your action screws.
Can take a 2" rifle to 3/4".

And Eric Cortina can jam his bullets if he wants. He's a match shooter, not a hunter.
I'd advise against jamming if for hunting!
 
Try different primers
Try different powder
Try different bullets
Try different seating depth

Just because a load worked in a loading manual doesn't mean it will shoot well in your gun.
 
std7mag said:
A 162gr Hornady is a long bullet for the 7mm-08 if the chamber isn't throated out.
Lots of bullet pushed into the case.
Add to that a medium fast powder.

I still don't know how you DIDN'T get a 140gr bullet to work!

Personally, i do a 10 shot ladder test going up 0.3gr per shot.
After charge found, i start at 0.005" off the lands. (Hunting rifles)
I'll go in 0.010" increments till i get something that settles in. Then go 0.005 up or down to fine tune.

Also, being a Savage, don't forget to tune the torque on your action screws.
Can take a 2" rifle to 3/4".

And Eric Cortina can jam his bullets if he wants. He's a match shooter, not a hunter.
I'd advise against jamming if for hunting!
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Did you watch his Video??? He doesn’t jam his bullets he finds the Jam then backs off .02 off that then starts adjusting his seating depth .003 until he finds two consistent nodes.

The OP hasnt found the right barrel harmonics for his load. His ES/SD look good but barrel harmonics are off
 
I still don't know how you DIDN'T get a 140gr bullet to work!
Click to expand...

To be fair this is based on factory loads and different component combinations with only 1 style of 140gr bullet that I have an abundance of as my other 7mm-08 loves these bullets.

I am not compressing the load until the bullet is seated with an excess of .100" jump.

Also, being a Savage, don't forget to tune the torque on your action screws.
Can take a 2" rifle to 3/4".
Click to expand...

I was unaware of this about Savage. This makes sense though. I removed the stock to oil the bottom of the barrel after having it out in the rain on a coyote hunt. Perhaps I over tightened the action screws.
 
think I found your problem, bullet is probably too long. you will need to go with a lighter and or shorter bullet.

I use the Hornady 162g eldx for a rough calculation
BC .63
Caliber .284
bullet weight 162g
length 1.478
velocity 2647
barrel twist 9.5
temp 59f
altitude 0ft

stability 1.27, marginally stable. you want to be above 1.5

If you want to run calculations yourself here are the sites.

Berger stability calculator
https://bergerbullets.com/twist-rate-calculator/

JBM bullet length charts
https://www.jbmballistics.com/ballistics/lengths/lengths.shtml#Hornady


I typically start at 0.020 off the lands, and go in 0.030 jumps, have had good results using this method. took my 30-06 from 1.5 to 2in down to .75, and my ar from 2.5-3in down to 1in. all at 100.
 
If it helps at all it's almost seeming like it is shooting with 2 separate zeros. 1 really tight group about 1.5" below another 1" group. It's NOT the scope, verified this on my '06. I'm not getting impacts between the two groups.
 
think I found your problem, bullet is probably too long. you will need to go with a lighter and or shorter bulle
Click to expand...

Plugged my actual data in and I'm right at 1.5 maybe I need to push it a little more and see if I can eek out a bit more velocity. I know with a 40gr charge I was getting ejector marks on the case head but this was with .005 jump just finding my max. Now that I'm at .080 jump I'm sure I can come back up a bit safely.
 
I always start at 0.020 and seat deeper in .003 increments. Usually 5-7 seating depth will get me a good group. But you should be able to push a bit more being farther off the lands now, if the sd/es will support it.

I never put too much thought into eric cortinas method, as far as why 0.003 increments. I was super frustrated and decided to try it. Worked like a charm.
 
If it helps at all it's almost seeming like it is shooting with 2 separate zeros. 1 really tight group about 1.5" below another 1" group. It's NOT the scope, verified this on my '06. I'm not getting impacts between the two groups.
Click to expand...

Like these ?

3xkz.jpg


stga.jpg


sxy9.jpg


I keep all my load development targets and they are stored with the corresponding data sheet of the load/s used . It took me 6 months to notice this pattern , only after pulling all my targets out and looking through them all at once did I see the double groups . That last one is a 10 shot string that gave me 2 separate sub moa groups and is what caused to go look through my targets .

I was doing 4 shot groups back then because that's what my mag held for that rifle . Longer story short . My action screws were loose . Only 15"lbs in front and 5 in the back when I checked . tighten them up and used loc-tite and that rifle has never shot another double group again .
 
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I had uploaded this for someone else some time back. These were in my Tikka T3x 7-08. Book loaded length. Not an excessive speed burner but was very efficient on a big old boar a few years back. Remington brass and CCI BR2 primer.
 

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Yes, miine are just a bit farther apart but basically the same. I'll double check my action screws, I tightened them down pretty good but things happen under recoil.
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Be careful , do you mean you just tighten them down now ? This will cause your zero to change and likely change what once was a good load to a not so good load .

You should use a torque driver to know where you were and where you are going to . Just tightening them down with out knowing to what specific inch pounds each screw was / is can be a waist of time and components .

Action screw torque can really effect accuracy and consistency . Lets say what ever you just did cures all your problems , no more double groups and it shoots everything great . Ok great right ? yep but what happens when they loosen up again and you'd like to tighten them back to where they were ? Or you want to do a deep cleaning that requires . removing the action from the stock Oops you don't know how tight you just made them that resulted in the rifle shooting great , so how do you plan to get the rifle shooting the same again . Or maybe the rifle now shoots worse , it would be nice to back them off to where you were . Then there's the most likely scenario which is the front will like a different torque then the back .

:eek:;):)
 
Never had a rifle that was sensitive enough for me to notice accuracy issues caused from over tightening the action screws. At least not one that made a difference inside of 300 yards. I took out torque wrench and tightened the screws to 30 in lbs. I definitely had them much tighter. We'll see if that makes a difference.
 
It’s not that they would be too tight it’s that the torque is different from before . The rifle may like them super tight . What you’re doing by changing the torque on the action screws is changing the barrel harmonics or the rifle harmonics in general which will affect point of impact as the barrel whips .

I did a torque test on the rifle that was shooting the double groups and a known good load I had . I started out at the manufacture recommended 40lbs each and it did not shoot good . Then started backing off in 5lb increments one screw at a time then the next . Best groups came at 30 in the front and 25 in the rear . Groups started getting really Squirrley if both screws were at 20 or less
 
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