Throat length for 6BR? Pics

[MDM]

I'm building my first 6BR on a Savage action. Everything is assembled and and I'm checking my COAL for my chamber. I keep get a measurement of 2.385 as my max COAL for the 107 SMK's I wanted to use. Is this excessive throat length? See the pic to see how far the bullet is seated to touch the lands. Doesn't seem like much bullet in the neck, but this is my first, so I really don't know.

 

[NorCalMikie]

I already told you what I thought now go shoot that thing. ;D

 

[MDM]

HA! Thanks Mike. I hadn't seen your reply on that other site.

 

[tclaunch]

Not to long at all. I have throats that the bullet has only about 1/8" grip and they shoot great. I had rather deal with a longer than shorter throat 10 to 1.

 

[NorCalMikie]

The "advantage" of having a shorter throat over a longer throat would be that as the throat wears from more bullets being fired, you'de have to seat the bullets to a longer OAL then where they were set when you started from. You might end up running out of enough neck contact. With the throat being shorter, you can shoot lighter bullets and go heavier as it wears. I'll take shorter anytime.

 

[zullo74]

I'm with you Mike. I'll take a shorter neck to begin with and chase it as it wears forward.

 

[MDM]

So what would be normal throat wear? For example, I have roughly .25" neck contact. How fast will it take to get to .10" neck contact? I know it's all subjective, just speaking in generalities.

 

[zullo74]

For the throat to wear .150" I would estimate 3-4 thousand rounds. YMMV

 

[NorCalMikie]

I ended up checking the OAL to the lands after about 200 rounds on my 22 and 6BR. Had a change of about .025 to the lands. I shoot 45s and 50s with "excellent" results and going to 60s won't be a problem. Matter of fact I got rid on all my bullets in the + 100 grain range because I figured it would take "a long time" before I would be able to use them.
From the looks of things you'll be shooting those bullets without any problems. Even with a shorter neck contact I think you'll be surprised at the accuracy. And the throat wear might depend on how hot you're running your loads. You don't need to be fast to be accurate. You'll find 2 different nodes. One lower and one higher. I prefer the lower load range. Your brass will last a lot longer and you won't have to deal with higher pressure as the weather warms up. And like Joe says, YMMV, Mike.

 

[queen_stick]

I was at the 1000yd shooting school a couple weeks ago in Williamsport. Jason Baney was talking about throat erosion in his 6BR. I don't know that the numbers are exact, because I didn't write it down, but I think he said he had about .002" erosion from 2500 rounds. (hopefully JB sees this and corrects me if I'm wrong). These little 6BR's are attractive for a lot of the same reason's the .308win's have been so popular, but with an advantage of reduced recoil, and disadvantage of crappy feeding out of magazines

 

[fdshuster]

MDM: I have some of those same 107 Sierra MatchKings loaded, and just took the over-all-length. Mine, seated to touch measures 2.382". Taking into account the variations in bullet lengths, probably the same as yours. Looks like the bullet contact length with the case neck is .167", and as Mikie said, just go and shoot 'em. Plenty of bullet/neck contact. My reamer was a .104" freebore and now with 1,210 rds. fired I'm having problems with my favorite bullet, the 95 gr. Berger VLD, just clinging to the front of the case mouth, so sent the reamer back to Dave Kiff and had it reground to a zero freebore. You have a lot of "life" remaining if you use the 105's and 107's.

 

[MDM]

MDM: I have some of those same 107 Sierra MatchKings loaded, and just took the over-all-length. Mine, seated to touch measures 2.382". Taking into account the variations in bullet lengths, probably the same as yours. Looks like the bullet contact length with the case neck is .167", and as Mikie said, just go and shoot 'em. Plenty of bullet/neck contact. My reamer was a .104" freebore and now with 1,210 rds. fired I'm having problems with my favorite bullet, the 95 gr. Berger VLD, just clinging to the front of the case mouth, so sent the reamer back to Dave Kiff and had it reground to a zero freebore. You have a lot of "life" remaining if you use the 105's and 107's.

After checking and rechecking I think the max oal is 2.403 for the 107 smk's. Seems long considering my barrel is new and yours has 1200 rounds down the tube. Anyway, I 'm going to shoot it and be happy. I'm getting ready to bed the stock to see if I can get the groups more consistent.

 

[deadlyswift]

I concur! As others have said I am liking the fact of a short throat. I recently had PT&G grind me a reamer for 6br. I went with the 95gr. Berger VLD. I seated the bullet approximately .050 above the shoulder neck/junction. The reamer came to me with a .021 freebore. I should be able to shoot the 95's for awhile. then moving to the 105s or 107s in the future. Conclusion, longer barrel life and accuracy with my desired bullets!

 

[deadlyswift]

I already told you what I thought now go shoot that thing. ;D

Like Mike said! Load up and go shoot it! Looks like you have plenty of bullet in the neck, and you should have plenty of barrel life at your starting depth!