New Problem

[wnroscoe]

Leading up to now, all of my chambers have been great. The advice here on BR Central has no doubt been the best anyone could hope for. The problem is this, after indicating my barrel in as close to .0000" as I could get I started to chamber. The barrel is a .277"/.284" Krieger and I used a .2766" bushing on the reamer. After chambering the barrel and firing a test shot the fired case measures .559" at the web. Spec says fired should be .555". The reamer is a PTG and appears to be .555" at the web. I used a pusher like the one Mike Bryant uses with a Sinclair case holder clamped in the flat of the reamer shank. During the reaming process the reamer tracked fine, no wobble or anything else that would cause alarm. My question is this, if the tap handle wasn’t clamped on the reamer shank square or in the flat of the shank square and it allowed the pusher to push harder on one side of the reamer than the other could or would this allow the reamer to cut an over sized chamber.

I checked the Tail Stock alingment with a test bar and test cuts, the test bar had zero taper.

This is the first chamber that I've had this happen on, all others have been dead on. Thanks,

William

 

[4Mesh]

almost certainly yes, side pressure somewhere caused the chamber to be oversized at the rear.

While cutting a straight test piece is usually a good indication of how well the tailstock is in alignment with the ways, it does not represent anything concerning the alignment of the headstock to the tailstock. It is entirely possible to have the headstock NOT pointing directly at the tailstock, yet cut a straight part because the tailstock is in alignment with the "front" of the headstock or center being used. In other words, let's say for example the headstock was at an angle to the ways, or, the headstock was higher/lower than the tailstock. You could easily still cut a straight test part, yet have issues with holding size when chambering due to angled entry.

Still though, I'd say side pressure is more likely your cause. If this is a WSM, .5586 is the sammi spec so don't worry too much about the dimension issue unless you have other reason to do so (dies, brass, etc).

Considering you saying that this is the first one like this, another possibility could be you got a chip on top of the ways and now it's stuck under the tailstock way surface. This would lift the tailstock slightly, and could possibly contribute to this sort of thing. When things are important, check that there's no gunk under the tailstock. From time to time I do this when getting a bit too hurried as I pull the tailstock back when working on quickie jobs. Sometimes it lifts the tailstock slightly and it doesn't take much to get a chip under there.

 

[Mike Bryant]

William, did you drill and bore out most of your chamber or let the reamer cut the complete chamber from start to finish? If you ream the complete chamber, I'd suggest pushing the reamer for most of the chamber with a center and then switching over to the floating pusher to finish the chamber. As long as your tailstock is in alignment, there's not much need to use a floating pusher but it will help if there is a little misalignment in the tailstock. Horizontal misalignment can be pretty easily fixed, vertical misalignment is harder.

It sounds to me though that the bore on your barrel wasn't straight and that could be what caused your reamer to cut oversize. Two ways to go about this, one in indicating your bore in at the projected throat and driiling and boring out most of your chamber as I do or indicating the barrel in by moving the muzzle end back and forth along with indicating the chamber end using a long range rod and two indicators as Gordy Gritters does in his Grizzly video.

Either way should get you a good chamber if you have enough barrel left to cut off the chamber and rechamber. As to which is the better method, everyone has their preferences. It's easy to cut a good chamber in a fairly straight barrel, but the curved bores are the ones that cause problems.

Another thought, do you have a reamer spec sheet for your reamer? Is that where you are getting your specs or is it from a published spec sheet? If the barrel shoots well, then I wouldn't worry about it as WSM brass can be all over the place in dimensional specs depending upon when the brass was made. I've seen early brass that varied considerably in diameters from later production brass.

