338 Lapua Zero Help

[Long Dog]

Problem: I cannot get my rifle to group. I have shot 251 rounds through the rifle (to include break in). I have worked through the below loads and cannot get consistant groups with rifle. There are no consistency to the groups - Some are flat, some are verticle, some start to look like a group then a flier (or two). Most groups are ~1.5"-2" at 100 yards. Occasionally, I get a group inside 1", but cannot get it to repeat. I have tore down and remounted the scope, swapped to different scopes (US Optics and Leupold), still no consistency. I have gotten some great load data with single digit ES/SD which I would expect to shoot well, yet they still are inconsistent. I am beginning to think it is me, but the rest of my rifles will clover leaf at 100 yards. Has anyone had a gun that gives you fits like this? Could it be just a finicky rifle and I have not found the magic load? Any recommendations, besides keep working through it? I have heard that some rifles won't group at 100 Yards but will start grouping at 200 Yards, anyone experience this?


Rifle: Remington 700DM w/ 28" Broughton 5C barrel (1:9.4 twist) W/ 6 port brake (long Shot Rifle Built); Nightforce 5.5-22x-56mm w/ Nightforce Rings on a DE 20 MOA base

Loads:
300 SMK - H1000 88 Grains to 94.5 grains in .5 increments - bullet length 3.680 - 3.650; FED 215M primers

- 300 SMK - Retumbo 92 - 98 grains in .5 increments - bullet length 3.680 - 3.650; FED 215M primers

 

[Long Trang]

The fact that you 'occasionally get a group inside one inch' means your system is functioning. It is likely those times that whatever is causing your problem is not applicable when you get those tight groups.

Typically, when a shooter has such a problem, it is attributal to shooter error. However, you indicated that the rest of your rifles cloverleaf at 100. Are you accustomed to the 338? Is the rifle comfortable to you to shoot? Is it too long? Too heavy? These are contributing factors which can cause a shooter to blow groups. Have someone you know who can shoot well test the rifle. If they can't group, then you've eliminated the 'shooter error' aspect...then move on to the next likely candidate. The scope.

You said you swapped out scopes and their bases. Did you ensure you had ample torque on the scope systems? (Please don't get upset, remember...you need to cover all possibilities) are you using the scope correctly?

Once you've verified it isn't the shooter nor the scope, then look to the ammo. Some rifles like a certain type of load rather than others. You've tried two. Have you tried standard factory loads? My guess is it is not the ammo. Nevertheless, be thorough.

Finally, the rifle. Are your action screws torqued properly? If not, you may have undue stresses on the barrel. I've personally ran into this problem and it's amazing how bad grouping can be. Are you firing cold bore shots?

Most rifles are well capable of grouping at 100, so your problem appears to be a major one. If you have eliminated all other possibilities, save the rifle, and you can't determine what is wrong with it, I recommend having a qualified gunsmith check it out and look for a defect.

Good luck.

 

[BountyHunter]

1. Check the bedding. Is it stress free? Does the barrel move slightly when action screws are loosened.

2. Have someone else shoot it and see if it is the headspacing (operator)

Really that should be done first to determine it it is the gun system or you. Then you can eliminate the possibilities with the gun/scope.

3. already mentioned swapping scopes. Try that also.

4. If you are getting 1.5-2 at 100 IT WILL NOT tighten up at longer distances no matter it is said on the internet.

5. Double check brake to make sure not bullets are making contact with it.

BH

 

[Kevin Cram]

4. If you are getting 1.5-2 at 100 IT WILL NOT tighten up at longer distances no matter it is said on the internet.

Wrong
A 1 1/2" - 2" group isn't good at all but try the load that was giving you the best numbers (SD) on the chronograph and back up to 200 or 300 yards. There's a pretty good chance the bullet isn't stabilizing. Give those heavy 338's a chance settle in. My 338 Chey-Tac will only shoot 3/4" - 1" groups at 100 yards but it will shoot the same size groups at 300 yards. See what that does and let us know. Worse case send it back to Chris and let him know what's going on.

 

[liltank]

I'm going to throw in the stock option. Is it a factory stock bedded, or an aftermarket? Just wondering if the stock is flexing due to not enough strength in material.

Tank

 

[Bravo 4]

Loads:
300 SMK - H1000 88 Grains to 94.5 grains in .5 increments - bullet length 3.680 - 3.650; FED 215M primers

- 300 SMK - Retumbo 92 - 98 grains in .5 increments - bullet length 3.680 - 3.650; FED 215M primers

You have only tried one bullet and two different powders, try a different bullet. Or try seating them longer.

