[Wildcatter]

Ok, forget my first two post, with this llong answer. The Cut and Paste got a little carried away, try this one...

Ok, Slash, let’s try to handle most of the problems in one posting. This is somewhat disjointed and I know what I'm talking about, even if no one else does, wink. I hope you can follow along.

First of all, Randal, a.k.a. Ar15 barrels, is giving you good stuff and you can see this isn’t his first Rodeo, but then again it isn’t mine either, with years of experience with the 45 Professional.

Now, the 450b is directly based off the .284win., and thus, turning or reaming should not be an issue, but what to do in the mean time? First, assuming you have full length resized and then trimmed to the factory standard of 1.700” (plus nothing, minus .003” and use the order given - resize and then trim), load a dummy cartridge and try the “THUNKING” test. Pointing the barrel down “drop” your reload into the chamber, it better have a decided Thunking sound when the mouth of the cartridge hits the end of the chamber. If it does not, take safety precautions and again full length resize and re-crimp, the reloaded cartridge; it’ll go “THUNK” now! Second don’t worry about squeezing the bullet a little in the resized loaded case; the bullet is a little over sized and the barrels are ever so slightly undersized and the dies (assuming they were made right) will not over crimp the bullet, so as to let the mouth of the case go pass the end of the chamber (remember we have the same set of problems with the 45 ACP). With that in mind put on a heavy tapper crimp, “NEVER any kind of roll crimp”, into the case, enough so the bullet is visibly dented, again don’t worry about denting the bullet, in fact you want to see a slight dent (you wouldn’t have to do this if you had the bullet sealing gum that Lake City uses, but normally we don’t, so not to worry). This will not affect accuracy at all and will assure proper bullet pull, and will stop any bullet travel, in the case, that can occur in the shooting/cycling process and still yield minute of angle accuracy and better.

Now, what to do about over pressure signs? It is very normal for under pressured cases to kick the primer out first, before the case releases, thus a flat or detached primer. It is my opinion; you may be very much under pressured. Randal gave numbers that say 35,000 to 37,000 psi are dangerous pressures (based on the program Quick Load), nothing could be further from the truth (no offence Randal, also none of the bolt thrust formulas are accurate either, more on that latter). We normally load the 45 Pro to 60,000 psi with 230 ball or FMJ flat points my favorite. Yes, I know that the 458Socom and the 50Beo are loaded to the 35,000 psi area, but then again those great cartridges do not have the barrel thickness the 450b has in the chamber area. Here’s my example, a “Mountain Rifle”, bolt action weapon, chambered for the 284win case has a SAMMI spec in the area of 63,000 psi and has a barrel chamber diameter the same as the 450b. The other proof is Bushmaster told me that twice they loaded to these pressures and fired 6000 rds + each time with no ill effect and my friends and I load to these pressures and have done so for years, normally. So, why does Hornady load for 38,000 psi, as they have quoted? They tell me the Lawyers won or that they did not want to over stress their SST bullet, which is designed for magnum muzzle loader velocities of around 2000fps and would blow up on deer, like a varmint bullet would do, if you pushed them as we can actually do. My personal loads in the 450b, for the 250gr. bullet START at 2500fps and go up, but then who can afford those bullets, sold in twenty packs. I’ve tried the 200gr SST and compressed a load of 296 and achieved 2800fps, with only slightly flatting of the primers. If you need a pointed expanding bullet, Barnes makes excellent 200 & 275 grain varieties.

As for “Bolt Thrust” with these pressures (70,000psi +), Wayne State University’s Engineering Dept., in a published article, I forget which gun rag ran it now, actually ran “MEASURED” test, not calculated and found that at these increased pressures, the bolt thrust was just a little less that the .223 case and this because of a effect known as Bernoulli's Theorem, which basically tells us that necked cartridges have way more bolt thrust than straight cases and all the bolt thrust formulas are based on those necked cases, hence not at all accurate for the 450b. My Buddies and I have never seen a bolt failure and don’t ever expect to and we only use, what you might call, max loads, we don’t think they are but others might and we’ve never had a problem and together we have maybe a million rounds down range or certainly many, many, 100,000’s at least.

