Lengthen chambers to 2 3/4" ??

[Dean Romig]

I really don't think there is a more accurate method of measuring chamber length than the Galazan 6-blade brass tool. Sure, you can use a tool with a dial indicator but that won't change how long your chambers are. The Galazan tool is quick, easy, accurate and it's by far more portable.





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[Stan Hillis]

No one has attempted to answer your question about who is a competent smith to do the chamber lengthening. I will. I use Dean Harris at Skeet's Gun Shop in Tahlequah, OK. He did a Fox 20 ga. for me last year, and also opened the chokes to .006" and .016", something more suitable for quail over dogs. He is very knowledgeable and easy to talk to over the phone. He won't make you feel like his time is too valuable to talk to you.

[Researcher]

The problem with the chamber gauges made to "industry standards", is that all chambers weren't reamed to "industry standards." If the chamber is a few thousandths undersize the gauge won't go in to the true measurement. If the chamber is a bit oversize the gauge will extend into the forcing cone.

I've posted this many times in the past --

Chamber depth is considered to be the distance between the breech end of the barrels and the joint between the chamber body itself and the forcing cone, which reduces down to bore diameter. This is loosely based on the length of the "Fired" shell. Today, theoretically when the crimp opens on the shell being fired the end would land at the junction of the chamber and cone. Prior to WW-II many companies had the practice of holding the chamber about 1/8 inch shorter than the shell for which it was intended. Fly in the ointment is nominal measurements often differ from actual ones in both chambers and shells. A very good method I have found of measuring chambers without much outlay of cash, and is quite accurate enough for virtually any situation, is a common 6" flexible machinist's scale which you likely have. Hold the barrels with muzzles toward a light source, not necessarily a concentrated one a window is great, while looking into the breech and the cone will be thrown in a shadow. May have to move the barrels around a little until it is distinct. While still looking into the chamber simply slide the scale in until you observe the end coming flush with the shadow line & mark position of breech end with your thumb. Remove and read the scale. I usually repeat this a few times to insure I am getting a consistent reading, but you will be amazed how accurate this can be done. While I own a Galazan chamber gauge, I use this more often than not. The chamber body itself has a taper of about .005" per inch. Sometimes chambers were cut with slightly worn reamers giving a slight undersize chamber. If the chamber is a bit undersize a gauge made to "industry" standards will not go in to the true depth of the chamber. A.H. Fox Gun Co. shotguns are known for having tight chambers. The machinist’s scale method can be more accurate.

[todd allen]

Originally Posted by George Neal

I'm interested in advice on the advisability of lengthening the chambers on a Parker 12 and a Parker 20 from 2 1/2" to 2 3/4". The 12 is a well worn DHE #1 frame and the 20 is a VH #0 frame. Both were manufactured in the 1920's and are in sound condition. Neither are high condition, and other than being sound Parkers have no special collectors value. It would be NICE the use low velocity 2 3/4" ammo that is readily available rather than being limited to the 2 1/2".
If this is feasible I'd appreciate suggestions on a competent source of having the work performed.
I welcome your suggestions.

I had this conversation with Chuck Webb from Briley's some years back, regarding a circa 1900 H&H Royal SLE that I bought from him.
I measured the chambers, and they were 2 1/2". He advised to not lengthen the chambers, as that would take it out of proof. Rather, to taper the chambers, which would relieve the pressure at the step-down to the bores.
This is what we did.
You have already gotten some good advice here, from people who know way more than I do.
That said, I would talk to a good barrel smith from a legit company, and see what they say.

[Drew Hause]

Todd: I don't understand "taper the chambers".
Do you mean lengthen the forcing cones? Which at one point did not take a gun out of proof, but a friend specifically discussed this with the Birmingham Proof House and lengthening the forcing cones now does takes a gun out of proof.

[Bill Murphy]

"Taper the chambers" refers to taking some metal out of the chamber ahead of the extreme front of the chamber at a bit of a taper, rather than starting the cut at the chamber mouth. It's a good theory, but doesn't do much to lower pressures. I don't measure my chambers and haven't for sixty years of shooting and buying shotguns. I use light loads in light shotguns and that seems to have eliminated any problems. When I bought my PHE 12 gauge trap gun, I used it as a pigeon gun, as have the previous owners, for roughly a century. I am sure that this gun has never shot many shells with less than 1 1/4 ounces of shot, because its previous owner was a competitive pigeon shooter and I have used this gun for a similar purpose. I have never measured the chambers, but I'm sure they are 2 5/8" or shorter as was specified in the stock book. It was proofed at PB with 1 1/4 ounces as I recall, but I'm not sure of the 2 5/8 and 1 1/4 ounces. I'll report back. I shot 50 rounds through it yesterday, and it is still undamaged.

[Drew Hause]

I still don't understand. Chambers were designed with a taper; 12g from .811" to .797". Removing metal would be increasing the diameter of the chamber, which if done toward the forcing cone would decrease the taper, and increase the angle of the cone if not lengthened.

[mobirdhunter]

Back in my (even more) naive days, I followed the gun writers of the day (about 35 years ago) and their recommendation to lengthen the chambers from 2 1/2" to 2/3/4" and lengthen the forcing cones. I sent a pristine, original Fox AE 16 to Griffen and Howe. They said that in their judgement the chambers could be lengthened, but there was insufficient wall thickness to relieve the forcing cones. Thank goodness for a professional to do the work, but I still regret lengthening the chambers those many years ago. Lesson learned.

I left another Fox CE with a dealer (same timeframe as the gun above) who said he'd get the chambers lengthened to 2 3/4." When I got it back, the chambers had been cut to 3 inches. According to the smith, he did so to "keep some dummy from sticking 3 inch shells in the gun." Another lesson learned (and I'm still wondering if I was the dummy or the gunsmith...or both of us).

[todd allen]

Originally Posted by Bill Murphy

"Taper the chambers" refers to taking some metal out of the chamber ahead of the extreme front of the chamber at a bit of a taper, rather than starting the cut at the chamber mouth.

I think this is a good summary. I don't know if the procedure made any difference, but it's a done deal. Along with choke tubes, which in retrospect, I wish I had not done.
BTW, my background is similar, though I'm a few years behind you, at 68 years.
Box birds were the game, and I was typically shooting them somewhere once a week, for about 30 years.
I had virtually quit shooting about 2008, except for a little upland bird shooting here and there.