20" vs 24" barrel velocities

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[ARCHIVED THREAD] - 20" vs 24" barrel velocities

Posted: 7/19/2003 4:43:42 PM EDT

Is there much increase in velocity from 20" to 24"? I bought a big heavy DPMS 20" and was wondering what advantage there would be with a bigger, heavier 24". The "Ammo-Oracle" website gives the difference between 16" and 20", but I don't see anything about 24".

Posted: 7/19/2003 9:10:35 PM EDT

[#1]

Strictly from memory about 350-400fps.

Posted: 7/19/2003 9:24:52 PM EDT

[#2]

Distance to 2700 fps
20" Barrel
16" Barrel
14.5" Barrel
11.5" Barrel

M193
190-200m
140-150m
95-100m
40-45m

M855
140-150m
90-95m
45-50m
12-15m

Got to work on that memory! I don't have figures for the 24" but if you guess-tamate a bit.

Posted: 7/20/2003 8:28:36 PM EDT

[#3]

Quoted:
Distance to 2700 fps
20" Barrel
16" Barrel
14.5" Barrel
11.5" Barrel

M193
190-200m
140-150m
95-100m
40-45m

M855
140-150m
90-95m
45-50m
12-15m

Got to work on that memory! I don't have figures for the 24" but if you guess-tamate a bit.

View Quote

Paul, TerryR., I think the numbers may be on the Bushmaster site. But then that thought is from that memory that needs work !!

Tom

Posted: 7/21/2003 6:32:26 AM EDT

[#4]

From [url]http://www.bushmaster.com/faqs/techdatafaqs.asp[/url]

55gr 62gr
10 2739 2627
11.5 2872 2738
14.5 3064 2907
16 3132 2989
20 3259 3095
24 3315 3158
26 3391 3231

It looks like the 24" barrel only gains 56fps (14 per inch) while the 20" gains 127fps (32 per inch) over the 16".
The 16" gains 68 fps over the 14.5 (45 per inch), so the difference between the 20" and the 24" is less than the difference between the 14.5 and the 16.

Posted: 7/21/2003 6:47:50 AM EDT

[#5]

In my experience over a long period of time, I have found the average to be in the 25 - 40 fps range per inch of barrel length.

Posted: 7/21/2003 8:44:23 AM EDT

[#6]

Working out the fps per inch from Bushmaster gives:

55gr 62gr
fps +fps +fps/in fps +fps +fps/in
10 2739 2627
11.5 1.5 2872 133 88.7 2738 111 74
14.5 3 3064 192 64 2907 169 56.3
16 1.5 3132 68 45.3 2989 82 54.7
20 4 3259 127 31.8 3095 106 26.5
24 4 3315 56 14 3158 63 15.75
26 2 3391 76 38 3231 73 36.5

The numbers for 26" look off, since the fps/inch is descending as expected as the barrel length increases until we hit 26".

Posted: 7/21/2003 5:51:48 PM EDT

[#7]

[url]http://www.accuratereloading.com/223sb.html[/url]

Dude took a 22" Sako bolt action, and did massive load testing withvarious components. 5 shot groups, noted velocity and best accuracy.

Chop off 1 inch. Repeat. Chop off 1 inch. Repeat. Chop off 1 inch. Etc.

OUTSTANDING work. Whoever did this is totally my hero. You can interpolate the data up to 24".

The answer to your question is in there. When you understand the data, you'll refine your question.

You ARE going to use different powder for the longer barrel- right? Which one? Ahhhhhhhhhhhh.

Pete

Posted: 7/21/2003 7:17:02 PM EDT

[#8]

I'm replacing my 14.5" barrel with 16" as soon as the barrel gets shot out.

Posted: 7/22/2003 6:58:37 AM EDT

[#9]

Maverick:
I hear you. My preferences aside, as long as it's less than 20, and scares people, I'm all for it!

Posted: 7/22/2003 3:47:32 PM EDT

[#10]

Thanks. I think I made the right decision. The extra cost and weight aren't worth the relatively small increase in velocity.

Posted: 8/4/2003 12:56:02 PM EDT

[#11]

I believe the Bushmaster website says there is about a 100fps difference between 20" and 24".

[ARCHIVED THREAD] - 20" vs 24" barrel velocities

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