Choosing the “right” barrel length.

[jlow]

Looking into buying a new precision bolt gun and have a choice of 20/24/26” barrel. This will be strictly a long range precision rifle for shooting 600 plus yards. I understand that for a factory round, the longer the barrel length, the higher the MV for the same round and so using the same bullet, the higher MV will help buck the wind better. The question is will this same line of thinking apply to handloads?

The specific question is if one looks at OBT calculations, the OBT for the different nodes changes as the barrel lengths changes. So using any particular bullet/powder combination, it would seem possible that because of changing node location, one may not get the theoretical increase in MV strictly due to increase in barrel length.

Am I thinking this correctly? Would appreciate any help from those that have made this journey.

 

[Keith Glasscock]

There are times when changing barrel length really doesn't change the node velocity in my experience. That said, a longer barrel that you have to throttle back a little isn't a bad thing. Brass life can increase a bit as a result.

Hope this helps

 

[jlow]

Good points - thanks!

Would be great to get more input but to add another question, apart from weight and length, any disadvantage of a longer barrel?

 

[jonbearman]

what caliber and what rifle and for what discipline.

 

[Joe R]

jlow said: Looking into buying a new precision bolt gun and have a choice of 20/24/26” barrel. This will be strictly a long range precision rifle for shooting 600 plus yards. I understand that for a factory round, the longer the barrel length, the higher the MV for the same round and so using the same bullet, the higher MV will help buck the wind better. The question is will this same line of thinking apply to handloads?

jlow, most of the guys shooting the F class 600+ distance have 30" or 32" barrels. The reason is because you want to keep you bullet supersonic at the destination (at 1K in cold weather) and that generally means Mach 1.2+ . Depending on your bullet weight you could have pressure problems. The extra barrel length gives you a little more speed without the pressure. The XTC guys do it with shorter barrel, but they use lighter bullets to get the necessary velocity, but of course they pay the price for it if the wind kicks up. Heavier bullets give you more wind resistance. Higher velocity and heavy bullets give you best wind resistance.

Which brings me to:

jonbearman: what caliber and what rifle and for what discipline.

Regards,
Joe

 

[Lapua40X]

Buy this book and read it:
http://www.amazon.com/Applied-Ballistics-Long-Range-Shooting/dp/0615452566/ref=sr_1_3?ie=UTF8&qid=1413432430&sr=8-3&keywords=ballistics
You'll be glad you did.

 

[jlow]

Thanks again for the input.

The gun will be an AI AT which only comes right now in 308 but will be picking up a 6.5 when that barrel becomes available. Mostly use for steel match but some F class. The 30”/32” will be too long for me and not available. I do have a number of Bryan’s books – they are great!

 

[Canadian bushman]

Im a barrel whore. Its free speed. I vote 26".

 

[jlow]

Thanks! I am leaning that way! ;D

 

[Road_Clam]

I'm shooting a box stock R700 .308 Varmint that uses a 26" heavy contour barrel. I'm hand loading about 41.7 - 42.4 gr. of Win 748 using both 155's and 168 gr's and my MV's are on the conservative side at approx 2560 fps. With my particular setup i'm not seeing any gain in accuracy by pushing my MV's over 2600 , as my groups start to open up. I am shooting both 200 meters, and 600 yds. Staying supersonic out to 600 no problem. Good luck, extended range is fun and challenging... (dam wind ) LOL

 

[jlow]

Thanks! Not really worried about shooting out to 1K and maintaining supersonic. I’ve shot out to that distance with a 18” barrel AR-10 using factory ammo with 175 SMK that clocks in only around 2450 fps and was still able to hit steel out to past 1k. Looking more for ability to buck the wind thus the longer barrel and higher MV.

 

[6BRinNZ]

FTR on the whole goes for long barrels (30" +) to get FPS in order to stay supersonic at 1 k. BUT short range precision rifles 100 - 200 yards typically go for short barrels, as I understand it the shorter barrels are stiffer.

My conclusion when first building an FTR rifle is that the requirements (weight, FPS) of the class vs accuracy were counter intuitive, so I went a long heavy barrel with a tuner to try and get the correct mix of FPS with precision.

I don't think there is any argument that a longer barrel means more FPS and while the accuracy node may/may not mean you can take advantage of it, you at least have a choice.

Palma brass has changed things somewhat with guys running much higher pressure loads and depending on what bullet you shoot might be a way of achieving a higher node with a shorter barrel - but you still have to burn all that powder efficiently. I don't and haven't used Palma brass as yet...but maybe something for you to research to see if it helps.

I see you are looking to buck the wind. IMO a long barrel with 185 class bullet is the best middle ground of all. High FPS, more than enough precision to run with 155s up to 600 and comes into its own 900+ but without the absolute perfection in shooting technique needed to shoot the heavy 215s, which on paper are the best in the wind.

