New 6BR Barrel, 1-8', Short Throat

[RugerOldArmy]

I ordered a 6BR Norma three grove 1-8" twist SSSM barrel. When I ordered it, I asked for a short throat, so I could seat bullets in the lands. My mistake was not sending a dummy cartridge with the 87 Gr VMax and 107 Gr SMK that I intended to use.

Assembled the rifle yesterday, and used the Stoney Point tool to check the throat. It's very short. 75 Gr Vmax,s) are a jamb fit at 2.200" OAL.

Lesson learned, send a dummy cartridge.

Questions:

- Will small bullets be accurate with 1:8"? I'd have preferred a 1-12" or 1-14" for 75Gr Vmax.

- Will 1-8" allow the 75 Gr Vmax to survive the trip down range?

- When the throat wears, will this work out allowing me to move up to bigger bullets?

- Or should I get the chamber re-reamed?

- Anybody with any good experiences shooting small bullets with a fast twist? What bullets?

Thanks much for any advice...

 

[Freestate101]

Just run a throating reamer in for the desired clearance.

 

[NorCalMikie]

Got 2 1-8 6BR barrels. One Shilen and one Pac Nor.
The Pac Nor was throated to a dummy round. 80gr. V Max with the base at the shoulder/neck junction. The Shilen was throated to "their idea" of a short throat. 80s are 1/2 way down the neck. I like as much neck contact as I can get.I wanted to shoot 55s and 60s but you can't have both in the same barrel.
Even with the limited amount of neck contact the lighter bullets are "very" accurate. As the throat wears you will be able to load heavier bullets. Shoot what you've got and make plans for your next barrel!

 

[RugerOldArmy]

No reamer FreeState, I'd have to send it back to Pac-Nor.

Thanks Mike. I'm hoping to give it a try this weekend. Maybe it'll work out. I'm hoping the Vmax,s) will hold together. At the moment I only have 107 SMK, 105 Amax, 87 Vmax and 75 Vmax, so I'm a bit limited on test bullets. Optimistically, it might not be too bad, most of the time I can only shoot 100-300yards.

 

[NorCalMikie]

Pick yourself up a box of 80gr. Bergers. Set the OAL at .005 jam.
Start with 29.0grs. of Varget and work your way up to 30.5 and watch the bug holes show up.
That will put the base of the bullet at the shoulder/neck junction. Lighter bullets won't have as much neck contact but you will really be surprised at the accuracy. Myself and a shooting buddy are doing 100yds. and having way too much fun. The only problems you might have with the V Max bullets is not having enough on hand!

 

[SplatCat]

A short throat will allow you to seat your bullets farther out as erosion takes place. I read an article a few years ago that advised considering asking the barrel maker to include a short throat because of throat wear. May not be a major consideration for one of the smaller cartridges where throat wear is less of a problem, but for a 6BR, I would have no problem ordering the short throat.....I am not speaking from a bench rest standpoint...purely from a varminting position, where many, many shots might be taken in a day.

 

[daveb]

My last reamer has a .060 throat and I can seat the 105 Lapua with the boattail at the neck shoulder junction. Must be the vld drag syle ogive. The nosler ballistic tip 70 gr bullets are magic in my 1_8 twist.

 

[RugerOldArmy]

A few findings for those that helped....did some testing.

I did get out Saturday, sighted in, and shot some test groups with the 75 Gr VMax at 2.200" OAL. They were pretty solid in the lands, and closing the bolt was a bit harder than on neck-sized cases that needed the shoulder bumped. I was concerned that if I did not fire a round, ejecting and extracting might leave the bullet in the lands.

I tried two 'shoot the barrel in and fire form' loads, 30.2 and 30.5 Gr of Varget and WSR primers. No pressure signs at all, and both loads shot about the same, maybe 3/4 MOA avg, and about a 1/3 of the groups near a 1/2 MOA. Some of this could have been my shooting...it was a long winter.

I never did have much luck with V-Max,s), so I ordered some 70 Gr SMK BTHP, and some 80 Gr Berger FBHP Match bullets. Got them today. After some playing, I can seat the 70 Gr SMK about .010 into the lands at 2.135", and loaded 10 ea at 31.0, 31.2,31.4, 31.6, and 31.8 gr of Varget. With luck, I can try them out next weekend.

I'd like to load the 80 Bergers to test too, looks like the ogive will be at about the same point as the 70 SMK, seated about the same in the neck, but I didn't measure yet. I need to scrounge up some load data for the Berger Bullets, and even with a half dozen manuals, I haven't found it yet.

It looks like, worst case, the short throat 1-8" would be a pretty good varmint barrel. No wierd flyers, cleaned very easily, very very little copper.

I just can't seat the 105 A-Max or 107 SMK without the boattail being below the neck shoulder junction. I might have to save them for the next barrel.

 

[NorCalMikie]

The "key" word. The next barrel! Couldn't seat both light and heavy bullets in the same "short throat" chamber so I ended up with one that will shoot heavier,Shilen) and one that will shoot lighter,Pac Nor). Can't have enough rifles.
I had noticed that the Shilen throat was getting longer so I got a shorter throat on the Pac Nor.
80gr. Bergers seem to be the best in weight for the Pac Nor. Right at the shoulder/neck junction. Just about anything that weight or heavier works well in the Shilen.
Try every bullet you can get your hands on in the weight that works for you. Same with powder.
Just about out of AA2230C so I got some AA2230 and AA2460. Also have Varget, N 135 and N 140 if I want to try it.
Don't care for the feeding of the Varget through my powder measure but it's really good stuff. Your targets will show for sure.
Just get out and get more rounds down range.