Explanation anyone?

[RCMSTER]

I'm seeing a labradar in the near future. I will probably look around online and see if I can find the powders you listed. I bough TV a pound of this supreme 780 just because the gunsmith where i picked up this rifle had some of it on the shelf yet, and think it's been discontinued for a while. Course, this same gunsmith still has at least 3 rcbs 10-10 scales, new in the box on his shelf, and according to rcbs, they were dropped in the mid 80's.

 

[vancewalker007]

So my question is this. Shot this 5 shot group tonight out of my 6.5-06 that I just bought off of Gunbroker. Of them 5 shots, the first 4 shots averaged 2898 fps, while the last shot plummeted to 2708 fps. I loaded up 3 more rounds with an increase of .5 grains of Supreme 780 to 49.5 grains. Them 3 shots averaged 2740 fps. I'm baffled to this, but my first thought is that I need a new battery in my chrono. My other question would the warm barrel cause this much velocity drop. Temp outside is 77 degrees.
In regards to the 2nd pic of the primers, what's ya'lls thoughts? To me they look fine yet, as in no high pressure.

Until you go out to a longer range and check your drop using known holdovers ie. dialing up, you can't really be sure what a chronograph is telling you. Optical chronys are notorious for giving wild numbers. Shoot some and get an average, then use that average to dial up correction and shoot at 400-500 yards to check your results. Likely you will need to adjust your data to match your rifles real velocity.

 

[RCMSTER]

Until you go out to a longer range and check your drop using known holdovers ie. dialing up, you can't really be sure what a chronograph is telling you. Optical chronys are notorious for giving wild numbers. Shoot some and get an average, then use that average to dial up correction and shoot at 400-500 yards to check your results. Likely you will need to adjust your data to match your rifles real velocity.

I'm sure you're correct, but the rifle is new to me, so just starting with it. I have a long, long ways to go.

 

[vancewalker007]

I'm sure you're correct, but the rifle is new to me, so just starting with it. I have a long, long ways to go.

I gave up on my shooting chrony for this very reason and went to a magneto speed. Its been great and very close but I still find some long range testing refinement is always needed once I settle on a load.

 

[RCMSTER]

I gave up on my shooting chrony for this very reason and went to a magneto speed. Its been great and very close but I still find some long range testing refinement is always needed once I settle on a load.

So, I have a question about the magnetospeed. Since its attached to the barrel, does it effect POI?

 

[vancewalker007]

So, I have a question about the magnetospeed. Since its attached to the barrel, does it effect POI?

Yes, if you use the barrel attachment. There is a new setup that can attach differently. I use the barrel setup and only use it to gather velocity data. It doesn't seem to affect groups but it does change POI. I shoot accuracy test groups without. It's just so much less of a hassel than the optical shoot through chronys and it gives very good data. Plus the spotter model only costs about $160-$180.

 

[Farmerboy78]

Yep, I use the V3 magnetospeed, as stated above, I shoot and find my accuracy charge. I then throw on the magnetospeed to get data

 

[RCMSTER]

Well, that about says it. Guess I'll be buying me a magnetospeed at the end of the month. Now that I have this high-powered 6.5-06 (well, not that high powered), I guess I just as well upgrade my chronograph too. Thanks for all the advice. I'm definitely in the learning mode with this rifle. It's a whole different animal than my dozen or more other rifles.

 

[Alibiiv]

So my question is this. Shot this 5 shot group tonight out of my 6.5-06 that I just bought off of Gunbroker. Of them 5 shots, the first 4 shots averaged 2898 fps, while the last shot plummeted to 2708 fps. I loaded up 3 more rounds with an increase of .5 grains of Supreme 780 to 49.5 grains. Them 3 shots averaged 2740 fps. I'm baffled to this, but my first thought is that I need a new battery in my chrono. My other question would the warm barrel cause this much velocity drop. Temp outside is 77 degrees.
In regards to the 2nd pic of the primers, what's ya'lls thoughts? To me they look fine yet, as in no high pressure.

