help diagnosing poor groups

[Bc'z]

I like your 145eldx also at 3550 - 3563.
Was that 2 loads with a .5gr increase in charge weight?

 

[yorketransport]

I like your 145eldx also at 3550 - 3563.
Was that 2 loads with a .5gr increase in charge weight?

Those two shots were 90.0gr and 91.0gr respectively. The 90.5gr load was one of the bullets with a damaged tip and it dropped very low on the target with a velocity of 3545. My target velocity with this wildcat was 3500 fps with the 140 class bullets from the 28" barrel, so I'd be perfectly happy if I could get a good node at 3550.

 

[Bc'z]

Seems like you. Found your flat spot.
Are you going to reshoot 90, 90.5, 91 charge weights to confirm?

 

[yorketransport]

Seems like you. Found your flat spot.
Are you going to reshoot 90, 90.5, 91 charge weights to confirm?

That's the plan. Then I'll start the whole process over with the second barrel I had cut. That one's a 25" magnum sporter contour that I intended to use as a mid weight hunting barrel.

 

[Bc'z]

Nice, keep us posted.
At least me anyways. I like trying to decipher targets.

 

[M14AMU]

Here's your problem:

"a 270 wildcat"

 

[yorketransport]

Here's your problem:

"a 270 wildcat"

I don't disagree! That's one of the concerns I had when looking at some of the initial groups; maybe the 270 just wasn't meant to get pushed this hard. Or more likely than that was the possibility that my case design was just terrible and it wasn't going to work out. That's one of the reasons I came to the folks here to get opinions on the groups. If anyone can pickup on weird anomalies caused by some case design I hand't thought of, it would be a competitive target shooter.

I've always had a fondness for odd ball projects in impractical and overbore chamberings so I got the idea to try this. The case on the left is the wildcat I just call the 27 Boondoggle and on the right is a 270 Win.

I played with a 270 RUM for a few years but I didn't like the OAL of the full length RUM case. I ended up with a design that's essentially the 27 Nosler, but about .130" longer. The other way to think of it would be a 27/338 RUM with the shoulder angle and shoulder diameter of the 26 Nosler. It was just intended to be a companion to a 6.5x338 RUM improved that I have and fit right in with a handful of other overbore rounds that I use for causal shooting out to 1800-2000 yards. I quit competing a long time ago so I stopped chasing bug hole groups in favor of just having fun and using chamberings that most folks wouldn't waste their time with. Heck, I've got a 338 Big Baer specialty pistol that Alex Wheeler built for me a while back just so I could shoot to 2000 yards with a handgun.

 

[crustyrusty]

i want to put my two cents in hereIt may not be welcome but hey maybe just another perspective may well help.I bought a savage .223 and instantly fell in love with it. it would not shoot worth a hoot so I cleaned and cleaned the barrel and I shoot like crazy for anything to group... well not so much.. I got a little dismayed an quit cleaning my barrel and that was all I did all of a sudden my 55 gr match started to group better so I got a hold of savage arms and asked for suggestions they had none so I went to my local smith and showed him my targets of before and after heavey bore cleaning and he suggested to NOT over clean the copper out of the bore because some barrels in the manufacuring stage are rough in the finish and all that I needed was to clean the powder residue out of the barrel It worked I went from 3 plus inch groups to 3/4 inch groups with factory ammo and 1/2 groups with my hand loads just saying

 

[Webphut]

The way you are developing your load and breaking in the barrel is too overwhelming to me.

To me I see three groups. Second, The bullets are not key holing, so this tells me the bullets are stabilized.

I think:

1. Finish breaking in your barrel.

2. Once your barrel is broken in, pick one bullet which has proven to be stable, and choose one powder. Go play with the two of these until you hit the tightest group possible.

3 be happy with the combination, or change to different powder. Go do try again



Yeah, you are trying to do too much, too soon.

Do 5 shot groups, clean the barrel bee ten each 5 shot group. This is all done after barrel is broken in though.

 

[yorketransport]

Since this got brought back up to the top, I'll give an update. I'm now 250 rounds into testing and after 5 different bullets and 3 powders tested in 2 different barrels, I'm just writing this project off as a bust. I've still been unable to get consistent groups better than .75 MOA.

I went to do a Berger seating depth test with the 170gr Berger EOL and I ended up with the best being a 3 MOA group at 270 yards, with an ES and SD of 1 for 3 shots. I thought that having the Magneto strapped to the barrel might have caused the poor grouping so I shot the remaining test groups without it and ended up with 2.5 MOA groups, some with 2 MOA of vertical and some with nearly 2 MOA of horizontal. Seating depth covered a .210" range of OAL going from .010" jam to .200 jump.

Just like before, I can put a different barrel chambered for a comparable wildcat on the same action/stock/scope combo and get consistent .5 MOA groups which is exactly what I expect from that barrel. There are too many variables here to point to either the barrel, chambering or smith work as the cause, so I'll just shut this project down and move on. If only one of the two barrels was a dud or if I were working with a more conventional chambering it would be a little easier to pin down the cause or point to bad smith work. At this point I'll just have the threads cut off and maybe rechamber the the barrels to 270 WSM or just sell them and go back the the 338s that I've had better luck with.