How short of a barrel on a semi auto .223, before 300 yard hits become problematic ?

on 20 inch diameter steel plates

I'm not sure of the answer. But no issues with my 10.5" as far as ballistics.

Others know way more than me but i'm guessing a 55gn is going somewhere in the 2500fps range in a 10.5" barrel.

Decreasing barrel length doesn't harm accuracy, just muzzle velocity.

http://www.ballisticsbytheinch.com/223rifle.html

Even out of a 3" barrel, you get ~1200 fps.

With good elevation and windage corrections, I bet you could hit a 20" plate at 300 yards with that without much trouble.

From the tests I've read, 11.5" is sort of the sweet spot of not much downside.

That said, I've got rifles in 10.3", 9" and 7.5". Its hard to say if barrel length alone causes dropoff in accuracy with sight picture lengths also getting shorter.

As velocity drops, range estimation and sight or point of aim adjustment becomes more critical. Higher velocities produce flatter trajectories that are more forgiving of range estimation errors. In addition, wind affects bullets traveling at slower speeds more, and therefore reading and adjusting for the wind is also more critical.

In a test I conducted, Lake City M193 ammunition (55 gr. FMJ) averaged ~3040 feet per second from a 16 inch barrel, and ~2750 fps from 11.5". The 16" velocity was therefore over 10 percent* faster, and the discrepancy obviously gets greater with shorter barrels.

With proper sighting and adjustments, though, I cannot imagine that a rifle with any decent barrel of reasonable length and decent ammunition wouldn’t be capable of hitting a 20" plate at 300 yards.

* (For those who don’t believe that 10% in bullet velocity matters, that’s less than the difference between the Speer 9mm 124 grain standard and +P loads when fired from a P226.)

This is going from memory of a carbine class a few years ago. I used my 16 inch carbine, another student borrowed a 11-ish inch Noveske SBR. Our primary targets at distance were unpainted steel pepper poppers at 200, 250, and 300 yards. IIRC the closest popper had an 8" center of mass, the farther ones were 12" COM. We also had a roughly double-sized IPSC plate at 500 yards, regularly painted white, with a 5" orange center aim dot.

My primary ammo beyond 100 yards was Hornady 55 grain Vmax. The Noveske SBR guy used American Eagle 55 grain FMJ at all distances.

My carbine sports Leupold Mark 4 1.5-5x glass, the Noveske had an Aimpoint red dot.

From prone or well-supported alternative positions, I could not only ding the poppers' COM, but I could choose which part of the popper I wanted to hit. The Noveske guy had equal rifle skills -- he had no issues with COM on the 200 and 250 yard poppers, but definitely wasn't 100% on the 300 yard target. He could not really choose where he wanted to hit the poppers. However, his accuracy did increase noticeably when I let him shoot the VMax ammo in his SBR.

At the 500 yard painted target, I could easily keep groups under 10" with my carbine. That distance was a challenge with the SBR -- maybe 30-ish inch groups with FMJ ammo, maybe 20-ish inches with VMax ammo. The unmagnified red dot didn't help, but I recall that centering the dot on the hanger above the plate worked pretty well for a holdover. I shot the Noveske quite a bit, well, because it was just light and fun. But the SBR was out of its element at distance.

Back to the OP's question, I think a 10-11 inch SBR should be able to ding a 20" plate at 300 yards quite easily. With good ammo, a decent optic, from a supported position, and a good shooter -- one should be able to more or less pick which general portion of the plate the impact will occur.

IMO there comes a point in relatively distant targets where the SBRs give up more accuracy than one might expect from just lower muzzle velocity. I can't explain how, but I've seen it happen in carbine courses. The SBRs often will hang with the 16" carbines at 100 and 200 yards, but then as distances increase, the SBRs really struggle to ding steel consistently. I've seen it in both elevation and windage variations.

its hard to compare an Aimpoint RDS vs. a 1-5 optic though.

quote:

Originally posted by fritz:
IMO there comes a point in relatively distant targets where the SBRs give up more accuracy than one might expect from just lower muzzle velocity.

That’s interesting and good to know: one more thing to use in my arguments against professionals’ using SBRs for serious purposes.