Just curious about what was done for case prep? Annealing, trim, neck tension, neck turning/reaming, flash hole deburring, stuff like that? Some of the primers look to be flattened out pretty good, but not excessively but getting close.

 

[RCMSTER]

Just curious about what was done for case prep? Annealing, trim, neck tension, neck turning/reaming, flash hole deburring, stuff like that? Some of the primers look to be flattened out pretty good, but not excessively but getting close.

Ok, so for case prep, I started out with new, Peterson 270 brass. First thing i did was to trim back to 2.485". Then i resized in a Redding, full length bushing die, using a .291 bushing. Checked length, and discovered they grew to 2.493", so trimmed back again to 2.485". Didnt do any neck reaming or turning, but deburred flash holes. Primed with cci200 primers. I was wondering about the primers. I was hoping for some opinions about how close I was getting to pressure. These were loaded with 48.5 grains of Supreme 780 powder, pushing a Speer Gold dot bullet @ 140 grains. I was figuring this to be max loading, based on just my opinion. Oh yeah, OAL was 3.250", which, if I measured correctly, was .150" away from rifling. Barrel is a 26" Brux, 8" twist, and has a brake in addition to the 26" barrel.

 

[Sierra1wardog]

Besides the chrony i would also consider excess solvent/cleaner in the barrel to be a cause. Maybe you just cleaned her and you had some burn off or maybe it just needs a good scrubbing If you didn't?

 

[Alibiiv]

Ok, so for case prep, I started out with new, Peterson 270 brass. First thing i did was to trim back to 2.485". Then i resized in a Redding, full length bushing die, using a .291 bushing. Checked length, and discovered they grew to 2.493", so trimmed back again to 2.485". Didnt do any neck reaming or turning, but deburred flash holes. Primed with cci200 primers. I was wondering about the primers. I was hoping for some opinions about how close I was getting to pressure. These were loaded with 48.5 grains of Supreme 780 powder, pushing a Speer Gold dot bullet @ 140 grains. I was figuring this to be max loading, based on just my opinion. Oh yeah, OAL was 3.250", which, if I measured correctly, was .150" away from rifling. Barrel is a 26" Brux, 8" twist, and has a brake in addition to the 26" barrel.

I am not familiar with Peterson brass, however from what I have read on the forum it is quality brass. I've actually been considering buying a batch. The prep that I do to make the .270 AI is to anneal new brass before I do anything, media tumble after annealing, trim to length, deburr inside/outside case mouth, ream the primer pockets to uniformity, full-length resize without the expansion plug, then neck size with a Sinclair mandrel die; then use cream of wheat to fireform. What I can state is there is a definite difference between annealed cases and those that are not. When full length resizing the brass resizes a lot easier, not saying this is the issue with the readings you are getting, just another variable to consider.

 

[RCMSTER]

Well, when you look at peterson brass, you can definitely see the annealing line in the brass. I suppose there's several ways to get to the same point as far as brass prep. As far as which way is best...., heckifino. I'm thinking I'm either gonna get a magnetospeed or a labradar very soon.

 

[Tiny Tim]

Ok, so for case prep, I started out with new, Peterson 270 brass. First thing i did was to trim back to 2.485". Then i resized in a Redding, full length bushing die, using a .291 bushing. Checked length, and discovered they grew to 2.493", so trimmed back again to 2.485". Didnt do any neck reaming or turning, but deburred flash holes. Primed with cci200 primers. I was wondering about the primers. I was hoping for some opinions about how close I was getting to pressure. These were loaded with 48.5 grains of Supreme 780 powder, pushing a Speer Gold dot bullet @ 140 grains. I was figuring this to be max loading, based on just my opinion. Oh yeah, OAL was 3.250", which, if I measured correctly, was .150" away from rifling. Barrel is a 26" Brux, 8" twist, and has a brake in addition to the 26" barrel.

I think the resizing may cause the case length to grow. If the base gets sized, it squeezes the case, making it longer. The shoulder is pushed back and you have a "longer" case.