This is starting to sound like one of those Glock threads, where the answer is to stick with OEM parts.
This is starting to sound like one of those Glock threads, where the answer is to stick with OEM parts.
Likes pretty much everything in every caliber.
Wandering zeros on shotguns aren't unheard of.
A four inch shift in zero after ripping off 25 rounds isn't anything that I would worry about. That's a whole lot of shooting in a short time frame and it's still close enough for a shotgun. The only place your going to realistically do that kind of shooting is a three gun match and you have a pretty good idea about your shift in zero.
Whether you think you can or you can't, you're probably right.
I would imagine it COULD, assuming it is mounted far enough forward... assuming we really KNOW why the OP has noticed stringing after heated up.Originally Posted by GJM
870 with a 12” barrel + T-1 Micro
Super X-2 with a 22” cut barrel + RMR
Super X-3 with a 28” barrel and 7 round magazine + Burris Speed Bead
You can get much more of what you want with a kind word and a gun, than with a kind word alone.
The mag tube wouldn't heat at the same fate as the barrel no matter what it was made of.
I have verified that it is square and true.
When the zero shifts, remkcong and replacing the cap instantly restores zero, and it is noted that the cap is tighter when removed, indicating impingement due to thermal expansion, as it does not feel tighter to remove if I wait until the weapon has cooled, which also returns zero.
Those shotguns have hangers that attach much closer to the receiver. Less barrel length to heat by far and thus less expansion and tension change at the juncture.
No, neither the barrel nor mag tube would heat at the same rate. But in this case, titanium and steel heat at different scales and thus have different linear change per temperature increase.
Linear Length of Change is:
Length of Change (dL) = Original Length in meters (L0) x alpha (thermal linear expansion coefficient) x change in temperature in Cº (dT).
In this case, titanium has an alpha (Ti-A) = 8.4x10^-6 (0.00000084) and 4140 steel (most specific steel I could find) has an alpha (4140-A) = 12.3x10^-6.
So let's look at those dTs -
L0 = ~19" = 0.4826m
Let's go with a temperature change of 75ºF to 150ºF (that's a dT of 41.6667ºC)
Ti-A = 8.4x10^-6
4140-A = 12.3x10^-6
dL-Titanium = 0.000016891m or 0.00665"
dL-Steel = 0.00024735m or 0.00973"
So based solely on thermal expansion coeff - titanium should not change length more than steel, given the same temperature change. But we're not dealing same temperature range...across the two tubes.
Instead, you have to calculate both thermal conductivity and the heat transfer coefficient. In this case, steel has higher conductivity than titanium and as a result steel has a lower heat transfer coefficient. For a given thickness, length, and area, steel will transfer heat less than titanium.
This means that when you're firing and your barrel heats up the same temperature range, your Ti tube and steel tube do not. And in this specific instance, it takes more barrel radiant heat to heat the steel tube up to make it move. How much more? Well, the thermal conductivity of steel is twice that of titanium and as a result the heat transfer coefficient is ~1/2 that of titanium. Which means the temperature needed to establish the same temperature change in steel as titanium is twice the amount of temperature.
So, we calculate half the temperature change for the steel tube to the titanium tube.
So what is dL of steel with half the temperature change? 0.0032" - OR half the change of titanium.
____
Seriously, swap the magazine tubes and find out if it cures the problem. I'd bet it does.
Last edited by RevolverRob; 10-19-2017 at 09:43 PM.
Ah.
So it sounds like it’s your shotgun that has a hidden liability with an RDS rather than shotguns in general.....
You can get much more of what you want with a kind word and a gun, than with a kind word alone.
It sounds like people are putting a whole lot of though into a non-issue. This thread reads like "why does the engine and brakes on my Honda Accord overheat when I race it at the track?" or "My gun does weird things when I do things with it that it's not designed to do."
Whether it's drilled or forged, you barrel is going to have to get straightened and stressed relieved as part of the manufacturing process. There isn't a lot of incentive for barrel makers to sink a ton of money into stress relieving shotgun barrels so that people can heat them up stupid hot and then try to test for zero. If it doesn't doesn't permanently warp when it gets hot, it's probably stress relieved enough. If you're lucky your barrel will hold zero when you do retarded things with it. If you're not so lucky, you just have a normal shotgun barrel.
Whether you think you can or you can't, you're probably right.
First, I've tracked a couple of stock Honda Accords before. It's not the brakes or engine that overheats, it's the clutch, always a weak link when you try to roll hot out of a corner or launch hard.
In this case, I think it's not the barrel. I think it's the mag tube. I think the use of Ti in the mag tube results in more movement of the mag tube when the gun gets to the same barrel temperature than it would with the stock steel mag tube. In turn the tube is clamped to the barrel and causes a wandering zero at a temperature/operating range that is probably close to "normal".Whether it's drilled or forged, you barrel is going to have to get straightened and stressed relieved as part of the manufacturing process. There isn't a lot of incentive for barrel makers to sink a ton of money into stress relieving shotgun barrels so that people can heat them up stupid hot and then try to test for zero. If it doesn't doesn't permanently warp when it gets hot, it's probably stress relieved enough. If you're lucky your barrel will hold zero when you do retarded things with it. If you're not so lucky, you just have a normal shotgun barrel.
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