Range Report I need explanation...

[bjay]

can pls someone explain how this happen? heres a range report yesterday milspec 308
loaded: lapua brass(2.005 trimed) fed210m primer RL15 powder Oal 2.83
target at 100yd trying to fish load.
first diamond was came from freshly clean barrel un zeroed scope..i totaly understand the first group for fouling purposes.then dialed it to zeroe from 2nd diamond to 5th(last). all aiming at the diamond each group.
heres what happen, i shot first ten shot (first and second diamond) no cooling off barrel in between (doing 5 group each diamond).then i prolly let barrel sit for 5-7 minutes then shoot 3rd diamond and 4th (no cooling off between all shots)and POI is 2 moa higher! what the hell.. lol.did i rush the colling process to the barrel?
then waited 10-12 minutes and shoot it again and boom! and back to the bullseye! (last group)
heres the load: RL15 all seated same oal
diamond 1: 43.50
2: 44.00
3: 44.30
4: 44.60
5: 45.00
can someone explain what happend to target 3 and 4
also shot #2. 44.00 to 420yd its 2" 5shot group little less than .5moa so i guess im ok with that avg. fps 2637
..one more thing YES i stapled target upside down lol i was rushing

 

[rduckwor]

Pretty large gaps between charges.

My guess is that you have nodes around the 44 and 45 Gr charges. You said that the 44 Grain worked out well at 429 yds. Work with it. Load some more up with 0.2Gr gaps and shoot them and verify. Then start working on seating depth at that load if it works out.

Good Luck.

 

[jfields]

Trying the same exercise with one powder charge may tell you something. You know... Load up 20 rounds at 44 grains and shoot a couple groups with a hot barrel and few with a barrel you have allowed to cool down. Is the stock bedded? I think the POI is too great to be sight picture/cheek weld issues.

-J

 

[rduckwor]

I agree with JF. I frequently see that much vertical when shooting OCW's. With the powder charge gaps represented in your series, I suspect you found a couple of "scatter nodes" as Dan calls them.

Good luck.

 

[bjay]

Tnx guys..yes stock is bedded..heres the rifle

 

[bjay]

Wait a minute!!! Just remembered as looking at the chrono chart.. i actualy attach the magnettospped chrono on the muzzle on those 2 groups 3 & 4..did tjis change POI? After removing it, it went back to bullseye POI..by the way what is a decent fps for 24" barrel 308?

 

[rduckwor]

Well, it may have. Others have reported no shift in the poi with this chrono. HOWEVER, anything you hang on the barrel changes the resonance, and that impacts poi, that's why those barrel deresonators are made.

I don't see a bullet weight listed. Generally, 168 SMK's run about 2650 GPS from Federal GMM commercial rounds.

 

[bjay]

Well, it may have. Others have reported no shift in the poi with this chrono. HOWEVER, anything you hang on the barrel changes the resonance, and that impacts poi, that's why those barrel deresonators are made.

I don't see a bullet weight listed. Generally, 168 SMK's run about 2650 GPS from Federal GMM commercial rounds.

sir it was 175 smk..
i did also read on a lot of blogs that this chrono does change POI even creaye bigger spread sometimes...

 

[D_TROS]

My first guess was bedding, but after seeing the rifle, and the fact the ONLY thing you changed is adding the chrono, that is more than likely what happened.

As to a custom action/barrel 308 using RL powders, I think 2700 should be easily attainable. My old 308 load was 45 of varget going 2660 in a 22" barrel. Just be careful with temp swings with RL powder as it is very sensitive to temperature, so the closer you get to a max load, the greater the danger of over pressure on a hot day.

As to interpretation of groups, I would try a group at 43,7 and 45.3 and see if they are tight, and go with either. The 175 going near 2650 is a darn good load.

Good luck.

DT

 

[bjay]

My first guess was bedding, but after seeing the rifle, and the fact the ONLY thing you changed is adding the chrono, that is more than likely what happened.

As to a custom action/barrel 308 using RL powders, I think 2700 should be easily attainable. My old 308 load was 45 of varget going 2660 in a 22" barrel. Just be careful with temp swings with RL powder as it is very sensitive to temperature, so the closer you get to a max load, the greater the danger of over pressure on a hot day.

As to interpretation of groups, I would try a group at 43,7 and 45.3 and see if they are tight, and go with either. The 175 going near 2650 is a darn good load.

Good luck.

DT

DT funny coz the first try on this powder all 43.5 just playing with seating dept they all prety much one hole..exept for the top left thsts a varget powder.. the only reason i sloely increasing powder and i got to 45.00 no preasure sign this all on the 175smk. The 43.5 shoots great but i was chasing fps a litle since it was only avg low 2500fps