So it looks like I am going to Boomershoot. After somewhere north of seven years of, “Damnit, I really should…” I am getting up off my arse and actually doing… mostly because fuzzyKBP is going to drag me whether I want to go or not. It certainly does not hurt that he is already planning on bringing the majority of the accessories that make Boomershoot a pleasurable experience.
So what exactly is Boomershoot? The simplest explanation I can think of is “explosive targets arranged between 350 and 700 yards away from a firing line”, and if that does not sound like fun to you, there is something seriously wrong with you. It is a multi-day evolution involving one core day of shooting targets, and then two lead-up days where you can attend a precision rifle clinic (fuzzyKBP and I will be doing so on Saturday), shoot at steel targets, or just hang out with folks.
All this, of course, raises the question of what I plan on bringing. To run down my rifle inventory, I have…
- Three .22LR rifles of various configurations. These might be useful for the “High Intensity” and “Cleanup” portions of Boomershoot, but for any real shooting… yeah.
- An M1 Carbine. Basically the same problem as the .22LRs.
- A .45-70 Springfield Trapdoor Carbine. While it would be hilarious to shoot Boomershoot with that caliber – and arguably possible, given modern loadings – that rifle is wholly unsuited for the task, even though its ladder sight goes out to 1100 yards.
- B.O.M.B.E.R. .223/5.56 is generally considered to be a suboptimal round for these events, except at the bare minimum of the ranges, and who wants to be limited that way?
- M1A SOCOM II. So this is pretty much the closest thing I have to a Boomershoot rifle, except for a few small details. First, 16.5”, non-match barrel. There are some interesting studies out there about how barrel length affects velocity and accuracy (*.pdf warning), with the upshot being it might be possible, but that brings us to the second problem. Mounting optics on this thing is hard (and, in my opinion, unsafe as hell), or requires really expensive glass. Finally, it shoots .308 Winchester / 7.62x51mm, which I find to be a remarkably stout round, especially out of a steel-butt-plated battle rifle. Sure, it is a heavy rifle, and I could get a pad for it, but sending 300-500 rounds through it over five days? Well, we will get to why that might be a bad idea for me.
So assuming I have one marginal rifle, what are my options, assuming I have a remarkably limited budget… because I do? Well, we might as well start from the ground up at calibers – I do have a pile of .308, but it is all milsurp, and its accuracy is anyone’s guess. While we were over at Dennis’ last weekend, Better Half brought up the possibility of .22-250, mostly because one of her former coworkers really liked it as a long-range varmint round, and partially because the thought of a .22-caliber round exiting the barrel at around 4000fps gives us both a raging case of the giggles. So how about we look at the two rounds side-by-side?
For the purposes of this comparison, I am using the cheapest “match-grade” ammunition I could find in-stock on GUNBOT as of 27MAR14. In the case of .308 Winchester, that looks to be Hornady’s 155-grain Boat Tail Hollow Point Steel Match round (found on Sportsman’s Guide for $0.78 a round), and for .22-250, I kind of had to stretch the concept of “match-grade” and went with HSM’s 55-grain V-Max loading (found on Selway Armory for $1.00 even a round). The latter is strictly a “hunting” round, but apparently there are no “match” rounds for that caliber, so I went with the first thing I could dig up enough ballistic data on. Sue me. On the flip side, I have never heard of steel-case ammunition as being “match-grade”, but, what the hell – I am cheap.
A rough breakdown of their pertinent details is below:
|Caliber||Weight||Ballistic Coefficient||Muzzle Velocity|
|.308||168||.405||2610 (24” barrel)|
Atmospheric and geographic conditions are assumed to be Boomershoot estimations – 3000 feet, 55° Fahrenheit, 29 inches of mercury, and 50% humidity. Both calibers are assumed to be zeroed at 100 yards – as far as I can easily reach in/around Raleigh – with the optic being 1.5 inches over the bore (a random-assed guess on my part).
All data and charts are generated by the Theory Ballistic Simulator developed by Frank Clarke.
[Update] Graphs have been adjusted after Davidwhitewolf accurately pointed out that I had to compensate for the M1A SOCOM II’s 16 inch barrel, versus the 24” test barrel used by Hornady. Based on information I have read, I subtracted 200fps from its muzzle velocity and reran the graphs accordingly. Disregard anything struck through. [/Update]
So, let us start with the easiest comparison – velocity drop over distance:
1500 feet per second is generally considered the absolute minimum necessary to detonate a Boomer, and you can see how .308 starts to dip under that right at
650 550 yards. That is kind of immaterial to me, given I doubt I can hit anything past 500 just on my own merits, but it is good to know. That is something of a concern for me, given that I figure 500 yards is about my maximum, personal engagement distance.
