Ammunition & Hand Loading > General Ammunition Discussion

55 grain to a 40 grain 22.250

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bigmountainskiercfg:
I have been shooting a 55 grain factory PPU ammo but recently thought about going to a 40 or 45 grain bullet.  My gun is dead on at 175 for the 55 grain, is switching to the lighter bullet going to throw off my accuracy?  Been reading a little bit about twist rates and all of that and now I am worried that I just made a mistake ordering a bunch of lighter bullets for coyotes. 

unfy:
Each firearm has it's own personality.  I'd suggest picking up a smaller box of the 40gr and seeing what your particular rifle thinks of it at a range or similar.

2 reloading manuals suggest the higher weighted bullets for the round (ie: 50-55).

Buy a small box and find out :)

bigmountainskiercfg:
Ya, thought that would be the case but figured I would ask.  I guess gotta find a range close to Omaha that won't break the bank.  Any ideas there?

SemperFiGuy:
bms................

My very uneducated guess is that the shorter 40gr bullet will be less stable around the long axis than the 55gr bullet.

Which might make it tumble or fly a bit when it gets way out there.   Or do some other silly stuff.   Lots depends upon the powder type/charge that you put behind it, which is a function of whatever velocity and accuracy results you might be seeking.   [Won't be the same as the 55gr load.]

Now....uneducated guesses aren't of much value when it comes to actually proofing a load by shooting a group.   So--like unfy sez, you'll want to work up various loads and try 'em out.

If you can't get to an Omaha-local range, then PM me and we can go to my gun club range [guests allowed].   The longest range distance is 200 yards, which is just about right for load testing.   A chronograph and spotting scope will be of help in this case.

sfg

wallace11bravo:
Trying to keep this all as simple as possible, I'd prefer not to write a book:

What is the rate of twist?

Faster twist rates are better for stabilizing longer (heavier) projectiles. In turn, slower twist rates typically like lighter (shorter) projectiles. Note: the weight has little to do with it, instead it is the length of the projectile and how it tends to pitch, yaw, and possibly even tumble, and how well it can be stabilized to prevent that. Heavier projectiles are almost always longer, and lighter is almost always shorter. The effects of this are not usually very noticeable at the ranges you are talking about, but I have seen groups open up quite a bit at 100m with no other explanation.

The lighter projectiles are probably going to have higher initial velocity, but because of less mass, will loose their velocity faster. Even though they loose the velocity more quickly, because they start off going faster, it should not likely be a real issue at the distances you are talking about*.

Lighter projectiles, by necessity, have lower BCs. In addition to not being able to resist drag as well (see last paragraph) they also cannot buck the wind as well. A higher velocity can make up for a lower BC to a certain extent, at shorter ranges. Again, for typical winds, at the ranges you are talking about, the effects will be negligible*.

*Assuming this is for hunting medium to large game

Consistency is the biggest factor. Brass of all similar dimensions and thicknesses, charge weights the same, even bore ride lengths of projectiles, consistently formed meplats, blah blah blah. Many people think that their weapon prefers a certain type of round because of that round's characteristics, however, more often than not, it appears  to prefer that ammo because that ammo is manufactured more consistently.

Now for barrel harmonics. Pretty much repeat everything everybody already said. There are simply too many un-measurable  factors to give any type of prediction. Thickness of the barrel, even temperament of the barrel, lands depth, barrel length, barrel weight, any muzzle devices, blah blah blah. You have to shoot it and see how it does.

Now for the real question: Why did you feel the need to change your load, given that it was "dead on"?

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