Need help with 450 Bushmaster loads.

[GunNut]

Very nice work! Has anyone tried PMC Small Rifel Primers? I did a search and found mixed results. Best I can figure is they are very similar to CCI's #41. A heavy cup primer. Anyone?

[Wildcatter]

Wildcatter,

Doing a quick caliper check, I have pretty uniform .498 case heads on the new Hornady brass used for this work up. The string I shot has average case head dimension of .501 I can "read" the extractor and the ejector on the case heads. However they are not extruded and sheared. based on my experience I'd take a WAG at 65,000 psi. (looks about like WBY factory loadings)

I don't want to turn this into a forum on the validity of case head expension as an indicator of pressure. So I'll speak my piece and then shut up about it.

While it does definately indicate high pressures, in my own experience and from all empirical data I've seen, it is useful as an absolute indicator of pressure only in a few very controlled circumstances as a compartive indicator. It never really can provide a quantifiable indication outside of a single sample of brass. if you can find Stan Watsons work on brass yeild in the 30-06, it makes interesting reading. He was going to incorporate it into his 30-06 loading manual, but I don't know if it ever did get published. Bsically his studies indicated that there is more measurable difference in result between different lots of brass, even from the same manufacturer, than there is measurable difference in result due to pressure. The metalurgy of cartridge brass is just not consistent enough to read absolute pressure by thousanths of an inch across a case head.

I need to charge up my camera battery, then I'll try and get a good pick pic of a case head to post.

BD

BD,

I concur with your wag, it's a very reasonable guess and helps allot and please do not shut-up, we're trying to get somewhere and your driving is perfect. I'd diffidently say your minor amount sampling is on the hot side ad would need some more exploring to verify "but" at real risk. Bring your data over to 450Bushmaster.net for a little tabulation..See ya all there

Safety First..t

[Wildcatter]

185-grain trials, part 3:

With one exception, the series 43-47 grain loads with Lil'Gun produced no obvious pressure signs.

The exception was one of the 45-grain loads. One measured 2802 fps and the other 2815 fps. The case from the slightly slower load showed a cratered primer.

Unfired case heads and most fired ones measure 0.4985" immediately in front of the extractor groove. The case with the cratered primer measured 0.4990.

Here's a labelled photo of the two 45-grain cases, and of case heads from a 44- and 46-grain load:


Here are some close-ups, also labelled:






There were no other indications of pressure. The bolt opened easily, there were no marks on the case heads, etc.

The red marks on the caliber stampings are a method of identifying cases.

I'm open to suggestions on the next step. Apparently increasing charges of Lil'Gun beyond 45 grains produces nothing beyond extra muzzle flash and blast.

Thanks.
--Bob

Hi Pit,

I see you're over at 450Bushmster.net and I am trying to wine this down here myself and then stay over there. Two suggestions, as you asked, 5rd samples would be much more helpful, 2 are just enough when just trying to get a peek, but if a spike or low occurs not much is learned, with two rounds, except what happened in that particular load and you could, with 5rds, get some kind of idea at the accuracy vs RPM's. Now for the BIG-ONE, pleas bring your photography expertise over to the other site and please teach us how to do that. I don't see pics in magazines as good as yours and your Case ID method is sheer genius.

I suspect that maybe your upper end data, according to your results to date with more needing to be done, might stop the AR action with the current gas set-up (see my post on how to set-up the weapon for increased Port Pressures and Timing).

Get that data tabulated in over at 450bushmaster.net , see ya there..

Safety First..

[Bistem]

Traded last one

Well....I traded my other 450 that i posted a pic of at page 51 of the thread. A co-worker kept worrying the crap out of me wanting it and I really didnt want rid of it but I eventually saw something that he had that I liked enough to trade for. Couldnt stand being without the 450 though so I bought a 450 upper and am going to have it coated to match the lower. The guy I traded with is one of 2 authorized people in NC on duracoat's web site so his work is very good. He has agreed to coat this upper and scope and magazine as part of our earlier trade. Picture attached of both uppers. The duracoat materials are on order.

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[thebrassnuckles]

i just jumped in on the sale bushmaster has goin on right now, just waiting on delivery of my upper.

i have a few boxes of factory ammo on the way.

any good sources on brass?
someone on gunbroker was selling the brass for about 75 cents a piece.

[Slash2]

i just jumped in on the sale bushmaster has goin on right now, just waiting on delivery of my upper.

i have a few boxes of factory ammo on the way.

any good sources on brass?
someone on gunbroker was selling the brass for about 75 cents a piece.

Most of the activity here has shifted over to http://450bushmaster.net, You will probably get a better response there.

Good luck!

[1norcalvarmintHunter]

Anyone interested in once fired 450 brass? Pm me