Seating Depth Progression

[atmoshpere]

Finally got around to shooting 160ABs in my 284, which is what I originally intended to shoot with it! After a few charge variations I settled on 50.8gr RL-17 and decided to look at seating depth. The top group (2.983" COL) is what I had done my initial testing at and is pretty much exactly what I was getting for groups at that COL before so no surprises there. The middle group is 2.970" COL and is a very familiar pattern :grin: The bottom group is a 2.957" COL and seems to be the sweet spot :!: I thought these three groups were an interesting representation of how seating depth adjustments can affect group characteristics. As a side note: these are also the first shots taken with the Vortex Viper HS midway special that my wife "let" me buy :mrgreen:
Don't worry, I was sure to tell her how awesome it was and what a great buy etc! Kidding aside, I'm very impressed with it.

 

[atmoshpere]

If anyone else has pictures like this illustrating their seating depth tests that they wouldn't mind sharing I think it would be cool to see.

 

[Ridge_Runner]

I have found once your happy with velocity and pressure, shoot a couple 5 shot groups, on 3 shot groups you get 2 in and 1 out, with a 5 shot group you will probably see 3 here, 2 there, the group within the group is an almost sure sign that your rifle wants the seating depth tweaked.
RR

 

[DrMike]

Fascinating information. You are correct about the lower group being a sweet spot. That is an enviable group.

 

[Ridge_Runner]

not a real good example of what your requesting but all I could find
This first target was berger bullets (140) loaded in my 6.5 Gibbs at the start of load developement/trajectory tests
loaded to 3300 fps with re22 on the lands, the small group was shot at 100 yards, the lone round was a POI correction, the other 3 were fired at 610 yards, the group measures around 8" or 1.3 moa.

brass life was terrible and was getting slight pressure signs, so the load was dropped to achieve 3200 fps, the marked group measures .63 moa

I then loaded them with the same load .030 off the lands, MV jumped up to 3260 IIRC and shot this group at 752 yards and measures .04 moa, was it luck? could be but I haven't changed it

RR

 

[FOTIS]

Damn! Good shooting RR

 

[DrMike]

RR,

Wish I could get all my rifles to do that. That is superb.

 

[jimbires]

last fall I did reduced recoil loading for a new shooter with a 308 axis . this rifle really needs a trigger .same load only changing seating depth . here are the targets .

and here are her 100yds targets with the 2.690 depth loads .

 

[Ridge_Runner]

Jim, thats awesome, good on ya!
RR

 

[DrMike]

That is pretty dramatic changes. I'd say that is one happy young lady. Good for you and your work with her, Jim.

 

[atmoshpere]

Thanks for sharing guys; I love stuff like this! RR, I've seen what you described a lot where 3or 4 make a tight cluster with one or two out of place. Sure enough those outlyers can often
be brought to heel w a seating depth adjustment.

 

[SJB358]

Great shooting ATM. Glad you got such good shooters with the 160 AB's. Whats the speed on them out of your 284? They look really good!

 

[atmoshpere]

With 51.5gr RL-17 I was hitting 2910fps, but getting slight pressure signs every once in a while so I backed these off to 50.8 and out of the 9 that I shot yesterday I didn't see anything to suggest high pressure and it jives pretty closely with what quickload says. I didn't chrono the 9 at 50.8 gr but I'm guessing right around 2850fps.

I'll try 5 of the same through the chrony when I get a chance and see how we do.

I'm thinking that backing them off as much as I did from 2.983 to 2.957 would probably have reduced my pressure enough that 51.5 woulda been ok (I was pretty much on the lands with the first loads I was shooting) but I didn't really feel like pushing the brass that hard.

Plus if I can replicate the results of yesterday at 2850, that's good enough for me :mrgreen:

 

[Elkman]

It looks to me you did find "the spot". That is really a graphic presentation of seating depth ! Thanks for showing us that!

 

[brianwyo]

Great topic! I have 2 rifles that are not quite there. I seem to mess with differant powders when things are not going well. I am probably closer than i think. Thanks Brian

 

[FOTIS]

Here is the BIG question...

Has anyone experienced this king of great results in weatherbies ?

They do have a 3/8" freebore..........

 

[Ridge_Runner]

Here is the BIG question...

Has anyone experienced this king of great results in weatherbies ?

They do have a 3/8" freebore..........

have read reports of guys building rifles chambered with zero freebore, getting ungodly velocities and great accuracy, factory guns, seaating depth never changed nuthin but velocities only if ya used more powder.
RR

 

[ElmerThud]

I have found once your happy with velocity and pressure, shoot a couple 5 shot groups, on 3 shot groups you get 2 in and 1 out, with a 5 shot group you will probably see 3 here, 2 there, the group within the group is an almost sure sign that your rifle wants the seating depth tweaked.
RR

I found this really interesting RR & fully intend to check my reloads thoroughly with 5 shot strings.
Mostly I rarely if ever shoot 5 shot groups, primarily because mine is a lighterweight sporting barrel, so I shoot 2 fouling shots then let the barrel get as cold as possible before shooting a 3 shot group.
Invariably I have two holes touching, usually first & third shots with the second shot being the 'Flyer'.
The 3 shots usually end up being with 1/4" MOA though. (Depends how 'on form' I am!!)

I added some pics for illustration, but the pic isn't a 1/4" MOA group.
Cheers, ET