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Post by csm19z5m on Jul 16, 2015 13:35:41 GMT -5
I know there are not a lot of members on this board yet but just curious about viewers thoughts concerning free bore. Recently had a 6BR heavy varmint rifle built by Jeff Hankins and finally got to start testing loads. While I was on my annual expedition out west I worked up a number of different loads and shot them in a variety of conditions and various ranges from 100 yds. to 500 yds. While being vary careful for signs of pressure which never happened it appears to me that, all other things being equal, some degree of freebore allows me to safely shoot loads in my rifle that others experience pressure signs when shooting. Now I am not saying this carte blanche and it is not meant as a golden rule or anything. But I simply did not encounter any signs of excess pressure whatsoever with any loads so far this trip with much more shooting to come. I have read so much about how 6BR bench shooters recommend no free bore when shooting the long bullets as they feel that free bore is detrimental to accuracy. I cannot disagree with any of them either as most have years of experience with the 6BR cartridge. I just wanted to get some other peoples perspective on the subject with my observation, antidotal as it is. By the way, the rifle that Jeff built for me is a trued Rem 700 SA with 26in. Krieger heavy varmint profile barrel in 10 twist with Jewel trigger and Shehane MBR stock. Optics are Leupold 8.5X25X50 scope with varmint reticle. It really likes the 58 gr. thru 79 gr. VMAX bullets and Nosler Balistic tips. I have so far shot various loads using Varget, H-4895, Benchmark, and V-135 with excellent results. The rifle has a no-turn .272 neck with .060 freebore. I initially thought this was excessive but can't argue with results so far and the consensus of those that have shot the rifle is that it will not have a measurable effect on barrel life either. We have fought the wind everyday and the sage rats are holed up right now so shooting a lot of paper and occasional jack rabbits. The rifle keeps shooting tighter and tighter groups at various distances (when the wind cooperates) with most five shot groups covered by a quarter with one quick three shot group covered by a dime at 200 yds and this was with 58 grain VMAX in slight wind. Everyone who shot the rifle remarked on how much they liked it. It is my first 6BR and it is becoming my favorite varmint gun. If anyone has thoughts on the subject of freebore I would appreciate your input.
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Post by airborneike on Jul 16, 2015 21:45:20 GMT -5
Your 10 twist barrel with .060 freebore is optimal for your BR set up. The 10 twist will shoot up to 87 grain bullets and maybe a little heavier if loaded hot.
Free bore is mainly determined by what bullet you are going to shoot and twist will limit the selection. An 8 twist Br will stabilize a 107 grain bullet but you need more freebore to use these longer bullets.
If you try to shoot longer bullets with a short freebore, the bullets have to be seated deeper into the case and here you can run into lessened case capacity and some pressure problems might show.
Most of us who have shot 6BR in competition use an 8 twist barrel and shoot 107 VLDS on or into the lands a tad. The reamer is made for a certain bullet and freebore of .120 or so is not uncommon.
Are you able to touch the lands with the 79 grn bullets? Excess freebore doesn't generally cause pressure problems but in some instances might inhibit accuracy a little.
The 6BR is very easy to load for and it seems to want to shoot most anything very good. One of the most accurate rounds out there in my estimation.
You might try some Xbr8208 powder. My brother uses it and he says it is his favorite.
Jeff set you up right for the twist of your barrel IMHO and sounds like an excellent build.
Mike
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Post by csm19z5m on Jul 18, 2015 23:59:32 GMT -5
Free bore is mainly determined by what bullet you are going to shoot and twist will limit the selection. An 8 twist Br will stabilize a 107 grain bullet but you need more freebore to use these longer bullets.
If you try to shoot longer bullets with a short freebore, the bullets have to be seated deeper into the case and here you can run into lessened case capacity and some pressure problems might show.
Most of us who have shot 6BR in competition use an 8 twist barrel and shoot 107 VLDS on or into the lands a tad. The reamer is made for a certain bullet and freebore of .120 or so is not uncommon.
Are you able to touch the lands with the 79 grn bullets? Excess freebore doesn't generally cause pressure problems but in some instances might inhibit accuracy a little.
The 6BR is very easy to load for and it seems to want to shoot most anything very good. One of the most accurate rounds out there in my estimation.
You might try some Xbr8208 powder. My brother uses it and he says it is his favorite.
Jeff set you up right for the twist of your barrel IMHO and sounds like an excellent build. Mike
Thanks for the feedback. I cannot touch the lands with a 79 grainer unless I seat the bullet out farther than I like. The rifle was built to shoot varmints only and I don't intend to shoot out much over 400 yds. with it. It seems to be performing better and better each day as I tweak the loads. It will shoot way better than I do typically. I have been surprised at how well it shoots the very light bullets though, even in the wind out here. I have been ramping up the loads slowly so far and have been surprised at how well it shoots just about everything I stuff in it. Never had a rifle so unforgiving and easy to tune. Now if we could get the Eastern Oregon desert wind to cooperate a bit more I wouldn't complain about anything:) So far it seems to like the 58 Grain VMAX and 70 Grain Noslers the best and I could quit tweaking right here and be happy I'm sure but we will see how far I can push it this week. As for the freebore issue, I know the guys shooting the long bullets like to touch or jam slightly and if they find that it adds to the accuracy so be it. I just see so much written about signs of excess pressure and so much of it seems to originate with the long bullet shooters it makes me wonder. Thanks again for the powder tip, will give it a try.
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Post by deadeye on Jul 19, 2015 18:01:04 GMT -5
I cannot touch the lands with a 79 grainer unless I seat the bullet out farther than I like
I might add if you have sufficient neck tension maybe .010 seating(into the brass neck) could be enough-of course depending on true bullet diameter & neck tension depending if you are jamming or jumping with a particular bullet that likes such load
example- a few yrs ago I had a shilen .243 barrel that 55gn noslers were only able to seat .010 in the brass & barely touch lands-shot in the .2's or less until I warped the brass with that hot load @ 4034fps
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Post by Richard on Jul 30, 2015 9:36:05 GMT -5
csm...........I shoot a 6mmbrx (shoulder pushed .100" forward and neck shortened .100")in 600 yard competition (with airbornike's brother Larry) Actually I used one of Larry's cases to set the head space on my rifle when I built it (I do my own chambering). I am shooting a 8.5" Brux barrel and seat my bullets about .010" off the lands. One excellent shooter was going .040" off and getting good results. Not everything with these rifles is "cut in stone!" As Deadeye mentioned, you do not necessarily have to have your bullet seated way down in the case. For varmint and BR your bullets, in all probability, will be handled with care and not stuffed in your pockets so only a small amount of the bullet shank in your case is not a bad thing. I have a 6br LR XP-100 pistol (1 - 14" twist) I built and the reamer is for the newer Lapua brass with the longer necks. The original Rem. br brass is about .050" shorter. I get results as good using the Rem. brass as I do with the longer neck Lapua brass and I keep my bullet to ojive exactly the same. In other words, I do not change the seating die when I switch brass. And BTW, there is only .050" of the 65 gr. V-Max bullet being held in that case with the Rem. brass. This reamer is configured with a more generous freebore to accommodate longer/heavier bullets but will work with the shorter ones if seated with minimal bullet grip. Richard
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