Cooper .300 Win Mag not grouping

[davecb]

Hello all, I've checked the forum out for a while now but just joined recently. I've been trying to work up some hand loads for a buddy's Cooper and I'm having issues. The gun is new and the test target that was sent was fired using IMR 4350 and 168 SMK's. I've tried dupicating the load and have not been able to get anything to group better than around 1.25"@ 100yds or 2"@ 200. I've tried different seating depths from .010 jammed all the way to .100 jumped.
I've even used the Berger 168 VLD's, 210 VLD's and a few of the Hornady 208 AMAX's. None have grouped better than the SMK's.

My buddy purchased several boxes of HSM ammo loaded with the Berger 168's and 210's. The 168's would not group better than 4" @ 100 and the 210's were way too hot(flattened primers and black smoke ring around a couple). If memory serves me right(at work right now) the HSM's were loaded with a .234" jump though. They were seated so deep that part of the ogive started in the case neck.

I know without a doubt I'm not flinching or having issues shooting the gun. It has a brake on it and is a pleasure to shoot. I'm certainly no benchrest shooter but have successfully worked loads up for other firearms that recoil MUCH more than this gun. I've been using a heavy front tripod rest and rear bags and have also tried a Bulls Bag with heavy sand.

The gun has a Ken Farrell one piece base and Ken Farrell rings holding a Nightforce 5.5x22 NXS scope. Base has been bedded and torqued as well as the rings.

Brass is HSM and neck sized and trimmed to length. I am not using a bushing die, just a standard RCBS neck die.

I'm getting to the point of contacting Cooper to see what they have to say. I know they shoot their test groups at close range but I'm wondering how many groups they had to shoot to get the one tight test group(pretty much one hole). Just thought I would probe the minds of some on here first.

Thanks for any help
David

 

[effendude]

I'd try some other factory ammo with traditional cup and core bullets, Federal/Win/Rem. If the same results, it would be time to get serious. Also, is the rifle torqueing in the bags? You are launching heavier bullets at a fair speed with a light rifle. Shooters often want to simply bag squeeze the rear bag and that style shooting isn't very consistent on larger caliber, fast twist calibers. The rifle may be moving differently each firing. Also check your action screws for proper torque.

Scott

 

[Larryh128]

Time to start checking things like action bedding and looking for shiny spots in the forearm. If you have the capability, I would spin the bolt on centers and check the lugs. 1/2 a thou on a bolt lug will do some nasty stuff.

 

[savagedasher]

If everything is tight a simple test change shooter. That will tell . Larry

 

[Zero333]

Swap the scope to verify it's not defective.

The proof target shot at the factory was done with the rifle in a vice, therefore it's not very realistic.

Try a different powder like H-4831. RL-25 is also accurate in the 300winmag

 

[bheadboy]

4" is a serious problem, to me that suggest a couple of things, CHECK THE CROWN
ammo - + try Rem/Win/Fed 165 or 180's - bullets that do not require long throat

as suggested, check the bolt lugs, coat the back of each with felt tip and then work the bolt to see if they show equal contact, if not stone the high one till they do, be very slow in this - little is a lot in result

take the time to double a $bill and run under the bbl and see if it is free back to the recoil lug, is there a sling screw in there that the bbl can bounce off on recoil take it out when shooting off the bag - shorten it

take the break off the bbl and shoot

check to see if the recoil lug is touching on bottom and free it if so also check to see if the rear of the lug is in complete contact with the bedding towards the but of the stock, if not this is a major source of tourque

check to see if the trigger body/bolt handle are touching stock anywhere

I would start - check the stock clearance, sling screw, bolt lugs, then try shooting the new ammo, it that does not help then the break off, and recoil lug clearance on its bottom, a

Bob

 

[savagedasher]

I work with shooters and help them with reloading . The first thing I do with a shooter that's gun isn't shooting good . I look at the target . If it doesn't have a pattern that is predicable . I changed the shooter . 99 percent of the time it works . Large gun tend to have big groups with new shooters. To find out if it the shooter load the gun with a fired case and video him shooting . Larry

 

[XTR]

Try more than one shooter. Heavy recoilers will mess with you.

The above mentioned torque is another thing to account for, esp in a light hunting rifle. They just don't ride bags like a competition setup. I came to really understand these phenomenon while working with my 45-70s, they just don't shoot like an 18lb F-TR rig.

