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Posted: 11/2/2009 9:40:31 AM EDT
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I'm in the process of Form 1'ing one of my lowers for an upcoming 10.5" SBR build. Knowing that I will not be able to replicate performance from longer barrels, would I be able to regain SOME of the lost velocity by using faster burning powders or using reloading data from pistols like the TC Contenders with a similar barrel length?
Any input would be greatly appreciated. Thank you. BC |
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Quoted:
Use std rifle loads... Uncle Sugar only uses M-193, M-855 in his short rifles.. same operating system, so port pressures need to be correct. I would imagine that this is more of a logistical and inventory restriction than a performance one. As I don't have these restrictions, I was wondering if I could tune a load more to the SBR side of things. |
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Seems like we should have enough folks around here to figure out a way to maximize the performance of a SBR.
What powder, which presumably would need to burn faster, would be a good starting point? Would a heavier bullet be the way to go? How about the 77? I would think that a reduced muzzle flash could be obtained, maybe not. Has anyone gotten chrono data using an SBR that would care to share? |
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This info is from an old article in a gun magazine. Compares velocity with factory ammo in a 11 1/2––––16-and 20" barrel:
––––––––––––––––––––––––––––––––––11 1/2––––––––-16––––––––––––––20"barrel Federal AE223-55fmj––––––––2553––––––––––2928––––––––––––-3058fps Win USA223R1F 55fmj––––-2483––––––––––2809––––––––––––––3007 Federal XM193 LC02 55fmj––2667––––––––3052––––––––––––––3187 Win Q3131 WC89––––––––––––2718––––––––-3117––––––––––––––3204 Federal XM193 LC01 55fmj––2648––––––––3111––––––––––––––3244 _____________ Federal 62gr Tactical LC03––––2365––––––2756––––––––––––––2750 Black Hills Blue 69HP LC00––––2357––––––2659––––––––––––––2758 Black Hills Blue 68 Match––––––2322––––––2625––––––––––––––2731 Black Hills Blue 77 OTM––––––-2253––––––2537––––––––––––––-2600 Black Hills MK262 77OTM Mod1––2385––2678––––––––––––––2713fps Even more velocity difference in a 10 1/2 versus 11 1/2" barrel. The only SBR loads fired thru my chrono was a guys 10 1/2" barrel and then thru my 20". Velocity with a 55 fmj was 2900 approx. thru my 20" and a little over 2200fps in his 10 1/2". Don't think you'd gain very little fps trying to use a faster powder. This info is just to add to the discussion. |
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I think you need to figure out what you'll be pointing your rifle out before you can figure out a load. There are a few ways to get velocity, and that's what 5.56 needs...
Were I trying to make an SBR load, I'd look at the military solution, and see what they did... |
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Quoted:
I think you need to figure out what you'll be pointing your rifle out before you can figure out a load. There are a few ways to get velocity, and that's what 5.56 needs... Were I trying to make an SBR load, I'd look at the military solution, and see what they did... Nothing. The M-4 uses the same ammunition as the M-16. 5.56X45 ammunition uses an average breech pressure higher than the SAAMI pressure for .223 Remington; that's how the government gets more speed from the cartridge. |
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Ok, since you didn't read the thread, SOCOM has adopted a round for short barreled rifles. It is 'optimized' for use out of short barreled rifles. It has an NSN. To distinguish it from other ammunition, it's being marked with a brown tip. It uses a Barnes TSX projectile. I do not know the specifics on the loading. So for 'nothing', that's pretty thorough.
Here's a link to an article about nothing: http://www.defensereview.com/556-optimizedbrown-tip-ammo-enhanced-terminal-ballistics-for-specops-sbrs/ Here's more nothing. http://www.dtic.mil/ndia/2009infantrysmallarms/tuesdaysessioniii8524.pdf On page 21 of this presentation from Crane, the MK 318 mod 0 5.56 cartridge with 'Short barrel propellant was specifically designed for this cartridge configuration'. So, let's review: 1. The government spends lots of money finding new and exciting ways to kill people. 2. We can learn from the government 3. Hooked on phonics doesn't work for everyone |
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Quoted:
Ok, since you didn't read the thread, SOCOM has adopted a round for short barreled rifles. It is 'optimized' for use out of short barreled rifles. It has an NSN. To distinguish it from other ammunition, it's being marked with a brown tip. It uses a Barnes TSX projectile. I do not know the specifics on the loading. So for 'nothing', that's pretty thorough. Here's a link to an article about nothing: http://www.defensereview.com/556-optimizedbrown-tip-ammo-enhanced-terminal-ballistics-for-specops-sbrs/ That may be true, but what AeroE says is true also. Because of peak chamber pressure limitations and the peak pressure being reached in the first few fractions of inch of bullet travel, rule #1 in reloading still holds: (This is not intuitively obvious until you study the load charts) #1 Given a particular case and bullet, the optimum powder load is the same for a pistol (short barrel device) and a rifle (long barrel device). The projectile is faster out of a longer barrel because the gas has a longer time and distance to apply acceleration force. |
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