My recommendations? Assuming you will take proper safety precautions and use great skill, use WW296 for the lighter 200 grain Barnes, which is a pointed-hollow point bullet and AA1680 for the Barnes 275 gainers, which is also a pointed-hollow point. But consider the Hornady 230 FMJFP, which the Flat Point will disrupt more tissue than an expanded bullet does. The flat point doesn’t really expand and will penetrate straight through an animal, as opposed to going squirrely, as is the case with many expanded bullets, on occasion, even to turning 90 degrees in side of flesh, been there, done that. Your loaded length of 2.1” is way short too, load the 230’s to 2.2” (but not much more, you still have to hang onto the bullet) or longer and the pointed bullets to 2.250”, max is 2.260", but you do need some clearance in the magazine. AA1680 & 230’s will increase your speeds and lower your pressures and still yield 2800fps, which is more than enough for any animal on this planet, if FMJ’s are used. In fact this combo has twice been to the Cameroon’s and has dispatched Cape Buffalo and Elephant, with reported ease. Keep in mind that this is with a version that is .070” longer, the 45 Professional. The standard 230gr hollow pointers are cheap and because of these highly increased speeds just explode on anything, making them good for home defense.

So, take care in your loading processes and creep up on the loads, using ww296 for the lighter pointed bullets and AA1680 for the heavier pointed bullets. For 230gr FMJ’s I use AA1680 exclusively. Do all this and the 450 Bushmaster will absolutely astound you and all the other cartridges for the AR system will not be comparable to the 450b for pure Horse Power and Versatility. Good Luck. Ok, Slash, let’s try to handle most of the problems in one posting. This is somewhat disjointed and I know what I'm talking about, even if no one else does, wink. I hope you can follow along.


So, take care in your loading processes and creep up on the loads, using ww296 for the lighter pointed bullets and AA1680 for the heavier pointed bullets. For 230gr FMJ’s I use AA1680 exclusively. Keep in mind, that the 450 Bushmaster was only released for sales this last July and that you are on the cutting edge. This is all in it's early stages. Many more bullets will be offered and Corbon is going to offer tons of stuff for us all and this is just the start.

Do all this and the 450 Bushmaster will absolutely astound you and all the other cartridges for the AR system, great though they are, will not be comparable to the 450b for pure Horse Power and Versatility. Good Luck.

P.S. I have used Hornady’s venerable 350gr jacketed “.458” bullets resized to .452” in a Lee bullet swagger, meant for lead bullets, with no jacket separation problems at all, as one might expect, probably because we’re only going down .003” per side. You can’t really shoot .451” bullets in a .458” dia. Barrel and expect to anything more than minute of Barn Door. NOW, how versatile is the 450 Bushmaster!

[Slash2]

Originally Posted by Wildcatter

Do all this and the 450 Bushmaster will absolutely astound you and all the other cartridges for the AR system, great though they are, will not be comparable to the 450b for pure Horse Power and Versatility. Good Luck.

Great information Wildcatter! I was beginning to think the 450B wasn't such good choice for a relative newbee to reloading such as myself, but now I can see that this gun might be worth sticking with!

I'm still not sure I want to keep messing with the 284 cases, of the 200 I started out with I've only got about 60 left that I haven't screwed up in one way or the other. I initially bough 200 rounds of factory ammo, of which I've fired about 150 and repeatedly reloaded, I think I'll stick with them.

I still have a bunch of questions related to loading these things, regardless of the case, that I hope you might be willing to help with without giving away the keys to the castle, I'd like it handed to me on silver plater, but I'm new and I realize I still have to earn my spurs.