 

[wapiti25]

clean the hell out of the barrel. May be copper fouling. Was the barrel broken in with one shot and clean? Get the barrel bore scoped when clean.

 

[effendude]

Guys, the rifle is new! Don't tell him to begin smithing on the rifle before we have eliminated simpler issues. I would be the warranty would be voided if some of the above suggestions were done.

Scott

 

[Jason Boersma]

I know exactly what you're going through, I had a cooper in 6br and it would shoot groups like that until I used Lapua brass then it shot just like the test target. You should try different brands of brass and try H1000 powder also.

 

[ericbc7]

Call Cooper before you do any material removal on this semi-custom rifle. I have heard good things about Cooper and would be surprised if they don't work hard to make this gun meet your expectations. Return shipping is far cheaper than the gunsmithing involved to fix a problem that should be covered under warrantee.

 

[davecb]

Thanks for all the reply's guys. I will definitely try some of the above mentioned "possible fixes". I won't go "smithing" on the rifle just because of the warranty issue. I will do some of the above mentioned checks that don't require that though.
I did do the dollar bill trick and the barrel is not touching anywhere. The front sling stud was removed before ever shooting the gun. I can tell the Bulls Bag definitely holds the gun tighter than when I use the front rest and rear bags. What I am not sure of is which method is better. Should it be held tight or should I let it recoil freely?

I absolutely know I am not having issues with flinching. We have done the "empty chamber" trick and I stay steady through the shot. My buddy has shot the gun too with the same results. I do have another friend who is an excellent shot so I might get him to shoot it as well. I know the gun is a fairly big caliber but it is really pleasant to shoot. May not be when I remove the brake though! It does seem to shoot a few rounds fairly well and then one will be out.
I have a factory Remington sendero in 7mm mag shooting 168 bergers. It seems to recoil much harder than the .300 and I am getting 2.25" groups at 425yds with it. I knew it shot well so I tried it while I was working on the .300 just to confirm I wasn't pulling the shots.

I have tried several different bullets, powder and primers but have not tried different brass yet. I have not tried the 4831, H1000 or Re22 though. I will give these a try along with some different factory loads.

As far as barrel cleaning goes, I'm using Wipeout foam and Montana Extremes copper killer. I cleaned the barrel after every shot for 10 rounds then increased to five shots and clean. I am now shooting 10 shots between cleanings. Have around 75 rounds through it now. I don't have a borescope but my patches are coming out clean when I'm done. I am using a Lucas bore guide while cleaning and a coated Pro Shot rod. I am very careful not to let the brass jag bang on the end of the barrel when it exits.

For a supposedly quality made rifle, this has been the hardest to get shooting. Hoping it doesn't have to go back to Cooper.

Thanks again guys.
Dave

 

[bheadboy]

Dave, you have done a great deal to eliminate possibilities, one major check which needs to be done early in such cases that remains and is not "smithin" is to do the recoil lug check,
take a felt tip and cote the rear of each side, then close bolt and rotate the handle up/down a time or two to let the lugs rub the action, remove the bolt and look

if the marking on the lugs are not uniform both sides, there is a serious problem, let Cooper deal with it if you don't want to but before you waste another grain of powder --that would be my suggestion.

Bob

 

[XTR]

I seriously doubt brass is making a ½ MOA difference in your groups.

I've never loaded for a 300WM so I don't know any "this always works" combinations like Varget and 175SMKs in a 308 but here is the process to get where you need to be:

What is your barrel contour? If it's a hunting rifle with a #4 or lighter you need to shoot no more than 3 shots and wait 30 minutes or you are getting barrel heat causing the POI to walk around. Hunting profiles are made for shooting 1 shot groups. If it is a light contour you may be throwing the 3rd shot.

Seating depth - find your distance to the lands with the bullet you want to shoot. Either start jammed and work back, or just go to .010 off the lands. We're not talking BR here, I've never had a bullet that would not shoot in a 30 cal jumping 10. I know guys who shoot 308s that hold right at ½ MOA at 1000 yards that just load to .010 off and shoot it. Some guns may shoot a little better somewhere else, but it's small, smaller than you need to worry about in a hunting rifle. (not talking about a finicky VLD here)

Powder - What ever you are shooting, work up, stay well below, like at least a grain, below where you see pressure. A 300WM is going to give you plenty of velocity, don't chase the top mark. You don't need it.

