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Post by buckeye68 on Dec 20, 2023 19:10:04 GMT -5
I’ve always wanted to know how much FPS a barrel would lose if you cut an inch or two off the end of the muzzle. I’ve heard 10 to 15 FPS but really never had any hard facts. So last week I took new black and blue 45/70 CVA Scout break action and had Jeff Hankins at Hankins Custom Rifles convert it to a SML. With this being a new barrel that’s never fired before. I had to setup a new smooth sizing die that came from Hanks Precision Gun Parts. I sized the bullet for a 2 finger easy push down the barrel. For my testing I would be using 55 grains of IMR 4198 powder, Federal large rifle primers, Fury STB 265 grain bullets and a Garmin Xero C1 chronograph to record FPS. I will use a bandsaw to cut 1” off the barrel and a hand deburring tool to clean up the crown. I also will run one dry patch down the barrel to remove any coolant from the bore. The only change that will be made during this test is cutting 1” off the barrel per test.      I started off with a factory 25” barrel and fired 6 shots to make sure the barrel was fouled and my die was set up correctly. 25” barrel produced an average velocity of 2443 FPS with an ES of 3. 24” barrel produced an average velocity of 2400 FPS with an ES of 16. 23” barrel produced an average velocity of 2393 FPS with an ES of 5. 22” barrel produced an average velocity of 2388 FPS with an ES of 10. 21” barrel produced an average velocity of 2340 FPS with an ES of 11. 20” barrel produced an average velocity of 2297 FPS with an ES of 19. 19” barrel produced an average velocity of 2248 FPS with an ES of 21. 18” barrel produced an average velocity of 2235 FPS with an ES of 8. 17” barrel produced an average velocity of 2305 FPS with an ES of 7. With 60 grains the 17’ barrel produced an average velocity of 2395 FPS with an ES of 12. With 65 grains the 17’ barrel produced an average velocity of 2496 FPS with an ES of 18. How did a 17” produce more speed than the same barrel at 18”? I did double check my readings and they are correct. I’m glad I did the test but shooting a 6 pound gun with no break is no fun and my shoulder sure knows it. Now what to do with another 17” break action………………. Loud Mouth 2.0 is born. |
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Post by Kyle on Dec 20, 2023 19:25:18 GMT -5
Very good information. This may also be an option for guys looking to cut off the choaked section on a choaked conversion. Probably will only loose 50-60 fps.
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Post by dennis on Dec 20, 2023 20:44:37 GMT -5
Good stuff, appreciate the testing and sharing you do. Useful info for now and future 👍
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Post by ballistic on Dec 20, 2023 21:09:43 GMT -5
Looking at the speeds - it looks like the barrel had speed nodes (like 24-22” didn’t change much.
On a curve you could say 25 fps average loss per inch but the test isn’t showing this. And then 17” picked speeds up a ton which might be fouling getting ahead of the bullet -creating more resistance -but who knows….
Smokeless isn’t always predictable.
Mark
How did the shots load on the 17” barrel ? If normal hard to explain right ?
Great test Mark !
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Post by buckstuds on Dec 20, 2023 21:27:20 GMT -5
while you have it like this, could you shoot a max charge (54) of 4227 with a 265. and dis or his
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Post by buckeye68 on Dec 20, 2023 22:29:53 GMT -5
while you have it like this, could you shoot a max charge (54) of 4227 with a 265. and dis or his This will be part of my next testing session. |
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Post by buckeye68 on Dec 20, 2023 22:42:00 GMT -5
Looking at the speeds - it looks like the barrel had speed nodes (like 24-22” didn’t change much. On a curve you could say 25 fps average loss per inch but the test isn’t showing this. And then 17” picked speeds up a ton which might be fouling getting ahead of the bullet -creating more resistance -but who knows…. Smokeless isn’t always predictable. Mark How did the shots load on the 17” barrel ? If normal hard to explain right ? Great test Mark ! When I was initially setting up the bullet for the barrel, I was adjusting the sizing die using the conventional method. Once I got the bullet started going down the barrel with my fingers at the crown, this is where I stopped and changed it up a little. I only do this on the CVA’s. I removed the barrel and start checking bullet fit from the breach end. I dropped the bullet down the powder chamber and used the ram rod to push it in the barrel. It may take me a couple of times to get it, but I know it is going to be correct because CVA’s are notorious for choked barrels. This method removes that variable. On this barrel, it was constant from the powder chamber to just before the crown. I could feel a little tight spot as the bullet passed through the crown. This told me that the crown had a burr from the factory. Once I started testing at the 25” length, the bullet was a little hard to get started, but once it went down the barrel a little it was easy. After I cut 1” off the barrel it was easy from the beginning till the bullet hit the powder charge. All barrel lengths from 23” down to 17” were all the same. I will say, IMO, the barrels on the black and blue scout are more consistent than the fancier SS version. Plus, there are no flutes on the barrel. This makes it a perfect rifle to cut down for a short barrel gun. Adding a muzzle break is the next step once you know what length you want to end up with. |
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Post by yoderjac on Dec 21, 2023 0:25:31 GMT -5
Really cool and interesting test! Thanks for posting this.
