30' barrel really needed?

[ptf18]

List: I rebarreled a Savage BVSS-S Model 12 to a 6mm/22-250 using a Pac-Nor prefit SS best they had 30" barrel. I havent been impressed with the results Ive got from the rifle since the rebarrel although perhaps its me.

Ive chronied my loads and get anything from 2700-3100 fps with SMK 107s. No pressure signs at 3100 fps but I feel that was plenty fast for ranges out to 1k. I settled on load that gives me a velocity around 2950 but Im not impressed with the accuracy. Perhaps its me...

Anyways I was wondering if the 30" barel is abit to long and wondered if I should cut it back to.... 26"??? Although I shoot a 30" Palma rifle which needed the barrel lenght to drive the SMK 155s fast enough at 1k Im wondering if this 30" barrel on my 6mm is really not needed.

Any thoughts before I get the hack saw out?

Thanks,
Lester

 

[Forum Boss]

Who cut the chamber? Try sorting those 107s or switch to the Lapua 105s...

I suggest you don't touch the barrel until October. There's something very interesting in the pipeline from Lapua. If you rechamber you'll want the full length.

Also, with my Savage, accuracy improved when I cleaned up the bedding a bit and cranked on the action screws pretty tight.

 

[Cheechako]

ptf

What powders are you using and how much? A 30 inch barrel will allow you to shoot the 105 - 115 grain bullets at 3000 fps with low to moderate pressure. If you cut the barrel back to 26 inches you will then have to use a hotter load to get to 3000 with the resultant increase in barrel wear.

 

[ptf18]

List: THe chamber was cut by Pac-Nor as part of the prefit service they offer. Ive been using Varget and AA4350. Does the SMK 107 really need to attain 3000 fps to perfore well at 1k?

Lester

 

[Cheechako]

lester

Don't give up on that barrel without trying a couple other powders. The 50 grain 6mm cases seem to work well with H4350 but the AA powder should be close to that. Varget is too fast IMHO. Try a couple of powders that bracket 4350 in burning rate. Also try match primers if you haven't done that already. The Sierra 107 seems to shoot best at 2950 to 3050 fps. That doesn't mean it won't shoot at higher or lower velocities but you would have to try it to see what the nodes are in your barrel. If you plan to shoot 1000 yards you don't want to go too low otherwise you'll give up all the ballistic advantage of the bullet.

When you say accuracy wasn't good, exactly what did you mean? Group size at what distance? What type of rest setup? How much shooter error?

Also, beg or borrow a handful of some other bullet like the Berger 105 or the DTAC 115 and try them. Maybe your barrel doesn't like the 107, although most barrels do.

Ray

 

[ptf18]

Ray: Thanks. I shot the scoped rifle yesterday but this time off a rest,front and rear) in the prone position w/o a sling. Ive been doing my load testing at 200 yards. I tried ,again) Varget from 31gn to 32.5gn in 1/2 gn increments. The 32 to 32.5 gn shot the smallest group which was about .75 moa and previous chronograph readings gave a AV FPS of 2870. There were no signs of over pressure. E-Z extraction, no ejector marks, etc.

My rest techniques leave abit to be desired.

Perhaps I should continue increasing Varget powder charges or do you think I should drop the Varget get and try the AA4350 I have or even a slower powder.

Makes me want to put the 6mm away and get the Palma out.....

Lester

 

[Cheechako]

lester

In looking at powder burn rates I guess Varget isn't as fast as I thought. I know it is a very good powder for the 6mm BR and the 308W so maybe it's worth some additional tests. If you can get up to 2950 fps it would be a much better 1000 yard load. Or, if a smaller increase in velocity brings your group size down to 1/2 MOA or less i'd go with that. At 1000 yards accuracy is so much more important than a few feet per second in velocity. Also try seating bullets on a jam and backed off .010 to .020". Sometimes that all it takes with those long skinny bullets. Don't give up. Good Luck.

Ray