Gas gun velocity question

Dark moon 63

New member
I was shooting a 224 valkyrie 18 inch barrel with 55 grain Nosler varmageddon with 29 gr CFE223 at 3150. I put a 24 inch barrel on it with the same load at 3310. I loaded some 40 grain Nosler varmageddon with 29.5 grain CFE223, noticeable difference in powder height in the case. My pro chrono was showing 3260 with the sun shades on. Time in flight paint fly on steel was like shooting a 204 ruger. Is there something about a gas gun that could make this possible or a chrono problem. The same bullet combo in a 223 bolt action I was getting around 400 fps faster with the 40 grain.
 
Good question. I had the same thing the other day in a .243. .5 gr higher load in a ladder test, and the speeds dropped. Next .5 gr set higher, the speeds came back to representative. This was a bolt gun. Grouped sucked anyway, so never went back, I guess.
 
1badshee, only problem with that load data is 29.5 is an 1/8th of an inch from spilling out. I'm good with 3310 with a 55 grain bullet. What I'm not getting is a 40 grain bullet with more powder is only 3260. I'm not expecting bolt action performance but was looking for 3500 or better. I'm sure a deep throat would cause this with a shorter bullet but a flaw is a short throat. Can't load magazine length without hitting lands. Ruled that out. Lol
 
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I did take an extra battery just in case. In the past it would show batt when getting low. I have more loaded.
I need to try it again and break the barrel in anyway.
 
Your right. A longer barrel helps but hotter powder could be the only answer. I did put an adjustable gas block on it and its not over gassed. If I can't kill a coyote at over 3300 I better find a new hobby. Thanks.
 
are you using any kind of stem on your powder funnel? i know its a ball powder that settles pretty nicely and all, but i'm wondering if you're getting a good tight kernel fill.

hodgdon reloading shows 3250 with 28.8gr as a starting load for a 50gr pill and a max load of 31.1 - in federal brass anyway.

also what primer are you using?


just thinking out loud.
 
Plant.one, I did go shoot it again before my last post and gave a new battery a try. I hit 3300 with a 40 grain but 53 and 55 were faster. I use a universal funnel that will go from 50 cal to 20 cal. I could pack the powder to get more in but in a bolt action the velocity would just be there. Big difference, I know. I use standard winchester primers. I didn't read the hodgdon data real close but I took it as bolt action specs. Mileage may vary. I might be wrong but came to the conclusion a gas gun can only do so much.
 
Originally Posted By: Dark moon 631badshee, only problem with that load data is 29.5 is an 1/8th of an inch from spilling out. I'm good with 3310 with a 55 grain bullet. What I'm not getting is a 40 grain bullet with more powder is only 3260. I'm not expecting bolt action performance but was looking for 3500 or better. I'm sure a deep throat would cause this with a shorter bullet but a flaw is a short throat. Can't load magazine length without hitting lands. Ruled that out. Lol

I would imagine this has to do with a calculation regarding dwell time in the barrel, gas system length and barrel length. Similar to some pistol caliber carbines actually being slower than longer pistol legnth barrels. The 55 gr while heavier, is also longer allowing pressures to build and velocities to increase. Since the 40 gr is so light and has a shorter bearing surface, it just might not be building enough pressure before it leaves the barrel.

I ran into a similar scenario with Nosler's Combined Technologies Lubalox coated bullets. Book was claiming 3250 fps from a 24" barrel with a 150 gr Nosler ballistic tip and a given charge of IMR4350. Using the same barrel but the slicker Lubalox coated bullet, I was getting an average of 2997 fps with a SD of about 5. Throw a standard bullet in there and velocities increased. I was surprised having never really played with the Lubalox bullets, at least not with a chrono but after thinking about it, it made sense.

This seems to be a common theme with "overbore" cartridge that are shooting light for caliber bullets.
 
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The barrel is a 24 inch 6.5 twist rifle length gas system. The 40 up to 55's are accurate. I thought about closing the gas block just to see what it would do. I was wanting to have a dual performance 204 and 22 cal all in 1 gun. I have everything on order for a 24 inch 22 nosler. It has load data for light bullets. Should be a flat shooter even if it doesn't like the light bullets.
 
CFE with 40gr that wasn't maxed out?
You need a faster powder, H335, AA 2230, fill er up. Bet you had blackened cases too.
 
When powder gets more available I'll give those 2 a try. I built a 204 and getting 3840 with 32 grain and 3650 with 40 grain. I was hoping to see something like that with 40 grain in the valkyrie.
 
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