140 gr Partition in 6.5 prc COAL

JWhit

Beginner
Jan 12, 2022
4
4
Finally got long-awaited 140gr Partitions for a custom rifle with tight SAAMI dimensions. I have reloaded Barnes 127gr LR, 143 AccuBond LR, Hornady 143gr eld-x and 140 and 156gr Bergers, as well as Sierra 140 gr Gamechanger. No problems with any of these when loaded at recommended COAL, with most being loaded at max SAAMI specs at 2.955 inches. I am using a Redding bushing die to give me a neck "tension" of 0.001 inches. When I loaded the Nosler Partitions, I noticed some resistance on chambering. I had loaded 3 rounds to initiate working up a load with the 140 gr Partitions, and the following 2 rounds met with similar resistance. I measured the brass, and everything was in spec, with the shoulder having been reset 0.002in, and all dimensions within specs. I then chambered a dummy round, and again could feel the resistance on chambering. When this was extracted and measured with an RCBS Precision Mic, the bullet had been pushed about 0.040 into the case. I reduced to COAL to 2.900, and chambering and accuracy was excellent. Looking at the AccuBond, and eld-x, when loaded to the exact COAL, the ogive is definitely further (higher) up the shaft of the bullets. The Partition, with its classic tangent ogive, at least in my rifle, can not be loaded to a COAL of 2.955in without jamming into the lands. As I am running minimal neck tension, fortunately the bullet was easily pushed deeper in the case, but if you are using standard dies, you may end up jamming the bullet into the lands if loaded to the listed recommended COAL for the Partition.
 

jimbires

Handloader
Aug 16, 2011
2,496
459
I'm not exactly sure what you're asking , maybe this will answer you .

different bullet profiles will have different ammo COAL in relationship to the rifling . when reloading you need to first check each bullet to find where it will makes contact to the rifling . as you found , ammo loaded with blunter bullets is usually shorter than the long slick VLD style bullets . once you find that bullet x in xxx weight touches the lands at x.xxx " length, then you can start to load develop at your preferred jump from the lands . some rifles magazine length will not allow ammo at the touch length to fit in the magazine box . if this is the case , you need to start load development at the length that fits the magazine , if you want to feed from the magazine . I brought up a sammi drawing on the 6.5prc . ammo length is spec at 2.755 - 2.955 . the reason for this is the different profile bullets .



a few years ago , I lengthened the throat on a 260 rem . I checked a bunch of different bullets to where they touched the rifling . I'll dig this info up and post it , you might find it interesting .
 

JWhit

Beginner
Jan 12, 2022
4
4
Hi Jim, Thanks for your reply. I was not asking a question, but making an observation, which is similar to the info you listed above. My comment is that in the Nosler load data, they list the COAL for the 140 gr Partition as 2.955in, which if it is loaded to this length it will engage the lands. The 120gr AccuBond for instance, the listed tested COAL was much shorter at 2.775in, appropriately. I was merely trying to provide information to those who might look at the listed Nosler COAL, and if they used that length, may run into pressure problems, or even not be able to chamber the round if the neck tension was higher. As you point out, bullets have different nose profiles, and that is why the AccuBond will chamber, where the Partition did not. I hope this clarifies my reason for writing the post.
 

SJB358

Ballistician
Dec 24, 2006
31,355
656
In my opinion it is actually a great thing the way they set up the PRC as a whole. I try to chamber my rifles the same way. I typically send my gunsmith the longest bullet I will use in regards to nose length and seat it so it fits in the magazine with a little space. That round should engage the lands at that length. Every other bullet I may way want to use will engage the rifling at a shorter COAL so I can seat them a little deeper. The PRC seems well designed with the throat COAL lengths. The long high BC job's tend to be near max length while the more blunt bullets like an AccuBond or Partition will need to be seated shorter. Makes for a very useful rifle.

I have made the mistake of having rifles chambered the other way and it has backfired a few times.
 

jimbires

Handloader
Aug 16, 2011
2,496
459
well heck , that explains why I wasn't sure of your question . good first post , and welcome to the forum .
 

orchemo

Handloader
Dec 13, 2006
544
16
JWhit. I recently bought a couple 6.5 PRC rifles. In one of the rifles, I noticed the same thing with partitions. LRAB and AB run fine at max COAL, but not the PT. Shortened to 2.85 and they cycle great. Will shot in the next day or two. Hoping to black bear hunt with it next week
 
Top