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Post by buckstuds on Dec 21, 2023 7:17:16 GMT -5
Plus I hate to be a pain, at 17 could you also shoot 60 and 65 gr of 4198 to see velocity. Basicly finding out amount of powder burned thru velocity..
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Post by Kyle on Dec 21, 2023 9:33:32 GMT -5
Mark,
Could you list the E.S. for each barrel length?
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Post by shindig on Dec 21, 2023 9:57:24 GMT -5
Awesome info.
Thanks for taking the time and sharing.
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sqezer
Junior Member
Posts: 83
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Post by sqezer on Dec 21, 2023 10:36:23 GMT -5
Very good information. This may also be an option for guys looking to cut off the choaked section on a choaked conversion. Probably will only loose 50-60 fps. I myself would put the time in and Lap the tight section out. I love making good guns Great guns. |
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jarhead TX
Junior Member
Getting ready for another season
Posts: 97
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Post by jarhead TX on Dec 21, 2023 13:59:34 GMT -5
Mark thats is some very extensive testing that you have done. Thank you for running these tests. Everyone that uses this message board can benefit from information that you have provided. We look forward to seeing you at the Polar bear shoot in Feb.
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Post by ballistic on Dec 21, 2023 15:23:21 GMT -5
I’m guessing you could go to a faster burn rate powder and get your 200 fps back that you lost ? Are you going to try that ?
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Post by Deputy819 on Dec 21, 2023 16:58:07 GMT -5
buckeye68What would you attribute to the reason why the 17” section produced higher velocity than the 20” section with all other variables staying the same?🤔 Was the chronograph kept in the same spot in relation to the rifle for all shots taken? How do you like that Garmin unit, by the way?
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Post by caseless on Dec 21, 2023 20:23:39 GMT -5
Great information Mark thanks for testing and sharing. How’s the shoulder 😂, maybe the next test should be done from a sled 🤷🏼♂️😁
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Post by buckeye68 on Dec 21, 2023 21:47:39 GMT -5
Mark, Could you list the E.S. for each barrel length? Added ES |
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Post by buckeye68 on Dec 21, 2023 21:51:50 GMT -5
Plus I hate to be a pain, at 17 could you also shoot 60 and 65 gr of 4198 to see velocity. Basicly finding out amount of powder burned thru velocity.. I can do that with no problem, just got to added a break. I shoot free recoil and shooting a 6 pound gun is no fun! |
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Post by buckeye68 on Dec 21, 2023 21:58:01 GMT -5
I’m guessing you could go to a faster burn rate powder and get your 200 fps back that you lost ? Are you going to try that ? Planning to make the switch to 4227. I can shoot less powder and gain speed with 4227 than 55 grains of of 4198. I’ll post my results |
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Post by buckeye68 on Dec 21, 2023 22:35:13 GMT -5
Very good information. This may also be an option for guys looking to cut off the choaked section on a choaked conversion. Probably will only loose 50-60 fps. I myself would put the time in and Lap the tight section out. I love making good guns Great guns. The only issue with is barrel was at the crown. Can you lap crown without damaging it or is it worth your time? I’m paying a gunsmith to thread barrel for a muzzle break and add a new crown. IMO, cutting off .250” isn’t going to hurt anything. |
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