 

[Steve Blair]

I see you are looking to buck the wind. IMO a long barrel with 185 class bullet is the best middle ground of all. High FPS, more than enough precision to run with 155s up to 600 and comes into its own 900+ but without the absolute perfection in shooting technique needed to shoot the heavy 215s, which on paper are the best in the wind.

[br]
...except for 230 Hybrids. [br]
The problem with both the 215 and 230 is whether the shooter can manage recoil dynamics on the bipod. Most cannot.

 

[6BRinNZ]

I see you are looking to buck the wind. IMO a long barrel with 185 class bullet is the best middle ground of all. High FPS, more than enough precision to run with 155s up to 600 and comes into its own 900+ but without the absolute perfection in shooting technique needed to shoot the heavy 215s, which on paper are the best in the wind.

[br]
...except for 230 Hybrids. [br]
The problem with both the 215 and 230 is whether the shooter can manage recoil dynamics on the bipod. Most cannot.

aah - true - incorrect statement on my part, intent of statement and typed out come - two different things

215s is much better on paper vs the 185 class and many seem to be trying the 215s (FTR). Possibly due to the success Bryan had.

Personally I have been tempted to try the 215s purely for a 1k load as depending on how much vertical is sacrificed they could change the outcome....on some ranges.

 

[jlow]

Thanks for the advice and perspectives. I am pretty sure I will go for the 26”.

To put where I am into perspective - can’t honestly say that I am a serious competitor as I make it a point to never take any competition too seriously mostly because it is a firm believe I have that when I take anything too seriously, it gets to be too much like work and it starts to lose its luster. At my age, I am definitely not looking for any achievements or accolades as they mean little to me. However, that does not mean that I don’t always try to do my best, just the end results in terms of ranking is not so important. This frustrates some of my friends but I have enjoyed my time in the many discipline of shooting sport competition via this route. Don’t get me wrong as I don’t mean that serious competition is in anyway bad, just not the right thing for me.

The Palma brass is a good idea, will look into that. My understanding is that the primer pockets being smaller can take higher pressure before getting loose?

Some of my friends shoot the 215s and like them, not sure about the 230s. I think the ATs are 1:12, would that twist rate stabilize these?

 

[6BRinNZ]

Thanks for the advice and perspectives. I am pretty sure I will go for the 26”.

To put where I am into perspective - can’t honestly say that I am a serious competitor as I make it a point to never take any competition too seriously mostly because it is a firm believe I have that when I take anything too seriously, it gets to be too much like work and it starts to lose its luster. At my age, I am definitely not looking for any achievements or accolades as they mean little to me. However, that does not mean that I don’t always try to do my best, just the end results in terms of ranking is not so important. This frustrates some of my friends but I have enjoyed my time in the many discipline of shooting sport competition via this route. Don’t get me wrong as I don’t mean that serious competition is in anyway bad, just not the right thing for me.

The Palma brass is a good idea, will look into that. My understanding is that the primer pockets being smaller can take higher pressure before getting loose?

Some of my friends shoot the 215s and like them, not sure about the 230s. I think the ATs are 1:12, would that twist rate stabilize these?

Palma brass - this is correct, I know of guys (first hand) that are running low to mid 2800s with 185s and are on their 6th reload and looking good.

Berger recommend 10tw, Bryans latest book suggests that more twist is better than less for optimal BC.

Oh - and I don't think barrel tuners are just for hard out competitors either, there is a lot to learn from watching what a change in harmonic does to a group or POI and they can make the job easier if you are fighting FPS, precision and ES/SD.

 

[Steve Blair]

Some of my friends shoot the 215s and like them, not sure about the 230s. I think the ATs are 1:12, would that twist rate stabilize these?

[br]
No, at least 1:10 for 215's and 1:9 is better for 230's at .308 velocities.

 

[jlow]

Thanks again for confirming the Palma brass.

Thanks also for the info on the twist for the heavies. Unfortunately the ATs only come with 1:12 from the factory but that does not mean I cannot get a custom barrel for it in the longer term.

Sorry I did not mean to dismiss the tuner, my comment about not being a serious competitor did not in any way mean I might not be interested in one for all the good reasons you mentioned. It's all good as I have been using a tuner in another caliber.

 

[mikecr]

There are prices for everything.
Too long of a barrel, given weight constraints, can be difficult for balance. A bag gun I built with a Shethane stock and 28" heavy palma barrel required 3lbs added to the butt stock to regain balance. It shot terrible until I made this adjustment. Luckily, I had suspected this up front.
Too short could be giving up to much, and could lead to excess muzzle pressures.

 

[6BRinNZ]

Thanks again for confirming the Palma brass.

Thanks also for the info on the twist for the heavies. Unfortunately the ATs only come with 1:12 from the factory but that does not mean I cannot get a custom barrel for it in the longer term.

Sorry I did not mean to dismiss the tuner, my comment about not being a serious competitor did not in any way mean I might not be interested in one for all the good reasons you mentioned. It's all good as I have been using a tuner in another caliber.

All good - no offence taken.

Good luck.