Strange Berger 105 Hybrid Fit

[Hoot]

I have this new for me but pre-owned, 6BR rifle that I got recently. I'm getting ready for the eventual arrival of spring up here, figuring on 2nd week in April. For each caliber that I experiment with, I have a log book and in the back, I list the different bullets I have for that caliber and their initial Distance To Lands DTL. Among the 12 or so bullets I have in 6mm, I observed that the Berger 105 Hybrids touch at 2.30 COL but a gentle nudge and the bullet then eases further to a hard stop at 2.47 COL. (not really forcing it) I accept that nuances in chambers exist but this is only the 2nd bullet in this rifle that I've found that exhibits what I call "a glove fit". The other one being the Lapua 108 OTM Scenar. The others are pretty much touch = stop unless I force them more than I'd like.

With that history comes my concern. With the 105 Hybrids, the guy I got it from said that they like to be .010 off the lands. At the 2.30 COL touch, the bearing portion of the shank is below the Neck to Shoulder (NS) junction but at the stop 2.47 COL its comfortably beyond. So, again, trying to play to the rifle's strength on the first outing, I wanted to reproduce his recipe for success minus a few tenths of a grain of Varget and work up. My dilemna is whether to jump the bullet .010 back from stop or back from touch. He didn't specify how he determined DTL. I can jump them .010 back from stop and the bearing surface is still beyond the NS junction..

In my situation would you say "Damn the torpedoes" and stick with .010 before touch or go with before stop? I'd like to keep the bearing surface outside the NS junction, so I'm leaning toward back from stop.

Obviously, this hobby comes with few guarantees where someone else's recipe plays the same with your bullets and powder, though they and the rifle are the same. Heck the experimentation part of the process is what floats my boat, so I won't be crushed if I have to go back to the drawing board after this first outing. The cumulative wisdom here is always appreciated.

Hoot

 

[Hoot]

Did I fart in church or something? No opinions in the house of plenty?
Well, I wound up loading them at hard stop plus .002 allowing for tolerances.
We will see how they fly in about 3 weeks (hopefully).

Hoot

 

[Rat Rifle]

Sorry Hoot, I meant to answer but stuff came up. I did a seating test a while back with 105 Hbds. Fired 16 two shot groups at 100yds. Started at touch and went out .003” at a time. Did this to .030” out. Touch was one hole. -9 and -12 were two holes touching. -18 was literally one hole, but was not good on either side, so that node is very narrow. -.030” was two holes touching. Then I finished up further out. -60, -65, -70, -75, and -80 were all two holes touching. Got 200 loaded for next week’s match. Going to final seat them to “touch”. Good luck to You. Let us know how You do.

 

[Sheldon N]

IMO there is no way that your “touch” point is 170 thou different than a hard jam. You are feeling something else besides the lands. Could be multiple things, carbon ring, tight freebore, or maybe your brass test case has a bit of runout causing the bullet to rub against the side. I would start your tests in the area 20-30 thou off the hard jam number.

 

[Dusty Stevens]

If this is a new barrel you may be feeling burs in the leade

 

[Ned Ludd]

A relatively "tight" freebore will generate that exact result, as would a bullet slightly over diameter. The first light "touch" you feel is probably not the bullet ogive contacting the rifling. Rather, it is likely the bullet ogive touching the leading edge of the tight freebore. It is the second "hard" stop you feel that likely represents the bullet touching the lands.

I have several .223 Rem F-TR rifles with very tight freebores that all behave exactly this way. It does make finding "touch" with a Hornady OAL gauge (or similar) approach a bit more difficult, because you have to push hard on the little plastic stick to get the bullet moving into the freebore after the initial contact, but still be able to stop it at the second [harder] touch without jamming it several thousandths further into the rifling. Nonetheless, it's totally doable with a bit of practice.

 

[1shot]

I found the word "touch" as used by us to be a highly variable measurement. One guy says touch, the next guy says "kiss". Are they the same? I, for one do not like to be in that area. I start firmly against the lands, and work my way back. I want that initial dimention to be easily found and repeatable. A secondary benifit to this aproach is that is a worst case scenario in regards to pressure. As you seat the bullet deeper in the case, the pressures decrease.
I hope this helps,

Lloyd

 

[Hoot]

The cat woke me up for breakfast and I'm not fully awake. He's lucky my wife loves him so much.