I've got about 150 Hornady 240 gr XTP/MAG Bullets. If I seat them to an OAL of 2.2" I only have .166" of bullet in the case. Is that okay?

I also have a butt load of Hornady and Zero 230 gr hollow points that I load for my 1911, it sounds like these hollow point pistol bullets should stay in the 1911 and I should invest in FMJ's for the higher velocities of the 450B.

For powder I've got 4lbs of H110 and 1lb if IMR4227, am I barking up the wrong tree? My goal is two basic loads, a range round for punching holes in targets out to 200 yrds and a hunting round for punching holes in pigs. The H110 @ 38 grs has given me velocities around 2100 using the 240 and 230 gr bullets, but the accuracy sucks, I figure I can afford to play with those as target loads because they are relatively cheap, but I want to use Barnes X 250 gr 454 Casull or Barnes X 275 gr 460 S&W for hunting pigs and they are pricey bullets to be experimenting with. I'm hoping this is where you can save me some grief, will the 110 or the 4227 work or should I not bother playing with them? With the very long 275 gr barnes X the case is pretty much packed with 38 grs of H110 and an OAL of 2.225". Can I get there from here?

I apprieciate the help, too bad you don't live down the street!

[ar15barrels]

Originally Posted by Slash2

I've got about 150 Hornady 240 gr XTP/MAG Bullets. If I seat them to an OAL of 2.2" I only have .166" of bullet in the case. Is that okay?

The general guideline is to seat one caliber's worth of bullet into the case at the minimum.
For example, a 22 caliber should have about 0.22" of bullet shank seated in the neck.
You don't necessarily have to follow that rule above 35 caliber though.
I would try and have at least 0.25" of bullet shank in the case neck with pistol bullets such as the XTP.

[bla]

I am seating the hornaday 240 XTPs to 2.017" I don't think the 450B has much freebore, the factory rounds only show about .025" before they start to taper. I am loading 36.5 H110 at 1950ft/s. I am staying there because these rounds print on target the same place as the factory rounds. My groups are running abou 2". The same as hornadays factory rounds in my gun. I don't need more speed, I'm Happy.

[Slash2]

Originally Posted by bla

I am seating the hornaday 240 XTPs to 2.017" I don't think the 450B has much freebore, the factory rounds only show about .025" before they start to taper. I am loading 36.5 H110 at 1950ft/s. I am staying there because these rounds print on target the same place as the factory rounds. My groups are running abou 2". The same as hornadays factory rounds in my gun. I don't need more speed, I'm Happy.

That's good info Bla, can't wait to get to the range and try it out, thanks for sharing!

what distance were you shooting?

[Slash2]

Originally Posted by bla

I am seating the hornaday 240 XTPs to 2.017" I don't think the 450B has much freebore, the factory rounds only show about .025" before they start to taper. I am loading 36.5 H110 at 1950ft/s. I am staying there because these rounds print on target the same place as the factory rounds. My groups are running abou 2". The same as hornadays factory rounds in my gun. I don't need more speed, I'm Happy.

Went to the range today, 36.5 h110, 240 XTP/MAG, 2.1 OAL.

I didn't crony them, but I got a ragged hole with a four shot group at 100 yrds using bla's recipe. The factory rounds gave me a 1.5" group about 1.5" to the right of the hand loads.

Now, I can understand different loads giving you different altitudes, but different loads being off left to right? What makes one load go left or right more than another?

[bla]

100 yds. I found that useing a filler wad ( my wifes quilters polester batting cut into 1/2" x 2" strips and rolled up)inserted between the bullet and powder to hold the powder against the primer. This reduced my max speed deviation to under 50 ft/s with the H110. I am also loading 230 gr. Magteck FMJs with the same good results. these are seated to 2.070" OAL.

[bla]

That should read polyester batting. I have used it for years to take up free space in under-filled rounds. This really increases shot uniformaty.

