Hi guys,

Not sure if this is better suited here or reloading section...but here goes.

TC Dimension, 6.5c

From the factory, using the hornady OAL gage, I was coming up very short of the spec overall length using 130gr nosler accubonds. I was also getting fairly flat primers using PRIME factory ammo.

I sent the barrel back to TC, they "polished the chamber" and sent it back.

used the hornady tool, same thing. I was 1/4" short of reaching the 2.825" COAL with the 130 ab's.

I took it to my smith and said please lengthen the throat so i can at least seat these bullets somewhere close to spec if i wanted to shoot them with zero jump. He did, i think...

So here's my question... How hard do I need to push on the rod on the Hornady gage? I can still clearly feel engagement at my short throat with the accubonds, and my new Berger Hunting VLD 130s....

However, if i push harder, both bullets will move farther and then really stop. But, there are slight marks on the bullet by doing so. So they will seat out longer, but there is still some engagement in there. To me, there should be no real engagement and I should be able to push with light pressure until i feel the rod stop, and that should be where the bullet starts to engage the lands. Is this correct? Do I need to take it back and have the throat recut a bit?

I was out with my buddy recently, and using the light pressure method with his Tikka t3 6.5c, he has quite a bit more freebore than i have. I was also shooting some of his factory Hornady 143 eldx, and his had nice round primers, my 3 rounds had flat primers.

I hate the way the Dimension platform looks, but love the way all my other barrels shoot. This one is being quite the pain. To seat the bullets where I'm off the lands even a little bit I have to compress even mild powder loads.

Any advice? Am I doing this all wrong? Thank you.

Your description of how you you use the OAL tool seems to be just how I’ve always used mine; I’d say you’re doing it correctly. Have you tried seating the bullets back to see if you still get flat primers? OAL doesn’t matter unless it’s so short you can’t fit the powder charge your after.

You answered your own question; if you are getting marks on the bullet, it is touching the lands. With any reasonable push on the bullet, it should come to a dead stop; you can't engrave copper by pushing by hand unless you are Arnold.
And as for "spec"; realize that no maker is bound to follow any spec whatsoever; including the suggested ones kept by SAAMI. Those are just for reference. Of course, most do basically follow them; also realize there are some pretty sloppy tolerances allowed too.
Throating reamers are only $50 so, depending on what he charges you, I would just get one and do it myself. In a lathe.
Ask your guy what throat angle he is using to re cut it. It should be .199 long freebore with a 1 degree 30 minute angle.
So, you need your throat lengthened.

I am getting marks, but i am getting those marks that are 1/4" long, which is about how far i can push the bullet when i put real pressure behind it. So i sort of seem to have a "not quite" .264" throat when my smith lengthened it. after that 1/4", it stops for real, when it is really jamming into the lands.

would a Tubbs final finish kit open this up a bit? is it worth a damn just in general for a somewhat new factory rifle anyway?

Thank you for your help, I really appreciate it!

quote:

Originally posted by dpcd:
You answered your own question; if you are getting marks on the bullet, it is touching the lands. With any reasonable push on the bullet, it should come to a dead stop; you can't engrave copper by pushing by hand unless you are Arnold.
And as for "spec"; realize that no maker is bound to follow any spec whatsoever; including the suggested ones kept by SAAMI. Those are just for reference. Of course, most do basically follow them; also realize there are some pretty sloppy tolerances allowed too.
Throating reamers are only $50 so, depending on what he charges you, I would just get one and do it myself. In a lathe.
Ask your guy what throat angle he is using to re cut it. It should be .199 long freebore with a 1 degree 30 minute angle.
So, you need your throat lengthened.

Then your "smith" has a reamer that is not large enough for your bullet. It needs to be at least .0005 larger than your bullet.
I know nothing about the kit about which you reference, but if it is any sort of throat lapping idea, NO.

ONe problem I have delt with over the years is how few rifle have a matching magazine and chamber, including factory guns, so your left with matching bullet seating to what will fit the magazine and the chamber will be long, or visa versa..

I like to seat a bullet one caliber deep, such as .308 in a 30-06, then do what needs to be done to the magazine..A 7x57 seat is .284, not written in stone but works pretty well in most custom guns..

dpcd:
yes the final finish is a bullet "lapping kit", with 40 lapping bullets
http://www.davidtubb.com/final-finish-bullet-kits

i've never tried such a thing, didnt know if it was a legit thing to do or not. I'm now guessing not

Ray:
to seat the berger bullet where it currently first makes contact, would be seated 0.611" into the case...makes for a pretty odd looking creedmoor round. I'd be thrilled to be able to seat it .264" into the case. Luckily for the switch-barrel gun, i can just get a long action magazine for it so cartridge length isn't an issue.

In a 6.5, a throat which is .2645" in diameter should always be just fine. However if you have a bullet which is .2646", it won't be so fine. This is where gunsmiths and reamer makers can run into problems. In an attempt to produce a precision throat, they may run into problems due to varying bullet diameters. I would be curious to know what the diameter of the bullet is in this particular instance.
A guy can mess around with this sort of thing for a match rifle and it may even pay off. For a hunrting rifle though, reliable function should probably trump precision. The relatively long, tapered throat, as used by Mauser may actually be the best throat for most applications. Some of my most accurate hunting rifles have been throated this way and they have shown themselves to be very tolerant of variations in ammunition. I am no longer able to proclaim any one throat configuration to always be better than anything else. I have come to realize, the older I get and the more I experience, the less I know for sure.
It IS possible to lap or polish a throat but it's not a practice I recommend or like. Regards, Bill.