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Just thought I'd throw some data out there for those interested in FPS after being chopped
Tikka T3X Aspire 7mm RM
Original length: 24.3"
Shortened length: 20"
Hornady Precision Hunter 162gr
Original: 2819.3 fps
Shortened: 2685.6 fps
Winchester Expedition Big Game 160gr
Original: 2980.5 fps
Shortened: 2838.5 fps
Measured with Garmin chronograph
So approximately 32fps per inch removed. Better than i'd have thought with a long magnum cartridge.
The .308 and 6.5CM tests of velocity loss per inch of barrel cut, that i've read online, showed an average of around 25-30fps/per inch.
That Winchester Expedition looks like a potent load! It's still going faster at 20" than the Precision Hunter did at 24".
Were those shot with a suppressor, brake or nothing attached?
I have always worked off 50fps per inch chopped...so good to know
....obviously each cal is different and always chrony...but interesting
Hamish
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Those Winchester rounds were indeed flying, they had a pretty tight SD as well with the longer barrel, unfortunately they grouped very poorly compared to the Hornady. All were shot with a DPT supressor with the same number of baffles, but the 20" has an extension towards the forend
Hornady ssts is very good for grouping.
Greetings,
Velocity loss when shortening a barrel is highly variable. For my .308 with AR2206H I allow 20fps per inch from the Hodgdon 24 inch barrel data down to my 20 inch barrel using the same cases. For slower powders like AR2208 it is more. Chronographing your load (or factory loads) in your barrel is the only way to be sure. Generally the slower the powder, the bigger the case and the shorter the barrel the more velocity you will loose.
GPM.
What velocity do the two say on the box ?
Winchester 2950fps and Hornady 2975fps, so the Winchester is pretty close to its stated muzzle velocity from the standard barrel. Someone showed up with a tikka 270 standard length throwing Winchester ballistic silvertip 130gr and that was shooting 3025.8fps where the box states 3050, also pretty good for factory ammo. Maybe the tikka Winchester combo is the way to go for those using box velocities, would be interesting to test a few more combinations
That hornady started pretty damn slow for a 24” barrel
Sako ammo i used to use in my 7rm with the 165gr sierra gamechanger while insanely accurate was only doing 2730fps from my 22in barrel. On the box it says 2887fps
It wouldn't be a linear relationship would it? I would have thought the relationship would be a curve.
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