[Wildcatter]

Ok Slash, once again Randal is correct. Yule of thumb is one caliber for the depth, and he is also right about those numbers aren't quite right for the larger calibers. It sounds like the xtp might be a little shorter than the FMJ’s. I normally seat my shorter .4515 bullets to a depth of .187” with no ill effects at all, your number of .166” is a little skinny, but hey, try’em, but get that OAL out there a bunch more, someone quoted a 2.017” OAL and that’s simply way too short, probably works great, but, the shorter the OAL the more the pressure. ; H110 is interchangeable with the data for WW296 and is a great powder for the 450b as is 4227, but AA1680 will keep the speeds up there and lower the pressures.

[Wildcatter]

P.S. The 45 Pro as does the 450b have a freebore of .200", which usually means poor accuracy, but everything changes in these big bores and sub MOA is very common. A friend of mine is buddies with one of the talking heads on the outdoor channel. Seems the outdoor channel is about to do a sit-rep on the 450b and I guess those guys actually shot on camera, a 100 meter .000" group, measured with very accurate equiptment. Now, if that where me doing the shooting I'd retire, right then, for fear someone would ask me to repeat that.

[ar15barrels]

Originally Posted by Wildcatter

The 45 Pro as does the 450b have a freebore of .200", which usually means poor accuracy

Long throats are only detrimental when they are oversized and let the bullet bounce around.
A properly centered and sized throat which has a lot of freebore will not necessarily be detrimental to accuracy.
One reason to seat bullets out to touch the lands is that you force the bullet to center up in the barrel where it would normally have 0.001" or more to move within the throat.

[bla]

OAL is dependant on two main things, Freebore and mag length. Seating too long (as in against the rifleing) WILL increase pressure. I have no feeding problems with short rounds in my ARs. I would advise against ignoring freebore just to fill up mag length. If that .200" freebore is correct I would stay off of it by at least .030"

[Wildcatter]

Originally Posted by bla

OAL is dependant on two main things, Freebore and mag length. Seating too long (as in against the rifleing) WILL increase pressure. I have no feeding problems with short rounds in my ARs. I would advise against ignoring freebore just to fill up mag length. If that .200" freebore is correct I would stay off of it by at least .030"

Yes sir your are so correct, I might have been somewhat confusing. Max Mag length is 2.260". If you are into the rifling, at that point, then of course the cartridge will have to be shorter. In the case of the pro & bm the freebore is an additional .200" from a normal chamber, per sammi spec., making any reload that was .030 off the rifling, at least, .200" longer that the mag. I was just answering your thought about the bm not having any freebore, as a fyi, sorry for any confusion.

[Wildcatter]

Jagermaster,

Of course 60,000 psi is high, although many of us think it is not Danger High. The barrel does not have any problems at these pressures. The .284 specs are 63,000 psi and that includes mountain barrels that have the same chamber dia as does the 450b and then gets smaller than the 450b out to the muzzle. Also consider the 460 S&W's pressures which are in the 60,000 arena. Which do you think is more durable the S&W or an AR? However, having said all this, I would not try to load for 60,000, until you become much more experienced. The only real consideration is bolt thrust. The .223 psi. spec. is for 52,000 psi and if one were to load the 450b for this spec, the bolt thrust will be way lower than the .223's, as per the copper crusher studies as sited by Wayne State University and re-quoted in the gun rags. These were studies done with a special copper crusher placed on the bolt face and then firing the cartridges, so as to compare the 223 to the 45Pro. This was done after they realized that the standard bolt thrust formulas did not apply. I suppose they had to re-learn the principal that bottle necked cartridges have much more thrust. So, maybe this will be over simplified, but in the example of the 450b, not any other AR cartridges, if you have enough wall thickness in the chamber and have a straight case, one can indeed pump up the pressures and stay in the safety margins. That’s the trick, safety margins. The arm chair warriors will do all the nay-saying and because they cannot do it, then neither can you, but I tell you this, it takes guys like you, with the guts, to find out that there are paradigms’ out here and were all along, that are being broken and will yet be broken.

