First Date Report

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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First Date Report

Postby Hoot » Sat Apr 17, 2010 8:16 pm

To sum up my first experience with the 450b in a metaphor. A fellow sitting 3 positions from me was shooting a similar looking .223 AR. him "Crack...Crack...Crack... me KA-BOOM! After the dust stopped falling from the cover above us, I looked over since he wasn't shooting anymore. He was staring at me and asked,"Did your gun just explode or something?" :lol:

That is one powerful caliber. I own a Browning .300 Win Mag BAR (semi-auto) and I'd liken the experience shooting the 450b to be very close. Not punishing like a bolt or single shot action, just authoritative. I did not choose to remove the muzzle brake, stock recoil absorber and Limbsaver recoil pad to see what the difference felt like. It was stout enough with them. I only shot 18 of the 24 rounds I brought with me, not because I was getting sore, but for reasons to be touched upon later. I could have shot it all day if I chose. It is not uncomfortable to shoot, but it certainly is not like shooting a varminter. I still feel that my friend Randy's Remington 760 pump in .270 hurts worse to shoot. The recoil impulse from it is like a stab as opposed to getting rocked.

The 37 gr of Lil Gun and 250 gr FTX reloads with taper crimp I was shooting turned out pretty close to factory loads. Velocity over the chrony ranged from 2223 to 2294 fps. Most of the brass showed light sooting around the mouth and one or two had mild sooting further down, but for the most part they ran clean as could be expected. Ditto on the barrel and action. I cleaned with Kroil every five shots. After sighting in the scope, best 3 shot group at 100 yds was 1.2" C-T-C, with several pairs touching. Plenty good for deer hunting.

When I first put it to my RRA NM lower, the fit was very tight. After 18 rounds, it was loose. That does not encourage me for the future, but time will tell.

After getting used to and exhausting the 250s, I switched to what I was most interested in. The 200 gr FTX which I hope to ultimately use for deer. The 250s are fine, but IMHO overkill for whitetails unless you want to shoot several abreast with one shot.

I referred to what published data I could find regarding the 200s and was going to start them out with 43 gr of 2400. Being conservative and not finding a lot of concise data WRT the 450b, I loaded up 3@41, 3@42 and 3@43 gr. I'm now glad I started with the 41s because even with an air temperature of 44 F, the first shot struck me as rather harsh. Certainly greater than the 250s did. The chrony told the first part of the tale with the first round fetching 2574 fps. Examining the brass told a more seriouse tale. Though the primers did not seem unduly flattened, both the extractor and ejector imprints could be plainly seen without even looking for them. Firing the other two rounds yielded 2569 and 2582 fps. Same effect to the brass. There was no sooting implying a good, tight seal in the chamber. My Limbsaver however, committed suicide, the plastic base plate having shattered. More on that in a minute. Needless to say, I did not shoot the 42s and the 43s. I'm not interested in hunting dangerous game, just deer. I was hoping to find one of the loads would push the 200 FTX to 2200 fps, (2150 ft/lbs), yielding a more pleasant shooting but serious round for cxp2 animals. While loading the 200s, the 2400 was right up to the base of the bullet with the 43 starting to feel crunchy during seating so I'd rate that at lightly compressed. IMHO, that leaves a safe region to reduce the charges and I intend to load some more up with 37-40 gr of 2400 and return the range tomorrow if I can repair the Limbsaver. At an average of ~2550 fps, the 200s shot 3 inches higher than the 250s at 100 yds and grouped looser, with the three shots grouping at 2.8" C-T-C. Still fine for deer, but for brush hunting ranges I encounter where I hunt, I dont need close to 3000 ft/lbs of energy.

WRT the model 10401 Limbsaver. The damage to it was not the result of the rearward recoil impulse, but the bounce-back forward afterward, as it broke outward, not inward. Here's my theory. I removed the foam from my A2 stock and replaced it with fiberglass entrained Bondo which held a 6 inch thick-walled steel tube in place, threaded internally and with a screw plug in the end of it. Inside that tube was a lead slug with springs attached to each end, mimicking the dead mule style of recoil absorber, just with a much heavier weight. All of those modifications adds about 3 pounds of additional weight to the A2 stock. Great for balancing right at the grip and rearward recoil mitigation, but not so good on the bounce-back. The plastic base of the Limbsaver just doesn't have the strength to withstand that kind of stress. When I first layed out my intended mods, I had thought about adding a 1/4" metal plate fit to the in-letting inside the A2 butt, where the standard recoil plate would rest and sitting flush with the end, then fitting the Limbsaver over that, but I did not want to commit the time milling it for a precise fit. This would not have happened with the standard A2 metal recoil plate, of if I had chosen to rig up the Limbsaver over top of the standard recoil plate with longer screws. I doubt I will be able to repair the Limbsaver, but you can learn from my mistake. BTW, this failure occurred after the three 200 gr shots, not during the previous fifteen 250 gr shots, to give you an idea of the difference in the recoil impulse. Whats weird is that if you plug in the values to a recoil calculator, the 250s should have had greater recoil than the 200s. The velocity difference between the two must have a bigger contribution to the recoil impulse propagated through the stock. The 200s sure felt more harsh as well.