Yes, I realize I’m being silly because Who engages serious targets at 300 yards with an SBR? But the next time I run an intermediate range rifle course, I’ll make the one guy with an SBR try to hit a 9×12" reduced silhouette at that distance. With decent ammunition I don’t have any problems with a stock Colt LE6940. Of course, that’s with a 5 or 6× scope rather than a red dot, but “Ya gotta dance with who ya brung.”

While's it's true that a RDS can't match the accuracy of 1-5x glass, I'm no stranger to Aimpoints and it was pretty easy to place the RDS on specific parts of the steel targets.

Another example, although not completely apples to apples. My carbine is a 16" Wilson Combat. I have an 11.3" Wilson 300blk upper, sporting a Vortex Strike Eage 1-6x, that I use on the same Wilson lower. I don't have as much time with the 300blk upper that I do with the 223 upper. However I do know that Sig Sauer's 125 HPBT ammo shoots really well in the blk upper -- almost to the accuracy of Hornady 55 vmax in the 223 upper at 100 yards

At 400 yards at my range, it's really easy to ding my 10" and 12" plates with the 223. Wind drift is 2.1 MOA for a 5 mph cross wind.

I don't find it so easy to hit the same plates with the 300blk SBR. Wind drift is 2.3 MOA for the same 5 mph cross wind, so not a huge difference. But I just don't see the same relative accuracy at 400 yards that I do at 100 yards. Sure, the 223 bullet starts and ends faster, but the 300blk bullet has superior BC -- .330 G1 versus .255 for the Vmax.

I think there's something not completely explained by an SBR's MV that reduces their accuracy down range.

very helpful indeed , thank you for taking the time

quote:

Originally posted by fritz:
While's it's true that a RDS can't match the accuracy of 1-5x glass, I'm no stranger to Aimpoints and it was pretty easy to place the RDS on specific parts of the steel targets.

Another example, although not completely apples to apples. My carbine is a 16" Wilson Combat. I have an 11.3" Wilson 300blk upper, sporting a Vortex Strike Eage 1-6x, that I use on the same Wilson lower. I don't have as much time with the 300blk upper that I do with the 223 upper. However I do know that Sig Sauer's 125 HPBT ammo shoots really well in the blk upper -- almost to the accuracy of Hornady 55 vmax in the 223 upper at 100 yards

At 400 yards at my range, it's really easy to ding my 10" and 12" plates with the 223. Wind drift is 2.1 MOA for a 5 mph cross wind.

I don't find it so easy to hit the same plates with the 300blk SBR. Wind drift is 2.3 MOA for the same 5 mph cross wind, so not a huge difference. But I just don't see the same relative accuracy at 400 yards that I do at 100 yards. Sure, the 223 bullet starts and ends faster, but the 300blk bullet has superior BC -- .330 G1 versus .255 for the Vmax.

I think there's something not completely explained by an SBR's MV that reduces their accuracy down range.

isn't 400yrds a bit much for a 300bo?
basically BO is a whisper with a different parent case, IIRC and designed for shorter distances correct?

quote:

Originally posted by lyman:
isn't 400yrds a bit much for a 300bo?
basically BO is a whisper with a different parent case, IIRC and designed for shorter distances correct?

At a certain distance, the bullet for every chambering runs low on gas. In my 11.3" barrel, the Sig 125 grain bullet remains supersonic to 735 yards. At 400 yards it's still motoring along at mach 1.37, which is generally a good velocity for true bullet flight. Windage becomes a challenge, though. The bullet retains 647 foot pounds of energy at 400 yards.

Contrary to what the webz sez, the blackout wasn't "designed" for anything other than shooting a .30 cal bullet from a .223-ish case, specifically in an AR-15 platform, with minimal changes to the AR-15 platform. Any fluid mechanics engineer with a touch of ballistics understanding will state that the very nature of the blackout cartridge means it works better than the .223 cartridge for shorter barrels and at closer targets. And that the 223 cartridge has advantages with longer barrels and at longer targets.

In team tactical competition I've shot my 18" AR-15 with Hornady 75 HPBT ammo out to 650 yards -- the bullet was moving at mach 1.42 at that point. In calm conditions that was well within the practical accuracy limits of the system. However in 15-25 mph Wyoming winds, I was finding it really difficult to hit steel.

