338 bullet stabilizing question

[simplicity]

This is my first post on the site and I have learned alot from reading everyones posts on subjects that I needed info on. So here is something I'm having trouble figuring it out. I'm getting back into long range shooting I have been shooting a 338 win mag ever since I was 12, my longest shot was at 1078 yards on a glass 1 liter bottle. I have recently bought a savage 110fcp 338 lapua with the HS stock. I have mounted a vortex pst 4-16. I have been shooting berger 300 otm's over retumbo. (90-93grains) adjusted OAL from on the lands (3.850) to being able to fit in the magisine (3.765). The best I can get is for groups at 100 is about .7-1. moa. My question is I have read some places that this caliber can shoot tighter groups at 200-300 then it can at 100. From what I have read this is due to the bullets not fully being stablised at 100 and they "settle" in to their flight path. I'm just wondering how true this statement/myth is? I'm just getting a bit discouraged only because this is the best I can get out of the rifle. My other rifles give me this accuracy or much better but getting out to beyond 100 I have to get out to places other then my range. The rifle now has about 100 rounds through it now should the barrel be broken on more to acheive better results? My other concern is resting the stock while shooting I have shot it both off a granite rest (cast iron with a pad) and off the bipod. Resting the buttstock on either my hand or a sand bag gives worse results then if just shouldered off the bipod (hopefully I'm explaining this correctly) What are you all using for media/ material in your gun rest bags? ie are they soft/ hard. loose/tight etc. I'm just trying to find answers from folks that know more about this subject then I do. Thanks for any info.

 

[varmintH8R]

I am not a ballistician, but I struggle with the "bullet settling in" theory (which I too have heard). You can always test it by moving out to 300 and seeing what you get.

It sounds like you tried OAL adjustments - did you check out the sticky on Bergers at the top of the reliading forum? It has a good system to try.

I have a few guns that just don't like certain bullets. You might try some 300gr SMK's and see if your rifle has a preference.

The rear bag I use is filled with sand, and is STIFF. Seems weird that a bag isn't an improvement over an unsupported rear, but weird has been known to happen . . .

 

[simplicity]

I have a hard time beleiving the theory myself but hey if there is soemthing different out there I don't know about. I am all about learning something new. I got the Berger OTM's (grabbed 200 of them) just due to thats all I could find in 300 grain. I'd like to get some SMK's but just can't find any. I have try'd 250gr game kings just cause I had soem on hand from my win mag components. I don't know what to say on the bag theory either. AllI can think of is Harmonics of the whole rifle. I do have more 250gr game kings to try I might shift gears and go try them some more. Also the oher info I didn't throw in is I'm using BH brass (50 tat i have been using for development) I did pick up 20rd of hornady brass and 100rd lapua brass (I have't touched it yet till I get something that shoots decent). i am also using RCBS dies, I have always had great luck with their dies so I thought I'd try them.

 

[MontanaRifleman]

There are arguments for and against the "settling out" theory.

My own personal experience is that I often shoot better MOA groups at 200-330 yds than at 100. I.e., if I shoot 1/2" @ 100, i might shoot 3/4" @ 200 with the same load.

If your shooting .7 - 1 MOA @ 100 you might have something else going on there?

As suggested, shoot to 200 and 300 and see what happens.

 

[Broz]

There are arguments for and against the "settling out" theory.

My own personal experience is that I often shoot better MOA groups at 200-330 yds than at 100. I.e., if I shoot 1/2" @ 100, i might shoot 3/4" @ 200 with the same load.

If your shooting .7 - 1 MOA @ 100 you might have something else going on there?

As suggested, shoot to 200 and 300 and see what happens.

I agree with this 100 % and have seen it on more than one rifle.

Jeff

 

[Engineering101]

I use RCBS dies and have found that the resulting ammo is not concentric most of the time. Runout can be as bad as 0.020" but is usually around 0.005" to 0.007". I use a Hornady concentricity checker/fixer to bring it within 0.002". I'm getting 0.75" five shot groups at 200 yards with my 338 RUM with 2 different bullets. I wasn't until I started paying attention to concentricity.

 

[simplicity]

Well on the concentricty note I ordered a set of forster benchrest dies. i have been using a Forster benchrest seater for all my 308 loads and it has worked well and all the match loads i load with it shoot quite well out of my AR10. I will give them a try to see if any differences come about. Thanks again for the advice and if someen else has something that might help by all means chime in.