.17 HMR ammo purchasing

[Al69ec]

Why would you want expanding ammo if your fac is only conditioned for use at ranges. I have expanding ammo on my fac and that's because I have land to control vermin.

[deadcenter]

Hi,

 

I didn't specifically want expanding, just ammo to shoot in my rifle. The place where I bought the rifle from told me at the time that this was the only way .17 HMR came. You have the calibre slot - you must be able to buy the ammo.

 

As for shooting it at the range - it's a relativly cheap round and an accurate one. After shooting my friends same model (who has permissions) I really enjoyed it and so requested it on my fac.

 

Now I know about the non expanding stuff, obviously that is what I will be buying. Future permissions are still an option.

 

Just as an aside, I cant find anywhere on my V-max packaging, any mention of it being expanding. Obviously it is, but still........

 

Shame they don't do an A-max.

[Al69ec]

Ye shame about the a-max. I think the v-max are about as expanding as were guna get till the new super hmr arrives

[The_Dogge]

 

The HMR has much higher retained energy levels at 25 / 50 / 100 metres than .22LR that will wear backstops out quickly and on an outdoor range, its bullet will cover a much greater distance if there is an ND that misses the backstop. It will also retain a life-threatening level of retained energy out to a longer distance.

 

Laurie, I'm surprised, given your ballistic expertise, that you posted this incorrect information. While HMR does have more energy then .22LR at 100m, it does not retain energy further than a .22LR, the energy is roughly equivalent at 200yd and less than a .22LR at all ranges beyond this, see this chart comparing the retained energy: http://www.varmintal.com/17hmr.htm#Energy

 

Also, the HMR does not have a significantly greater maximum range than .22LR, using the JBM ballistics maximum range calculator indicates that both will travel between 1800 and 2000yd, but crucially the HMR will have only 2.3ftlb at impact while the .22 will have 6.4ftlb. I believe this may actually overstate the HMR's figures as it is less likely to remain stable at subsonic speeds and may tumble and lose energy even faster.

 

All your points about range certification etc are correct of course, but physically the HMR is a significantly safer round than .22LR in every important respect.

[gbal]

Laurie, I'm surprised, given your ballistic expertise, that you posted this incorrect information. While HMR does have more energy then .22LR at 100m, it does not retain energy further than a .22LR, the energy is roughly equivalent at 200yd and less than a .22LR at all ranges beyond this, see this chart comparing the retained energy: http://www.varmintal.com/17hmr.htm#Energy

 

Also, the HMR does not have a significantly greater maximum range than .22LR, using the JBM ballistics maximum range calculator indicates that both will travel between 1800 and 2000yd, but crucially the HMR will have only 2.3ftlb at impact while the .22 will have 6.4ftlb. I believe this may actually overstate the HMR's figures as it is less likely to remain stable at subsonic speeds and may tumble and lose energy even faster.

 

All your points about range certification etc are correct of course, but physically the HMR is a significantly safer round than .22LR in every important respect.

Well,there are lots of 22rf ammo,and a few 17HMR,but even allowing for some selective choice-you can have your Hi vel 22rf if you wish-then there isn't much to trade handbags about....maybe 10 ft lbs,at about any range from1-200 yards,where backstops matter most...hardly a game changing difference.On the graphs referenced,which are vague wrt rf brand,,at 300y the ft lbs are about 58,and 50,depending on just which loading you pick.....big deal?

Relatively few rf bullets make it to 1800-2000y,but if we just take your figures,of 2.3 (HMR) and 6.3 (22) what does "crucial' mean....these are rather low energy levels(max air pistol is 6ft lb),so the difference is crucial to what,exactly......a mouse? Maybe yu are overstating things here-you would not like either to hit your eyeball,but otherwise....?

With all these small difference energy figures,It's mischievous to conclude either is "significantly" safer on energy alone-they are pretty much in the same ball park-tumbling,richochet etc etc are unknown too,but unlikely to be 'sig' different.

