Barrel length and muzzle velocity

[Wjesswheel]

30 inch barrel shooting 168 gr federal gold medal match 308. Been shooting 750 and was thinking about trying to qualify out to 1000yds on Sunday. I know I should have already chronological it but been working way to much. Called out to the range to day and set an appointment to try 1000. While speaking to the range guy on the phone about some ballistics charts he made the comment that with the 30 inch barrel I would have less muzzle velocity then a 24 inch barrel, from everything I have read that seems incorrect, I was expecting the opposite from what I have read. Something like 70 to 80 ft per sec more.

Do any of you have any experience with barrel length on muzzle velo? Actually have the money for a chrono but been thinking I would be better off waiting till Christmas and my wife buying me one that attaches to the end of your barrel. Either way would not of had time to use it the last 3 weeks. Any info would be helpful

 

[jonbearman]

I don't think so.

 

[dkhunt14]

I believe there is info on Dan Lilja's website. He had a barrel at 46 inches and kept cutting it off. The velocities get less as he cut it off. Some were larger then others. Matt

 

[Wjesswheel]

Yea that's the article I read I thought he gained velocity all the way out to 40 inches

 

[Lapua40X]

All of Lilja's published barrel length tests support the increased barrel length equals increased velocity axiom.

 

[savagedasher]

Here is some numbers for my Dasher with 105 HYBRIDS and 61500 PSI
Varget H4350 N550
24'' 2928 2960 3024
29'' 3036 3073 3140
40'' 3202 3249 3319
The 29'' are accurate with H4350 and N550 The Varget load took 64300 PSI for the numbers.
Larry

 

[chkunz]

In your case muzzle velocity is still increasing with barrel length at 30 inches, but probably less than 20 fps per inch. It is true that there is a barrel length for any given cartridge where additional barrel length causes a decrease in velocity (approximately 18 inches for the 22 rim fire for example) but for most center fire cartridges it is longer that we normally encounter. Normally folks do not choose the 168 grain Sierra Matchking bullet for 1000 yards because it is difficult to keep it super sonic at 1000 yards.

 

[Rustystud]

The are many factors related to a barrel length and bullet velocity.
Bullet weight, bearing surface length and diameter, ogive, base, BC. and SD.
Barrel length, bore diameter, throat/free bore, number of lands, land/groove ratio, rate of spin, barrel bore surface condition, and temperature
Primers,
Powder burn rate, temperature, volume,
Case thickness, volume, and neck tightness

As one can see this is not as easy as just barrel length.

I can take a 26" AMU contour, 30 cal., 1;11.27 twist, 5R, barrel from 5 different manufactures and shoot the same bullets, primers, powders, and cases, all having the same chamber, COAL and shoot five "like" rounds and have a 300 fps variation between the fastest and slowest barrels.
Nat Lambeth

 

[chkunz]

It's not difficult to keep a 168 SMK bullet supersonic at 1000 yd per se, it's difficult to keep it stable because of the boattail design. You'd be far better off using FGMM load with the 175 SMK bullet. If you decide to use the FGMM 168 load at 1000 yd and they're hitting all over the target, have your puller check because they might well be keyholing. I've seen it happen more than once.

As far as velocity, in the barrel length range you're describing, the velocity will continue to increase going from a 24" to a 30" barrel. It just won't increase as much per inch extra barrel length as it would going from something like 18" to 24".

The 175 SMK was specifically developed for 1000 yard shooting with the M14 and as you say it is a better choice than the 168 SMK for 1000 yards. The 168 SMK was developed for 300 meter competition but also does well at 600 yards and was the most popular NMC (aka XTC) bullet until the sub caliber cartridges were allowed and now dominate that competition. I would take issue with your statement about the boat tail causing the instability. The instability results from the aerodynamics involved with the transition from super sonic to sub sonic conditions.

 

[Joe R]

Do any of you have any experience with barrel length on muzzle velo? Actually have the money for a chrono but been thinking I would be better off waiting till Christmas and my wife buying me one that attaches to the end of your barrel. Either way would not of had time to use it the last 3 weeks. Any info would be helpful

Ask and you shall receive. The first picture is the chrono (Oehler 35P) data using a 30 inch Krieger 1:11 twist with the FGMM 168grain HPBT.

The second picture is using the same ammo, same chrono with a Savage 10, 24 inch barrel 1:10 twist.