Is 400 yards a challenge for an SBR 300blk? You bet.
Is 650 yards a challenge for a 223 match bullet. You bet.
Is 1200 yards a challenge for a 6.5 creedmoor bullet (Mach 1.40 at target)? You bet.

Those who play the long distance games regularly deal with such conditions.

I was hitting steel out to 300 with my 10.5" with iron sights. With a 50 yard zero I had to hold at just the top of the steel to get reliable hits.

I have a 7.5" pistol and accuracy is good. However as others said, velocity drops and is about 2300fps with 55 gr.

Oh, yea, then there's the 2' fireball with rifle powders in a short barrel. Quite a blast literally, but you may not like it in serious settings.

I have an 11.5 with a red dot that is capable at 225-250.

I have never shot it farther than that. Although I would if it had a magnified optic.

I have also never fired it without a suppressor attached which really tames down the muzzle blast. It is not much louder than my 16" gun with the same suppressor attached.


I think it would be fine at 300 yards with some magnification.

If you want to effective terminal performance at 300m with 55gr or 62gr FMJ I would stick with 16". With my 11.5" with 55gr TSX my effective range is ~225m as it supposedly opens at 1700FPS which is what I use in it.

If you are using "premium" ammo your distance envelope increases a bit.

While I love my 11.5" my "go to rifle" is a 16" SOCOM barreled upper. The SBR is in my bedroom with a suppresor....my wife prefers it.

Velocity vs barrel length was addressed several times back in the 1980s by cutting off 1" of barrel starting at about 20"-24" down to 16" and testing several calibers.

The rule of thumb from these tests was that 1" less of barrel equaled loss of 100 fps.

.

quote:

Originally posted by redleg2/9:
The rule of thumb from these tests was that 1" less of barrel equaled loss of 100 fps.

That's an over simplification of the effects. The site www.ballisticsbytheinch.com lists deltas per inch in the 200 fps per inch ballpark for short pistol-length barrels using 45-55 grain ammo, decreasing to roughly 50 fps per inch once 16" to 18" barrels are compared.

In my own case, for multiple ARs with barrels from 14.5" to 24" long, I see average deltas in the 30 fps per inch ballpark for 69-77 grain bullets, and 50-55 fps per inch for 55 grain bullets. These averages are across the entire 9.5" difference in barrel length. For the heavier bullets, the delta per inch is closer to 40 fps at carbine length, decreasing to roughly 20 fps per inch for my longest barrels. All my barrels are match-grade, hand-lapped, stainless steel.

quote:

Originally posted by fritz:

quote:

Originally posted by lyman:
isn't 400yrds a bit much for a 300bo?
basically BO is a whisper with a different parent case, IIRC and designed for shorter distances correct?

At a certain distance, the bullet for every chambering runs low on gas. In my 11.3" barrel, the Sig 125 grain bullet remains supersonic to 735 yards. At 400 yards it's still motoring along at mach 1.37, which is generally a good velocity for true bullet flight. Windage becomes a challenge, though. The bullet retains 647 foot pounds of energy at 400 yards.

Contrary to what the webz sez, the blackout wasn't "designed" for anything other than shooting a .30 cal bullet from a .223-ish case, specifically in an AR-15 platform, with minimal changes to the AR-15 platform. Any fluid mechanics engineer with a touch of ballistics understanding will state that the very nature of the blackout cartridge means it works better than the .223 cartridge for shorter barrels and at closer targets. And that the 223 cartridge has advantages with longer barrels and at longer targets.

In team tactical competition I've shot my 18" AR-15 with Hornady 75 HPBT ammo out to 650 yards -- the bullet was moving at mach 1.42 at that point. In calm conditions that was well within the practical accuracy limits of the system. However in 15-25 mph Wyoming winds, I was finding it really difficult to hit steel.

Is 400 yards a challenge for an SBR 300blk? You bet.
Is 650 yards a challenge for a 223 match bullet. You bet.
Is 1200 yards a challenge for a 6.5 creedmoor bullet (Mach 1.40 at target)? You bet.

Those who play the long distance games regularly deal with such conditions.

thanks for the info, good to know,

I was thinking heavier bullets like in the original Whisper loads, (200-240 gr) and had forgotten that BO used lighter bullets on average