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  • #16
    Pighunter, that crown does not look real bad but the serious crown damage can only be seen with a bore scope. Typically, the ends of the rifling become worn down at irregular angles allowing high pressure gas to pass the bullet and deflect it upon exit from the muzzle. Crowns are important though and do make a difference. I re-crown my long range precision rifles every 400 shots.

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    • #17
      Originally posted by DakotaMan View Post
      Pighunter, that crown does not look real bad but the serious crown damage can only be seen with a bore scope. Typically, the ends of the rifling become worn down at irregular angles allowing high pressure gas to pass the bullet and deflect it upon exit from the muzzle. Crowns are important though and do make a difference. I re-crown my long range precision rifles every 400 shots.
      Wow, re-crown after 400 shots sounds high frequency but I bet you have a very good reason. What causes you to do that?

      I took the rifle to my gunsmith buddy and he's going to polish the crown for me. He's done the same on my brother's .300 Win Mag and it greatly helped the accuracy. My rifle should be ready in a couple of weeks and then I'll resume testing out different bullets and powder.

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      • #18
        Originally posted by DakotaMan View Post
        Today I'm finishing the build of a phenomenal 6.5 PRC elk hunting rifle. It has a titanium Tuebor action (awesome) with a 22" Proof Research barrel on a Grayboe light weight stock. This is a real light weight long range thumper that you can carry over your shoulder all day.

        Later this afternoon, I hope to get to chambering a home-made AR-15 barrel. I have a take-off 26" 6mm Creedmoor Bartlein 8 twist barrel that has a burned throat after 3000 rounds. The rifling is still pretty good so I cut the bad throat out and still have enough decent rifling to support a 22" heavy barrel. I've cut and threaded the barrel already and installed the barrel extension. I rented a 6mm Grendel reamer from 4-D Reamer Rentals and will cut it in that. My other upper parts should arrive today or tomorrow so I can finish contouring the barrel, cut the gas hole and install it and test it. I'm hoping that it will shoot as accurately as a 6mm PPC bolt rifle but time will tell. Once this experiment over, I'll most likely order a new barrel and cut it the same way for a 6mm ARC (or maybe I'll stay with the 6mm Grendel). It has just been so hard to get a 6mm ARC reamer that I just went with the 6mm Grendel for now. Next week I'll try to develop some loads to test it.

        My rifle building hobby has been in full swing and I've built some mighty fine rifles during the Pandemic because I've been sequestered since February and hate watching TV all day. I've read lots of books but prefer rifle building for the fun of it.

        I recently completed a blazing 6.5x284 Lapua for F-Class competition. It has a 30" Bartlein 8 twist no-taper barrel on a Pierce titanium action, bedded in a Masterpiece Arms chassis with a Bix 'n Andy 1.5 oz trigger. Shooting the Berger 153.5g, it is lights out at 500 meters. Tomorrow I test it at 600 yards.
        Do you Cryo relieve your barrels ?

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        • #19
          Originally posted by PigHunter View Post
          Good morning, very impressive Dakotaman! I'm not that motivated and will spend some of the day reading and obviously posting on here.

          However, I'm going to do some yard work, then start loading a variety of bullets for the .308 Remington 788. This is a continuation of my experiment with IMR 4064 that I started with the .30-06 Remington 7400.

          With the .30-06, I've loaded the following using Remington brass and CCI 200 primers. I plan to do the same for the .308

          > Barnes 120gr TAC-TX
          > Barnes 150gr TSX BT
          > Hornady 150gr RN InterLock
          > Hornady 150gr SP InterLock
          > Hornady 150gr SST
          > Nosler 150gr B-Tip

          Last Tuesday at the range, I shot 10 rounds each of the B-Tips, SST, and TAC-TX off sandbags. The most promising was the SST with the first 4 rounds going into 1-1/8 inches at 100 yards. The B-Tips were just so-so and the TAC-TX spread out like a shotgun blast. However, I chronographed those 120gr black tips at over 3100 fps. That's pretty good for a carbine length 7400!

          I'm starting to suspect the muzzle crown as the cause of fliers. Here's a pic with my cell phone. You can see it's a little rough even though the cell phone photo is slightly blurred. I'm considering taking it to my gunsmith friend for a little touch-up.

          Click image for larger version Name:	20200730_153142a.jpg Views:	0 Size:	241.4 KB ID:	740843
          PH, there was an article about 4 good shots and then a fifth flyer with BT bullets. After 4 rounds the fifth gets an uneven push by the escaping gas thus the flyer. I think the article was in Shooting Times magazine. Shoot flat base bullets and that is not a problem. Don't know how much truth there is to this but the article was backed up by high speed, convincing photographs.

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          • #20
            Originally posted by jhjimbo View Post

            PH, there was an article about 4 good shots and then a fifth flyer with BT bullets. After 4 rounds the fifth gets an uneven push by the escaping gas thus the flyer. I think the article was in Shooting Times magazine. Shoot flat base bullets and that is not a problem. Don't know how much truth there is to this but the article was backed up by high speed, convincing photographs.
            Jim, I haven't seen that Shooting Times article. Was it recent?

            However, I found a similar article at Guns and Ammo. Apparently, the boat tail bullets let more gas slip past them as they move down the barrel.
            https://www.gunsandammo.com/editoria...ectiles/375628

            Here's the 5 different bullets I'm trying. Two are flat based.

            Click image for larger version

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            • #21
              Originally posted by jhjimbo View Post

              Do you Cryo relieve your barrels ?
              Jimbo, I just use the standard Bartlein or Proof Research barrels. I'm not sure whether they are cryo-relieved or not. They probably are. All I care about is that the bullets hit where I'm aiming. These guys seem to have that down, however they do it.
              Last edited by DakotaMan; 08-05-2020, 01:21 PM.

