I have a big problem

[runtohunt]

Took the STW out today to re-verify zero and suddenly the impact holes on the target are elongated as if there were 2 shots in one hole. I am thinking that some how the bullets are hitting at a sharp angle. The load is the same one that I had just used in Wy for antelope. I had no prior problems. Does this sound like a crown problem?
The load is 168 grain LRX over 72 grains of 7828. Primer is 215 match. Again no prior problems.

 

[DrMike]

What is the twist on your barrel? I suspect your twist is too slow for the LRX.

 

[Guy Miner]

Seems like they're not quite stabilizing, just starting to tumble a bit.

I've seen bullets impact the target completely sideways after going unstable.

Since you haven't changed the load (a longer than normal bullet, or rifling that is too slow a twist are the usual culprits, sometimes coupled with a lower velocity than normal) then... How's the bore? Has it accumulated sufficient copper/jacket fouling to interfere with the previous accuracy?

Kind of musing through some possibilities here...

Guy

 

[runtohunt]

Thus far, I have shot about 70 of the LRX through this rifle. The only change is the brass is now once fired nosler brass. Incidently, the once fired brass is shooting about 100 feet slower. I am now getting speeds of 2960 instead of 3060. The rifle is a Cooper with 26" barrel. I believe that the twist is 1:9.5. I hate to go out and buy factory loads but would it be worth it?

 

[FOTIS]

Seems like they're not quite stabilizing, just starting to tumble a bit.

I've seen bullets impact the target completely sideways after going unstable.

Since you haven't changed the load (a longer than normal bullet, or rifling that is too slow a twist are the usual culprits, sometimes coupled with a lower velocity than normal) then... How's the bore? Has it accumulated sufficient copper/jacket fouling to interfere with the previous accuracy?

Kind of musing through some possibilities here...

Guy

Guy is spot on... That would be my initial diagnosis also.

 

[IdahoCTD]

Marginal twist and now lower velocity= tumbling. You might try shooting @ 200yds to verify. Most likely it will look like a shotgun pattern @ 200. You can try to load them hotter to see if they will stay stabilized but your really on the ragged edge where a 20* drop in temps can cause stability problems. I would try some 160Ab's or something similar.

 

[runtohunt]

The barrel shouldn't have too much build up. After about the first 100 rounds, I cleaned with JB's bore paste and Kroll oil. At one point, I think I cleaned the barrel too much. I use to clean about every 6-8 rounds. The twist is a 1:9 not 9.5.

Unfortunately, I am fresh out of 160 grain accubonds and all the local shops are out.

I do have 150 grain Scirocco's that shot well during initial testing. So I will re-shoot them tomorrow as well as some 140 grain factory remington rounds that I bought when I first bought the rifle.

I have two days off, that I had planned to go deer hunting, that I will use to shoot the sciroccos. I leave in 19 days for a Colorado Elk hunt. I hope that the 150's will be good enough for elk.

Thank you for the input.

 

[IdahoCTD]

I wouldn't have a issue shooting a 150gr Scirocco through a elk. I zipped through a caribou with one at 600yds out of my .30-.338wm.

 

[Guy Miner]

Right, I'd try the lighter/shorter bullets as a first step. Bump the velocity a tad too, and that should do fine. Sure hope so!

 

[Oldtrader3]

I would go with the 150 gr Scirocco's myself. They should shoot and work fine for elk.

 

[DrMike]

The 150 grain Scirocco will work quite well on elk. I would have no particular concern. I believe Guy has given you some good advice, however. Reduce the bearing surface and increase velocity and you'll find the rifle works very well.

 

[300WSM]

The barrel shouldn't have too much build up. After about the first 100 rounds, I cleaned with JB's bore paste and Kroll oil. At one point, I think I cleaned the barrel too much. I use to clean about every 6-8 rounds. The twist is a 1:9 not 9.5.

Ok but are you saying you now have 100 rounds since your last cleaning? Someone here mentioned cleaning and let me say this....you claim the rifle was not doing this before...and now it is doing it. So something has changed since your last shootings. More fouling? Damaged rifle? Especially since you cite the rifle shooting fine before and now you are getting oblong holes.

Just out of curiosity sake how many rounds would you claim have been sent down the bbl.....and has anything else whatsoever changed in your load outside of the brass being once fired now.

 

[elkeater2]

Is it still grouping? I have had bullet holes in targets elongated slightly because the target wasn't directly facing the firing point. Also had targets not stapled tightly to stiff backing, kinda tacked up with a slight bulge to the target paper. Wish it was that simple for you!
EE2

 

[DrMike]

Is it still grouping? I have had bullet holes in targets elongated slightly because the target wasn't directly facing the firing point. Also had targets not stapled tightly to stiff backing, kinda tacked up with a slight bulge to the target paper. Wish it was that simple for you!
EE2

Excellent point. I normally smooth out wrinkles and bulges before driving the final staple.

 

[OU812]

Took the STW out today to re-verify zero and suddenly the impact holes on the target are elongated as if there were 2 shots in one hole. I am thinking that some how the bullets are hitting at a sharp angle. The load is the same one that I had just used in Wy for antelope. I had no prior problems. Does this sound like a crown problem?
The load is 168 grain LRX over 72 grains of 7828. Primer is 215 match. Again no prior problems.

This may sound silly but is your target pulled nice and tight or is it possible the target backboard is some how splintering upon bullet impact and enlarging the hole?

Does it still group?

 

[runtohunt]

The target was straight and flat--I wish that was the problem. The groups went from 3/4-1" groups out to about 2".
I think that I have about 70 rounds down the barrel since the last JB's bore paste/kroll oil cleaning. So a sum total of about 170 rounds through the gun since brand new.

I think that Guy was right about the bullet not stabilizing. I suppose that the decrease in speed of 100 fps was enough to allow the bullet to angle.

Took the STW out again today. Shot the 150 grain Scirocco. Velocity was 3160. No elongated holes. Groups were not that good 1.25" to 1.5." Still have some work to do with the load. BUT, at least the wholes are not elongated.

Also just purchased #200 160 grain accubonds from SPS to work up if I have time.
Thank you everyone for your input.

 

[Oldtrader3]

Sciroccos have never shot really accurately for me, 1-1/2 inches is probably typical.

 

[DrMike]

I have had rifles that did not like Sciroccos, regardless of what I tried. There are other instances that come to mind when the Scirocco saved the day.

 

[SJB358]

Good luck getting it tuned up. Hope your bullets get there in time. Sounds like the 160 AB's at around 3150 should do the trick!