12.5 inch barrel vs 13.7 inch barrel velocity

[markm]

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

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.

[JediGuy]

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

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

[mack7.62]

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

[1168]

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.

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.

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

MosTek.

[markm]

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.

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.

[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.

[SHARPSHOOTER282]

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.

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

[JediGuy]

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”.

[jnr4817]

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.

[themonk]

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