Home Forums Hunting & Shooting Gunsmithing Cuttign an improved chamber with a hand reamer?

Has anyone cut an improved chamber with a hand chamber reamer? Does it work well? TIA.

Unless it’s a rimmed cartridge (not a bottleneck) you have to set the barrel back a thread in order to make a AI chamber.

Yes, you can cut an improved chamber by hand. It's not a different "hand chamber reamer" though, just a normal chamber reamer and you turn it by hand instead of in a lathe. Take your time, keep things centered, and it goes pretty easily for the most part. If you're doing something like a Brown or Hawk chamber that pushes the shoulder forward it'll take more work but still pretty easy.

A source of compressed air to blow chips out is helpful.

You will end up with an overly long chamber unless y set the barrel back

Make sure you get Ackley Go / no-go gauges before you start.... and here is the PTG (pacific tool & gauge) info on the 220 switch AI gauge - notice the little note he put below about the should / neck junction on a Ackley chamber being .004” shorter than a standard.... this is because the standard cartridge indexes (headspaces) off that junction....
I.e. use a normal go/no-go and it will be too long...

Unless you have a Savage, or Remage... where you can adjust the headspace, or are doing a rimless.... Not sure how one can skip setting the barrel back (shortens the chamber) and just hand cut a AI chamber (unless it’s rimmed that doesn’t headspace on the neck / shoulder.


Link and excerpt of text on AI gauges-

http://pacifictoolandgauge.com/wild...ft-ackley-improved-headspace-gauges.html


Compatibility of Ackley Improved 40° Shoulder Cartridges: P. O. Ackley had a standard process for improving existing cartridges. He measured headspace on the corner between the chamber neck and the chamber shoulder, not at a datum lower down on the shoulder (which is what almost everybody else does). For fire-forming brass to the 40° shoulder angle, Ackley would shorten the headspace at the neck/shoulder corner by .004". That way, the chamber would interference fit (positively support) the neck-shoulder corner of the case during fire-forming. The interference fit probably also stressed the brass so it would yield more readily in the right direction when fire-forming.

Thus, the GO gauge for Ackley Improved cartridges is .004" shorter than the GO gauge for the parent case, and this GO gauge isn't compatible with any other chambering. However, the standard GO gauge for the parent case, being .004" longer than the Ackley version, CAN be used as a NO-GO gauge for the Ackley Improved version of the cartridge. The shoulder angle doesn't matter, because the headspace contact is on the neck-shoulder corner, not on the shoulder as such.

Have to?

A whole thread? Really?

You only need a whole thread if the barrel has sights or you want any barrel markings to remain the their same location. Otherwise, you only NEED to set it back as little as .004" really depends on how accurately you can ream. The average joe might benefit from setting it back about .010".

The only reason to mention this at is for safety - excess head space when shooting a standard round in a AI that wasn’t setback... meaning if you don’t set it back and put a 280 in a .004 longer chamber it could be loose / sloppy when firing it to make 280 AI brass. If you happen to have two guns that are AI, one that was setback and cut right and the other one not - there is a chance your brass from the non-setback barrel would bind up in the other rifle (.004 too long).

The reason smiths setback a “entire thread” is that most smiths “time” the barrel, which means the barrel seats to the action so that the bore leaves raising (not left, right, or down).. yep bores are not 100% parallel when they leave the muzzle so we purposefully time it so it’s raising.

A setback of .004-.006 in general will only set you off 20-30 degrees but it can change how the rifle shoots...

Remember setting back means moving the tenon shoulder & very possibly the barrel tenon where it meets the nose of the bolt forward so the chamber moves back.
To do that squarely one typically uses a lathe.

It’s something they hammered into us at Smith school when making a AI for a customer.
Again, rimmed cartridges like a 30-30 AI don’t have this problem because they headspace on the rim... but I doubt anyone would shorten the neck should on one of those barrels either way.

In regards to setting the barrel back, there is also the issue of barrels with extractor notches (and in the case of Savage 99, a cartridge guide on the nose of the bolt which fits into its own notch in the barrel tenon as well as an extractor notch)- which dictate a full thread's length of shortening.