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              • #22
                Originally posted by PigHunter View Post

                Wow, re-crown after 400 shots sounds high frequency but I bet you have a very good reason. What causes you to do that?

                I took the rifle to my gunsmith buddy and he's going to polish the crown for me. He's done the same on my brother's .300 Win Mag and it greatly helped the accuracy. My rifle should be ready in a couple of weeks and then I'll resume testing out different bullets and powder.
                PH, these are long range rifles and when the rifling at the crown is worn even a little bit, the group sizes grow noticeably. 3 inch groups at 1000 yards go to 6 inch groups quickly. I just remove the scope and pop the barrel in the lathe for a quick spin. A national champion F-Class winner (after he reitred) advised me of this long ago as his secret sauce that set him apart from the competition and he was right. It's easy for me to do because I have a gunsmith lathe.

                The muzzle blast blows by the deep boat tails on heavy VLD bullets as they exit the muzzle, causing them to yaw. It takes them about 250 yards of flight before they straighten out. The influence of a crown defect may rock them so bad, they never recover before hitting the target. I've never had a problem with gas blow by in the barrel using these heavy VLD bullets. I shoot about 75 rounds in a match and don't see fliers unless I messed up the brass or seating depth. If high pressure gas is passing the bullet in the barrel, it must be doing it consistently.

                Flat based bullets don't have this issue as most of the exit pressure stays behind the bullet. That's why 100 yard benchrest shooters use flat based bullets. They can shoot in the .0's while the big VLDs will average around .3" at 100 yards because they are still yawing in a circle. The VLDs take over at about 300 yards though because of the high drag on flat based bullets and the fact that the yaw disappears at that range on the VLDs.

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                • #23
                  Thanks DakotaMan for that explanation. That is thought provoking as I find a new load for the 7400. With it, I'll probably never shoot at game greater than 250 yards.

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                  • #24
                    Originally posted by DakotaMan View Post

                    Jimbo, I just use the standard Bartlein or Proof Research barrels. I'm not sure whether they are cryo-relieved or not. They probably are. All I care about is that the bullets hit where I'm aiming. These guys seem to have that down, however they do it.
                    I hear stories how the Swiss age their barrels and also Krup in Austria ages to stress releave.

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                    • #25
                      Originally posted by PigHunter View Post
                      Thanks DakotaMan for that explanation. That is thought provoking as I find a new load for the 7400. With it, I'll probably never shoot at game greater than 250 yards.
                      You really have little need for a long, heavy-for-caliber bullet if all your shots are within that range PH. Another thing to think about is that bullets become more difficult to stabilize, the longer they get. Therefore, the longer the bullet, the more it will tip and deflect upon contact with brush. Your short round nosed bullet on the left is likely to chop through branches or brush much better than the long copper Barnes bullet of the same weight.

                      I actually shot a similar looking .35 Rem 200g round nosed Interlock bullet at a 100 yard deer. His face is all I could see in the brush so I aimed right between his eyes through a clear tunnel in the brush between us. I hit him right where I was aiming but as I was walking toward him after the shot, I saw where the bullet had penetrated a 3" limb slightly above my scope's line of sight. Obviously, the bullet's trajectory took it above my line of sight where it hit the limb and a few pieces of brush. I could never have made that shot with a spire point or VLD bullet. They would have deflected off severely I'm sure. It would interesting to test your bullets by shooting a five shot group through a few bushes 30 yards in front of the target. I'll bet the short, fat bullet on the left would be the most accurate by far.

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                      • #26
                        Originally posted by DakotaMan View Post

                        You really have little need for a long, heavy-for-caliber bullet if all your shots are within that range PH. Another thing to think about is that bullets become more difficult to stabilize, the longer they get. Therefore, the longer the bullet, the more it will tip and deflect upon contact with brush. Your short round nosed bullet on the left is likely to chop through branches or brush much better than the long copper Barnes bullet of the same weight.

                        I actually shot a similar looking .35 Rem 200g round nosed Interlock bullet at a 100 yard deer. His face is all I could see in the brush so I aimed right between his eyes through a clear tunnel in the brush between us. I hit him right where I was aiming but as I was walking toward him after the shot, I saw where the bullet had penetrated a 3" limb slightly above my scope's line of sight. Obviously, the bullet's trajectory took it above my line of sight where it hit the limb and a few pieces of brush. I could never have made that shot with a spire point or VLD bullet. They would have deflected off severely I'm sure. It would interesting to test your bullets by shooting a five shot group through a few bushes 30 yards in front of the target. I'll bet the short, fat bullet on the left would be the most accurate by far.
                        You make some great points. That round nose 150g is what I load for the wife's .308 and I have a couple hundred on hand. It's fairly accurate in her rifle but she's never shot a deer with it. They're lower cost than the spire points and generally are available when other styles are out of stock.

                        Talking about busting through obstructions, I've run into that twice and both times there was enough deflection to cause total misses. The first time I clipped a twig when using my crossbow. My aim was good and the distance was only about 30 yards so I was puzzled when the small buck ran off seemingly unhurt and with no blood trail. Looking back along the path of the shot, I found this neatly cut twig...

                        Click image for larger version  Name:	Twig Deflection 2010_11_07.jpg Views:	0 Size:	280.4 KB ID:	741313

                        The second time, I shot at a doe with my muzzleloader using a 240g XTP. Once again, no blood trail and the bullet had furrowed a trench under where the deer had stood. I spotted this limb when looking back up the hill along the bullet's path...

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