12.5 inch barrel vs 13.7 inch barrel velocity

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Originally Posted by WillBrink

Decent discussion. SF group using 10.3" out to 600 yards.

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We've run the 10.5 out to 750 yards... with a spotter. The only reason it's not a regular thing is because you don't put glass worthy of that distance on a 10.5 barrel. So it's irons or an RDS with crazy holdover.

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Originally Posted by 1168

I’m putting a 13.5” in the handguard you loaned me.

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Nice. Cut or MosTek? Unless someone is making a 13.5” now…

Ammo selection is going to make a lot more difference than 1-2" of barrel IMO.

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Originally Posted by markm

We've run the 10.5 out to 750 yards... with a spotter. The only reason it's not a regular thing is because you don't put glass worthy of that distance on a 10.5 barrel. So it's irons or an RDS with crazy holdover.

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The real problem with SBRs isn’t distance (within reason); it’s estimating that distance accurately. The shorter you go, the less forgiving of range estimation errors. Or bad data entry in your ballistic calculator.

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Originally Posted by JediGuy

Nice. Cut or MosTek? Unless someone is making a 13.5” now…

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MosTek.

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Originally Posted by 1168

The real problem with SBRs isn’t distance (within reason); it’s estimating that distance accurately. The shorter you go, the less forgiving of range estimation errors. Or bad data entry in your ballistic calculator.

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Absolutely. When we shoot crazy shots like that it's just a "sling it" and correct effort. Without the spotter fixing the misses, I could should gobs of ammo and never have an idea if I was close at all.

I'm not sure I completely get the 13.7 length. I had one for a while. And, assuming you aren't going to SBR it, by the time you P&W it's the same overall length as the 14.5 P&W. Which is what I eventually sold it for. I do want to build a 12.5 SBR next and play with it along side my 10.3 and 11.5. I think the 12.5 is at the length where a compact LPVO might make sense.

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Originally Posted by Dutch110

I'm not sure I completely get the 13.7 length. I had one for a while. And, assuming you aren't going to SBR it, by the time you P&W it's the same overall length as the 14.5 P&W. Which is what I eventually sold it for. I do want to build a 12.5 SBR next and play with it along side my 10.3 and 11.5. I think the 12.5 is at the length where a compact LPVO might make sense.

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i'm siding more to the 12.5inch barrel to be honest! i have the LMT for long range . Just intrigued when i saw that uk ranger rifle uses a 13.7inch barrel - but military contracts dont always make sense

As has been mentioned, the UK KAC KS-1 contract had an overall length requirement including the suppressor. According to media, that barrel and suppressor combo meets the requirements.

As has also been mentioned, I believe, the 13.7/13.9” barrel moves a suppressor slightly to the rear. If pinned, the overall length doesn’t change unsuppressed but does suppressed. Additionally, I believe when I checked the weights on the KM6315 and KM6315-L, they were the same. So reduced barrel (and overall) weight by .4oz on a pencil barrel, reduced overall length suppressed by .8-.6” vs a 14.5 or 2.3-2.1” vs a 16, and mass shifted toward the pivot point (your body).

I probably wouldn’t get another 13.9”, personally, but neither would I get another 14.5”.

I’ve built a 12.5 mid length gas system and a 13.95 mid length. I can get you some fps with Winchester white box, pmc, or federal 223 and 5.56. It might be a while, but happy to run some numbers next time at the range with chrono.

Big fan of 12.5. If I could just have one, it would be a 12.5 carbine gas with a dot and magnifier.