Headspace aside, alignment is difficult to maintain and it's real easy to introduce chatter when reaming by hand. In many cases, the pilot on the improved reamer won't engage before the reamer starts cutting. I had a friend who cut a few chambers using a floor mounted drill press which worked relatively well.
The headspace issue which can arise is something which is little understood by many. Just look at the problems Nosler hadf when trying to standardize dimensions for the 280AI. The thing is, the distance tp the juncture of the neck and shoulder will vary depending upon the neck diameter and the actual shoulder angle on the parent brass. Headspace gauges are made based upon the measurement to a datum. This means a gauge made to -.004 may not gauge the distance to the neck shoulder juncture correctly. I have seen a whole bunch rifles which had been chambered by well respected, skilled gunsmiths and were undoubted cut to precisely -.004 according to the gauge they used yet, the chamber was too long to headspace correctly on the neck/shoulder juncture of the parent cartridge.
In at least one case, Ackley drew up his chamber specs using the datum line -.004" rather than the distance to the neck/shoulder juncture. This produced an error of about .030" which was then perpetuated by reamer manufacturers for over fifty years and may still be.
All this has little to do with the original question though. The OP asked if anyone had cut an improved chamber by hand and if it worked well. I have done so and it did not work well. In the end, the chamber was OK but getting there was not. It may be that the OP is more capable of controlling the reamer than I (I'm sure many people are) but I had a heck of a time getting the reamer to cut smoothly. By the way, a reamer which is ground with too much clearance or insufficient margin will be more difficult to control. By the way, I cut one other chamber using a variable speed Black and Decker drill and it worked out surprisingly well. This was on one which was too difficult to set up in the lathe. Still, I wouldn't recommend it. GD

Gnoahh - Thanks I completely forgot to mention that...

Model 70’s have barrel extractor cuts as well - setting a barrel back a thread means only deeping the cut vs. moving it ... you still need clearance from the nose of the extractor to the barrel.

Great catch.

Be very careful using a chamber reamer by hand. As mentioned above maintaining alignment is critical and it is easy to 'wallow out' a chamber.

You're more likely to get chatter when cutting with a drill than by hand, so it sounds like you had two completely different experiences, one good and one bad. Personally I've done several by hand with good success, before I had my own lathe.

If your reamer chatters, try wrapping it with a turn or two of wax paper; sounds weird but it works amazingly well to get it cutting smoothly again. I got that tip from Fred Z at 4D Reamers when reaming some shotgun forcing cones by hand; the long contact area of those reamers is really prone to chatter otherwise.

The comments about "wallowing out" the chamber are a valid concern for hand reaming. I prevent this by holding the barrel vertically in a vise and taking care to keep the reamer straight. Only a little more pressure than just the weight of the reamer is needed, if the reamer is sharp. I think most of the troubles happen when a reamer is worn and needs to be resharpened.

Wax paper works, cloth works, paper towel works, so does plasticene or very heavy grease. In my opinion, a reamer which chatters in the lathe is a reamer which is incorrectly ground. By hand is another matter and I knew there were people who were likely to be more capable than I. GD

Listen to GD. He has been around the ranch maybe more than 3 times and still has not fallen off the turnip truck.

And which truck do you think I fell off, exactly?

Easy there, I don't think Butch meant any offense just as you did not. We both gave the OP our take on it based on many years of experience as professional gunsmiths. I happen to think reaming an improved chamber by hand is not a great way of doing things for various reason but this doesn't mean it can't be done. I know at least one guy who is so exceptionally skilled at doing things by hand that he could probably get a good result most of the time. It is my opinion that most people will not. As for myself, I'm better off using the lathe, for sure. GD

Feller, I don't know and didn't mention that you had. If you did, was it a chebbie, Fered, or a Derdge?

You quoted me and said I need to listen to greydog cause he hadn't fallen off the turnip truck. Did you mean to reply to the OP instead?
Otherwise what makes you think greydog's comments are any more valid than mine?

I should not have quoted you, just saying that I value GD's advice.
Sorry

You don't owe anyone an apology, Butch. If Yondering is full of anything, he's full of himself. He has derailed your discussion, and I agree with GD too.