185-grain SWC trials - Chapter 1

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185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 5:43 am

Here is a reposting from Calguns of my three-part report of some initial work with light bullets. That report was divided into three posts, which I'll do here also.
- - - - - - - - - - - - - - -

185-grain Trials, Part 1

I began my 450b reloading trials for the 1903 Springfield (see my 15 May post) with the Hornady FTX 250 gr bullet with Lil'Gun, and worked up to the maximum loads listed by Hornady without incident. My next project was to try lighter bullets at higher velocities.

There was some concern in posts above that my barrel's faster-than-factory 1:16 twist would overspin and perhaps destroy light bullets, so I picked the Hornady #45137 .451 185-gr FMJ SWC encapsulated for initial trials. It is advertised as having a stronger than normal jacket, which seemed appropriate for this application.

I used new Hornady cases, Lil'Gun powder, and CCI BR-4 primers for my first trial series. Cases went through the Hornady FL sizer and expander dies before loading, altho they probably didn't need the sizer. The initial series used loads of 38-42 grains, in 1 grain increments, with two cartridges for each load. The bullets were seated to an overall length of 2.040 inches. The crimp in the seater die wasn't used, but I did use the taper crimp die. The cartridges readily passed the "thunk" test that has been described in earlier posts.

My PACT chronograph uses a 2-foot screen spacing, and the midpoint of the screens was 8 feet from the muzzle.

The chrono readings averaged for two shots per powder weight, were:

38: __ 2512 fps
39: __ 2501 fps
40: __ 2664 fps
41: __ 2701 fps
42: __ 2765 fps

All the cases extracted easily. The case diameters measured immediately in front of the extractor groove showed no measurable expansion. The primers showed no pressure signs, and the case heads were unmarked with extractor grooves, etc.

The bolt gun is pretty light at a smidgen over 7 pounds, so its recoil with the 185 gr bullet at better than 2750 gets attention; 185 at 2750 is more energy than the 180-grain 30-06 factory.

Based on the lack of pressure, I decided to load a similar series with greater weights of powder. See my next post.


Here's a photo of the loaded 185-grain FMJ SWC. (The camera was tilted but the cartridges will appear ok if you just tip your head a bit.)

Image
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185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 5:44 am

185-grain Trials, Part 2:

For the next series, I substituted Winchester small rifle primers for the CCI BR-4s. I thought I had detected some slight hangfires, and went to the Winchester primers which have a local reputation as being a bit hotter.

With the same tools and techniques, I loaded a series of 2 cartridges each with 43-47 grains of Lil'Gun in 1-grain increments. I'm probably over-careful with the powder weights; they are measured to +/- 0.03 grains.

Firing these over the chronograph produced some odd results. Again the velocities were taken at 8 feet, and are the average of two readings:

43 grains: __ 2720 fps
44 grains: __ 2661 fps
45 grains: __ 2808 fps
46 grains: __ 2711 fps
47 grains: __ 2776 fps

Some observations: The apparently low reading at 43 grains was caused by one reading of 2598 fps, with the other at 2724 fps; there was no obvious reason for the low reading, and if discounted, the progression of velocity with increasing charge is logical.

Logic ends, however, at the 45 grain load. The velocity appears to have reached a plateau at about 2800 fps, and increasing powder charge does not increase velocity.

I have little experience with straight-walled rifle cartridges, so I do not know whether this plateau is typical of light bullets.

Would a powder that burns slightly faster than Lil'Gun be appropriate in attempting to achieve higher velocities?

The next post will have some observations and photos about pressure indications with this series.
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185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 5:51 am

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:

Image


Here are some close-ups, also labelled:

Image

Image

Image

Image

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
Last edited by pitted bore on Mon Jun 08, 2009 11:53 am, edited 1 time in total.
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Re: 185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 6:01 am

For purposes of discussion, below is the response that Wildcatter wrote to these three posts on Calguns:

Wildcatter on Calguns wrote: 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..
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Re: 185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 6:56 am

Wildcatter-
More degrees of freedom is always better, so I'll attempt a series of 5-round loadings, now that I know about where some pressure problems might occur.

I can also try to evaluate accuracy. However, it will have to be relative measurements, given old eyes peering thru the iron sights on this rifle.

Later, I'll start a couple of threads on the case ID technique, and something about photos.

Thanks.
--Bob
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Re: 185-grain SWC trials - Chapter 1

Postby wildcatter » Mon Jun 08, 2009 7:46 pm

pitted bore wrote:Wildcatter-
More degrees of freedom is always better, so I'll attempt a series of 5-round loadings, now that I know about where some pressure problems might occur.