4. If you are getting 1.5-2 at 100 IT WILL NOT tighten up at longer distances no matter it is said on the internet.BH

Wrong
A 1 1/2" - 2" group isn't good at all but try the load that was giving you the best numbers (SD) on the chronograph and back up to 200 or 300 yards. There's a pretty good chance the bullet isn't stabilizing. Give those heavy 338's a chance settle in. My 338 Chey-Tac will only shoot 3/4" - 1" groups at 100 yards but it will shoot the same size groups at 300 yards. See what that does and let us know. Worse case send it back to Chris and let him know what's going on.

Kevin, I believe BH means that the bullets will not magically get closer together because the bullet goes to sleep...and he is correct. If the groups are opened at closer range then that amount of damage is done. The groups will not shrink is size, but can in terms of MOA. A gun that shoots 2MOA at 100 yards can be a 1MOA gun at 200 yards if the group doesn't open. But that guns groups will not magically go from 2" at 100 to 1" at 200. No matter what is posted on the internet.

 

[liltank]

I agree about powder too. Try some IMR powders such as the 7828 or 4831. I have played with Hodgdon and Alliant. I went back to IMR and my groups shrunk and all shots were 3/4" or less with equivalent loads in the aforementioned powders. I am going to give ramshot a try and see if anything is equal or improves. If not, its back to IMR for good.

Tank

 

[Kevin Cram]

If the groups are opened at closer range then that amount of damage is done. The groups will not shrink is size, but can in terms of MOA. A gun that shoots 2MOA at 100 yards can be a 1MOA gun at 200 yards if the group doesn't open. But that guns groups will not magically go from 2" at 100 to 1" at 200.

I agree with how you described it. I'm not saying the groups will shrink in size but by moa it may. A 1 1/2" group at 100 yards is terrible, it's 1.5moa group. But the same 1.5" group at 300 yards now a .5moa group, that's not too bad. Who shoots a 338 Lapua under 300 yards anyway?

 

[436]

I'd say go with rechecking the brake... not just for strikes.. but the design may well not agree with the cartridges pressure curve at the muzzle.. Try it with the brake off, if it's consistent no matter what the group size; then think about another brake design.
just my .02
436

 

[Bravo 4]

I'm taking a stab in the dark on this but guessing the 3.680 is your max OAL to fit in your magazine...and you are trying to keep it a repeater instead of single loading? If that's the case you might not get your cake and eat it too. I can load the 300smk to fit in my mag but accuracy goes to h@ll. Lots of possibilities being thrown at ya. Have you spoken to the smith that put it together? Did he shoot it at all?

 

[Long*range*Lapua]

I have to agree with Bravo 4. If you are forced to use a magazine then you may not be able to seat the bullet close enough to the riflings for optimal accuracy. My 338 Lapua AI would only group about 1 inch with the bullets anywhere from touching the riflings to .006 away. Finnally (after wasting lots of powder and bullets), I began seating the bullets .010 from riflings and can consistanly group both 300grn SMK and Bergers in the .2's and .3's. Just a thought.

 

[Long Dog]

Lots of great advice. I will work through some of it and report back. Talked to Chris as well and he gave me some thoughts. More to follow after the weekend shoot.

As for the COL. To the lands it is 3.786 and I can only get 3.680 due to the mag length. I am going to stack some to the lands and see what I get. If it improves, seekings bottom metal is in order

 

[rscott5028]

I had the same problem with a Weatherby Mark V once. After converting it to Winchester Model 70, it works great. ;-)

Good luck with all the excellent advice above.

 

[Long Dog]

The good news story here is the problem is solved. It took a trip back to the gun builder for him to rework the gun. "436" was correct on the brake. The brake was reamed too tight. The gun plumber opened the brake up and voilla, problem solved. Went to the range yesterday and shot 5/8" groups at 200 yards with two of the 4 loads I shot. The ES/SD leveled out and muzzle velocities increased (slightly). Needless to say I was estatic.

I almost forgot, I also got a Seekings Precision detachable magazine system put on the gun to help with the bullet length problem. Not so much of a problem now and I can stretch the bullets to the bullet-ogive magic length of 3.005. I will do some more load tweaking [seating depth] to confirm this is the optimum length.

I appreciate all the help and advice everyone gave me in helping solve the problem.