Hand finish chambering

[bentongunclub]

I just put together two rifles in 6.5x55 Swedish Mauser. Adams & Bennet barrels on sale for $89.99. I hand finished the chambers with a PTG chamber finishing bit to acceptable tolerances using appropriate GO NOGO gauges. I am using Norma brass in both of the rifles and during load development I identified a confusing issue.

One barrel is ok with brass trimmed to 54.85mm but the other needs the brass trimmed to 54.45mm or the bolt is VERY hard to close. COAL for both using Hornady seating tool is the same for both (2.965" with Sierra 120 gr Pro Hunter (Twist of 1:8.5)) I even checked the projectile necks with layout fluid to look for marks and 2.965" is good.

I need to talk to PTG about the chamber finisher because it came with a ding in it that leaves a ring on my brass when fired. You can see the ding with the naked eye. My burning questions is: Is the chamber finishing tool supposed to cut forward of the shoulder and advance the neck also? What happened? Anyone else got any ideas (other than buy a more expensive barrel)?

Once I got the brass length issue identified I can now shoot 3-5 shots inside a nickel at 100 yds.

 

[Jim K]

I don't know about a special chamber finishing tool, but normal reamers (rough and finish) cut the chamber neck and the leade (throat) as well. You do need to make sure the chamber neck is the right diameter because if it is not large enough to allow case neck expansion, pressures will skyrocket.

Jim

 

[bentongunclub]

Diameter(s) seem to be good. The problem is with the length in the neck portion of the one barrel.

I don't have a problem with 54.45mm. I am just wondering why, with using the same tool by the same person, aren't things the same.

 

[rcmodel]

54.85mm but the other needs the brass trimmed to 54.45mm

How much is that in American inch measurements?

Some of us are really Metric Challenged.

And I don't have a single book that gives SAAMI case dimensions in MM.

rc

 

[evert]

divide by 25,4!

54,85mm's is 2.15944882"

54,45mm's is 2.14370079"

 

[Seedtick]

mm/25.4 = inch

.4 mm = 0.015748031496062992125984251968504"

~ .016"

Seedtick

 

[rcmodel]

Well, it sounds like the chamber neck is too short then.

SAAMI Max case length is 2.165".

Or, 54.991mm.

rc

 

[dirtyjim]

they are different because you reamed them by hand, instead of in the lathe.
i've seen a few chambers cut sloppy by hand reaming, i did it myself before i knew better.
the main problem i've seen with hand reaming is people putting side pressre on the reamer and cutting the base oversize.

your reamer shouldn't have any nicks in it, if it came that way it should have been returned. did you buy it through midway ot through ptg?

 

[bentongunclub]

dirtyjim - i'm pretty sure i ordered it from ptg. I am new to this and did not notice a nick until my fired brass came out with the ring on it. I guess i should say bump instead of nick because the ring on the brass is slightly raised indicating a cut into the chamber and brass expanding into the cut. Probably in the real of 0.001". I have not cut anything with my 30-06 finisher yet and will inspect it more thoroughly before I use it.

 

[dirtyjim]

where exactly is the ring? if its near the base you probably cut the chamber oversize by putting a side load on the reamer.
some of the a&b prethreaded & short chambered barrels are also not very well centered at the factory. i've seen a 6.5x55 barrel where the chamber was cut about .025 off the centerline.

 

[fguffey]

I cut chambers, before cutting the first chamber I was told "Measure often, no one knows where they are when finishing the chamber, so! Check often" and I thought to my self "That is the dumbest think I have every heard a machinist say", just maybe we are not talking about machinist. For the most part most of the information is repeated by someone that that heard the information from someone repeated the information they heard etc., etc., etc..

Before I finish a chamber I short chamber it .015 thousands (under a go-gage length chamber), I install the barrel, assemble the rifle and head for the range and road test it WITHOUT A GO-GAGE, I did not say I can not use a go-gage to check the length of a short chamber, I am saying I do not use go-gages, they are nice, not necessary and, I do not know of one shooter that shoots gages, they all shoot ammo.

