Gunsmithing 7 WSM Reamer Dimensions Tolerances

[Ratbert]

I've got a new 7 WSM reamer from PTG that I used to chamber a couple of barrels. The drawings on this reamer specified 0.5563 +- 0.001" at the base of the cartridge (0.2000 in front of boltface). However when I went to start load development with one of the rifle today I discovered that it appears to actually be a fair bit larger than that at the base, fired brass is measuring 0.5609" @ about 2.5" from the boltface, where it abruptly tapers back down to the .551 where the case web did not expand. It is so large now that it fails to insert into my Redding instant indicator by full half and inch.

So my question is, is this something I should make a stink about with PTG and get a new reamer within their published specs, cut back the barrels and rethread/chamber? Or is this "normal" for a 7 WSM reamer and I should just expect to have to fireform all my brass (and I haven't even examined what it's going to mean as far as fitting into my reloading dies).

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Running the fired brass through the body die (Redding Type S with no bushing installed) required a fair bit of force and two passes w/ Imperial Wax but it formed it back to a perfect 0.5510" max diameter and correct (0.002" under minimum) headspace. Trying to move that much metal with RCBS water based lube (my preferred method for easy cleanup) required 3-4 passes and even then the resulting headspace was iffy (resulted in anywhere from 0.000 to 0.004" under minimum.)

Unless I plan to run the reamer up into every single die I've got, not resizing really isn't an option. It's way to big to fit into my seater or neck die. Fired brass still chambers nicely in the gun, though.

Harder to measure accurately, but dimensions at the shoulder appear correct, it looks like they just put too much angle on the body taper.

 

[Dave-O]

Re: 7 WSM Reamer Dimensions Tolerances

I just pulled my 7wsm print from PTG.

@ .200 from the bolt face its .555

My brass measures .553 on a fired case. I can't get as exact as you are on measurements on the brass. I suspect I'm real close though.

Not sure what to tell you otherwise, other than to call Dave Kiff and ask him.

 

[MikeeBooshay]

Re: 7 WSM Reamer Dimensions Tolerances

Have you measured the reamer itself yet? The possibility exists that it is to size, but the chamber is large. Can be caused by the reamer not running true to the bore, ie not centered and cutting harder on one side.

You could always ream a quick chamber in a piece of cutoff and check that too. I asked the question, since you mentioned only one of the rifles having the issue.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

No, both rifles are like this. I can try to measure the reamer, but obviously that is much more dependent on exactly where I measure and the angle of the cutter rotation, etc. I will try and make a case gauge using a piece of scrap, but I need to wait until I get 308Nate's new truing faceplate because I don't currently have any way to hold a 4" piece of stock true to the bore.

 

[MikeeBooshay]

Re: 7 WSM Reamer Dimensions Tolerances

If you have a piece of bar stock, just chuck it, drill it and bore it, then run your reamer thru it. As long as it starts with your .284 ID, then it will be centered. You could even use a 3 jaw and save some time.

I think I have a PTG 7 WSM reamer also, I'll try to get some type of measurement for you this weekend too.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

I'm not sure I have anything that can bore a .276 or .284 hole deep enough, but I'll check.

ETA: NM, I guess it's not really all that deep. I should have a drill long enough.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Well, no need to cut the scrap, I guess. I just tried using my Wilson seating die (which the fired brass will not fit into) as a case gauge and the reamer slipped in easily. So now the fun part of figuring out where the tailstock went out of true...

 

[MikeeBooshay]

Re: 7 WSM Reamer Dimensions Tolerances

How are you holding the reamer when you are running it? Floated, chucked etc.....?

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Floating.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Well crap, it looks like my floating reamer holder was frozen up. One of the retaining screws is gorked down way too much. Ah well, a quicker fix than needing a new reamer.

 

[MikeeBooshay]

Re: 7 WSM Reamer Dimensions Tolerances

Yes, now to pull a pair of barrels and attempt a set back?

I'm working at home today, trying to watch the 2 1/2 yr old, and mess with a 6PPC gun I am building. Mess ing with brass today mainly, mounted a scope etc.

Glad you got to the bottom of it without undue expense. Still the suck is strong tho....

 

[300sniper]

Re: 7 WSM Reamer Dimensions Tolerances

bummer. what floating holder are you using?

