Chamber Mates do not reduce chamber pressure. Your choice of ammo is your control over your chamber pressure.

20 gauge Maximum allowable chamber pressure is higher than 12 gauge. In effect, if you are shooting factory ammo, you are likely shooting 20 gauge loads that are higher pressure than factory 12 gauge loads.

 

Sherman Bell in 2006. He did not document the usual 20g AA Sporting Clays or 28g AA Target pressures or fps, and I have not seen independent measurements, but they were/are likely about 11,000 psi. Same payload in a bigger tube = lower pressure

In the 12-gauge gun with 20-gauge adapters:

A Winchester 20-gauge A-A Sporting Clays factory load of 7/8 ounces of #7 1/2 lead shot, fired in a Silver adapter, gave a velocity of 1319 ft/second and developed a pressure of 7700 psi. The same 20-gauge load fired in a Go1d adapter gave a velocity of 1324 ft/second and developed a pressure of 7800 psi. With all 0-rings removed from the Gold adapter, per your request, the velocity was 1302 ft/second and the pressure was 7900 psi.

In the 12-gauge gun with 28-gauge adapters:

A Winchester 28-gauge A-A factory target load of 3/4 ounces of #8 lead shot, fired in a Silver adapter gave a velocity of 1247 ft/second and developed a pressure of 8300 psi. The same 28-gauge load fired in a Gold adapter gave a velocity of 1285 ft/second and developed a pressure of 8400 psi. With no 0-rings in place on the Gold adapter the velocity was 1255 ft/second and the pressure was 8100 psi.

A different lot of the same Winchester 28-gauge A-A factory target load was fired with Gold adapters. The velocity was 1318 A/second and the pressure was 8200 psi. With 0-rings removed the velocity was 1297 ft/second and the pressure was 7700 psi.

 

Sherman Bell in 2006. He did not document the usual 20g AA Sporting Clays or 28g AA Target pressures or fps, and I have not seen independent measurements, but they were/are likely about 11,000 psi. Same payload in a bigger tube = lower pressure

In the 12-gauge gun with 20-gauge adapters:

A Winchester 20-gauge A-A Sporting Clays factory load of 7/8 ounces of #7 1/2 lead shot, fired in a Silver adapter, gave a velocity of 1319 ft/second and developed a pressure of 7700 psi. The same 20-gauge load fired in a Go1d adapter gave a velocity of 1324 ft/second and developed a pressure of 7800 psi. With all 0-rings removed from the Gold adapter, per your request, the velocity was 1302 ft/second and the pressure was 7900 psi.

In the 12-gauge gun with 28-gauge adapters:

A Winchester 28-gauge A-A factory target load of 3/4 ounces of #8 lead shot, fired in a Silver adapter gave a velocity of 1247 ft/second and developed a pressure of 8300 psi. The same 28-gauge load fired in a Gold adapter gave a velocity of 1285 ft/second and developed a pressure of 8400 psi. With no 0-rings in place on the Gold adapter the velocity was 1255 ft/second and the pressure was 8100 psi.

A different lot of the same Winchester 28-gauge A-A factory target load was fired with Gold adapters. The velocity was 1318 A/second and the pressure was 8200 psi. With 0-rings removed the velocity was 1297 ft/second and the pressure was 7700 psi.

So the obvious questions are: What's a Silver adapter? What's a Gold adapter? How are they different from each other, and how are they different from Chambermates? :mrgreen:

 

Ditto - and also explain the "O-Rings" and their positioning and/or role in the "adapter". Also, how do they compare to Chambermates, or is this an "Apples to Grapefruits" comparison?

 

Chamber Mates came in Gold and Silver. Silver was just a machined cylinder with a hole the size of the smaller gauge/caliber. The Golds were similar but they had a split in them the length of the adapter.

I have a silver 12 gauge to 44 mag (no rifling).

Drew Haus has a lot of solid information. However I wonder if those AA loads were really close to 11,000 psi if shot out of a straight 20 gauge as suggested. It doesn't seem reasonable to me that outward pressure would drop 3,000++ psi just because they were fired in an adapter. Unless I'm misunderstanding his post, they didn't test those loads in a standard chamber for comparison.

Chamber Mates specifically never claimed that their product reduced pressures on the firearm. It may have been a liability concern but they were specific about that.

 

It depends on where you are measuring the pressure. In the chamber, there's no reason that I know of why the pressure would be any less in a Chambermate than in a gun made for that gauge load. However, forward of the chamber, there is plenty of reason to believe that the pressure would be less for a 20 gauge shell in a 12 gauge bore than for a 20 gauge shell in a 20 gauge bore. Likewise for a 28 gauge in a 12 gauge bore.

