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Little Creek
PostPosted: Thu Dec 15, 2016 10:42 am  Reply with quote
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Seems to me there has been evidence that longer forcing cones can decease pressure at the chamber. Sherman Bell, who wrote a series of articles for Double Gun Journal Called "Finding Out For Myself" about shooting old guns, says that he always lengthened the forcing cones in his old, sometime damascus guns to reduce the pressure. I followed his advice and did that in one damascus barreled gun I own and shoot. It originally had 2-5/8" chambers but the LFC's enable 2-3/4" loads in this gun without a problem.

I also have a 1920's vintage Francotte that was originally built with 2-5/8" chambers, that someone before me had lengthened the forcing cones on. I'm sure this was done to handle 2-3/4" cases.

Except for the relief of pressure, I have not seen dramatic evidence that lengthening forcing cones is important.
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Dogchaser37
PostPosted: Thu Dec 15, 2016 5:30 pm  Reply with quote
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Longer cones do not affect pressure.

Heck you can fire a 12 gauge 2 3/4" load in a 3 1-2" chamber and it doesn't drop the pressure. I know that to be fact.

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Little Creek
PostPosted: Thu Dec 15, 2016 6:17 pm  Reply with quote
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Pressure will be lower if you are shooting 2-3/4" shells in shorter chambers according to Sherman Bell, and others, who pressure tested guns and loads.
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Dogchaser37
PostPosted: Thu Dec 15, 2016 6:28 pm  Reply with quote
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Tom Armbrust is the person that made me aware of this, and I tested it and had the same results. I did it with Steel, Lead and Bismuth loads. The pressures do not change.

The peak pressure is attained and measured before the wad clears the hull. Now maybe overall pressure is lowered because of the removal of metal leaving more volume in the barrel. But chamber pressure is not affected.

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Little Creek
PostPosted: Thu Dec 15, 2016 6:54 pm  Reply with quote
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I'd like to see the Armbruster or others tests results that say there is no pressure increase putting a 2-3/4" hull in a 2-1/2" chamber.
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Dogchaser37
PostPosted: Thu Dec 15, 2016 7:47 pm  Reply with quote
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I didn't say a longer shell in a short chamber..........but since you brought this up........I have tried that too and got maybe a 500 to 1,000 PSI gain. Again Tom Armbrust was the person that brought this to my attention.


Since you follow Bell, then you know that Tom has done a lot of his testing.

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Little Creek
PostPosted: Thu Dec 15, 2016 7:51 pm  Reply with quote
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Thanks Dogchaser! Merry Christmas!
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Dogchaser37
PostPosted: Fri Dec 16, 2016 8:31 pm  Reply with quote
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Merry Christmas!!!

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WyoChukar
PostPosted: Sun Dec 18, 2016 9:12 am  Reply with quote



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Excellent point about the pressure peak. Pressure is greatest when resistance is greatest. A well known fact in the realms of physics is that starting friction (resistance) is always greater than once an object is in motion.
A longer cone does reduce resistance and affect the pressure curve some, but not until well after peak pressure has subsided.

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Bobsthedog
PostPosted: Mon Mar 05, 2018 8:11 pm  Reply with quote



Joined: 01 Mar 2018
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Sorry to bring up such an old post. But this is kind of a pet peeve. What i find funny is that there are so many people out there that are ademate that the lengthed forcing cones do nothing and clain there is no proof that they work. There is equally no prooof that they do not. The fact is that they may do nothing but I have never seen them make a shotgun pattern worse. That pretty much meewna they do something positive, and there is some other reson for a lack of inprovememt in some guns.

Often times the forcing cones are lengthed in a full choke barrle and the patterns dont change. But in SK or IC chokes they do seem to get better patterns. Maybe the chokes are deforming pellets hence negating the positive affect of the longer cone?

Do yo also think that back boring a gun is just a way for gunsmiths to make more money?

I have seen some of this work performed where the polish of the chamber and cone was terrible. You could simply glance into the barrel and see the forcing cone had been lengthed by the finish of the bore.