Neck tension - this one can be big. I'd get a Lee collet die. Size in two steps, body and neck. You say you are using a standard RCBS. Do you know your neck tension? How tight are they?

New Brass - RUN IT OVER A MANDRELL BEFORE YOU LOAD IT. New brass had notoriously tight neck tension. I've seen Lapua 308 that had nearly .010. That's ridiculous tight.

Bullets - VLDs have a reputation for finicky, SMKs or SGKs have tangent ogives and are a lot easier to get to shoot. Try the 165 SGK hollow point. I seem to recall reading it has a heavier jacket for higher velocity loadings. Out of the last hunting 308 I had they shot under an inch at 200 yards with almost no work. (like one load series, I jumped them .010)



At 200 yards what are you holding on for an aiming mark? If you are shooting at a big shoot n see you aiming mark is pretty large, that leaves a lot of wiggle room on the hold.


Download and print these:
http://accurateshooter.net/targets/targetaccshooter.pdf

or these:
http://accurateshooter.net/targets/6mmbrvert.pdf

edit: and Take effendudes advice, try shooting some factory ammo and see what it does. Reloading can create a whole host of accuracy issues if you aren't doing it the right way.

 

[effendude]

Have you called Cooper yet? I have heard they are great with customer service. This is a SAAMI cartridge, in a repeater action. Before you waste a bunch of time and money on components, I still recommend a box of factory ammo before doing anything else. It should shoot SAAMI spec ammo with enough accuracy to tell you its potential. Every Cooper I have handled shoots well, right form the start.

Scott

 

[Dusty Stevens]

Shoot it at the same distance they did for the test target

 

[Shynloco]

Have you called Cooper yet? I have heard they are great with customer service. This is a SAAMI cartridge, in a repeater action. Before you waste a bunch of time and money on components, I still recommend a box of factory ammo before doing anything else. It should shoot SAAMI spec ammo with enough accuracy to tell you its potential. Every Cooper I have handled shoots well, right form the start.

Scott

Dave,
IMHO I agree 100% with Scott. If you have a new rifle (any make), I'd shoot a couple hundred rounds of Factory Ammo through it before ever trying to tune a load. The Sierra Manual under the 300 Win Mag section (pg 601) shows the powder they used for their "Accuracy Load" using 168 gr SMK's is 77.2 grs of MagPro that created a velocity of 3000 fps. Now their test rifle was a Savage with a 1:10 twist, similar characteristics as a .308. I've not shot or loaded for a Cooper so I don't know. But my rifle never liked a jammed bullet and shot lights out with a hefty jump. But check your barrel twist to verify the twist rate. I have used IMR 4350 before BUT NOT in a 30 Cal rifle with much success. Worked better in 6.5 bullets. But I claim no expertise with Coopers, other than I think they make a beautiful rifle. Good luck.

BTW...keep in my mind that a Test Target shows you the potential for your rifle that was test fired in a completely different atmosphere, probably in vice set-up and not from a open bench setting. And you don't really know what batch number of powder was used. So don't get too carried away in your reliance on the Test Target. Different conditions deliver different results.

Alex

 

[Zero333]

I have a hunting 300winmag Savage 111 and I could not get better than 1 moa with handloads until I shot Federal Premium 130ttsx (chrono'ed at 3,550fps in the summer and 3,500 in the freezing cold). It has a skinny barrel contour #twig and probably whips like hell, so I theorize the 130ttsx leaves the muzzle before it's fully whipping ?

 

[LHSmith]

I've been trying to work up some hand loads for a buddy's Cooper and I'm having issues. The gun is new and the test target that was sent was fired using IMR 4350 and 168 SMK's. I've tried dupicating the load and have not been able to get anything to group better than around 1.25"@ 100yds or 2"@ 200.

I think Dusty nailed it on the head. What's the big mystery here. The test targets are 3 shot group shot in Coopers basement at a longgg 47 yards. You are shooting at twice the distance (or more)....in "conditions" /they shot in a controlled environment. Your results are very close to their "guarantee" of 1" @ 100 yards .