7mm and or 30cal Bushmaster?

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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Sat Jan 30, 2016 6:16 pm

Al in Mi wrote:hoot, and difference in case capacity?


Did some more lathe work. With the neck opened up with a letter "N" drill (.3020) but not yet fireformed, the wall was .017. Factory cases average .015. Important point: This was measured with a digital caliper, not an appropriate case neck micrometer. Anyway, with .017 wall neck, the sized 450b case capacity again not fireformed yet, was 43.3gr of water. Unfired factory 30RAR cases measure 43.7gr and fireformed resized factory case read 44.3gr. So we're in the ballpark.

Dialing in the case with an independent 4-jaw lathe head is a little slower that I would like to do it, so if one was going to consider this seriously, it would be a good move to get an actual neck reamer setup, or at the least fabricate a QR case holder to chuck in the lathe. Getting the correct sized custom reamer would be a good move as well, though the letter N drill is darn close. Good luck finding a shell holder for an RCBS trim-pro. :|

Again, this segue was out of curiosity. We're not hurting for brass that badly yet.

Hoot

Edit: Turns out I forgot to deburr the mouth. Having done that, the 450b case neck wall was .015, just like the factory 30RAR cases. What's the odds of that happening? Oh yes, the case chambers fine in the rifle. Satan, get thee behind me! :lol:
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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Sat Feb 06, 2016 9:34 pm

Followup to the list of bullets I have on hand and their COL at the lands now that my box of 125gr Hornady Interlock SST bullets arrived. Their fit is almost like they were designed with the 30RAR case length in mind. I'm surprised we never saw a factory loading using that bullet.

Add to the chart on page 1

Hornady 125 2.34 Interlock SST Cannelure lines up at 2.25 COL

Based upon the shortness of the case in order to fit in an AR platform, I really believe that playing to its strengths means not trying to load heavier, longer, .308 Winchester class bullets and to that end, there are some great flat base 125gr bullets to choose from. Even some flat base 130gr bullets if weight means that much to you. Of course, the payoff is in velocity. If you want to go large, the price of admission is slower velocities, so you have to pay more attention to the bullet's optimum expansion design speed. Modeling suggests that with optimum powder selection, those 125's can clock out of the 22" barrel at 2900 fps. That's plenty fast. Admittedly, the modeling software does not test for accuracy, which can very well be at a lower velocity. If you're looking for a long shooter, the BC on the 125 SST is .305 and yes the 125 Nosler Ballistic Tip has a BC of .366, but that' no doubt due to the boat tail on them. Again, WRT playing to the 30RAR strengths, boat tail bullets eat up case capacity but since they don't contact the neck walls, they don't contribute to neck tension which is a asset in autoloaders to discourage bullet pulling when chambering and just like the 450b, it allows slower but greater energy yielding powders to be used. This of course just an informed opinion, albeit not informed about the 30RAR yet. Temps are slowly inching up and it won't be long before range time returns to the great white north.

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Re: 7mm and or 30cal Bushmaster?

Postby m113103 » Sun Feb 07, 2016 6:17 am

We had to qualify in the winter and couldn't use gloves. Good thing that the range provided heaters. They sure extended the months that the range was open. Of course the officers running the range wanted it open all year so they wouldn't get reassigned to traffic somewhere :P :P :D :D .
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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Thu Feb 18, 2016 11:28 am

Keeping the thread alive.
In case no one has done this already and FWIW, The Remington 150gr PSP loads have 32.5gr of factory powder and the 123 FMJ have the same powder as far as I can tell at 30X under the stereo microscope, but 34.5gr.
Have all kinds of load testing planned once it gets comfortable out.

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Re: 7mm and or 30cal Bushmaster?