Differences are small,"significant' seems unlikely,but unless you specify for what they would be significant,it's a meaningless term anyhow,especially wrt public safety/backstops etc which is relevant. Figures need interpreting....when applied to the real world.

Gbal

[Laurie]

Ouch I shouldn't have opened my big mouth here. Many years back there was some REALLY bad tempered correspondence in a shooting magazine over the maximum possible range of the .22LR bullet, claims for which vary by a factor of two or more. It's actually very difficult to calculate this - don't take the JBM Ballistics facility as gospel. I had some correspondence with Bryan Litz on this issue, and his opinion is that maximum range calculation requires some very sophisticated software and complex ballistics assumptions. This is particularly so for supersonic bullets as their drag coefficient rises as the speed drops towards the speed of sound, peaks just above that point, stays high until 0.95 MACH, then drops dramatically below 0.95 MACH when it is in low turbulence subsonic flight.

 

That's why we had battalion size machinegun formations during WW1 that used the good old Vickers-Armstrong and its ballistically unexciting 174gn MkVII flat-base bullet at ~2,500 fps MV out to ~5,000 metres dropping a rain of lead onto enemy communications trenches.

 

Anyway as George rightly points out there are a lot of .22 rimfire loadings and bullet weights out there. That most likely to be used on a rimfire range and which the army uses as its ballistic template is the 40gn LRN SV (standard velocity), nominally rated at ~1,070 fps MV, but in the days when I chronographed a lot of makes and models, it was usually around the 1,100 fps mark.

 

So, let's use that as our base with its 107.5 ft/lb ME. A standard 40gn LRN .22 bullet is usually rated as 0.120 G1 BC at all speeds, G1 being very appropriate here as this bullet is very close to the G1 reference bullet shape.

 

CCI claims 2,375 fps for its 20gn .17HMR FMJ round, the only legitimate target version of the cartridge. (A nonsense about the expanding versions - but we are where we are!) Not being a .17 user - never fired a .17 rimfire ever would you believe? - I'll have to take this valuer as given, likewise Sierra's G1 BC of 0.130 for all velocity ranges albeit it must vary more than the .22 bullet as it is (1) a more pointed shape and (2) sees greater velocity changes during a long distance flight. Stability? We can only work on either bullet remaining stable throughout the flight at all speeds - if they don't everything changes. Assuming the .17 bullet remains stable at longer ranges, its effective BC will actually rise somewhere beyond 300 yards as it drops below the bottom edge of transonic speeds.

 

Let's say that for proper field use - ie aiming at targets sitting on open ground - the 17HMR will usually be safer than the .22LR because of its very frangible bullet and the reduction in the risk of a ricochet. If the .17 DOES become unstable at long ranges and tumble, that could actually make it MORE dangerous in this scenario because it could be more likely to ricochet.

 

Forgetting Varmint Al who seems to have taken the hottest .22 he can find, here's how the two look at up to 300 yards in energy terms.

 

Yards ...... 17HMR/20 ...... 22/40

 

0 ............. 250.5 ............. 107.5

50 ........... 177 ................ 88

75 ........... 161 ................ 81

100 ......... 138 ................ 75.5

125 ......... 119 ................ 70

150 ......... 101 ................ 66

175 .......... 86 ................ 62

200 .......... 74 ................ 59

225 .......... 64 ................ 55

250 .......... 56 ................ 52

275 .......... 50 ................ 50

300 .......... 46 ................ 47

 

So, your point is taken - from ~250 yards, there is not a lot of / no difference between them in retained energy levels. However, rimfire range certification is based on (a) terminal energy levels at the backstop which will be 25, 50, or 100 yards and/or metres normally. Even at 100 yards, the .17 has a lot more energy ~80% to be contained by the backstop wall or whatever is used. If it is a wall, or sleepers, not an angled and deep sand backstop, regular HMR use will chew through it a fair bit quicker. On 25 yard rimfire ranges, the 17 has well over double the .22's retained energy.

