6mm Blues

[tom baker]

I need help my freind has a custom 6mmRem with a 26" Shilen heavy bbl with about 100 rds thru it. This thing shoots 3"-4" groups, It had all the signs of a bad scope so I tried the scope on my 308, one hole groups. Its beaded, the screws arnt to tight,I tried 70gr and 100gr bullets with 3031,4831 and it shot the same could it be that the barrel isnt broke in yet or am I trying the wrong powders, I know the gun builder and have shot his work, dont think the problem is there. Please Help I dont have much hair left to pull

 

[Randy in Va]

Did it shoot when it left the smith? If not put it on him before going crazy.

If it did, what has your guy done to change it?

 

[jcpython357]

stich, I shoot a 6mmRem. with 39.6grs. H4895 under 75gr Sierra , factory Rem. barrel, I'm getting in the 2s and 3s. Varget, 4895, VV140 and RE 15 should work as good with 70-75gr. bullets, for 90grs. and over try 4350 range powders, I had Rem 7400 6mm that would group an inch for 5 shots @100yds. with 41.5grs IMR4350 with 100gr. Hornady, yes a 7400! I was truly amazed, too.

Jay.

 

[jcpython357]

stich, Whats the twist in his rifle, and what kind of stock? Jay

 

[tom baker]

Its a 1 in 10 with a custom made walnut thumhole made by the same person that made the gun.
Tom

Semper-Fi

 

[Guest]

Is the dispersion horizontal, vertical, or both?

 

[tom baker]

Hey S1, Three seam to be in about a 2.5-3" group and two will be about 10 o'clock 2" futher out, it dosn't seem to matter if you clean it or not.

Tom

Semper-Fi

 

[Guest]

Check your firing pin/bolt assembly, make sure you are not getting a light primer strike. Next I would inspect the last inch or two of barrel very carefully, the closer I got to the crown, the harder I would look. Your base/mounting system would be the third thing I would triple check.

 

[tom baker]

Hey S1, are you talking about the base being tight and the rings being alined or parallel with the other? I am going over to his place after work and check the barrel and crown, I checked the primer strike while I still had hair

Anyway I really thank everybody for the help and will let you know what I find

Tom

Semper-Fi

 

[SDS]

Well, the 70-grainers ought to shoot with that twist at least.

First thing to do is to check and make sure all the scope mounting screws are tight. That includes the ring screws, the dovetail clamp screws and the base screws. Sounds like you already did that. Barrel screwed into receiver tight? Holes in target are round? Crown on muzzle has no dings? Ammuntion has decent runout out of dies? Ammunition still has decent runout (use dummy round!) after trip in and out of chamber?

The thing that gets people with custom stocks is variations in the thickness of the stock and screw specifications.

If the stock is vertically shorter than the factory stock, when you tighten the screws, it might be that all you are doing is clamping the magazine between the triggerguard and the receiver without ever grabbing the stock. So the action rattles around and you get oversize groups. Even if you bed it, it probably won't be tight enough. The solution is to take some height off the magazine, which should be a free-floater between the triggerguard and the receiver. If the magazine is integral with the triggerguard, there should be clearance between it and where it contacts the receiver. If you can remove the magazine and test fire it as a single shot with the screws reasonably tight between the triggerguard and the receiver, you can check to see if that is the problem.

If the screws are too long for the new custom vertically shorter stock, they may bottom in the holes (depends on receiver design) before they clamp the triggerguard and the receiver in the stock. To fix this you take some length off the bottom of the screws as needed. I try to be 1/4 to 1/2 turn short of the bottom of the hole when tight. Make sure the bottom of the hole is not filled with junk left over from inletting or bedding.

If the screws have some shank above the threads that is of a greater diameter than the threads, the shank won't enter the hole in the receiver, and maybe the receiver and triggerguard won't clamp the stock between them. For this problem you can switch to screws with less shank and more thread, or (sigh) get the die and the die stock out and cut threads on the shank.

3-4" groups sound like something is loose somewhere, especially after you have switched scopes to one you know is reliable. Let us know what you found when you get it to shoot.

Saving money on haircuts means you can afford more gun stuff. Keep pulling....

 

[Savage99]

SDS has good advice. After the easy stuff like loose sights it's usually the bedding.

It's almost never the loads with groups like that.

 

[tom baker]

Well first off, I want to thank everyone for all the good advice, having said that this is where I stand; I have checked the scope mts for trueness and thightness, primer strike, barrel from one end to the other to include chamber and crown, screw thightness on action and there length, I checked the neck runout it was exactly what my nosler book said it should be .276 and the head of the shoulder .430 that was .001 over what the book said I think thats ok primer strike is exactally in the center, the rifle is full length bedded so as I see it Im back to removing the bedding under the barrel and back to the loading bench. What do you think??? And by the way after 20 yrs in the Corps I gave up haircuts for a spitshine rag

Tom

Semper-Fi

 

[SDS]

Right now would be a good time to say I don't know much about Remington actions.

My best theory about what the rifle is doing is that the barrel is slapping the stock on firing. The zero-clearance full-length bedding is letting this happen because it is so close to the barrel. So out it goes. I wouldn't expect, though, that that by itself would be enough to explain 3" groups. Maybe 80% of the problem, though.

I would free-float the heavy barrel (dollar bill clearance) with a pad of epoxy one inch long in front of the recoil lug.

When us potatoheads say runout, we mean, is the case with a bullet in it radially symmetrical around the longitudinal axis? Put another way, we mean, if you grab one end of the cartridge and spin it, does the other end wobble or just go round and round?

 

[tom baker]

Hey SDS, its a 98 action, no don't shun me

I know most of you find them crude but I have a few that shoot pretty good, any way thats what I plan on trying as soon as my friend aproves it and then we will start loading for it again. I will let you know what happens.
Tom

Semper-Fi