All in all, a very educational and enjoyable outing. There are no nuisance hogs up here so this is as fun as it gets until deer season comes around. I look forward to many more learning opportunities to come.

Hoot

BTW, the other two shooters positioned near me at the range said the disturbance from the muzzle brake was not objectionable. Both, like me were wearing hearing protection. Not like when someone, a couple positions away touches off a .50 BMG. Been there, felt that... OMG! :o
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Re: First Date Report

Postby bushmeister » Sat Apr 17, 2010 8:34 pm

Sorry to hear about your limbsaver, I've shot a few hundred factory loads with mine, and havent had an issue. What I did, was grind down the buffer tube spacer about an 1/8" to make the limbsaver meet the standard stock flush. At least you got to go shooting tho!! Surely you can find some coyotes to go after until deer season gets here. :D
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Re: First Date Report

Postby Hoot » Sat Apr 17, 2010 10:58 pm

bushmeister wrote:Sorry to hear about your limbsaver, I've shot a few hundred factory loads with mine, and havent had an issue. What I did, was grind down the buffer tube spacer about an 1/8" to make the limbsaver meet the standard stock flush. At least you got to go shooting tho!! Surely you can find some coyotes to go after until deer season gets here. :D


I ground mine down also and even angled it to accommodate the angle of the rear WRT the buffer tube. When the Limbsaver meets the spacer, it meets the end of the stock at the same time, flush. I don't know your stock, so I don't know if you increased its weight by three pounds. Unlike commercial spring-weight products, which employ a ~4 ounce weight, mine is ~8 ounces. That was just a guess along the lines of more being better. Every recoil cycle there is a, for lack of a better term, standing wave imparted by the sliding weight bouncing back to rest. It forces the stock away from the tube. This was how it failed. Not by being forced towards the tube. An interesting twist. Some manufacturers of spring-weight recoil reducers dampen the return with oil, much like a conventional shock absorber does. Some use a different strength spring on the return side. Right now, the Limbsaver has been glued with good old JB Weld. We'll see how strong the bond is in the morning. I have some longer screws to permit piggy-backing the Limbsaver on top of the standard recoil plate. Though not as aesthetically pleasing to the eye, it will eliminate the stress being placed upon the area immediately around the screw holes. If everything goes according to plan and I make it back out to the range tomorrow, I intend to assess the felt recoil with the spring-weight, with just the weight immobilized and no weight in the tube. I left options with the screw plug. Lacking gunnut's accelerometer setup, my observations will be strictly anecdotal. Fun with science... ;)
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Re: First Date Report

Postby MudBug » Sat Apr 17, 2010 11:41 pm

I've had no trouble with the limbsaver on my chopped cav arms lower.
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Re: First Date Report

Postby Hoot » Sun Apr 18, 2010 7:31 pm

Never made it back to the range for more work on the 200 gr FTX'. The limbsaver JB Weld fix lasted as long as it took to tighten down the buffer tube screw and the bond failed. Will be looking for another but I doubt I'll find as good a deal as I got on the first one. Also keeping me away from the range was my scope rings. They're a skosh too low, requiring an uncomfortably tight cheek weld to open up the view and I didn't want to re-zero the scope twice, so I'll wait until I get a set of YHM mini risers. They seem like a more frugal solution rather than buy yet another set of rings. I have lots of quality rings, just not quite high enough for the AR mechanics. Needless to say, I'm glad I got this rifle and will report my travails with the 200 gr FTX in the reloading forum. If they don't work out, it won't be for lack of experimentation and the 250s are certainly effective and reproducible. I'll tell you. If I had the materials and tooling to fool around with, I'm certain a screw could be developed that retained the standard trapdoor butt plate and was itself hollow and tapped to accept a screw that's sole purpose was to retain the limbsaver by a smaller screw. For example a 1/4-28 hex head bolt drilled and tapped to accept a 10-32. That way, the 1/4-28 would bear the strain of securing the A2 stock using the strong, load bearing surface of the trapdoor plate while having the 10-32 from the limbsaver screw into it under much less tension. Hmm... off to the shop...
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Re: First Date Report

Postby wildcatter » Mon Apr 19, 2010 3:56 pm

Just soze ya noze, the 200ftx's penetraite about 3-4 times less than the 250's. On, gallon milk jugs, lined up in a row, in a jig, the 250's will do about 5-6, the 200, do about 1, sometimes two, kinda sorts. So use them for the right mission, or that elephant hunt you've got going on down there might be a real bust with them, when you make'em madder than a hornet.

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Re: First Date Report

Postby Hoot » Mon Apr 19, 2010 6:16 pm

Out of respect for Mudbug's advice and to benefit those searching for reloading experiences, I'll be continuing the 200 FTX dialogue in the Reloading for the 450B forum.
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