Reading Pressure and Velocity (short barrel)

[beerbucksducks]

I recently had my .243 barrel cut to 18” and threaded. My old load did not shoot well after cutting and floating the barrel and bedding the stock. I am working on a new load now. H414 and 95 NBT are showing promise for accuracy and is at 2880 fps at hodgdon’s max of 42 grains. I also did a velocity ladder with Midwest Powder 551 which is supposed to be the same burn rate as h414/w760. I loaded in .5 grain increments up to 45 grains with out a sticky bolt or pressure signs on brass. Velocity was 3050 at the top end. Looking at the data max loads for h414/w760 are 40-42 grains and 2900-3100 out of 24” barrels. Where do most people stop while looking at velocity out of a short barrel compared to 24” data? If book data is giving 3000 with 40 grains and 24” I’d imagine 45 grains and 3000 out of 18” is pretty hot, despite the lack of pressure signs.
I am planning on staying around 42-43 grains and 2900ish, since h414 isn’t temp stable and I won’t have the ability to test it in the heat for a couple more months. I am curious how other people interpret pressure in relation to velocity in shorter barrels.


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[beerbucksducks]

Bump


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[RME]

With a 6" shorter barrel I'd probably knock 150 fps off the max velocity. It's not an exact science, other people will figure a little more or a little less. I don't load for 243 but based your numbers I'd call 3k pretty hot too.

I'm not an expert on Midwest powders but I've used them some and treat them as similar to canister grade powders, not the same. I don't push them hard since I don't know what they actually are. I just find a good velocity with accuracy and call it good.

 

[Jebel]

With a 6" shorter barrel I'd probably knock 150 fps off the max velocity. It's not an exact science, other people will figure a little more or a little less. I don't load for 243 but based your numbers I'd call 3k pretty hot too.

I agree with this. I use a rough rule of thumb of 25-30 fps per inch of barrel length.

 

[beerbucksducks]

Thanks for the input. Following hodgdon data for h414, 24” barrel, 42 grains gives 3138 fps. If I use 30 fps per inch max would be 2950ish. I think my goal of 2900ish should be a good place to be.


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[Tylsmith33]

Running 43.4 gr of h4350 in a 16” suppressed .243 90gr eld-x right around 2800fps, could have got more speed but it grouped great and the higher powder charges didn’t give me as good of accuracy. so far both my wife and daughter have 1 shot killed 4 Muley bucks and a wt doe with it from 110 yards out to 295.