PS. Try sizing the Hornady 350gr. 458 bullet to 452. You are only shrinking them down .003" per side (less than half the size of a human hair) and doing this with other similar bullets has not shown jacket problems in flesh. I don't think this will work with copper/brass solids; of course this trick is only if you just have to have heavy bullets and want to fully realize the full potential of the 450b. Good luck.

[ar15barrels]

Originally Posted by Wildcatter

Jagermaster,

Of course 60,000 psi is high, although many of us think it is not Danger High. The barrel does not have any problems at these pressures. The .284 specs are 63,000 psi and that includes mountain barrels that have the same chamber dia as does the 450b and then gets smaller than the 450b out to the muzzle. Also consider the 460 S&W's pressures which are in the 60,000 arena. Which do you think is more durable the S&W or an AR? However, having said all this, I would not try to load for 60,000, until you become much more experienced.

The only real consideration is bolt thrust. The .223 psi. spec. is for 52,000 psi

Commonly used maximum bolt thrust loading on AR-15's is 7000 lbs.
A 223 at 55,000 PSI makes about 6300 lbs of thrust.
7.62x39, 6.5 Grenade (grendel) and 6.8 SPC all run right at 7000 lbs.
Using the same formula, a 450 Bushmaster at 60,000 PSI makes 11,775 lbs of thrust.

As a comparison, a 308/7.62x51 makes 10,500 lbs of thrust.
308's use a bigger bolt for obvious reasons...

[ar15barrels]

Originally Posted by Wildcatter

Of course 60,000 psi is high, although many of us think it is not Danger High. The barrel does not have any problems at these pressures.

All you need is some of that special GM steel to make bolts and barrel extensions and the gun would hold together.
Regular AR-15 bolts and extensions will never hold pressures like you are talking about.

Hi Tim.
Welcome to the fray.

For those not aware, Wildcatter is none other than Tim LeGendre of LeMAG FIREARMS LLC

He loves to push his high pressure 45 professional, but often forgets to mention that it takes a special bolt and barrel extension and that the high pressure rounds would be unsafe with regular parts.

[Boarding-Team-Leader]

Slash2
Nice meeting you and the other two CalGunners today at the range. That 450 puts out some muzzle blast. I was at the forward portion of my lane looking for fired brass (adjacent to yours, left side) when you sent one down range. Glad I was wearing the plugs and muffs. I saw the muzzle blast as well as felt it... big blast.
BTL

[Slash2]

Originally Posted by Boarding-Team-Leader

Slash2
Nice meeting you and the other two CalGunners today at the range. That 450 puts out some muzzle blast. I was at the forward portion of my lane looking for fired brass (adjacent to yours, left side) when you sent one down range. Glad I was wearing the plugs and muffs. I saw the muzzle blast as well as felt it... big blast.
BTL

I've been told that I don't even have to hit what I'm shooting at, the muzzle blast alone will scare it to death!

[jagermaster]

thank you ar15barrels.
You have cleared up some very important facts.
At first glance to a novice like me Wildcatters info is very intreging.
Tim if you would like to shear some safe loads with the forum that would be great, we would love the help.

[Wildcatter]

Thanks for the welcome Randall, I've enjoyed your expertise...Just to be clear, one can never really fully prove all the engineering wonders in a forum like this, it wouldn’t matter to some, that you state, Leonardo Da Vinci painted the Mona Lisa. There are some who would belabor the point and then insist that you prove it. I’m not suggesting you are like that at all, it’s just that I want to make a point that will bother some others.

We have not used those special steels for some time now. If you were to follow my examples you’ll find that the 450b at the 52-55,000 psi does indeed exhibit much less bolt thrust than the 223 and the only way you can prove that is two ways, both subjective in nature. First, the copper crusher test and second, is the absolute fact that we have “Never” had a bolt failure.