 

[Bnhpr]

Leading up to now, all of my chambers have been great. The advice here on BR Central has no doubt been the best anyone could hope for. The problem is this, after indicating my barrel in as close to .0000" as I could get I started to chamber. The barrel is a .277"/.284" Krieger and I used a .2766" bushing on the reamer. After chambering the barrel and firing a test shot the fired case measures .559" at the web. Spec says fired should be .555". The reamer is a PTG and appears to be .555" at the web. I used a pusher like the one Mike Bryant uses with a Sinclair case holder clamped in the flat of the reamer shank. During the reaming process the reamer tracked fine, no wobble or anything else that would cause alarm. My question is this, if the tap handle wasn’t clamped on the reamer shank square or in the flat of the shank square and it allowed the pusher to push harder on one side of the reamer than the other could or would this allow the reamer to cut an over sized chamber.

I checked the Tail Stock alingment with a test bar and test cuts, the test bar had zero taper.

This is the first chamber that I've had this happen on, all others have been dead on. Thanks,

William

Interesting William, thanks for sharing your experience.

A few questions:

Is this the first chamber you've done with this reamer? If not, were the others oversized?

How much of the breech did you face off or cut off before chambering?

Is it possible the barrel moved on you? Did you re-indicate after threading? What kind of shims do you use between the 4 jaw and barrel?

As a note, I did several chambers with the reamer in a drill chuck and got great chambers. I have switched to a "floating" reamer holder and have gotten good chambers still, but often wonder if the whole floating thing is a bunch of bull.

Thanks

Ben

 

[Rustystud]

William, William, William

It sounds like the electricinan is overtaken the machinist. Cutting holes is just like shooting. If the bullet doesn't start off straight it is not going to end up straight. You are working in more than one plane when cutting holes, one being concentric and the other being co-axial. Even though you are cutting a round hole the tooling must be square. Reamers are relatively long tooling, small in the front and larger in the back. They can flex in pre drilled/bored chambers. This happens in the juncture of the bearing surface and the throat. This can occure from bushing slop or shear preasure from the tail stock.

Here in the south where you and I hale from you have just demonstrated another way to "waller out a hole". The next time we talk on the phone I will expain were you picked up this habit. And tell you a simple cure.

Have a great weekend.

Rustystud

 

[wnroscoe]

Answers

I'll try to answer all questions. I did not pre drill/bore the chamber and I did cut the entire chamber with a finish reamer. Yes, the parent cartridge is a 300/270wsm and the spec sheet I was referring to is the one on 6mmBR.com. I asked the girls at PTG to email a reamer spec sheet to me but, they haven’t as of yet. All of my chambers to date have been dead on, not over sized at all.

I indicate with a PTG tapered range rod using bushings fit to the bore. I try to get as close to .0000" run out as possible. I indicate at two points on the rod, one next to the chamber end and once at the end of the rod. The rod goes into the bore and the bushing is at the throat area. I ream at 70rpm and never crowd the reamer. I ream / clean / lubricate .100" at first then .050" after the chamber has started.

This is the first chamber the reamer has cut, I use a piece of #4 solid copper wire for shim stock and I only faced off the breech enough for a smooth finish. I used a .277" bushing on the indicator rod and a .2766" bushing for my reamer.

Thanks to all

William

 

[jackie schmidt]

What Mike Said

One of the things I absolutly hate is when one of those "squirrlely jig" in the bore spots is right where the throat is going form.

That is why I adadament about predrilling, indicating the throat area, taper boring the chamber to darned near finish, and then using the reamer as nothing more than a final finish tool. That way, you are minimizing any affect that a crooked bore will have on the performance of your reamer.

If your reamer has a tight, snug pilot, and it does encounter a spot in there that is not as true as it should be, something has to give. What will usually happen is the runnout at the pilot end will be transfered to the entire reamer body, and since a reamer will not bend, it will cause the situation you are encountering. Deflection is something that is inherant to using reamers.

Last Week End, I had a bunch of my buddies come over and watch me chamber some barrels for them. I just do this for my shooting friends out at Tomball. Here is the way I explain the proccess to them.

Barrels are not straight. If they were, all of this we go through would be a moot point. But since they are crooked, (not bent), you have to figure out a way to get three places running dead true in a crooked hole.

I call it the "two point indicate method". You decide what two points you are going to indicate dead true, then you machine the third point to match these. I declare the muzzle end, and the throat, as my starting points.

