25 wssm coyote, part 2

25WSSM (Winchester super short magnum)

Varmint loads……….velocity velocity with a good bit of accuracy to boot! The target fps I wanted to have was 3600 along with tight accurate grouping. I had some varieties of powder on hand however I will admit while sitting on 8+ pounds of IMR4064 I was driven to make that powder work! Funny how things work out and I did learn some unique traits of this short fat power house of a .257 caliber.

I start by prepping my fired cases with a shoulder bump die three thousands less than fire formed length, I used a Sinclair shoulder bump gauge and a caliper. CCI BR2 primers are used thru out all the load development ( I have found them to be good performers in past cartridge/load work and they are my go to primers ). These wssm cases have the thickest necks you will find (.022”) on the average, I turned the necks to .014” thick and will talk more about that later……ughh. Hornady V-max was the bullet of choice at 75 grains and IMR4064, Varget and IMR4320 were the powders.
Starting loads with what I thought was a great powder (since I had so much of it). A quick run thru Quick Load gave me starting charges along with safe estimated chamber pressures. A shoulder bump length of 1.218 measured with gauge and cartridge overall length (C.O.L.) ranging from 2.340” – 2.380”, 45.5 up to 46.3 grains of IMR4064 was sitting under a 75grain v-max, ignited by a CCI BR2 primer. Plenty of test loads and now some range time, I soon found out 4064 was not going to get along with this 25wssm no matter how bad I wanted it to, nothing grouped better that ¾” with erratic flyers, along with this struggling attempt I decided to turn the case necks to .014” and a C.O.L. of 2.360” was picked. With necks turned and 46 grains of IMR4064 loaded in groups were still terrible and now I was splitting necks on cases fired twice. Lesson learned don’t turn the wssm necks on a factory chambered rifle.
Giving up on IMR4064 I moved to Varget and started with a C.O.L. of 2.360” and after various load charges I settled with 47grains and a nice 3600fps. Sounds good except the groups were all 1+” all over the paper! I remembered reading an article on the wssm cartridges, the author mentioned bumping the shoulders just a little more to eliminate what he called the wssm sticky bolt. A new shoulder bump length of 1.212” measured with a gauge, 47grains of Varget, then set a v-max down the neck and back to the range. The fraction extra shoulder bump was the trick to smooth extraction with the wssm case but groups still did not improve with the switch to Varget powder. Not getting groups better than 1” at 100 yards had me putting the Varget back on the shelf now on the IMR 4320.

With a C.O.L. of 2.360, CCI BR2 primers, factory Winchester cases with unturned necks and 75 grain V-max’s I started yet another try at getting this rifle to cooperate. A clean bore and proper bench setup set the stage for these loads: IMR 4320 @ 46.5, 47, 48grains as usual I started with the low charge looking for pressure signs while measuring group size. Three shot strings would be checked for down range results and slow fire timed shots will keep the barrel form heating up to quickly. The day wrapped up with these results 46.5 grains @ 3565fps, dirty case necks and 3/4″ groups. 47 grains @ 3601 resulted in clean necks, better groups but a nasty flyer opening the group to 1.1/4”. Finally 48 grains @ 3681fps produced ½” groups, nice brass but still somewhat larger groups than I wanted. I prepped some brass and loaded a slightly lower charge @ 47.4 grains to try and sweeten up the load. Touching off rounds at the bench give their own type of satisfaction and this range day was no slouch! With three shots measuring a tiny ¼” and clocking in at 3625fps. A nice accurate varmint load was found and boy was I happy, one tight group does not evaluate a load as “the one” so I loaded up twenty proof rounds with 47.4 grains of IMR 4320 for another days shooting.
A nice cool 15 degree Michigan day with little to no wind had me kicking snow away from the 100 yard back stop. The pet load still produced tiny bug hole groups consistently so I went and shot a group with six rounds knowing my odds were good at opening up the group. I posted a picture of the group showing four of the rounds in a ¼” hole with two opening the group to ½”. I would never have thought IMR4320 would be such a good performer in this round and this brought me to remembering the wildcat 22-284 I build previously. Looking at ballistics between the two with one a .22 caliber and the other a .25 caliber, both shooting 75grain V-max’s at close to the same velocity. Bullet drop being very similar at extended ranges I highly doubt a crow would know the difference between the two cartridges as he turns to black dust. Case forming for the 22-284 is required while the 25wssm was a factory round, funny how close these two cartridges preform and it will be a tough choice which one will see more field use in the crow fields with me.


25wssm varmint loads

25wssm varmint loads


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2 responses to “25 wssm coyote, part 2

  1. LR2010

    Nice read on the 25 WSSM. LR2010 from MC

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