I can also try to evaluate accuracy. However, it will have to be relative measurements, given old eyes peering thru the iron sights on this rifle.

Later, I'll start a couple of threads on the case ID technique, and something about photos.

Thanks.
--Bob

Is it just me or do you guys agree, Pit-Bull takes the best pics and needs to teach us sooner than later how to do it. Hey Bad Bob, I for one hope you can take pics of you taking pics, with the lighting, angles, everything, Holy Cow your pics are great and allow all to more fully evaluate..

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Re: 185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 08, 2009 11:39 pm

Wildcatter-
I started a thread on photo techniques in the "off topic" division. Let me know if you need
more information than that blurb supplies.

Thanks.
--Bob
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Re: 185-grain SWC trials - Chapter 1

Postby BD1 » Tue Jun 09, 2009 3:09 pm

PB, from your chrony data it looks like you might be running out of barrel length. Beyond a certain point you're just burning more powder and raising the peak pressure level without gaining any velocity.

I'm a fan of ten shot strings while developing loads in the AR platform. 10 is a statistically significant sample for velocity data, and it lets me see how things change as the barrel heats up a bit.

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Re: 185-grain SWC trials - Chapter 1

Postby wildcatter » Tue Jun 09, 2009 10:04 pm

BD1 wrote:PB, from your chrony data it looks like you might be running out of barrel length. Beyond a certain point you're just burning more powder and raising the peak pressure level without gaining any velocity.

I'm a fan of ten shot strings while developing loads in the AR platform. 10 is a statistically significant sample for velocity data, and it lets me see how things change as the barrel heats up a bit.

BD


I am too and fifty rds are better, Buuutttt, components are scarce, so we cut some corners, getting just enough of a peek, kinda-sorta, and when we find a sweet spot then we have to increase the sampling and we did it with a minimum of expended ammo..Hopefully??
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Re: 185-grain SWC trials - Chapter 1

Postby pitted bore » Mon Jun 15, 2009 10:00 pm

185-grain Trials, Part 4:

Here are the 11 June results of the trials I outlined on 8 June. While acknowledging that 10-round trials may provide tighter confidence intervals than 5-round trials, I merely wanted to get an indication whether some sort of disaster awaited further shots at the upper end of my loads with Lil'Gun.

Procedures were as before: New Hornady cases, Lil'Gun powder, and WW SR primers. Cases put through the Hornady FL sizer and expander dies before loading, altho they probably didn't need the sizer. This series used loads of 44, 45, and 46 grains, with five cartridges for each load. The 185-grain Hornady encapsulated SWC bullets were seated to an overall length of 2.040 inches. The crimp in the seater die wasn't used, but I did use the taper crimp die. Again, cartridges readily passed the "thunk" test that has been described in earlier posts.

And again, my PACT chronograph screen midpoint was 8 feet from the muzzle. I fired the series in alternating loads, 44 grains first, then 45, then 46, back to 44, then 45, then 46, etc. I used the 8" bull of the 100-yard smallbore target, holding center as my point of aim off a bench with the targets at 100 yards.

My objective was primarily to measure velocity and observe signs of excess pressure. Secondarily, I was interested in accuracy.

Velocities (fps)looked like this:

trial ___ 44 gr __ 45 gr __ 46 gr
1 - - - - 2611 - - - 2899 - - 2770
2 - - - - 2824 - - - 2718 - - no reading
3 - - - - 2724 - - - 2740 - - 2799
4 - - - - 2745 - - - 2703 - - no reading
5 - - - - 2664 - - - 2740 - - 2791
Ave - - -2713 - - - 2750 - - 2787

There were no pressure signs, such as the cratered primer at 45 grains that I reported on 8 June.

All three loads showed three-four impacts snuggled into 1 to 2 inches, with 1-2 flyers landing 3-4 inches
outside of the group. The first shots for each trial landed outside the group; the other flyers were not
predictable.

NOTE: These loads are DEFINITELY NOT recommended for anybody else. As far as
I know, there are no other published results for 185-grain bullets in the 450B. I'm acutely aware of the
warnings that one is already in pressure trouble when any signs show up, like ejector marks, etc.

I'm happy with the relatively low fps spreads at 46 grains (ES=29). The 44-grain velocities were erratic,
even discounting possible low velocity caused by a cold fouled barrel. I have no reason to discount the
high or low velocity measurements.

Questions, thoughts and interpretations will be welcome.

Thanks for your attention.
--Bob
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