I set the barrel up, and get the muzzle and as far as I can reach into the chamber end bore running dead true. I then core out the chamber using a .400 drill. Ths allows me to reach up into the area where the throat will be. I then indiacate this dead true. (don't be surprised if there is as much as .002 difference in that length as what you indicated before). I then kick my compound off at a pre-determined mark on the degree dial, and taper bore the chamber to where the reamer fits in almost 1/2 way. I then, using the appropriate pilot, ream the chamber. I go a little deep, establishing the best chamber I can. Then, I check the chamber with the indicator, (sometimes it will show a couple of tenths), get it running dead true again, and procede with all of the other machining operations.

Notice, this is backwards from the way many do chambers. As a machinist, I feel that the most difficult part of chambering is establishing the finiest chamber possible, dead true with what the bullet first "sees" as the round is chambered. I then do all other operations, which will then run dead true with this chamber.

Of course, I do only Benchrest stuff, mostly my own. As I said, I do a few barrels for close friends, and I can take as much time as I want. I strive to make every chamber exactly the same, so I can use the brass from one Rifle in the next.

I also strive to do this for my friend's barrels as well. It is a real pleasure to be able to interchange any case, in any Rifle........jackie.

 

[JerrySharrett]

Just got in from Knoxville. ORSA 600 yard rained out.

My first and quick guess is that the reamer is a SAAMII reamer ground on high tolerence (maximum chamber)?? This allows the reamer to be easily resharpened.

Nat, what is the SAAMII max on this chamber?

Try this, put the reamer in the chamber with the pilot bushing removed then press the reamer up to the chamber shoulder then see if you can feel a looseness at the back where the reamer intersects the chamber base.

 

[Con Cross]

Leading up to now, all of my chambers have been great. I checked the Tail Stock alingment with a test bar and test cuts, the test bar had zero taper.
This is the first chamber that I've had this happen on, all others have been dead on. Thanks,

William

Mr. William you appear to know what you'r doing. Still better option would be to pre bore the chamber body taper within 0.02" or less and finish the job with the reamer.

Con

 

[Rustystud]

Jerry

Dave Kiff's print showes .5586 at the bolt face and .5563 at the 200 mark.

William said he thinks his barrel slipped in the 4 gauge wire under the lathe jaws.

I told William to dust it down with some alum, eh.

He is setting it back as I type this response. I am sure William will give us a report.

I am not aware of a SAAMI spec on the 7mm x 300WSM. Maybe we should call and ask Rick Jamison.

Nat

 

[JerrySharrett]

Nat, the only thing I have is a virgin 270 WSM case. It is 0.550" just ahead of the extractor ring.

Where's Tooley when we need him? In Chattanooga doing a deer management show!!

His chucking on copper wire is not good especially for a case body with that much surface area. And then the Sinclair case holder could have caused some of the problem. The holder I use, a home made rig from ages ago, was bored and faced together. It doesn't take much to get a chamber base 0.005" oversize.

 

[wnroscoe]

All barrels mentioned have been Krieger.

Well, just finished chambering a 300RUM. No, I'm not setting back my 7/300wsm unless it's a dud. After indicating the RUM barrel in to less than .0002", off of the bore with the tapered rod and a .300" bushing I cut the tennon and threaded. I rechecked the run out and found I had .001" that needed correcting at the chuck and spider. Corrected that and cut my counter bore, rechecked again and had .0005" run out that needed correcting at the spider. Indicated back to less that .0002" and cut the chamber. This time I attached the handle to the round shank of the reamer, not in the flat as I did earlier. I also used a .2998" bushing on the reamer. The handle fit better and was straighter on the shank. I started the reamer with a dead center as Mike Bryant suggested and switched over the floating pusher about .750" into the chamber. When I was finished chambering the reamer was tight in the chamber, no slop or wiggle. My 7/300wsm chamber allowed the reamer to have a slight wiggle when it was finished.

Using a small snap gauge (telescoping gauge) I measured the rear of the RUM chamber after all was finished, it measured .5505". Chamber run out was zero


7/300wsm mistakes as I see them.