Next up, what about drop?
65 inches at 500 yards will equate to about 13 minutes of angle (generally abbreviated MOA), and it is interesting to see how the 1000fps difference in muzzle velocities plays out.
By subtracting 200fps at the barrel from the .308 round, its drop went from 65 inches to “holy crap”. Interesting.
But now the real clincher – what about wind drift? Assuming a 10MPH wind at 90 degrees off (something of an average case, from what I hear)…
Ouch. But, surprisingly,
the .22-250 is not as much more “ouch” than the .308 than I might have thought the .22-250 is no more ouch than the .308 out of the SOCOM II. I went ahead and checked the numbers generated by this program against those created by Modern Ballistics (which happened to have been built by Joe Huffman, the proprietor of Boomershoot)*, and they are close enough that I am comfortable with them – 26.1” at 500 yards from the former versus 25.7” from the latter.
At this point, I can see no reason to go with .308 over .22-250.
But those are all the ballistic properties of the rounds… what about things on the operator’s end? Thanks to this handy table from Chuck Hawks, we learn that .22-250 creates about 4.7 foot-pounds of energy at 6fps out of an 8.5 pound rifle. On the other hand, .308 Winchester creates 18.1 foot-pounds at 12.5fps out of a 7.5 pound rifle. Now, that is huge for me.
Why? Let me show you something:
Yes, I am a hairy bastard. No, I am not shaving my chest for you. But that picture was taken Wednesday night, after I sent approximately 20 rounds of 7.62x54R and 10 rounds of Trapdoor-safe .45-70 downrange on Saturday and another couple .45-70 rounds on Sunday, plus a smattering of 6mm Bench Rest and .243 Winchester across the weekend. The first two rifles had plastic or metal butts, while the last two had rubber pads. Interestingly, according to that table I linked above, x54R has less recoil energy and speed than .308, and .45-70 is right even with it.
Granted, I am not going to buy any rifle that does not have or cannot support a mother of a rubber pad on its back end, but still… I need to be able to use my arm after that.
On a similar note, the .22-250’s light recoil would be fairly handy for Better Half to use as a medium- to long-range rifle too, so that is a not-insignificant consideration.
If we are trying to balance wind drift, velocity at target, and overall recoil, what about the seemingly natural middle step between .22-250 and .308 – the .243 Winchester? It seems you can land some Federal Premium 80-grain Power-Shok for about $0.90 a round from SGAmmo (again, this round does not have a “match-grade” option, so work with me), with a ballistic coefficient of 0.365 and a muzzle velocity of 3330. Time for the charts:
Interesting. So in exchange for a 75% to 100% increase off .22-250’s recoil, you get a round that retains its velocities better at the ranges I am interested in, has much the same ballistic path, and is a good 30% more resistant to wind drift – in fact, it is more resistant to wind drift than the .308 we examined above, which honestly kind of surprises me. .243’s recoil still comes in at about half that of .308’s, but having shot fluffyKBP’s .243 last weekend, I have to wonder about either the accuracy of that table… or how he loads his rounds.
Given that it is tremendously likely that this rifle will finally propel me into reloading, how do the three calibers line up there? The Hornady .30 caliber 155-grain BTHP bullets run $29 for 100 ($0.29 each), Hornady .22 caliber 55-grain V-Max bullets cost $40 for 250 ($0.16 a shot), and Hornady 6mm/.243 caliber 80-grain FMJ rounds (I do not know what Federal Power-Shok is equivalent to) is $23 for 100 ($0.23 per). I am figuring the powder costs are “in the noise”, and while that is not strictly accurate, run with it for the time being; I am too lazy to do all of the necessary conversions.
Granted, reloading is something I am not going to get into until after Boomershoot, but it is something to consider now. When it comes to Commercial Off The Shelf (COTS, since that acronym is surprisingly not common) ammo, .308 is clearly king in both selection and cost, with .243 next and .22-250 trailing the pack.
So what do you, the readers, think? Suck it up and go with the .308 and maybe unable to help drive back cross-country afterwards? Have a blast with a round that seems to defy the laws of physics? Or drive right up the middle?
We will talk about actual rifles during a following post, but the good news is that, in most cases, the same rifle model can be had in all three rounds, which makes sense, considering they all trace their lineage back to the venerable .30-06.
(* – The only reason I am using Ballistics Tables rather than Modern Ballistics is that the former allows for the creation of those handy comparison charts, while the latter does not.)