To say otherwise is to also ignore my examples of a .284 Mountain Rifle and the 460S&W analogies’, which are also subjective.

But I tell you what, between you and I we may be able to solve Slash's loading problems, which as I have pointed out are not low pressure related, I think, assuming we have all the details, subjectively speaking, and the fact we are not standing at his bench, we never will, but we'll help some.

[ar15barrels]

Originally Posted by Wildcatter

Just to be clear, one can never really fully prove all the engineering wonders in a forum like this, it wouldn’t matter to some, that you state, Leonardo Da Vinci painted the Mona Lisa. There are some who would belabor the point and then insist that you prove it. I’m not suggesting you are like that at all, it’s just that I want to make a point that will bother some others.

I disagree on Bernoulli's principal being the main reason you can get away with elevated pressures that SHOULD be blowing bolts to smithereens.
I believe that the case shape with that nice large cylinder is also playing into it by having really good chamber wall adhesion.

My simplified bolt thrust comparison spreadsheet is only a means of comparison and therefore it does not take chamber adhesion or Bernoulli into account as I don't have a realistic way to quantify those factors.
My spreadsheet calculates thrust more like what you would see with oiled ammo.

I would love to have access to a lab where I could run tests by changing cartridge shape and controlling for pressure to be the same.
It would be eye-opening to know what actual changes you see in bolt thrust loading.

There's always the issue of feeding though.
It's impractical to design some cartridge that has great performance and minimal bolt thrust if it won't feed from a magazine...

[Wildcatter]

Once again Randall, I'm with you. Bernoulli does not explain it all, and really says more about why bottle necked cartridges have less adhesion, as you call it. It is only an engineering guess as to why there is less bolt thrust in the 450b example, making your logic probably correct and very intuitive, on your part. The fact that we can achieve the increased pressures/speeds without blowing the bolt apart is only part of the total equation. One also needs enough steel left over in the chamber to achieve the pressures in the first place. Example, we could chamber an AR in 50 BMG and shoot it, but the pressures and bullet speeds, would be very low, if the AR were to survive, making this exercise wasteful. It appears that the 450b is very close to the end of the line, in this pressure curve idea, before you get into Diminished Returns. Example, same thing happens if far too heavy bullets are used. We could probably build a 1500gr bullet for our test, only to find that, sure it functions the weapon, but what about the speeds? So what is the perfect weight for this family of cartridges, in an AR? The answer in part is in bullet construction and its speed. There are problems in all of this, of course, 300-350gr bullets are great, but if they were design for pistol speeds, they will just blow off the shoulder of a big game, with no penetration, letting the animal to die much later, very bad scene. Thus, the hollow point bullets in .451 cal’s, just are not the one’s to use on big game, that is, at the speeds I’m talking about, unless zero penetration is desired. However, FMJ’s penetrate everything and at these speeds are very cheap and cause catastrophic internal damage, surprisingly with very little meat damage, comparably. I really love the FMJ-FP most of all.

[ar15barrels]

Originally Posted by Wildcatter

Bernoulli does not explain it all, and really says more about why bottle necked cartridges have less adhesion, as you call it. It is only an engineering guess as to why there is less bolt thrust in the 450b example, making your logic probably correct and very intuitive, on your part.

We observe from experience with the TC contender/encore that when you cut an ackley improved type chamber with straighter walls and load to similar pressures as the parent case, that the thrust actually reduces.
We attribute this to the fact that the angle of the case body changes to a degree that internal pressures are no longer pushing the case rearward out of the chamber, but just making the case stick in the chamber.

You must have read your PO Ackley along the way right?
Remember when he backs out the 30-30 barrel from the receiver and extends the firing pin?

[Wildcatter]

Originally Posted by ar15barrels

We observe from experience with the TC contender/encore that when you cut an ackley improved type chamber with straighter walls and load to similar pressures as the parent case, that the thrust actually reduces.
We attribute this to the fact that the angle of the case body changes to a degree that internal pressures are no longer pushing the case rearward out of the chamber, but just making the case stick in the chamber.

