Does a half of grain of powder make that much difference?

[deertroy1]

Below is the first handloads out of my new Cooper. The small group in the center was fired first from a cold clean barrel. Do you think the load got worse as it was increased or the rifle just doesn't like to be shot warm. Temperatures were in the high 50's. I didn't allow the barrel to get hot but it was warm during the last two groups. I guess the only way to be sure is to shoot the same loads again but this time in reverse order. Regardless, if the load is that sensitive I probably should abandon it.

 

[Mikecr]

That's a really big difference. Too much for powder alone.
I would definitely try it again

 

[varmintH8R]

That's a really big difference. Too much for powder alone.
I would definitely try it again

+1, I agree. Are these your first handloads through the rifle or your first significant shooting of the rifle? I ask, because I had a similar issue in the past. The problem turned out to be, well, me. I have found that each new rifle has a bit of nuance in how it likes to be shot. Anymore, I'll load and shoot a box or two of a random load just to get a feel for what is most consistent on terms of form/set-up/trigger pull. Then, when I go to ladder test powder weights, I'll shoot 3 or 4 groups first just to get settled in. That has proven to be a good system for me.

Please note that I am in no way trying to be offensive or cast doubt on your ability. Just sharing my experience in case it helps you. I hate the randomness of these forums as I am certainly not looking to insult someone who just took third place at Camp Perry...

Ps I am a big Cooper fan and have several that shoot really well. I hope you enjoy yours!

 

[deertroy1]

I'm not insulted at all. I appreciate you taking the time to offer your advice. However, I didn't do anything differently while firing the first three rounds than I did the last three.

The same thing happened last week while shooting the very first rounds out of this rifle. A random handload, shot very well. The next group, Remington factory rounds, was terrible. Although this could very well be the difference in loads. Maybe not. Maybe the gun is only going to shoot well cold or maybe it likes a really clean barrel. Maybe it just need to get broke-in. I guess it's too soon to tell?

 

[Derek M.]

There are no shortage of opinions on either side of the fence as to whether or not break-in is a necessary procedure or not. In my opinion, there's truly no way to tell because every single barrel and bullet is different. I, for one, do it because I don't believe it hurts the barrel and I've been very pleased over the past 10+ years with all of my rifles and the results of my loads.

I don't know anything about Cooper rifles or their barrels. I believe you should put 20-30 bullets down the bore before you take a serious look at load development unless something magical happens during break-in. I did experience this with 3 rifles. My 308/Obermeyer barrel, my 30.06/PacNor barrel, and my 270 with a Broughton-Richards barrel. Correction: 4 rifles, I forgot my Shilen barreled 280

The loads through the 30.06 originally shot so well that I had around 5-8 bullets through it and I used the remaining 20 to hunt with and all killed something. Same thing with my 308.

 

[HARPERC]

I'm going with be patient it's early. I'd be encouraged that the groups overlap pretty well. If you put the 9 shots together they almost fit in the worst group. If anything clean it after each group and see what happens. How are you cleaning it?

My Krieger 338 RUM prefers clean, my My Douglas .375 H&H is the least fickle I ever had . I have a 6mm Remington, Shilen barrel, that shot patterns until we were between 150-200 rounds. Then tightened up from then on. I also started more aggressive cleaning with JB, I suspect I hand lapped it myself. You aren't there yet.

Their all different, but 0.5 grain powder isn't likely the issue. If all your groups were 1.75"
another bullet or change in seating would do more.

 

[deertroy1]

Derek

I agree. This rifle has only 15 rounds down the spout plus what ever Cooper shot. This is the second barrel on this gun as the first had a problem. I did the shoot one clean, for the first five or so, then shoot three and clean etc. but nothing would shoot. I returned it to Cooper and they re-barreled and re-bedded the rifle. This time I shot six and cleaned and now nine and cleaned. I have noticed some pretty heavy copper fouling during this cleaning. Hopefully it well settle down after some more shooting.

 

[Derek M.]

Get all of the copper out. Spray wipe out down the tube and let it sit for 18-24 hours. Scrub and patch it all out, then do it again, laying the rifle on the opposing side. There's no harm in cleaning until you are down to bare bore metal.

Who makes cooper barrels? are they hammer forged? lapped? button? cut rifled?

 

[deertroy1]

I've pretty much got it out. Bore-Tech Copper Remover.
Wilson makes Cooper barrels. I believe they're button rifled.

 

[deertroy1]

Made it back to the range a couple more times. This rifle seems to shoot the first two or three rounds into a half inch or less and then it starts to really spread things out. With only 26 rounds down the tube so far it may still need some more shooting before it starts to come around. It still copper fouls quite a bit. How about some other Cooper owners. Did your rifle shoot good right away or it it take awhile?

 

[varmintH8R]

How about some other Cooper owners. Did your rifle shoot good right away or it it take awhile?

I have a 22-250 that shot better as I got more rounds through it, but nothing like what you are seeing. It went from a MOA gun to about a half MOA shooter after 70 or 80 rounds, but I attributed it more to load development than break-in.

I have a Cooper in 280AI that shot fireforming rounds like complete crap (they were jammed and not charged ideally) so maybe that attributed to a break-in. When I got into actual load development it was the easiest I've ever done.

It seems weird that groups would open up that much. I'm sure you don't want to hear it after sending it back once already, but it sure sounds like something isn't right... In my (often wrong) opinion i wouldnt expect flyers that far out there to settle in after more break-in...

 

[deertroy1]

I've got some 139gr Hornady Inter-bond's, so I'll try them. The best I can do and still load them in the magazine is to within 70 thousandths of the lands.

 

[myownman]

I had a rifle doing the same thing a long time ago. It ended up being the scope. It would shoot a couple close, then the next few wouldn't even be close.

 

[TOM H]

Derek

I agree. This rifle has only 15 rounds down the spout plus what ever Cooper shot. This is the second barrel on this gun as the first had a problem. I did the shoot one clean, for the first five or so, then shoot three and clean etc. but nothing would shoot. I returned it to Cooper and they re-barreled and re-bedded the rifle. This time I shot six and cleaned and now nine and cleaned. I have noticed some pretty heavy copper fouling during this cleaning. Hopefully it well settle down after some more shooting.

This is from Cooper Site

The now famous 1/2" at 100 yards Cooper Firearms of Montana, Inc. accuracy guarantee for center fire rifles began in 1998 with the introduction of the "Varminter" in Models 21 and 22. Soon after, the Montana Varminter became an instant classic.

Don't they send test target and I'm not sure of the yardage but why don't you call them see what they shot?