 

[Grimstod]

Here is a really well done study by a college grad student working on his masters in engineering. Its very complete and he did the test in about as scientific a way as you could on a budget. Longer barrel almost invariably equals more MV.

http://honors.usf.edu/documents/thesis/u82488180.pdf

 

[Wjesswheel]

Ask an ye shall receive? Got any extra 6 figure cash laying around. LoL. No seriously thanks for the help. So i am going to figure 75 fps more then the advertised 2650 that federal advertises. That sound reasonable to start with?

 

[chkunz]

Ask an ye shall receive? Got any extra 6 figure cash laying around. LoL. No seriously thanks for the help. So i am going to figure 75 fps more then the advertised 2650 that federal advertises. That sound reasonable to start with?

Hold on a minute big feller! Lets review. You are too hung up on knowing exactly what your muzzle velocity is. Your objective is to be on paper with your first sighter at 1000 yards and then go from there. I assume that you have a 600 yard zero so the standard come up from 600 to 1000 is 22 minutes. That is for the M118 173 grain military match bullet with a muzzle velocity of 2550 fps. You are going to shoot a 168 SMK at 2650 fps (the mfg stated MV is probably higher than actual) plus maybe an additional 70 fps. So you will be in the ball park (on paper) for elevation with the standard come up. But a ten mph cross wind will move you from the center of the target to just off the paper so a good wind call is probably more important than knowing a few fps on muzzle velocity. Now here is the most important thing, get squaded with an experienced 1000 yard shooter, come up 22 minutes from your 600 yard zero, get a wind call from your experienced score keeper and put it on the sights and have him get exactly behind the axis of your gun and watch for the bullet trace. If you are on paper all is well. If not correct off his bullet trace call or pick something in front of your target like a clump ten feet below the target number board and shoot another sighter and have your experienced scorer watch for dirt to fly. Being a 750 XTC shooter and with your set up a reasonable expectation would be to keep all shots on paper. And that is ok but what you learn is more important and most of all have fun. If you need to know more send me a PM and we will get on the phone and answer any questions. Take care, Clyde.

 

[Joe R]

30 inch barrel shooting 168 gr federal gold medal match 308. Been shooting 750 and was thinking about trying to qualify out to 1000yds on Sunday. I know I should have already chronological it but been working way to much. Called out to the range to day and set an appointment to try 1000. While speaking to the range guy on the phone about some ballistics charts he made the comment that with the 30 inch barrel I would have less muzzle velocity then a 24 inch barrel, from everything I have read that seems incorrect, I was expecting the opposite from what I have read. Something like 70 to 80 ft per sec more.

Do any of you have any experience with barrel length on muzzle velo? Actually have the money for a chrono but been thinking I would be better off waiting till Christmas and my wife buying me one that attaches to the end of your barrel. Either way would not of had time to use it the last 3 weeks. Any info would be helpful

I provided you with velocity figures you asked for, just to play along, but I really don't know what to make of your post, it seems to raise so many red flags I don't know where to start.

IMO you should take Clyde's offer and visit with him a bit, the 1K yard range is more of a journey than a destination. It takes a lot more than a phone call to schedule range time and a couple boxes of FGMM ammo.

 

[s4s4u]

with the 30 inch barrel I would have less muzzle velocity then a 24 inch barrel

Not with a 308. If you were shooting the 30 Herrett I might agree with him but there is plenty of capacity in the 308 to use up 30" of steel.

 

[Wjesswheel]

Joe, sorry I raised so many red flags with you, but here's where iam at. I shoot at a range that is 750 yds. The last 15 shots I shot hit 12 inch steal at 750. That range does not go out any father. So to shoot at a 1000 I have to go to another range to shoot a 1000 yds that they make you qualify to get out there, beacause the do not want you missing the backstop. This is the problem I have. I walked it out to 750 yd with 6ft x6 ft paper to get my holdovers. But since I have never shot over 750 I did not know that the holdover from 600 to 1000 was 22 moa. But I do now thanks to the info I got on accurate shooter . When I qualify I get 5 shots to put 3 hits at 2 moa at 800 yds 2 moa at 900 yds, 2 moa at 1000 yds. I have no where to shoot a 1000 so I can't walk it out there and work up a hold over. I was just asking for info to get out there, and since I don't have a chrono to know my fps I asked. I actually went to buy a chrono at the gun shop, but he he only keeps one in stock, that he sold. I do not have any info on muzzle velo to work off I asked and appreciated your help. I could order a chrono off ebay but for some reason I would rather pay a little more and purchase it from a business in my local area

