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boomershoot 2014 preparations, the caliber

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. 

- Trollsin.  7.62x54R is certainly a Boomershoot-able round, but ~3MOA is an unacceptable accuracy.  It is possible we could improve on that, but there is no guarantee. 

- 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)
.22-250 55 .255 3610

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: 

velocityoverdistance

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? 

dropoverdistance

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)… 

driftoverdistance

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: 

bruisedshoulder

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: 

velocityoverdistance2

dropoverdistance2

driftoverdistance2

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.) 

17 comments to boomershoot 2014 preparations, the caliber

  • I’d look at something in the 7mm range. Hit up some of the guys that shoot Woodys match in Apex and see what works best for them. His match sounds very similar to Boomershoot, but without the boom. http://www.woodysmatch.com

  • Davidwhitewolf

    Caldwell Lead Sled II. I will bring mine and you’re welcome to borrow it and its up to 100lbs of lead shot ballast. Bear in mind it raises the rifle a few inches higher than most rests, so you might need a taller chair or a pillow. :)

    For your ballistic tables be sure to factor reduced velocity from the Socom’s shorter barrel. Stiffness may help with accuracy but you need velocity to set off boomers. And my 16″ and 15″ .308 pistols have hit plenty of boomers at 650-plus, but only detonated one out that far that I can recall.

    At the shorter ranges I’d imagine you’d do fine with your Socom with a pistol scope and a solid rest. If you try irons alone you’ll just drive yourself crazy.

  • Better Half

    I like that fuzzyKBP has morphed to fluffyKBP….I wonder what that says about him.

  • @ Luke: Unfortunately, it does not look like the next match is until Boomershoot, coincidentally enough, so I will see what I can do about tracking down information on it.

    And there just does not seem to be a full-up 7mm round that can reach the distances necessary with the velocities needed that does not hate my shoulder for some ungodly reason.

    @ Davidwhitewolf: Good catch! I completely neglected to look at the barrel lengths for the test rounds, and adjusting the charts for that actually changed things significantly.

    The catch with optics and everything is that I have already lined up on to borrow, so it is basically no cost now, and for the cost of a decent LER optic, I could get another rifle. Since I am buying ammo in either case… yeah, I am not sure where I come out ahead.

    I may bring the M1A for the high-intensity side of things. Or the Trollsin. We will see :).

    @ Better Half: Well, he was somewhat fluffy last we saw him…

  • fuzzyKBP

    @ Linoge: I hope to be scruffyKBP one day… That was actually .243 Win. Winchester Super-X 80 gr JHP “Varmint & Predator” at the range. No calling it my super secret +P+… although if the .243 win goes out I’ll almost certainly load it with 80 gr Fowler FB. I’ll save the ballistic discussion for a post of its own, but it should do quite well at Boomershoot, assuming it goes out.

  • You need a graph of shots fired vs. bruise diameter/tint.

  • […] John Hardin on boomershoot 2014 preparations, the caliber […]

  • @ fuzzyKBP: Well damn. Maybe I had already tweaked out my shoulder for that weekend and it just was not having any more of it regardless.

    @ John Hardin: That would involve far more time – and potentially pain – than I am probably willing to invest ;).

  • […] Linoge on boomershoot 2014 preparations, the caliber […]

  • […] Boomershoot 2014 preparations, the caliber […]

  • Windy Wilson

    According to the father of one of my school mates, that bruise would have gotten you shot on the spot in Madrid when Franco took it over in 1939. They’d go down the streets and tear the shirts off the men, and if they showed bruises, Bang!Blood and brains everywhere.
    As for calber for Boomershoot, how do you feel about 300 Win Mag?

  • Windy Wilson

    @ Windy Wilson:
    I want to add that I once shot an M1A that was (If my fevered brain is working) chambered in 300 Win Mag. (I have the brass somewhere as a souvenir). I’m a bit of a recoil wuss, but it wasn’t bad, something on the order of the usual M1A.

  • Mike

    Linoge – I commented more about caliber in one of your later posts, but one thing to potentially keep in mind is round count. You’d have to be shooting non-stop to go through 300-500 rounds in three days at Boomershoot. I usually bring that much along, distributed among several calibers, but on the actual day, unless you’re missing an awful lot, you may go through 60-80 rounds, with all the time-outs, lunch breaks, cars passing by and shutting down the range, etc. On the field days, typically you’ll get your zeros verified and plink a bit more, but if you shoot 100 rounds a day, that’s probably well high of average. So, for the three days, figure more like 250-350 rounds – which may make a difference in your recoil-induced tatoo.

  • fuzzyKBP

    @ Mike:
    Mike, how do you plan your breakdown between calibers?

  • Mike

    I usually bring several rifles to Boomershoot. The .308 is my “go-to” rifle – it’s the Remington 700 SS 5R Milspec mentioned elsewhere. It’ll easily hold 1/2 MOA at distance (which you need to do, since you need to hold at the bottom 1/2 of the boomer boxes). If I was to go again, I’d have a second .308 with me – so would plan on shooting about 60 rounds through each, per day. I’d round that up and take about 200-240 rounds of .308, either handloads, custom reloads, or factory match.

    I’d also take my Grendel, with probably about 100 rounds for it – planning to shoot something like 60 rounds (three, 20 round mags out of the AR).

    Finally, I’d tote along 60-100 rounds for my .204 Ruger. If I brought along a magnum rifle, I’d bring 50 rounds or so for it. So, I’d probably bring along about 500 rounds of ammo, total, but I’d likely expend something in the neighborhood of 180-250 rounds. The extra is just to make sure I have enough to run a particular rifle if I happen to be enjoying it a lot, to let other folks shoot my guns, etc.

    This ammo would last me through two days of field course plus the main event. Of course, this is just me – but the whole group I travel with have about the same ammo expenditure. YMMV, of course, but I honestly don’t think it’s even possible to shoot more than about 180 rounds of carefully aimed shots on Boomershoot day itself, assuming that you’re trading off with a spotter, take a lunch break, etc.

  • I certainly cannot speak to individual shooters’ rates of consumption, but Joe recommends at least 100 rounds for the actual Boomershoot day, and Mr. Econ recommends at least 100 rounds for his clinic, for which we have signed up on Saturday. Plus, we will be there for the Friday Free Fire period, and sighting in and working out the kinks will involve more than a few rounds downrange as well. Unfortunately, I know a lot of my shooting will consist of “walking” the rounds in, so my round count will probably end up being higher.

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