You must have read your PO Ackley along the way right?
Remember when he backs out the 30-30 barrel from the receiver and extends the firing pin?

I had almost forgotten about this. We did a similar thing during the copper-crusher-bolt-thrust studies. The crusher itself looked like a washer with two opposing tits, fitted to the bolt that was cut for the .473” standard and recessed for the crusher, taking care for proper head spacing. Using barrels chambered for the .223 and the 45 Pro., the crusher’s tits were at the same distance from the center-line of both cartridges, this in an effort to keep everything apples to apples, of course the extractor for the 45p would not work for the .223, requiring that they be manually extracted. A standard firing pin worked well, even though it appeared to look like it was lengthened when the crusher was not in place.

Question, just curious, do you know if those other Big Bore/AR-15’s, on the market, were ever tested for actual bolt thrust, not calculated and how about max chamber durability studies?

[ar15barrels]

Originally Posted by Wildcatter

do you know if those other Big Bore/AR-15’s, on the market, were ever tested for actual bolt thrust, not calculated and how about max chamber durability studies?

I don't know for sure.
I can tell you that the 50 Beowulf or 502 Thunder Sabre will start blowing out case heads due to the extremely rebated brass before it will run into bolt thrust problems.
Not sure about the 500 LeitnerWise as it did not really get sold in volume.
458 Socom runs a larger case head which solves for case problems, but then weakens the bolt by removing a significant portion of the lug roots.

[Wildcatter]

Originally Posted by ar15barrels

I don't know for sure.
I can tell you that the 50 Beowulf or 502 Thunder Sabre will start blowing out case heads due to the extremely rebated brass before it will run into bolt thrust problems.
Not sure about the 500 LeitnerWise as it did not really get sold in volume.
458 Socom runs a larger case head which solves for case problems, but then weakens the bolt by removing a significant portion of the lug roots.

Interesting. I was taking to Pete Pi about a year ago and Starline was having some kind of a problem with the SOCOM Brass or was it the 50B brass or both, I forget. Anyways, something about splitting, supposedly they have corrected the problem. Do you know anything about that?

[Wildcatter]

Then again you may have already answered that question, I think Pete said something about a thicker web, which would up pressures. I guess they must have lowered the powder load some? Just going from memory and I probably don't have it right yet.

[ar15barrels]

Re-posting this because it ties in with the above post:

Originally Posted by ar15barrels

Commonly used maximum bolt thrust loading on AR-15's is 7000 lbs.
A 223 at 55,000 PSI makes about 6300 lbs of thrust.
7.62x39, 6.5 Grenade (grendel) and 6.8 SPC all run right at 7000 lbs.
Using the same formula, a 450 Bushmaster at 60,000 PSI makes 11,775 lbs of thrust.

As a comparison, a 308/7.62x51 makes 10,500 lbs of thrust.
308's use a bigger bolt for obvious reasons...

If the AR-15 could run all day long with 10,000lbs of thrust loading, why did they bother making the bolt bigger on the AR-10?

[Wildcatter]

Originally Posted by ar15barrels

Re-posting this because it ties in with the above post:



If the AR-15 could run all day long with 10,000lbs of thrust loading, why did they bother making the bolt bigger on the AR-10?

Randall, with all due respect, the .308 acutally does have very much more bolt thrust than the 450b on an AR bolt, remember that very real cohesion thing. Example, you could rechamber the 7.62x39 AR to a .308 chamber, open the bolt head slightly, single load the weapon and in short order break the AR bolt, not so with the 450b @ 50,000++psi.

[Wildcatter]

PSS.. Make sure that during your work-up faze that you keep your bolt face cleen, take a tooth brush with you. The crud build-up will mark the case head and can be prematurely mistaken for bolt thrust/pressure problems.

[ar15barrels]

Brush-up on pressure signs as they appear in 5.56 AR's...

