Huge velocity swings?

[Sirshredalot]

Hello all,

Not new to reloading, but new to the forum.

Im looking for advice. Alliant and shilen offered none.

Ive got a savage 110 in 280 ackley, 26in shilen barrel, McMillan stock.

Hornady 280 rem fire formed brass, wlrp, rl23 powder, 150gr lapua scenar loaded to .030 of lands. I dont have my data in front of me but it was close to 3.365?

Each charge was trickeled and weighed at 59gr, brass annealed and neck sized.

If i let the barrel cool to static temperature(8-10 min), i get very consistent velocity, however upon "rapid" fire strings i am seeing over 300fps variations. Rapid being an 8 shot string in 5 to 8 minutes.... and a safe load speeds up to an overpressure load, with regards to my gun and my tested velocities.

Also, clean bore fouling shots are very low on speed compared to fouled shots(150fps).

Chrono is a caldwell set up 12ft from the muzzle using the led lights and direct sunlight.... verified velocity with another rifle and factory ammo and it meets posted speeds.

Any advice?
Ive got about 300 rounds through the new barrel and followed the suggested break in procedure fairly closely.

 

[spife7980]

Try it over a good chrono. Shoot it on paper at distance and see if it’s a real world problem or an electronic/mental problem. If it shoots well at 800 yards there is no problem.

 

[black5.3]

Try it over a good chrono. Shoot it on paper at distance and see if it’s a real world problem or an electronic/mental problem. If it shoots well at 800 yards there is no problem.

I would agree with this... some of the cheaper chronos can be very finicky and lead you to believe you have problems when you really don’t.

 

[Steel head]

Try it over a good chrono. Shoot it on paper at distance and see if it’s a real world problem or an electronic/mental problem. If it shoots well at 800 yards there is no problem.

This!

 

[ken4570tc in WY]

Not new to reloading - OK. How consistent is your neck tension, primer seating and powder measuring, do you use an expanding mandrel? There are so many variables it's impossible to cover them all in a forum thread. Another possible problem is, letting a cartridge set in a hot chamber too long before firing. You'll have to turn over every stone in your reloading and shooting processes.

 

[Sirshredalot]

Been a while, still the same problem.

My neck tension seems to be a very consistant .002.
Primers are all seated below flush with an rcbs bench prime....as far as measuring them..? Never have.

Powder goes into a hornady digital bench scale, is trickled, then confirmed on a dillon dterminator...both warmed up and left on for the entire loading session....only led lights above the bench.

I have gone over my loading process in my head and physically at least two dozen times.

All cases annealed, neck sized only on a lee collet, trimmed, deburred, vld reamed, and weights are within 2ish grains of each other after prep.

Seating is done with a hornady 7mm seating die with vld? plug and micrometer.

The problem is also not just increasing velocities, but inconsistant everything.... not getting the groups i would expect. I replaced the chrono and got the same results.

I cannot reach the lands in this barrel and still feed from the mag...max mag length is 3.425...if i seat further than this i loose bullet grip?

What do i look for? Where do i look?

Suspect barrel? Try another powder?

Ive tried 5 different primers and 3 powders.

All advice is appreciated and sorry about the hiatus, just coming out of the busy season at work.

Shred

 

[briang7511]

so how much jump do you have? try to load a few closer to lands and just single feed to see if there are changes?

 

[b2lee]

Try loading 150 thousandths off the lands with those scenars....yep...you read that correctly... One Fitty. Nope...not joking...try and few and see if you get better results.

 

[Sirshredalot]

Will give it a shot... going to be a while though. Its 28 degrees and weve got the flu.

Thanks

Shred

 

[Steel head]

Try loading 150 thousandths off the lands with those scenars....yep...you read that correctly... One Fitty. Nope...not joking...try and few and see if you get better results.

this.
Jump is good.

I personally don’t trust optical chronys.

 

[Sirshredalot]

That did it.

Seated the lapua to 3.305
Backed the charge weight down to start.

5 shot group .550"
Avg 2981fps
Sd 2.28
Es 6

Now i have a starting point.

Thanks for all the help

Shred

 

[Sirshredalot]

Update...ive since introduced many more steps into my reloading regimen to include longer annealing, case volume sorting, and neck turning.

Turns out...most of my problems where either donut related or neck tension related.

I segregated 14 cases with tighter necks than the others, even though they had the same prep.

Just had a 10 round string with an es of 25... now i just have to learn to shoot better.

Shred

 

[918v]

If you anneal too much the necks will be too soft and lego the bullets prematurely before the powder can combust properly. I suggest you do over without annealing.