Instead of purchasing gages, I make gages, press, shell holder and a full length sizer die with the companion tool to the press, the feeler gage, , again I do not grind dies, I do not grind shell holders, I size (short chamber) cases from .015 thousands shorter than a go-gage chamber to cases as long as a field reject gage in thousands. With a press, die, shell holder and feeler gage, and I do not get hung up of the 14 threads per inch thing.

When someone tells you the only way to ream a chamber is with a lathe, smile, nod your head approvingly, carefully back away and after that avoid them, I am lucky, in the real world I am not surrounded by those that think the world revolves around them.

I have depth micrometers, depth gages, dial calibers, anyhow, once I establish the chamber once, I know where I am, I know how far I have advanced the reamer, I know how far to advance the reamer to finish, when I cut a chamber I do not use SAMMY as an excuse.

F. Guffey

 

[dirtyjim]

i've cut a few chambers myself and i've fixed a few other have tried to cut, i've also botched one chamber.
the main thing i see on botched chambers is the chamber being cut oversize causing the brass to bulge at the base. the two main causes for this are hand cut chambers and floating reamer holders. for every chamber botched on a lathe i see at least 10 that are botched by hand.
i would only hand ream a chamber .010 or less, anything over that & it would go in the lathe. the lathe is not the only way to cut a chamber but i would have to say that it dramatically increases your chances of cutting the chamber correct.
the only chamber i botched on a lathe was simply because misread my depth mic and cut the chamber .025 to deep but since the barrel was in the lathe i simply faced .025 off the breach face & set the shoulder back the same. it took a whole 5 minutes to correct it, if i would have been hand reaming i would have been screwed.

i do have to agree with fguffy on the Measure often b.s. thats intended for people without any measuring tools who are trying to cut a chamber one turn at a time.

when i cut a chamber i've already figured the go gauge protrusion down to the thousandth of a inch. as soon as i make a cut i check the go gauge protrusion with my depth mic then set the reamer stop for dead on then i cut the chamber to finish.
some people like to stop about .010 short and finish by hand, i've seen people get chatter by trying to hand ream that last .010 or .015.

i will say that chambers in stainless barrels absolutely need to be cut in a lathe, especially the stainless that l.w. uses. you flat out cannot cut the chamber in a l.w. stainless barrel by hand and get a decent finish.

 

[bentongunclub]

dirtyjim, I agree with your opinion(s) on hand vs machine. Hand finishing is OK with me too. I have the technicalities down. I kept good thumb pressure on the bit and if the mouth of the chamber is out of round it is a miniscule bit.

Also, thinking about the ring on my brass. I have resolved that it is not a bump but rather it is a visual phenomenon. I speculate that it is due to slightly raised distortions (like the rim of a crater is raised) at the edges of the nick on the finishing bit. These cause scratches on the brass that give the appearace of a raised band. I will post a photo of the brass and the nick on the bit one of these days.

 

[Howard Roark]

Sounds like a piece of swarf got under a flute of the cutter and caused a gouge in the chamber.

Hand finishing a chamber is OK if done properly. It takes practice to be able not leave a score mark when retracting the reamer. Keeping it turning while withdrawing it is the key.

 

[Fleet]

RC, to convert mm to inch, simply type "54.85mm in inches" in the Google search bar. Works for most any conversion.

 

[Slamfire]

Once I got the brass length issue identified I can now shoot 3-5 shots inside a nickel at 100 yds.

That is great accuracy. With groups like that, I would learn to live with trimming the brass down.

some of the a&b prethreaded & short chambered barrels are also not very well centered at the factory. i've seen a 6.5x55 barrel where the chamber was cut about .025 off the centerline.

Gundrilling is not precise. I have talked to a number of gunsmiths and one barrel maker. Gun drill bits wander from end to end on a billet.

The barrel maker, he spins his blanks between centers and holds the most concentric for target shooters.

He had one krieger barrel he installed for a Palma shooter. The thing shot so far to the right that it used up all the windage on the guys rear sight. The barrel was taken off.

A bud wanted a cheap barel long range barrel and here was this Krieger barrel. The barrel maker turned the shoulder so the barrel was rotated ninety degrees on the new action. This fixed the windage problem and the barrel shot excellent groups.

And that is what matters.