Those kind of poignant ideas was what I expected when I first started this thread and I appreciate all of them. The barrel is far from new but there is only a very small ring of fire cracking, where I would call the freebore, begins. I'm talking tiny, as in the width of mechanical pencil lead. If my technique and/or Stoney Point OAL gauge case were the culprit, I would have expected similar behavior from more than 2 of the 13 bullets that I have. Admittedly, the 2 bullets where it manifests are both scenar styles, as opposed to the others. Its safe to say that an appointment with some Dykem is in the immediate future, later this morning, after I'm fully awake. First however, I gotta watch the Zoomcast of my nephew's wedding in The Netherlands at 0830, because my wife can't figure those things out on her laptop.

One thing worth mentioning and perhaps some creative member has already done this, is the first thing I did when I got my Stoney Point, many moons ago, was to remove that plastic push rod and fabricate one out of brass rod stock, Much better feel and I don't need to worry about the tip of the thumbscrew scarring it so easily. Second thing I got was that dagnabbit 5/16-36 tap. Those case prices add up.

If that brass rod stock idea is something that nobody ever thought of, I could post a how-to thread (with pictures) on making one. I doubt I can find the original plastic push rod after all these years, assuming I didn't toss it.

Back to bed...

Hoot

 

[Rat Rifle]

I like to go by the “square” land mark on the bullet, as suggested by Lou Murdica. As soon as you back off from that, the loaded round will fall out of the chamber easily.

 

[Hoot]

Well, they're hitched. A lengthy process but completed. My nephew, who has 10X the money I have tied up in firearms, got the better part of the deal IMHO. Nuff about that...

I'm not lying awake at night agonizing over the behavior of those two bullets in my barrel. I've seen this before in a couple of other calibers that I reload for and always with long for caliber bullets. Truth be told, they all shot very well. That will remain to be seen for a few more weeks. The perma-snow is down to only knee deep now with daytime temps bobbing up above freezing for a while each day. Its the nights that rule the snow melt. When they dip down into the single digits, like its been lately, that days warmth is negated and everything refreezes. Evvebtually, the night time temps will creep up and the snow will creep down.

I'll pursue the bullet marking process for my edification and will report back once I get out to the range.

In case anyone's wondering, I have scrubbed that tiny fire cracking ring with all manners imaginable and feel confident that there's no carbon ring hiding under it.

Hoot

 

[Hoot]

This is weird. I did thr marker test on the 105 Hybrid and it came out with a roughly defined circle all the way around it. No individual rifling marks like I've seen with newer barrels. My first instinct was this is a carbon ring imprint but looking at the area with a Teslong, there is literally no carbon to be seen, just that pesky rough looking what I would call, fire cracking ring just past where the case mouth ends. It's hard to see 3D through a right angle borescope so who's not to say it has height? I will address that tomorrow with some more scrutiny. I'd hate to be wrong about the "not crud on top of a carbon ring" proclamation I made earlier but I'm going to find out for sure. I may give it the JB compound and bronze wool treatment. The previous owner definitely ran it hard, I'll get a picture or two of it.

Hoot

 

[Rat Rifle]

Yep. Somethings going on there ???

 

[6MMsteve]

lead angle I found that the 140 ber target matches perfect with my 260.... with what little I know about chambering and leade or whatever you cal it, the degree of the start of the lands is that what it's called i get confused sometimes

 

[22BRGUY]

Did I fart in church or something? No opinions in the house of plenty?
Well, I wound up loading them at hard stop plus .002 allowing for tolerances.
We will see how they fly in about 3 weeks (hopefully).

Hoot

That corned beef and cabbage from St Patty's day will do it every time.

 

[Hoot]

In this image, you can see the beginning of fire cracking beyond the end of the case mouth. The dark space between the two is not carbon. It's quite clean down to the metal. Its just a shadow. Happily, my suspicion that it was the source of the rough ring around the bullet, was wrong.



That fire cracked ring is not raised but rather lower than the rest of the freebore, which measures .189. It looks like the beginning of the rifling has eroded from previous use and the rise of the rifling is very slow. At least slower than what I'm accustomed to seeing in my other barrels with less mileage on them. There is a slight amount of fire cracking in the rifling for a few inches, albeit barely discernible. Given the mileage on this barrel, if it winds up not shooting as well as I'd like, I'm of the opinion that having it set back and rechambered may be throwing good money after bad and I'll just order a new Shilen Select Match barrel for it from Northland Shooter Supply. Jim is a good guy to deal with.

Hoot