Seems to me if you hit 15 in a row at 750 the next obvious step is to try to get out to 1000. I really like your tag after your name. Life is short, have fun and shoot more often. Words to live by and that's what I am trying to do. Either way I sincerely appreciate the post. I am about 140 reds into this hi power, long range stuff. My previously most high powered experience is with a 22 mag that I have shot a couple hundred coyotes at out to 225 yds, thousands of. Rounds thru it and I know exactly where it shoots between 100 yds to 225 it's a coyote killing machine. But again thanks for your pictures of fps it helped me out, let me know what your red flags are I will try to answer them. Don't really know about about the trip out to a 1000. Hope your correct about it being a journey, not a destination. Just hope you will welcome me when when I get out there.

 

[Wjesswheel]

Just ordered the the oehler at midway 350.00 , probably use it a few times, it has a printer, if I can afford the paper.to put in it. Hope it helps my journey

 

[Joe R]

Wjesswheel,
I'm new at this too, and I have found the guys at 1K to be a generally a welcoming bunch, they seem to like company. You're certainly welcome to visit with us in Houston anytime, you can be my guest.

Kindest regards,

Joe

 

[Wjesswheel]

I went and qualified today at 1000 yds. Shot a really nice tight sub 5 inch group at 600. The range officer asked me if I felt like skipping over 700, 800,900yd and just shooting at 1000. Your 22 moa info was very helpful my first shot was high and adjusted down to 21 moa and hit the 48 inch steel that cut my miss to about half and adjusted to 20 moa and was really close to center but a little right. Moved to 20 inch steel and clicked in about half a moa windbag and put the next 3 Into about a 10 inch group. I really appreciate the help.

I shot about another 20 rds adjusting as I went and shot some really nice groups moving toward center. Pretty much got it dialed in minus the wind changing. There was a life size steel standing ground hog target at a thousand that I shot at and missed then would shoot the 20 inch steel for corrections. Actually hit it on my 3 rd shot dead center but 4 inches higher then I was aiming. Totally impressed with the way this savage model 12 ft/r shoots with federal 168. Thanks for the help.

You mentioned finding some experienced shooters to learn from. Been to the range 7 times and have only seen 1 other guy other then me and my buddy trying to shoot that far. Did not really experience any verticlle problems with the federal 168 that I was expecting. But still wanting to try reloading some accurate reloads if you have any reloading experience I wouldn't mind taking you up on the offer of some help if you are okay with it. Again thanks for the help.

 

[chkunz]

I went and qualified today at 1000 yds. Shot a really nice tight sub 5 inch group at 600. The range officer asked me if I felt like skipping over 700, 800,900yd and just shooting at 1000. Your 22 moa info was very helpful my first shot was high and adjusted down to 21 moa and hit the 48 inch steel that cut my miss to about half and adjusted to 20 moa and was really close to center but a little right. Moved to 20 inch steel and clicked in about half a moa windbag and put the next 3 Into about a 10 inch group. I really appreciate the help.

I shot about another 20 rds adjusting as I went and shot some really nice groups moving toward center. Pretty much got it dialed in minus the wind changing. There was a life size steel standing ground hog target at a thousand that I shot at and missed then would shoot the 20 inch steel for corrections. Actually hit it on my 3 rd shot dead center but 4 inches higher then I was aiming. Totally impressed with the way this savage model 12 ft/r shoots with federal 168. Thanks for the help.

You mentioned finding some experienced shooters to learn from. Been to the range 7 times and have only seen 1 other guy other then me and my buddy trying to shoot that far. Did not really experience any verticlle problems with the federal 168 that I was expecting. But still wanting to try reloading some accurate reloads if you have any reloading experience I wouldn't mind taking you up on the offer of some help if you are okay with it. Again thanks for the help.

I misunderstood the type of competition you were into in my reply above but glad you could use the standard come up from 600 to 1000. It sounds like you had a fun day. I would recommend you look for an NRA 1000 yard match to attend. You would be able to have fun with your equipment and experience and also learn from the experience. The NRA 1000 yard matches these days normally have both F Class and conventional prone shooters and many of the competitors are very helpful. You would have a lot of visibility of what folks are using and would have the potential to learn a lot. If you have any specific questions about the NRA 1000 yard competition let me know or send a PM and I will be glad to help. Take care, Clyde.