The beauty of the Chambermates idea is that even though the pressure is less for a 12/20, the velocity doesn't suffer at all because the pressure is acting on a larger surface area as it shoves the load toward the muzzle.

 

meanwhile out on the ranch.
using a tapered 12ga. wad in a straight wall 12ga. hull is the end of the world.

 

I have some original Chambermates - they are RED anodized aluminum in 12 ga. and do NOT have O-rings. (My full set is for 12 ga. and is for 20, 28, and .410). I got them for a reasonable price out of curiosity, even though I have guns in all the gauges.

They worked OK for skeet and 5-stand. While I didn't do any velocity testing, and do not have a pressure-test set-up, they patterned normally with the smaller gauges to the choke I had in the gun. (The 2 1/2" .410 obviously gave the normal "patchy" patterns with skeet chokes in the gun.)

Velocity must have been pretty good, too, as the recovered wads were deformed and flattened out well to apparently fill in the bore to a reasonable degree, with the possible exception of the .410 which flattened out, but might not have filled the bore of the 12 ga. And they did break clays OK.

Anyway, they were a way to shoot a smaller gauge shell in a larger-bore gun and worked for my purposes, but manual removal and replacement of the fired shell with my Chambermates was a PITA, and I carried a dowel for easily ejecting any stubborn hulls that occurred.

Incidentally, mine are made to fit a 3-inch 12 ga. chamber, and they also work fine for determining chamber length for 12 ga. guns. I have used them to easily determine chamber lengths on older guns of 2 1/2", 2 9/16", and 2 3/4". (And yes, some old guns were made in all 3 chamber lengths!)

But the bottom line is either get a set of more expensive tubes for your beak-open gun, or better yet, get a gun in the gauge you want, it's just much, much more convenient.

 

OK gents, let's distill this information for the less technical readers (me). Reduced shell diameter (20X12) will not reduce chamber pressure but will reduce pressure down the barrel because of the smaller volume of shot? I have a silver colored set with O rings.

 

OK gents, let's distill this information for the less technical readers (me). Reduced shell diameter (20X12) will not reduce chamber pressure but will reduce pressure down the barrel because of the smaller volume of shot? I have a silver colored set with O rings.

No. The pressure is less down the barrel (compared to being in a 20 gauge barrel) because of the greater volume of the 12 gauge bore (compared to a 20 gauge bore).

I also have a set of the silver colored 12/20 Chambermates and didn't know until I read this thread that they were made in any other color. These gauge reducers work great, but you have to use Win AA or Rem STS hulls for the fired shells to extract easily. Leave the El Cheapo shells at home when using the Chambermates.

 

There is a bit of incorrect information on this thread.

Chambermates were made of stainless steel and had an integral extractor.

They were never "split", were never "red anodized aluminum", and never "came in Gold and Silver". These descriptions reference completely different products.

THESE are Chambermates, made by Seminole Gun Works of FL:

 

OK gents, let's distill this information for the less technical readers (me). Reduced shell diameter (20X12) will not reduce chamber pressure but will reduce pressure down the barrel because of the smaller volume of shot? I have a silver colored set with O rings.

No. The pressure is less down the barrel (compared to being in a 20 gauge barrel) because of the greater volume of the 12 gauge bore (compared to a 20 gauge bore).

I also have a set of the silver colored 12/20 Chambermates and didn't know until I read this thread that they were made in any other color. These gauge reducers work great, but you have to use Win AA or Rem STS hulls for the fired shells to extract easily. Leave the El Cheapo shells at home when using the Chambermates.

Correct.

First off, TYPICALLY, you will find a smaller powder charge inside a smaller gauge shell.

Just to start with, less gunpowder makes less hot gas when burned. When burned in a smaller volume shell, this makes equal (or more) pressure.

Once all the gunpowder has burned (with light target loads this CAN be before the hull ever opens up) pressure drops according to Boyles Law of Gasses. With every doubling of the volume of the space between the projectile and the inside base of the case, pressure falls by half.
This normally assumes a constant diameter tube barrel. Dump that gas out of a reduced-diameter case (20-gauge) into a larger diameter (12-gauge) barrel, pressure drops FASTER.

 

Does this help

 

and these
http://www.littleskeeters.com

 

Little skeeters! That's what my red anodized ones are! They seemed to work OK, broke clays, but just were a PITA to use because of removing the empties.

Sorry for the confusion, but they are stored in my son-in-law's house due to me moving.

 

Thanks Wildlew for setting things straight. Gauge Mate was the producer that had silver and gold adapters. Wish I'd snapped up a couple of those 10 to 12 adapters when they were still in production.

 

Hal4son yes i bought them at the end. clarence at that two for one.