Lilja Short Barrel... New Poll

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  • cory
    Chieftain
    • Jun 2012
    • 2985

    #61
    Your argument seems valid to me. Dan goes deep in his calculations and does it right determining the barrels deflections and moments of Inertia.

    Explaining all of that in the link will take some studying and a lot more than can fit in a post. No way around it.

    A simpler way of looking at it, is through Moments (or shear Force). M = r x F where M = moment r = distance from static point (for us the upper receiver) F = Force (for us at the end of the barrel).

    So we assume a 10lb Force for ease of calculations and a 20" barrel has a moment of 200 lb in and a 12.5" barrel has a moment of 125 lb in. If the contours are identical I believe this will be effective for demonstrating the stiffness of a barrel compared to another barrel.
    "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

    Comment

    • cory
      Chieftain
      • Jun 2012
      • 2985

      #62
      Just did the math and if we went from 0.750" to 0.725" a 0.025" difference, we'd be looking at a weight savings of 0.000549 lb/in +- 0.000015 lb/in depending the exact density of the Stainless Steel Lilja uses.

      With a carbine length gas system I think we can assume roughly a 3" section of either 0.750 or 0.725. At 3" we're looking at a max difference of 0.073oz.

      I know I would have thought it would of been at least a couple of ounces.
      Last edited by cory; 07-22-2014, 12:43 PM.
      "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

      Comment

      • Variable
        Chieftain
        • Mar 2011
        • 2403

        #63
        Originally posted by cory View Post
        Your argument seems valid to me. Dan goes deep in his calculations and does it right determining the barrels deflections and moments of Inertia.

        Explaining all of that in the link will take some studying and a lot more than can fit in a post. No way around it.

        A simpler way of looking at it, is through Moments (or shear Force). M = r x F where M = moment r = distance from static point (for us the upper receiver) F = Force (for us at the end of the barrel).

        So we assume a 10lb Force for ease of calculations and a 20" barrel has a moment of 200 lb in and a 12.5" barrel has a moment of 125 lb in. If the contours are identical I believe this will be effective for demonstrating the stiffness of a barrel compared to another barrel.


        [Jayne Voice]"Nothin' into nothin', carry the nothin'"[/Jayne Voice]

        Okay, I'll take your word for it.LOL
        Life member NRA, SAF, GOA, WVSRPA (and VFW). Also member WVCDL. Join NOW!!!!!
        We either hang together on this, or we'll certainly HANG separately.....

        Comment

        • Variable
          Chieftain
          • Mar 2011
          • 2403

          #64
          Originally posted by cory View Post
          Just did the math and if we went from 0.750" to 0.725" a 0.025" difference, we'd be looking at a weight savings of 0.000549 lb/in +- 0.000015 lb/in depending the exact density of the Stainless Steel Lilja uses.

          With a carbine length gas system I think we can assume roughly a 3" section of either 0.750 or 0.725. At 3" we're looking at a max difference of 0.073oz.

          I know I would have thought it would of been at least a couple of ounces.
          This one confuses me a bit. I meant to reduce the barrel diameter on the straight sections both behind and in front of the gas block journal.


          ---CAUTION: I'M TRYING TO THINK OUT LOUD HERE, MY INSANE PRATTLE COULD BE DAMAGING TO INTELLIGENT FOLK. I BEAR NO RESPONSIBILITY FOR ANY PERMANENT REDUCTION IN ANYONE'S MENTAL FACULTIES FOR TRYNG TO FOLLOW MY LOGIC---


          For example---- On Lilja's contour page ( http://www.riflebarrels.com/products...ion_rifles.htm ) they list .30 bore weights per barrel inch at different diameters. A .750" bore ("C") diameter weighs .103 pound per inch, while a .700" bore weighs .087 pound per inch. I ignored the bore sizes, because they are the same in both examples, and merely subtracted the .087 from the .103 to get a difference of .016 pound per inch of metal removed from the outside of the barrel.

          I measured my 10.5" barrel and determined (guestimated) that there is almost exactly 6" of straight barrel under the handguard and forward of the gas block journal that could reduced down to .700" inches in diameter (for this example).

          .016 pound X 6 inches = .096 pounds (1.536 ounces)

          That's 1.536 ounces shaved off of a non-fluted 12.5" barrel by reducing it .050" from .750" diameter down to .700" diameter.

          I can't think up a way to guess well at how much fluting would actually remove per inch (weight wise) from a .750" barrel, so I'm having a hard time comparing the weight reductions between the two methods.