1. I didn’t check for run out after cutting the threads and counter bore
2. I used a .2766" bushing on the reamer and should have used a .2768"
3. I didn’t pay close enough attention to the reamer handle fit


Thanks to all for your help, that’s what I love about this site, the depth of knowledge that’s here and the willingness to help others.

 

[JerrySharrett]

Using a small snap gauge (telescoping gauge) I measured the rear of the RUM chamber after all was finished, it measured .5505". Chamber run out was zero


Thanks to all for your help, that’s what I love about this site, the depth of knowledge that’s here and the willingness to help others.

William,one other thing to consider. Get a few pre 1982 pennies (1982 and later are not solid copper). Instead of chucking on the copper wire, use the pennies. Chuck so that each penny is only holding by two chuck jaw serrations.

The fact that you are having to realign after turning and counterboring means you are having some movement of the chucked barrel. The fact that you are reindicating is a good practice though!

 

[Bnhpr]

If anyones interested, this was a brainstorm I had and is working well for me. It's 6061, ring, 1.250 ID and then slit with a slitting saw. Outside edge has .375 radius and 1/8" flat spot.

Stuff is moving less that <.001 so far.

I'm really thinking hard about Jackies method though....I may try that on a new sexy Broughton barrel I just got.

Ben

 

[wnroscoe]

William,one other thing to consider. Get a few pre 1982 pennies (1982 and later are not solid copper). Instead of chucking on the copper wire, use the pennies. Chuck so that each penny is only holding by two chuck jaw serrations.

The fact that you are having to realign after turning and counterboring means you are having some movement of the chucked barrel. The fact that you are reindicating is a good practice though!

I was using small brass shims before the wire. The problem was they didnt allow the chamber end of the barrel to move enough when adjusting the spider and the barrel would flex pretty good. The wire allowed the barrel to move just enough for adjustment but I like the idea of pennies, I'll give it a try, thanks.

 

[JerrySharrett]

I was using small brass shims before the wire. The problem was they didnt allow the chamber end of the barrel to move enough when adjusting the spider and the barrel would flex pretty good. The wire allowed the barrel to move just enough for adjustment but I like the idea of pennies, I'll give it a try, thanks.

Note to only chuck on the first two serrations of the jaws. This allows the barrel to pivot. About 3/4 of the penny will stick out beyond the jaw.

 

[Con Cross]

William,Instead of chucking on the copper wire, use the pennies. Chuck so that each penny is only holding by two chuck jaw serrations.

Mr. Jerry Sharrett, why are you advocating Mr. William to use pre 1982 old pennies? A copper strip may be easier to find and work with.

Con

 

[JerrySharrett]

Mr. Jerry Sharrett, why are you advocating Mr. William to use pre 1982 old pennies? A copper strip may be easier to find and work with.

Con

True, so true. Paper money like $100 bills might be even easier to come by, just dial 1-800-FED and they will print you a few bales. That is how we got our recent "bail-out" check!!

I just went through the change in my pocket, 3 pennies, a 2001, a 1994 and a 1966. There are still some solid coppers out there.

Investment advise, take your pre 1982 pennies to the salvage buyer and make a bundle!!

 

[wnroscoe]

I finally spoke with Dave Kiff and got my reamer specs. .5568" at the web and fired is .5585 to .559". I still had a small alignment issue but not as bad as I thought. New, unfired brass was/is .549".

 

[Mike Bryant]

I finally spoke with Dave Kiff and got my reamer specs. .5568" at the web and fired is .5585 to .559". I still had a small alignment issue but not as bad as I thought. New, unfired brass was/is .549".

It's been awhile since I ordered any WSM reamers, but that's about what I found. Sammi minimum is quite a bit larger than what the unfired brass measured at the base. I think I had some of my WSM reamers cut to .553" at the web. I'd have to check my chamber prints for sure, but that's what I remember. I was afraid to have them made too close to brass dimensions as a change in brass dimensions would make the reamers unusable.