A real test that I have never seen would be before and after a lengthed forcing cone and a cylinder bore/choke with no other constriction in the barrel after the cone. My bet is that there would be at least slight increase inpattern density under those circumstances. Then start increasing chooke restriction and determine scatter and density as the choke was closed. Befroe and after longer cones.

Wonder if somewhere arrround modified or full choke the postive effcts of the longer cone are outweighed by the choke? Just a thought.

There has to be a method to the testing, not just i do it to this gun or that gun or any gun you know of and saw no difference.

My reasoning here is this. I had an IC cylinder 12 ga with lenghted FC that patterned beatifully, It was IC and when compared to an older 1100 rem 12 ga with IC and short cones the difference was night and day. But that doesnt mean that something else wasn't going on there. Two differnt gund and i have no idea what the gun did before the cone work.

Most of us dont want to spend our own money to run the type of testing that would be required to provide conclusive results, and if someone does the oposition to the results imdeiatly question the authority performing the testing. To say they dont work is just as bad as saying they do. As i know on no tests that have been performed that I would consdider to be scientifically accurate, i do know though that the theory plausible and i have never run across anyone that said their gun got worse after lenthening the cones.

Again just a thought.

I have a 16 ga project gun with 2.5" chambers. I will buy a combination reamer and ream the cone and the chamber at the same time. Dont care if you thinkit works oir not. Smile
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Dogchaser37
PostPosted: Tue Mar 06, 2018 1:24 am  Reply with quote
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Easy Bob,

I think most here appreciate the benefits of longer forcing cones and other barrel work.

Have a good day!

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Bobsthedog
PostPosted: Tue Mar 06, 2018 8:54 am  Reply with quote



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Sorry wasn't teaming to sound confrontational
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Dogchaser37
PostPosted: Tue Mar 06, 2018 9:05 am  Reply with quote
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It's OK.......been known to get a little edgy with my writing, even when I didn't think I was.... Cool Cool Cool

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Ohio Wirehair
PostPosted: Wed Mar 07, 2018 9:51 am  Reply with quote



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Mike Orlen believes in it and he is a very well respected barrel smith. Check out his website.
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WyoChukar
PostPosted: Wed Mar 07, 2018 10:35 am  Reply with quote



Joined: 16 Jul 2015
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Here is some food for thought. Take a lead shot pellet and squeeze it with a pair of pliers. Pretty easy to knock it out of round isn't it? I doesn't take much force at all. Now consider the fact that these malleable spheres are blasted from zero to 800mph under thousands of pounds of pressure in milliseconds. This a good bit more force than you or I can create with pliers.

The first destructive forces they encounter are those imposed by layers of pellets ahead of each individual pellet, thus the old illustrations and photos showing pellets being progressively more deformed further back/ down in the shot column (a good case against long shot columns). This is where most deformation occurs and can be reduced through a variety of measures.

The second round of impact comes from this high speed charge entering the forcing cone. At 1,100 to 1,400+ fps, this transition is anything but gentle. And we thought hitting a pot hole on the interstate was rough! However, a short abrupt cone angle gives a pretty violent deflection/ squeeze from all sides and shot has to shift position faster than it actually can. The result is pellets deformed by lateral forces. Ever notice how recovered pellets are deformed where other pellets have made contact from the sides as well as above and below? A long gradual cone reduces this. A larger bore diameter does too since the degree of constriction and repositioning of the shot is less.

The third round of deformation occurs in the choke itself and tighter chokes have been documented to actually cause just a tiny bit more deformation to the pellets, although it is minor. However, long choke tapers do help here too. The caveat is that more constriction is required with a longer choke taper, so gains are small.

So why does any of this matter? Round pellets fly straighter than lumpy ones. The greater the difference between the round ones and the not so round ones there is, the longer the shot string becomes. Short strings tend to hit birds harder. Tight patterns reach farther with authority.

However, in tight woodland settings where shots are very close and opportunities brief, this works against us and lumpy shot is good. At 15-20 yards with plenty of foliage for a bird to zoom through, I will take all the help I can get.

Hope that clears things up a bit and makes sense of things. If not, well I gave everyone a chance to finish their coffee.

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