 

[19Scout77]

Re: 7 WSM Reamer Dimensions Tolerances

Ouch...how much barrel are you gonna need to hack off?

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

I forget the name, not the PTG one, JPT or something like that. I promised to take the boys camping this weekend so I'll have to look later, but I figure I'll probably need to push it back a touch more than the neck length, plus whatever is necessary to retime it properly. Fortunately there's a relatively thick lug so I've got some space availabe, hopefully there will be enough that the front threads will just roll into the relief area and I won't need to chase them back further. Worst case I've got enough shank to just saw it off and start over.

 

[mcfred]

Re: 7 WSM Reamer Dimensions Tolerances

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ratbert</div><div class="ubbcode-body">Well crap, it looks like my floating reamer holder was frozen up. </div></div>

So this caused the reamer to cut a chamber too big?

I've chambered 6 barrels using a 7mm WSM reamer from PTG and haven't had any problems. From memory, I think the fattest part of fired brass comes out at 0.555", and everything works fine in Redding dies. I've just been using a center to push the back end of the reamer, with a wrench to keep the reamer from spinning. Not fancy but it seems to work fine.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: McFred</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ratbert</div><div class="ubbcode-body">Well crap, it looks like my floating reamer holder was frozen up. </div></div>

So this caused the reamer to cut a chamber too big?

</div></div>

It was frozen very close to center so it wasn't visually immediately apparent, but a few thou out of center turns it into a single-point boring bar once it's in far enough that the pilot bearing alone can't flex it into position. I was letting a friend use it to cut his first chamber who wasn't familiar with it, so he didn't notice when setting up the reamer or guiding it into the chamber and it wasn't visually obvious to me standing by him that anything was wrong. Lesson learned, another step added to the checklist.

It looks like i'm going to need to push it back 4-5 threads in order to completely re-cut the neck. I'll have to pull it off later today and figure out how many spare threads I've got under the lug. I'm guessing it is two. I'll run the mic over the necks of the fired brass some to figure out how much they are being effected and if I can get away with simply having two threads floating then I'll probably just cut a relief groove and do that. Otherwise I guess I'll have to recut the entire shank and she'll be a full inch shorter.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Just a small update, it is the Dave Manson reamer holder, not anything from JG. I'm terrible with names.

In any case, it appears to have been a conflagration of the holder having a strong bias to cutting on one side and a pilot bushing that was labeled .2762 but actually only being .2759 when the bushing on the range rod was labeled .2762 but actually mic'd out @ .2763. I'm beginning to think that PTG just cuts random sized bushings and then reaches into the grab bag and writes whatever number you ordered on the label before shipping it out.

The holder is a bit of a puzzler, if I pull the reamer out and turn it 90* in the holder the "cutting side" stays the same (doesn't move with the reamer.) However if I pull the MT-3 shaft out of the tailstock and spin it 180 and reinsert the cutting side moves 180*. Removing the holder from the jacobs taper side of the MT-3 shaft turning and reinstalling causes the cut bias to move, though I haven't determined if it is in a predictable way. Using a MT-2 shaft with a MT-2 to MT-3 adapter doesn't seem to have quite as much bias to one side as with the MT-3 shaft. Using shim stock wedged between the floating holder and base I was able to move the bias around somewhat, but not really in a controlled manner and never really got it to cut completely true.

In the end I chopped an inch of the barrel, redid the tenon and got a good chamber cut but I'm definitely going to be looking around at other options, either tuning the Dave Manson, replacing it, or building my own design.

 

[300sniper]

Re: 7 WSM Reamer Dimensions Tolerances

I've been very happy with the jgs reamer holder. It floats every way it needs to and with a prebored hole, despite a misaligned tail stock, it cuts an incredibly true chamber.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

That's one thing I was unsure about with the JGS, does it float radial and parallel? Sounds like yes.

I'd like to get one I can put an ER or DA collet on so that it can serve more purposes than just holding 7/16 reamers, considering trying to track down a used Kennametal DA or something.

 

[Ratbert]

Re: 7 WSM Reamer Dimensions Tolerances

Hard to beat $23 delivered...

http://www.ebay.com/itm/160781945231

 

[Straight Shooter]

Re: 7 WSM Reamer Dimensions Tolerances

I really like my JGS floating reamer holder. Here it is being used with a Micro Reamer Stop.