Ladder Testing .308 99f

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Ladder Testing .308 99f

Post by Macd »

Reporting on this here rather than Rifle Reloading Section.

Conducted this test today with interesting results if somewhat confusing. Rifle is a 1964 dated Savage 99f. Test loads were all IMR4064 starting at 40.0 and going to 42.5 in .5 grain increments. Winchester FL sized and trimmed brass from the same lot 3x fired. Bullet was the Hornady 168 Grain HPBT "Match". No crimp used. OAL (2.2866)was set to allow a .010 jump to the lands. This is well beyond magazine length. I loaded 24 with CCI200 and 24 with CCI250 (Magnum) primers. Overcast morning, about 15 Celsius and dead calm. Chronograph was working perfectly. All shooting done at 50 meters. I stopped between strings to let barrel cool a bit.

I started by dialing in scope from POA to POI using rounds made from same brass lot and bullets but with 43.5 grains of Varget and a magazine length of 2.819". It took a couple of shots to warm up the barrel and then get the scope adjusted. This worked about as expected for this rifle with the final three shot group at about 2MOA.
July 17 302 Sighting In.jpg
I then started the tests and the first 4 shots (CCI 250 40.0 grains) strung vertically about an inch apart and I suspected something had loosened but on checking nothing was found amiss.
July 17 308 CCI250 IMR4064 40.0.jpg
I then fired the next 4 and this set the pattern for the remainder of the testing, a group of 3 shots and one outside the group. Here are two examples. It didn't matter which primer was involved they all more or less shot the same with slight differences in group size, centre and shot dispersion.
July 17 308 CCI250 IMR4064 41.0 Grains.jpg
July 17 308 CCI250 IMR4064 42.5.jpg
I was checking every case for pressure signs when I noticed the telltale shiny ring on some of the cases. Then it happened. First shot of the second to last string of the CCI200 loads.
July 17 308 Case Head Separation.jpg
That was the end of the testing. All that brass lot is going to scrap. Just to be sure the rifle is going to the GS for headspace check.
I will report the velocities etc in the next post.
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Last edited by Macd on 17 Jul 2019 13:19, edited 1 time in total.
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Re: Ladder Testing .308 99f

Post by Macd »

I haven't figured out tables on this forum yet so I will summarize results.

CCI 250 Primers
40.0 g Avg 2,463 FPS SD 18.41
40.5 g Avg 2,473 FPS SD 26.41
41.0 g Avg 2,497 FPS SD 11.02
41.5 g Avg 2,520 FPS SD 25.30
42.0 g Avg 2,520 FPS SD 23.30
42.5 g Avg 2,559 FPS SD 22.01

CCI 200 Primers
40.0 g Avg 2,433 FPS SD 12.66
40.5 g Avg 2,445 FPS SD 5.48
41.0 g Avg 2,471 FPS SD 23.80
41.5 g Avg 2,487 FPS SD 29.86
Testing halted after case head separation

The magnum primers only made a difference of 28-33 FPS. This is not as much as might have been anticipated. On average there was more SD in the strings using the magnum primers. The string with the least SD was not the best group (ignoring the outlier) with a 3 shot group of over 3 MOA while the string with the worse SD had a 3 shot group of less than 2 MOA again ignoring the 1 shot outlier. I believe the rifle needs some tuning up once I confirm its head spacing is correct. I may try partial sizing rather then FL even though the general rule is to always FL size for lever actions. Finally I don't think jump is critical in this rifle. The sighting in shots that were kept to magazine length shot as well and in most cases better than the longer OAL rounds. This is a hunting rifle and loading single shot makes no sense. It was a nice way to use up a morning and get some recoil therapy.
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Re: Ladder Testing .308 99f

Post by Ranch Dog »

Dang, it. The head separation sucks. What kind of pressure did QuickLoad say they were running?
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Re: Ladder Testing .308 99f

Post by GasGuzzler »

See that y'all...magnum primers smagnum primers. :)

Could getting the bullet started so close to the lands be a reason for the possible pressure spike?
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Re: Ladder Testing .308 99f

Post by Macd »

GasGuzzler wrote:See that y'all...magnum primers smagnum primers. :)

Could getting the bullet started so close to the lands be a reason for the possible pressure spike?
The velocities are within what I expected so I don't think I am getting pressure spikes.
Ranch Dog wrote:Dang, it. The head separation sucks. What kind of pressure did QuickLoad say they were running?
QL predicted 47,955 and 2520 FPS. Interestingly this was exactly the average velocity I got with the magnum primers at 42.0 grains. The Varget loads I used for sighting in were predicted at higher pressure 52,774 and the average velocity for them was only 20 FPS under the QL prediction. I did some rough measurements of the fired cases using a 10 mm deep socket as a gauging tool. The flats on a 10mm are exactly .400 apart, the SAAMI spec for the diameter on the shoulder at which headspace is measured from the base. Allowing for the inaccuracies this jury rigged measurement is sure to introduce, I am more convinced the chamber on the rifle is very close to or even over maximum allowable headspace. Bringing it into the GS tomorrow if he is in. In the meantime going to trial some partial resizing to see how the cases chamber.
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Re: Ladder Testing .308 99f

Post by Ranch Dog »

It would be nice to have a local gunsmith that works on firearms and not just assemble black rifles.
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Re: Ladder Testing .308 99f

Post by GasGuzzler »

So it's just a failed case, right?
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Re: Ladder Testing .308 99f

Post by Ranch Dog »

GasGuzzler wrote:So it's just a failed case, right?
So far it seems.
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Re: Ladder Testing .308 99f

Post by orerancher »

Ranch Dog wrote:It would be nice to have a local gunsmith that works on firearms and not just assemble black rifles.
+1
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Re: Ladder Testing .308 99f

Post by Macd »

GasGuzzler wrote:So it's just a failed case, right?
Yes but eight other cases are showing incipient head separation as evidenced by the shiny ring on the outside bottom above the web and the ridge inside the case. All cases are from the same lot. The GS is away until Monday but in the meantime I consulted a friend who is a fellow collector of mil surplus rifles. He suggested I might have a combination of long chamber and an aggressive sizing die. This leads to significant case stretching, work hardening of the brass and premature case failures. Unfortunately I don't keep a record of trimming brass but these were only 3x fired and in the same rifle. Using my makeshift measuring gauge I found that the fired cases average .014 longer than the FL sized cases as measured to the same point on the shoulder.
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