Optimal barrel length

[talentrec]

I’m looking at getting a carbon stalker for my daughter. Right now I have her shooting a suppressed SBR Grendel with a 10.5 inch barrel. For those of you who’ve had multiple length barrels, in your experience, what is the shortest barrel that will still wring out +\- 90% of potential velocity? This would be for hunting weight bullets.

[gldprimr]

If not shooting suppressed I don’t like going shorter than 20” though a Grendel doesn’t have the muzzle pressure that higher pressure/velocity rounds do. Just mention that as your daughter probably still has most of her hearing left unlike lots of us. If shooting suppressed then you can probably go shorter though I don’t have experience with SBRs so can’t offer any advice there.

[talentrec]

Thanks! I’m thinking non-suppressed on this one. Want it as light and handy as possible.

[gldprimr]

When teaching/training a friend of mine’s kids he used a BLR in 308 which had a 20” barrel length. I loaded 125 gr. Nosler Ballistic Tips with a moderate charge of Varget for it to keep recoil down. It was/is a deadly little deer killer. I know it’s not a Grendel, but concept is the same.

[Popeye212]

I went to an 18' Carbon Fiber barrel made a substantial difference in weight

[talentrec]

I went to an 18' Carbon Fiber barrel made a substantial difference in weight

What kind of velocity are you getting with 18”?

[JASmith]

I’m looking at getting a carbon stalker for my daughter. Right now I have her shooting a suppressed SBR Grendel with a 10.5 inch barrel. For those of you who’ve had multiple length barrels, in your experience, what is the shortest barrel that will still wring out +\- 90% of potential velocity? This would be for hunting weight bullets.

There is a nifty chart on page 33 in Volume 1 of the Grendel Reloading Handbook that can help.

The max barrel length on that chart is 28” and we can use it as an approximation of the highest velocity attainable with a rifle that can be readily carried.

The chart tells us that a 14” - 15” barrel gets about 90% of the velocity obtained with a 28” barrel.

[Stinky Coyote]

from early research I had 19" in my memory banks

with factory barrels I've had between 23.5" and 16.1" it's been a 22.4 fps per inch spread and I'm currently getting 2386 fps from hornady black from a 16.1" ruger and with same ammo I got 2503 fps from a 20" Howa(took a bit to break in tight bores on howa...it started at 2475 fps fyi) and 2552 fps from a 23.5" (cz 527 American)

[talentrec]

There is a nifty chart on page 33 in Volume 1 of the Grendel Reloading Handbook that can help.

The max barrel length on that chart is 28” and we can use it as an approximation of the highest velocity attainable with a rifle that can be readily carried.

The chart tells us that a 14” - 15” barrel gets about 90% of the velocity obtained with a 28” barrel.

Thanks for the info! Where can I find this book?

[gldprimr]

https://www.ar15buildbox.com/shop/65-Gre...dBooks.htm

[lazyengineer]

Personally, I've settled on a 14.5" pin and weld as my ideal general length. It's very short and very light, but not so short as the 12" and retains some nice velocity. With a 14.5", firing the common 123gr Hornady SST general purpose hunting ammo, you get over 1000 ft-lb impact energy at over 200 yards. with Supersonic flight still at 700 yards. That's pretty good for a very light handy barrel. 16" will go even longer, and is more common.

[LRRPF52]

Personally, I've settled on a 14.5" pin and weld as my ideal general length. It's very short and very light, but not so short as the 12" and retains some nice velocity. With a 14.5", firing the common 123gr Hornady SST general purpose hunting ammo, you get over 1000 ft-lb impact energy at over 200 yards. with Supersonic flight still at 700 yards. That's pretty good for a very light handy barrel. 16" will go even longer, and is more common.

What mv are you getting with 123gr SST factory, and your hand loads from 14.5”?

I haven’t seen much difference between 12” and 14.5”. This is also true with 5.56 NATO.

[lazyengineer]

What mv are you getting with 123gr SST factory, and your hand loads from 14.5”?

I haven’t seen much difference between 12” and 14.5”. This is also true with 5.56 NATO.

That's a very surprising result if you aren't seeing much difference adding 2.5" of length to a 12" BBL.

[LRRPF52]

The 12” Faxon barrels from the group buy have the EE (Easy Engraving) rifling, and velocities have been faster than I anticipated.

120gr Federal OTM box ammo does 2393fps, for example. 2384fps 15ft from the muzzle. (19 shot sample)

90gr TNT does 2683fps 15ft from muzzle, 2695fps mv. (11 shot sample)

With the same loads and a 14.5” barrel made with the same chamber and bore/rifling, we should expect to see 2430-2487fps for the 120gr OTM, and 2800fps from the 90gr TNT.

From my 17.6” Lilja, I’m seeing 2892fps average 15ft from the muzzle with the same 90gr TNT factory ammo. 10-shot sample

17.6” with the same 120gr Federal factory OTM averaged 2484fps, 20 shot sample.

Not much to write home about performance-wise even between 12” and 17.6”.

[Popeye212]

What kind of velocity are you getting with 18”?

Haven't chrono'ed it yet just put put it on there. Will update you on it.

[lazyengineer]

The 12” Faxon barrels from the group buy have the EE (Easy Engraving) rifling, and velocities have been faster than I anticipated.

120gr Federal OTM box ammo does 2393fps, for example. 2384fps 15ft from the muzzle. (19 shot sample)

90gr TNT does 2683fps 15ft from muzzle, 2695fps mv. (11 shot sample)

With the same loads and a 14.5” barrel made with the same chamber and bore/rifling, we should expect to see 2430-2487fps for the 120gr OTM, and 2800fps from the 90gr TNT.

From my 17.6” Lilja, I’m seeing 2892fps average 15ft from the muzzle with the same 90gr TNT factory ammo. 10-shot sample

17.6” with the same 120gr Federal factory OTM averaged 2484fps, 20 shot sample.

Not much to write home about performance-wise even between 12” and 17.6”.

Neat. I've grown to quite like FAXON

[tdbru]

Talentrec,
my mini howa is the 22" bbl std. it is NOT a heavy setup (almost same as factory carbon stalker now except for hokeypokeykid's hinged bottom metal). I'm sure your daughter could handle it fine. longer barrel = more MV and less muzzle blast. gldprimr is correct that you need to preserve your daughter's hearing. unsuppressed longer tubes reduce muzzle pressure and put it further away from the ears. and as a bonus gives more MV. For an AR that has decent (to me) barrel length and is not a heavy weight is the FAXON 20" gunner profile, which is what is on my light weight upper. since everything I run is unsuppressed, i want long tubes if possible. more MV and less muzzle blast. mv isn't drastically different from 16" to 20" but muzzle blast changes by quite a bit. your daughter will not want to wear hearing aids like I have to. trust me on that. Do what you can to reduce the risk to her (and yours too) hearing.
-tdbru