Effect of cold on .303 bullet speed with reduced load

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crusoe

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I've just worked up what seems a nice reduced load for .303 of 22 gr IMR 4759 behind a Sierra .311 150 gr Spitzer. This seems to produce good accuracy for me out of all my Lee-Enfields on my 100 yd range and is easily powerful enough for varmint at that range and more, but without the crack of the full-strength round that alarms the (distant!) neighbours.

I've just chronographed it for five rounds and come up with 1705, 1706, 1679, 1697 and 1720. It's the first time I've used a chrony - am I right in thinking that's a pretty acceptable deviation? It seems a pretty close cluster to me. It's just one of those basic green box Chronys (F-1).

It was minus 14 degrees C, probably minus 18 or so with a bit of wind chill. Can anyone suggest about how much faster the bullet will fly in warmer temps? I'm just guessing that if I'm getting 1700 fps in minus 14, I might be getting at least 50 or 80 fps faster than that in 30 degrees C in the summer, maybe more? This is just a guess based on internet hearsay as I've never measured these differences before.

I was thinking of trying a gr or two more of 4759 to get closer to 1800 fps, but perhaps not if I'm going to be getting about that in the summer with the present load.

Thanks!
 
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That is pretty good deviation for a five round sample. The big thing is ACCURACY. As long as you are getting tight groups with the load, deviation of 30-50 fps does not really matter. I think sometimes we get too obcessed with things when reloading, but you have to realize that rifles are like fingerprints --they are different and what works with one may or may not work with another.

You should get a bit more speed in the warmer weather, but again, it may vary with each rifle. Load the cartridge for ACCURACY, and don't worry or sweat the small stuff like differences in deviation.

You are shooting at 100 yards with a reduced load that is accurate in your rifle when driven at an average of about 1700 fps. At 1800 fps, the time of flight difference will be measured in 100th. of a second. You have to ask yourself, "What would I gain by loading to 1800 fps?" I "rough" calculation should give you the answer that a bullet at 1800 fps will arrive at a 100 yard target about .06 seconds faster (by "rough" calculation I did it in my head without a calculator so if someone really needs to pick nits, I am sure that they will post an answer, correct to at least 10 decimal points.)

The big thing in reloading ammunition is consistency, and trying to make every cartridge the same. Deviation, for example, can be affected by many factors, even the thickness of the cartridge neck and neck tension, so variations in velocity are bound to occur.
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Thanks buffdog - good advice. I'm looking forward now to doing some controlled bench shooting with this load and seeing what accuracy I can get. I've discovered since posting that several others have worked up virtually the same load (22-23 gr 4759, same bullet) with the same range shooting requirements as me, so I'm glad I was on the right track.
 
A good reinforcement to Buffdog's statement was a recent range trip with my .223 target rifle. One load I was using was seeing deviation of 30fps, another 10-14fps. The 30fps deviation load produced groups as small as 1.4" @300m, the 14fps load was more like 4". Guess which load I'm sticking to!
 
At 100 yards,..just look for the consistent groups, don't worry about standard deviation or even extreme spread on a string of shots. That is a very mild load for a Lee-enfield. Smellie has nice accurate concoction driving a 180gr Sierra at around 2200fps??

He said that the British Army through testing discovered that the .303 was most accurate when leaving the muzzle at 2200fps. I don't recall if it was MkVII or previous heavier bullets. I do know that I zeroed a Parker-Hale sporter in for a chap some years ago using W-W 180 PPSP. I had my chronograph set up for load development and the rounds were clocking a mere 2260fps, versus the published 2480fps on a 24" barrel.
Not exactly a sledgehammer but you know, that old P-H was the most accurate on the 100 yard bench that day, even with my handloads in .270, .30-06 and .308!!:eek:

Try to find Smellie's load at 2200fps, I think you will be impressed, plus it's letting you know just a little more you are firing a full power Battle Rifle, the best of all time, and helping overcome wind if you want to stretch out to 200-300 yards!
 
^ive had good luck with that load out to 700+ in my repro 4T, not to mention it working great in all my other Lee-Enfields. It's 38gr 4895 under a Sierra 180 pro hunter seated to ball round length, 3.05". It's a near perfect load IMO!
 
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flying pig said:
^ive had good luck with that load out to 700+ in my repro 4T. It's 38gr 4895 under a Sierra 180 pro hunter seated to ball round length, 3.05". It's a near perfect load IMO!
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I agree, that's my favorite SMLE and No.4 load to.

As for the OP's question. I've found that at -14c my loads seem to have lower pressure which is felt by my scientific device called my shoulder.

After -20c I find that my reduced loads often have sooty necks which is a sign of low pressure. Sometimes I put a slight crimp on my necks for cold weather rounds as I find that it often helps with low pressure during extreme cold.
 
flying pig said:
^ive had good luck with that load out to 700+ in my repro 4T, not to mention it working great in all my other Lee-Enfields. It's 38gr 4895 under a Sierra 180 pro hunter seated to ball round length, 3.05". It's a near perfect load IMO!
Click to expand...

It will stay supersonic to 800 yards. FP does the accuracy fall off really bad at 700? You are starting into the transonic range at 700.
 
Doesn't seem to, but I haven't really shot for groups out that far with it yet, just for fun at my gong which is about 18" square I think. I'll do some real testing this summer and see where things fall apart.
 
That would be very appreciated.

If we get our 400 open this year I'd like to try my rifle, my pony, and me at that distance. That's probably only CQB for competitive rifleman of a bygone era. It would just be nice seeing what these old rifles can do being fired at distances they once relished in at a time when the .303 was king on CDN ranges. I am getting the bug to set up my press again though there's nowhere really here for it.:(
 
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