 

On a no danger area range which applies to many outdoor rimfire ranges, no danger area means exactly that. I used to shoot on a range in worked out sand quarries with three ranges in a fan - 25 and 50M ranges parallel, 100 yards range almost at 90-degrees to the other pair. There is a motorway behind this range and which curves as the traffic on the nearest carriageway passes behind the range backstops. At 25 and 50 there is separating field maybe 150-200 yards deep and at the 100yd range, the motorway boundary almost skirts the backstop, so the distance between muzzles and vehicles probably varies from 150 to 250 metres. At the shortest distance, an escaping HMR bullet could do a lot more damage, at 250 they are equally dangerous.

 

This raises the issue of what is a dangerous retained energy level. If you're very unlucky a <12ft/lb air rifle pellet can kill at near nil range as happens occasionally. There was the notorious case of maybe 40 or 50 years ago ion which a guy fired a .22 at a bird in a tree at a high angle thinking he had a safe backstop in the form of a hill behind. The angle of the shot was such that the bullet just cleared the hilltop and plunged down the other side where unfortunately a family was picknicking. The father was lying on his back sunbathing and the barely travelling bullet by a really bad fluke went though his eye socket into the brain and killed him. The odds against that? At the shooter's trial for manslaughter, forensic evidence was that the estimated terminal energy was 7-10 ft/lb, normally just causing a bruise even on unprotected flesh.

 

When the British War Office set up the Ideal Calibre Panel immediately after WW2 to set out the parameters for a new post-.303 generation of service rifles and ammunition (it gave us the .280/30, one of the great lost opportunities of NATO policy thanks to our US partners), the first step was to identify minimum ballistics standards. For military use, both research and experience suggested that around 60 ft/lbs (90J) retained energy was needed to reliably inflict death or severe injury on an unprotected adult male and that was the benchmark that any new cartridge had to achieve at its intended maximum range. The .22LR SV is in that ballpark until 125 yards, the 17HMR to around 200. In practice, this may not (thankfully) apply with either cartridge due to their small bullet size - as we've seen with the ongoing at times desperate search to find an alternative cartridge capable of using the M16 etc chassis and whose bullet has greater wounding power than that of the 5.56mm NATO cartridge

[Laurie]

Incidentally just a further thought on the pair's maximum ranges. Common or garden physics says that two bullets fired at the same angle take exactly the same time to fall to earth irrespective of weight and velocity. That's because gravity is a constant. A high velocity / high BC combination travels further in that fixed period of time than a low velocity / BC example, so hits the ground further from the muzzle.

 

So, on that basis, the calculated flight time for the pair gives us an indication of which would travel further if the muzzle is raised to the optimum angle for achieving maximum distance. Sierra Infinity says the 300 yard flight time for the 40gn .22 SV bullet is 1.0389 seconds, that of the 20gn FMJ CCI .17HMR is 0.6117 seconds. Even if there is nothing much between them after 300 yards (the .17 is still going faster, but loses out in energy thanks to being 50% of the .22LR bullet weight), it should therefore travel further before gravity pulls it down to the ground.

[The_Dogge]

Sorry Laurie, but that's obviously not true at all. Consider 2 bullets fired straight up, with equal drag, the one fired faster will obviously take longer to return to earth, since it falls from rest from a greater height.

I disagree with much of your other post too but I cant respond now.

[gbal]

Sorry Laurie, but that's obviously not true at all. Consider 2 bullets fired straight up, with equal drag, the one fired faster will obviously take longer to return to earth, since it falls from rest from a greater height.

I disagree with much of your other post too but I cant respond now.

Not neccessarily,if the faster initial bullet sheds velocity at a much highr rate (BC etc)....it may not achieve a higher height....

 

As Gallileo asked,If two handbags are dropped simultaneously from the top of the Leaning Tower of Pisa,which one reaches the ground first-the one that is right,or the one that is wrong ? :-)

 

Gbal