          I got lost somewhere on what Kentucky Buddha was answering specifically with his barrel weights (i.e. were his two fluted AR740 barrels both 20" Grendel barrels?). If his two barrels go about 2.043 pounds, and they are 6.5 bored, then I'd try to calc how much of the weight loss was from the larger bore (approximately .0045 pound per inch for a total of about .078 pound).

          Then I'd take the stock print weight of 2.43 pounds and subtract 2.043 pounds from that to get .387 pounds difference between his barrels and the stock one. I'd take the .387 pounds and subtract the bore weight reduction of .078 pound and come up with .309 pounds removed via fluting.

          Then it would possibly get crazy.LOL How many inches of his barrels are fluted? 10"? Are the flutes the same width and depth both fore and aft the gas block journal? I dunno... If they are somewhat equal in amount removed per cut inch, and they were good for about 10 inches of total flute length (really wild guess), the for example I'd divide .309 pound by 10 inches, and guess .0309 pound removed per inch.

          I'm probably really lost out in the weeds by now with too many wild guesses, but if the flutes were good for .0309 pound per inch (I expect less though), then I'd look at my 10.5" barrel as an example and guess they'd only flute about 4" total of a 12.5" barrel. That'd yield .0309 X 4 inches for a total net reduction via fluting of apprx. .1236 pounds (1.978 ounces).

          So if my crazy guesses were anywhere near close, then reducing barrel diameter from .750" to .700" would net .096 pounds reduction, while fluting instead might shave off .1236 pounds. That extra .44 ounce for fluting would be mighty expensive at 115 dollars.LOL!

          I'm probably off by a fair bit in either direction though. I'm just doing punch-drunk redneck napkin math....
          Last edited by Variable; 07-22-2014, 03:24 PM.
          Life member NRA, SAF, GOA, WVSRPA (and VFW). Also member WVCDL. Join NOW!!!!!
          We either hang together on this, or we'll certainly HANG separately.....

          Comment

          • KentuckyBuddha
            Warrior
            • Oct 2012
            • 972

            #65
            You were correct. I had two 740's fluted in 6.5 Grendel and there was a little difference between the two, but around the same weight. Somebody probably has a barrel or two of the regular 740 to compare to which will hopefully keep you from "damaging your calm" and having to do any calculus to evaluate the mass of the cleared area of the fluting of those barrels. : D

            Comment

            • Variable
              Chieftain
              • Mar 2011
              • 2403

              #66
              Originally posted by KentuckyBuddha View Post
              You were correct. I had two 740's fluted in 6.5 Grendel and there was a little difference between the two, but around the same weight. Somebody probably has a barrel or two of the regular 740 to compare to which will hopefully keep you from "damaging your calm" and having to do any calculus to evaluate the mass of the cleared area of the fluting of those barrels. : D
              Hee Hee! Thanks for not damaging my calm man!

              Life member NRA, SAF, GOA, WVSRPA (and VFW). Also member WVCDL. Join NOW!!!!!
              We either hang together on this, or we'll certainly HANG separately.....

              Comment

              • cory
                Chieftain
                • Jun 2012
                • 2985

                #67
                Originally posted by Variable View Post
                This one confuses me a bit. I meant to reduce the barrel diameter on the straight sections both behind and in front of the gas block journal.

                For example---- On Lilja's contour page ( http://www.riflebarrels.com/products...ion_rifles.htm ) they list .30 bore weights per barrel inch at different diameters. A .750" bore ("C") diameter weighs .103 pound per inch, while a .700" bore weighs .087 pound per inch. I ignored the bore sizes, because they are the same in both examples, and merely subtracted the .087 from the .103 to get a difference of .016 pound per inch of metal removed from the outside of the barrel.

                I'm getting a 0.178 lb/in for the .750" bore, 0.14 lb/in for the 0.70" bore, and a difference of 0.0022 lb/in. However, my calculations don't take into account a taper of the barrel, so I'd suspect his calculations are right on.

                I measured my 10.5" barrel and determined (guestimated) that there is almost exactly 6" of straight barrel under the handguard and forward of the gas block journal that could reduced down to .700" inches in diameter (for this example).

                I went back and looked at the drawings to determine how close my 3" really was. Taking the AR740's gas system from rifle length to carbine length takes its measurement of 13.265" to 7.875". Subtract that difference from the length of the 0.750" of AR740 barrel under the handguard (9.15") and you get 3.76".

                This changed my weight reduction to 0.132 oz, 0.0022 lb/in.


                .016 pound X 6 inches = .096 pounds (1.536 ounces)

                That's 1.536 ounces shaved off of a non-fluted 12.5" barrel by reducing it .050" from .750" diameter down to .700" diameter.