[Wildcatter]

I guess you can't sleep either, ah?...Great pictures! What do you think the pressues are when a 5.56 case has major ejector marks and blows its' primer, like you show? I'd dare say we'd be into the 70,000++ psi realm and did these loads break there bolts? Maybe, maybe not and overtime, probably. Bottom line, this is what I was talking about for excessive pressure signs. The Slash loads don't even approach the ones you are showing and have no visiable bolt thrush problems. Now Slash has a visiable rum line to stay away from, thanks Randall, you're the greatest.

[ar15barrels]

Originally Posted by Wildcatter

I guess you can't sleep either, ah?...Great pictures! What do you think the pressues are when a 5.56 case has major ejector marks and blows its' primer, like you show? I'd dare say we'd be into the 70,000++ psi realm and did these loads break there bolts? Maybe, maybe not and overtime, probably. Bottom line, this is what I was talking about for excessive pressure signs. The Slash loads don't even approach the ones you are showing and have no visiable bolt thrush problems. Now Slash has a visiable rum line to stay away from, thanks Randall, you're the greatest.

Brass hardness is a factor so pressure levels can't often be determined by these signs.
In proper brass, ejector and extractor flow is probably around 65K to 70K
Primers probably go around 70K to 75K

Proof loads for 5.56 run 70K and don't pop primers, but I believe that black pill loads are made up in crimped LC brass.

Those pictures above are from Remington factory ammo with soft brass.
No bolts were broken in the firing of that ammo.

[Wildcatter]

[QUOTE=ar15barrels;1228674]

Proof loads for 5.56 run 70K and don't pop primers and they don't break bolts

[ar15barrels]

[QUOTE=Wildcatter;1228686]

Originally Posted by ar15barrels

Proof loads for 5.56 run 70K and don't pop primers and they don't break bolts

They also fire only ONE SINGLE ROUND per gun.
The reason is to over-stress the barrel and bolt prior to magnetic particle inspection.
The theory is that if the barrel and bolt can take a proof load and pass, it should be able to handle regular 55K loads year after year without problems.

[Wildcatter]

[QUOTE=ar15barrels;1228820]

Originally Posted by Wildcatter

They also fire only ONE SINGLE ROUND per gun.
The reason is to over-stress the barrel and bolt prior to magnetic particle inspection.
The theory is that if the barrel and bolt can take a proof load and pass, it should be able to handle regular 55K loads year after year without problems.

Except, you may forget that on numerous occasions, as in gobs of times, the various testing outfits do the standard 6000rd test with blue pills.

But let's not quibble, the 450b just doesn't have any bolt thrust problems, even at the higher (safe) pressures.

[44magnum]

I have a test and evaluation 450 bushmaster, but can't find ammo anywhere to try it out. Does anyone know where I can get some?

[44magnum]

Anyone know where you can find any ammo?

[Wildcatter]

Originally Posted by 44magnum

Anyone know where you can find any ammo?

Its highly available and all over the internet. Hornady just ran another half million rounds. If all else fails and you can't find any at your local store, call Hornady direct. Who you writting for? Good Luck.

[Wildcatter]

PS..I can help with interesting background and developmental intel.

NOTICE: To all you guys who want once fired brass. I will be decommissioned for the next 2 or 3 weeks. I wanted to ship to you today, but that just isn’t happening. But to wet your whistle a little, I call your attention to Slash’s great work to date. 45gr’s of H110, 240gr bullet, 2550fps, no real pressure signs, all this in a mere 20” barrel and this is just the beginning. Consider…2550fps is the Gov, published speeds, with a 147gr bullet, for the 7.62 NATO ball rd. and a 24” barrel. Now, put a 240gr bullet on that case and what will the speeds be, what 1500/1700fp maybe? Slash’s load with AA1680, would drive the pressures down and boost the speeds up, giving speeds in the 2600/2700fps area. Starts to look startling, doesn’t it?