6mmbr groups

[AussieRob]

I have just purchased a .243 Savage low profile stainless varminter and had it re-chambered to 6BR minimum SAAMI chamber no neck turn and use Redding s type dies for reloading. I tried all of the 6mm loads but could not get any groups less than 2" with Sierra, Noslers from 70gns to 90 grains and used different ADI powders 2207, Benchmark and 2208,Vargent). My other rifles shoot better than 1" at 100m shooting on the lands or just a few thou off. It was not till I backed the 85 grn Sierra Game Kings off 20 thou that groups shrank to .5 inch or better at 100m and 2.5 inches at 500m,which I was pleased with). I tried the 75grn Speer hollow points that started me on the 20-25 though clearance before groups started to tighten. NB barrel has the standard 91/4" twist for a .243 and I only lost 1" from the standard 26" barrel when it was re-chambered.

Any thoughts as to why this rifle likes a long lead to the rifling. I thought it might have something to do with the barrel harmonics but would appreciate any thoughts on the subject. I would also like to try for a higher ballistic coefficient bullet and wonder if anyone knows what the upper limit of what this twist might be. I currently shoot 85gr Sierra Gamekings 20 thou off lands using 29.1 grans of 2208,Vargent).
I like to shoot the "Fly" but need a higher ballistic coefficient bullet to be more competitive as most of the guys shoot 7mms, 300 Rums or magnums and a few .384's. I have had a retinal tear and don't want to go to a high recoil rifle.

Have a great day

Regards

Aussie Rob

 

[JoePellegrene]

Rob,

None of the bullets you listed would I consider using if I wanted to shoot for the best group, but they would all make decent hunting bullets.

Why don't you give the 95 grain Bergers a try they are Match Grade Bullets with a .514 bc and you can still hunt with them.

Regardless of how the previous bullets shot I would start with them jammed hard into the lands and work back for there.

The 95 grain bullet is about the limit for the twist you listed.

 

[AussieRob]

Joe/Donovan,

Thanks for your replies.But I still have no idea why this rifle likes a long lead compared to my others. 85 grain Blitzkings seem to be a good compromise and I have shot 2.1" at 500m with these but the wind does play havoc with the lower BC of these.
The 90grain Nolsers should work but I have not hit a good combo yet.

Joe by the way the Berger 95's in Aus seem to run out at about $30-$35 for a pack of 50 which is getting up in cost when I shoot 500odd rounds a year in 6br not counting 500 in .223 and 200 odd in .222.

Thanks again for the replys and have a great week.

Regards Rob

 

[fdshuster]

AussieRob: We think alike: I also rechambered a Savage 12BVSS .243 to another 6BR, PTG reamer, .272" no-turn neck. Lost 7/8" of barrel length. Twist is 1-9.25, and yes, there are reamer & tool marks across the lands & grooves, as seen w/ my borescope. Copper fouling was a problem when new, but used JB and "hand lapped", and now at 675 rds fired, copper is minimal. A really big improvement in group size resulted in properly bedding the receiver in the stock: the factory "bedding" is a joke: just a hole in the stock into which the receiver fits. Tighten the front guard screw, then watch the rear of the receiver bend-down as you tighten the rear. Flat-topped "pillars" were not even contacting round bottom receiver. Brownells "Steel-Bed" was used for a superior bedding job. Tried Varget with so-so results, but the rifle has really "come alive" using 30 grs. of N135, 85 gr. Match H.P. flat-base bullet, seated .020" off the lands. 5 shot groups @ 200 yds will average 1/2 moa.

 

[gambleone]

With a .272 no neck turn, varget 29.5 to 30 gr, 107 smk 20 thou off lands with a 1/8 twist lapua brass & that seems to be the sweet spot in most 6br's. If your doing your part.
gambleone

 

[Leeroy]

G'day AussieRob

I have just finished the load development for my REM 6BR. All though i have a custom 8 twist barell.
The 85 Gn SGK shot very well in my rifle <0.75 MOA, but only seated to just contact the rifling. The 70 gn SMK wasn't to bad either.
I now shoot the Berger 95 gn VLD's.. These shoot much tighter,0.2-0.3 at 100)and with the much higher BC have more down range energy and less wind deflection.
The bergers are a getting hard to get here in OZ but Parrabellum imports in Melbourne are now the new importers. They expect there first shipment by the end of this month.
Quoted price was around $60 for 100. Expensive, but for what you get in performance worth it in my opinion..

I would give them a try in your 91/4 twist barrel.

Cheers

Leeroy