                I can't think up a way to guess well at how much fluting would actually remove per inch (weight wise) from a .750" barrel, so I'm having a hard time comparing the weight reductions between the two methods.

                Given the intended dimensions of the fluting from Lilja we could calculate it, but I suspect it would be significantly off from what is removed real world at least width wise. I say significantly in respect to how exact we're trying to get our calculations. I believe scaling down from a known weight is a better bet here. It'd really help if we had real world measurements of the weight of a NON fluted AR740 and 319.

                I got lost somewhere on what Kentucky Buddha was answering specifically with his barrel weights (i.e. were his two fluted AR740 barrels both 20" Grendel barrels?). If his two barrels go about 2.043 pounds, and they are 6.5 bored, then I'd try to calc how much of the weight loss was from the larger bore (approximately .0045 pound per inch for a total of about .078 pound).

                They were 20" barrels. All of Lilja's AR740 barrels are 20" OAL. Once Dan alters the drawing for our barrels it'll be given a nomenclature different from AR740. Even if it were just length.

                Then I'd take the stock print weight of 2.43 pounds and subtract 2.043 pounds from that to get .387 pounds difference between his barrels and the stock one. I'd take the .387 pounds and subtract the bore weight reduction of .078 pound and come up with .309 pounds removed via fluting.

                For our intents and purpose, I don't think those drawing weights are accurate enough for us.

                Then it would possibly get crazy.LOL How many inches of his barrels are fluted? 10"? Are the flutes the same width and depth both fore and aft the gas block journal? I dunno... If they are somewhat equal in amount removed per cut inch, and they were good for about 10 inches of total flute length (really wild guess), the for example I'd divide .309 pound by 10 inches, and guess .0309 pound removed per inch.

                I follow you here and agree that the value of fluting is directly proportional to the length of the barrel. Which very well could be throwing off my scaling method. I tried to work on the conservative side, so I don't think it will much.

                That being said I don't opt for fluting because of weight savings, that's a bonus for me, albeit a big bonus. I get the fluting for the increase in heat transfer performance. A fluted barrel will shed heat much quicker because of the increased surface area. In that respect fluting becomes more valuable as the barrel gets shorter. I'd suspect this would help extend the life of the barrel.


                I'm probably really lost out in the weeds by now with too many wild guesses, but if the flutes were good for .0309 pound per inch (I expect less though), then I'd look at my 10.5" barrel as an example and guess they'd only flute about 4" total of a 12.5" barrel. That'd yield .0309 X 4 inches for a total net reduction via fluting of apprx. .1236 pounds (1.978 ounces).

                So if my crazy guesses were anywhere near close, then reducing barrel diameter from .750" to .700" would net .096 pounds reduction, while fluting instead might shave off .1236 pounds. That extra .44 ounce for fluting would be mighty expensive at 115 dollars.LOL!

                I'm probably off by a fair bit in either direction though. I'm just doing punch-drunk redneck napkin math....

                Hopefully, JASmith will jump in here and give us some direction on which way to go with our calculations.
                So mass is calculated as density times volume. Weight is mass times gravity. This whole thing is very straight forward and clean in metric units. When working in lbs it's very complicated in deriving and comes out to be weight = density times volume. Confused yet? haha

                Well I that say that to say I did my calculations by determining the area per inch we were looking at and got a density value for stainless steel from engineering toolbox.
                Densities of some common metals, metallic elements and alloys - aluminum, bronze, copper, iron and more.


                It gives us a small range for the material because the value varies slightly depending on the type of stainless steel used. I took a min max and mean lb/in calculation.

                So I'll start responding in your quote in red from here.
                Last edited by cory; 07-22-2014, 04:32 PM.
                "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

                Comment


                • #68
                  I try to do all the math in the metric system and then convert results to the Imperial system. Even then we have the 'Systeme International' CGS, MKS sets of units but with fewer surprises than with the Queen's (or King's) English system.

                  Comment

                  • cory
                    Chieftain
                    • Jun 2012
                    • 2985

                    #69
                    Originally posted by Variable View Post


                    [Jayne Voice]"Nothin' into nothin', carry the nothin'"[/Jayne Voice]

                    Okay, I'll take your word for it.LOL
                    Been there. HAHA

                    Basically take a 6" piece of rebar, clamp it at one end, and try to bend it at the other. Now try the same thing with a 16" piece of rebar. Much easier!

