280 AI weird groups??

[Jakeweb09]

I'd shoot one or the other. I have shot many rounds of 180 hybrids at near the same velocity, then shoot 10 monos, switch Back to bergers and I'm 20fps slower

 

[Texis]

As I ponder the fouling, the fast 1:8 twist and 2900fps may be a quick fouling combination with Barnes monos.
Shouldn't a fast twist and high velocity foul heavier??

 

[Koda_]

As I ponder the fouling, the fast 1:8 twist and 2900fps may be a quick fouling combination with Barnes monos.
Shouldn't a fast twist and high velocity foul heavier??

I have an 8 twist 280ai and only shoot copper Hammer bullets and it doesn't foul quickly. Easiest barrel to clean actually.
My guess is still on the proper bedding is your culprit.

 

[Troutslayer2]

Both 280ai barrels I've had have been picky about fouling and shoot best when cleaned then just fouled a little. My consistency goes haywire after maybe 40-50 rounds.

 

[Rflshootr]

Too heavy of a firing pin spring can cause strange harmonics.

 

[MagnumManiac]

Two things standout here, stock is not bedded in the recoil lug, bed it tight everywhere except underneath the lug. The rifle should be difficult to remove the stock, if you want easy removal, put electrical tape on the sides and in front of the lug. I use tapered sided lugs for this.
Secondly, you have too much headspace, this changes ignition causing inconsistent start pressure. Try running .0015"-.002" and see if the groups stay tight.
The other notable thing, stop shooting cup and core bullets in the same fouled barrel as mono's.
Deep clean between using the two types.

Cheers.

 

[Ldigio21]

Getting strange groups, 2 touching.. next shot 1/2"-1" away. Repeat the best load, .350" and then get a 1.5" group.

Background:
I built the rifle, Remage 700 with a 22" 1:8 twist Criterion barrel. HS stock, Trigger Tech, NF SHV 5.5x20. Scope mounts are tight. I've owned this NF for years, it has been rock solid.

To start, I love the round, smooth, no pressure signs pushing 160gr AB or LRX at 2900 with 58.7 gr 4831SC. COAL at SAAMI.

I'm an experienced hand loader, I've tried moving the COAL in .010 increments in both directions, shoots the best at SAAMI lenght. I've tried working the load in 1/10gr increments, 58.7gr works the best.

I use RCBS dies and Whidden bushings and mandrel, bump the shoulder back .004-005 (it's a hunting rifle) Redding scales. I have been seeing 9-15 SDs, all good there.

I keep round counts, currently at 143. My next move is give the barrel a deep cleaning then lead it with dozen rounds or so, and try again!! This is about the point I typically deep clean, but it hasn't degraded in accuracy.. it's shot like this since I started.
Any ideas are appreciated.

Get a Hornady bullet comparator and measure CBTO. There are plenty of Youtube videos on this. Much more consistent than COAL. In my 280 AI with 23" barrel getting 2980 with 60 gr RE 26 with 160 gr Accubond. With 150 gr scirocco , 60.4 gr RE 26 3090 FPS. I can actually get better accuracy going faster than these loads but the group improvement doesn't seem with the extra pressure. Both those loads are consistently .5 MOA

 

[AussieWriter]

If it's not bedded, you have 2 mass produced illfitting surfaces being crushed together by a couple of bolts. Its a mechanical stress point.

Once it's bedded, if you move the seating depth, move it .005"-.006", not .010" which is too much movement with a light profiled barrel.

 

[Texis]

I use a Whidden universal bushing for measuring at the ojive base to check the seating depth when loading. Very accurate setup, I recommend Whidden.
Correct, using the metplate (pointie end) as your measurement location yields inconsistent numbers. Sorry, I used the term "COAL" generically.

 

[Texis]

It's not a light profile barrel, it's a varmint profile.

All of you guys have given me some areas to check on the rifle and things to consider, thanks.

 

[Texis]

To answer an earlier question "before I changed the barrel"… the action came from a 25-06 that I owned for 40 years and a tack driver. It started to lose accuracy and I wanted more juice. I'm guessing it had well over 1,000 rounds on the original barrel.
When I installed the current barrel, the lugs blued square.

 

[LouisianaHunter]

Getting strange groups, 2 touching.. next shot 1/2"-1" away. Repeat the best load, .350" and then get a 1.5" group.

Background:
I built the rifle, Remage 700 with a 22" 1:8 twist Criterion barrel. HS stock, Trigger Tech, NF SHV 5.5x20. Scope mounts are tight. I've owned this NF for years, it has been rock solid.

To start, I love the round, smooth, no pressure signs pushing 160gr AB or LRX at 2900 with 58.7 gr 4831SC. COAL at SAAMI.

I'm an experienced hand loader, I've tried moving the COAL in .010 increments in both directions, shoots the best at SAAMI lenght. I've tried working the load in 1/10gr increments, 58.7gr works the best.

I use RCBS dies and Whidden bushings and mandrel, bump the shoulder back .004-005 (it's a hunting rifle) Redding scales. I have been seeing 9-15 SDs, all good there.

I keep round counts, currently at 143. My next move is give the barrel a deep cleaning then lead it with dozen rounds or so, and try again!! This is about the point I typically deep clean, but it hasn't degraded in accuracy.. it's shot like this since I started.
Any ideas are appreciated.

Following

 

[JAYgs8163]

Two things standout here, stock is not bedded in the recoil lug, bed it tight everywhere except underneath the lug. The rifle should be difficult to remove the stock, if you want easy removal, put electrical tape on the sides and in front of the lug. I use tapered sided lugs for this.
Secondly, you have too much headspace, this changes ignition causing inconsistent start pressure. Try running .0015"-.002" and see if the groups stay tight.
The other notable thing, stop shooting cup and core bullets in the same fouled barrel as mono's.
Deep clean between using the two types.

Cheers.

^^^^^ This.For sure bed the action to the stock and make sure the barrel is not in contact with the stock. Check barrel is now floated after your third shot, if not this could be issue.

Also, don't mix bullets during load development. Strip the barrel clean and pick a bullet and work with it. If it's not to your liking be SURE to strip the barrel clean before changing bullets. This is especially important with going between Mono/Cup-core type bullets. For instance- don't shoot a Barnes and a Berger during the same session. Ok to shoot a 168 Berger and then a 180 Berger as alloys are the same. I always clean my barrel if I'm switching to a different bullet mfg. I would say the majority of the time you're not getting a true indication of what your rifles doing when mixing projectiles during load development. Different alloys getting fouled into the barrel just change the barrel performance and consistency. JMO and experience.

 

[med358-boise]

You might wish to read the following post. Yes, it is written with humor and there wasere a lot of "funning" back and forth, you will see that there is something to this.

Many people will not want to try this but you can also see more than a few have.

Two data points do not a test make but they are interesting... - Topic

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