Postby m113103 » Thu Feb 18, 2016 3:38 pm

Hoot, have you ever put a bucket of lit charcoal under your bench to keep warm? We use to put it under our cars so they would start. Saves the battery and wear on the engine. In Minn like Mich you either have snow and cold or rain and mud. :P :P :D
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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Thu Feb 18, 2016 3:56 pm

m113103 wrote:Hoot, have you ever put a bucket of lit charcoal under your bench to keep warm? We use to put it under our cars so they would start. Saves the battery and wear on the engine. In Minn like Mich you either have snow and cold or rain and mud. :P :P :D


I have a propane sunflower heater and was once tempted to buy a ground blind that I could drop over one of the shooting benches. Probably wind up asphyxiating myself. Remember, I'm from Maryland. "Land of Pleasant Living". If its so cold out that I have to take extreme measures to shoot, then its not shooting weather. Bad enough that being the Rifle Range Coordinator, I have to replace shot up target boards all winter, that the heartier members don't seem to mind peppering. The older I get and not to imply I'm that old, the less tolerant of the cold I become. Add the Raynauds Disease to the calculation and I'm pretty much like Punxsutawney Phil.

We're not to the mud phase yet, but the temps for the remainder of the week could definitely make things sloppier than a spaghetti sandwich. There are bare spot on slopes facing to the south along the highway. I'm praying that this "milk toast" winter gives way to an early spring for those of us with piss for blood. ;)

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Re: 7mm and or 30cal Bushmaster?

Postby m113103 » Thu Feb 18, 2016 8:11 pm

Sorry to hear that. :( I hunt out of one of those blinds and even with the door open they can be comfortable with a sunburst heater. The heater will go out before you even get a buzz from the monoxide. In most ranges if you shoot it up you get the pleasure of fixing it. :D Your range reports have been very informative. Looking forward for a syllabus of upcoming topics. :D
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Re: 7mm and or 30cal Bushmaster?

Postby PRKL8R » Mon Feb 22, 2016 7:57 pm

Thanks Hoot for the links. Those are fantastic values. Unfortunately the boss reminded me of the need of new furniture, new flooring in living room and kitchen. Oh well sometimes a man has to "bite the bullet".Maybe an unexpected bonus will come along. Until then looking forward to your post on the 30RAR.
"a citizenry armed with riles cannot be tyrannized." Jeff Cooper
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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Sun Feb 28, 2016 9:19 am

Well, I loaded up reference 5-shot runs using Benchmark, H322, H335, AR-Comp and W748, pushing the Hornady 125gr SST, which fits the 30RAR like a glove, to see how much I need to adjust QuickLoad to predict what they actually do in the field. I used pulled down 150gr Core Lokt rounds with their necks resized and their primers replaced with 7 1/2's . Looking back, I should have just shot them and re-processed the 1-fired round. That would have been time better spent since I would not have had to lug along all the testing gear. Just show up and shoot. I was not thrilled with how easily the 7 1/2's seated in the unfired primer pockets. Makes me wonder how many times they can be reloaded, even before starting

We had a spike in temperatures for one day yesterday and I had planned on getting out to "seize the day". I wasn't alone however. We have a Pancake Breakfast at the club once a year and that was also yesterday. A lot of members brought along their shooting irons, having also spent the winter cooped up. The rifle range was seething with shooters and the frost under the ground between the shooting positions and the 100yd target boards has not gone out, down more than about 2 inches. So we had soft, soaked turf, with snow melt water standing on it, on top of rock hard frozen ground.
Was starting to look like a "Buffalo Wallow" by the time I got there and the day had a long way to go. There were folks cued up, waiting for one of the 8 shooting positions to become available. I decided to wait for when spring really returns, not this messy teaser. As the rifle range coordinator, which means I do everything maintenance related, it was painful to watch it take such a beating. So I left and went home to erect the new outdoor weather station that the kids got me for Christmas, to get them off of my back. Sunday mornings, you can't shoot until noon and I take advantage of the later start to do my preventive maintenance. It'll be interesting to see what yesterday wrought, when I go there in a few minutes.

Today is back to late February weather. Spring will come in its good ole time, albeit a little early this year. Certainly not in February, but its always nice to get a "peep show". ;)

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Re: 7mm and or 30cal Bushmaster?

Postby Hoot » Sun Mar 06, 2016 8:02 am

We're going to get a new Sub-forum called 450b Variants. Once Mudbug sets it up, I'll move this and any other similar threads there.

The weather is improving temperature-wise. Supposed to be sunny and eventually get above 50 today, but looking out the window, the wind is gusting strongly. There still snow in the shady spots, so it will be damp as well. I am still hoping to get out nevertheless since I go to the rifle range late Sunday morning to do preventive maintenance anyway. I'll pack my world to take along and assess the comfort level while doing my PM.

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