                    Your putting the same amount of force into it, but your moment on the bar is an order of magnitude grater on the longer rebar.
                    "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

                    Comment

                    • Adam Lilja
                      Warrior
                      • Dec 2013
                      • 267

                      #70
                      Originally posted by KentuckyBuddha View Post
                      I weighed one at 927.4 grams or 2.04457lb

                      the other was 926.6 grams or 2.0428 lb


                      Two and a half is a pretty good guess Adam!
                      I can't tell if this is sarcasm or not haha :P

                      Comment

                      • KentuckyBuddha
                        Warrior
                        • Oct 2012
                        • 972

                        #71
                        Originally posted by Adam Lilja View Post
                        I can't tell if this is sarcasm or not haha :P
                        It is usually a good bet to think I am making a joke whenever my mouth is moving but in this case that is a pretty good guess if you ask me. : )

                        Comment

                        • cory
                          Chieftain
                          • Jun 2012
                          • 2985

                          #72
                          I've updated the OP with the barrel count and barrel length score.

                          Barrel Length Score
                          12.5" - 8
                          11.5" - 7
                          10.5" - 2

                          I've asked for your first and second choice of barrel lengths in the spread sheets. I've using a weighted scoring system to determine the winner, possibly 2 winners. Each first choice is 3 points and each second choice is 2 points.
                          "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

                          Comment

                          • cory
                            Chieftain
                            • Jun 2012
                            • 2985

                            #73
                            Just updated #2 post of this thread with the black nitride information. I'll post it here too.

                            Quote Ferritic Nitrocarburize per AMS2753C
                            H&M Black Nitride™ process.

                            $5.00 each RIFLE Barrel
                            $250.00 Minimum Lot Charge
                            $7.00 Certification to the process, if requested
                            $50.00 Certification with actual lab results, if requested (Customer must supply material for destructive testing)

                            Plus Shipping

                            I'm not sure who would be interested in a certification or lab test, but they gave me a quote so it's available.

                            With shipping I'd think ~$6-$7 a barrel.
                            "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

                            Comment

                            • Variable
                              Chieftain
                              • Mar 2011
                              • 2403

                              #74
                              Regarding twist rates: I just found this quote (of a quote of a quote...LOL) from Bill Alexander that I found back on Sniper's Hide long ago. It may even have been from the old board. I dunno, but it is pertinent, so anywhooo:


                              The stability of the projectile is given by the rate of rotation and is usually expressed as radians per second. It is for most purposes independent of the forward velocity, but in the case of a rifle the spin is created by the rifling. Longer barrels producing more velocity can therefore use a slower twist rate to produce the same rate of rotation.

                              Barrel materials and the shape of the rifling will also effect how the projectile is stabilized and the complexity of the choices is then extended by the economics of tooling and the process by which the rifling is formed.

                              For Grendel the following set ups are used.

                              - 28" cut rifled stainless 5 groove 5R 1 in 9
                              - 24 cut rifled stainless 5 groove 5R 1 in 9
                              - 24" button rifled stainless 6 groove 1 in 9
                              - 20" cut rifled stainless 5 groove 5R 1 in 9
                              - 19.5" button rifled stainless 6 groove 1 in 9
                              - 18" chrome lined 6 groove 1 in 7 1/2
                              - 18" stainless 6 groove 1 in 8 1/2
                              - 16" cut rifled stainless 5 groove 5R 1 in 8
                              - 16" chrome lined 6 groove 1 in 7 1/2
                              - 16" button rifled stainless 1 in 8 1/2
                              - 14.5" chrome lined 1 in 7 1/2
                              - 10.5" chrome lined 1 in 7 1/2

                              As can be seen from the above, there are some anomalies. The chrome lined barrels like a fast twist rate and at 18" the 1 in 7 1/2 that Sabre produces, produces very fine accuracy. Interestingly the 14.5" barrel with the same twist is also very accurate as is the 10.5" barrel. When we ran the 16" stainless button barrel in 1 in 7 1/2 the accuracy was marginal but 1 in 8 1/2 works well for both the 16' and 18" . The oddity is the cut rifled barrels. These can run slower than anything else but do not seem to care about faster twists either. We have set up 16" barrels at 1 in 9 with great success equally 24" barrels will stabilize 140 grain projectiles at 1 in 10 but this is not at minus 60 at sea level, so we edged towards caution.

                              Bill Alexander
                              Life member NRA, SAF, GOA, WVSRPA (and VFW). Also member WVCDL. Join NOW!!!!!
                              We either hang together on this, or we'll certainly HANG separately.....

                              Comment

                              • cory
                                Chieftain
                                • Jun 2012
                                • 2985

                                #75
                                Great find!

                                I'm feeling a lot more comfortable with the 8" twist.

                                It's interesting that the 6 groove button barrel doesn't need as fast of a twist. To bad there aren't any 3 groove examples there.
                                "Those who sacrifice liberty for security, deserve neither." Benjamin Franklin

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