Modern Sporting Rifle Evolution
Sign up Calendar Latest Topics

  Author   Comment  

Avatar / Picture

Posts: 3,143
Reply with quote  #1 

Thought i would start this thread to keep track of the data and info on my new wildcat the .257 Bobcat 

As stated with H's help the reamer print is done and reamer is ordered. so hopefully in 6 weeks i will have a reamer and the first barrel will be made. I will be starting with a savage barrel for testing just to work out the loads and it will be easier to get pressure data from the savage. Then if all is good we will be making 2 ar barrels for testing. all barrels will be 24" to start out with so we can see the max potential of the round. When testing begins on the ar barrels i will start cutting down the savage barrel an inch at a time down to 18 to see what the changes are in velocity.

This post will be a work in progress for a few days, i will try to put all the info i have to this point in the thread. 

Intro: The .257 Bobcat is based on the 270AR made by AR15Performance. the 270AR is a 6.5x47 lapua shortened .120 and necked up to .277. 
My performance goals are 100 grain bullets at 3200+ fps and the 115 bergers at 3050 fps that will make it a very flat shooter 

It is being set up to run at 2.30 oal with the exception of the 115 berger it will need to be run at 2.358-2.36 which is accomplished by windowing the mag at the front. I am doing this to run the 130 berger in the 270AR and it gives 5 round capacity which is just right for hunting in my opinion. Pri 6.8 mags work best and give 2.3-2.31 oal grendel mags also work. I want to test the new Elander mags for function. a 10 round pri can hold 7 rounds.


6.5x47 Lapua first choice will handle the pressure best and has second highest case capacity. will require neck ream and turn but will last the longest. In the 270 i have some at 10 fires and still going strong.

6.5 Creedmoor second choice has highest case capacity but brass is soft and it can't handle the pressure as well. primer pockets loosen after 2-3 fires if running toward max.

308 brass can also be used but most of it has really thick brass so it has reduced capacities compared to the lapua and creedmoor. it will also require neck turning and reaming.

all 308 based cases will work and all will require neck reaming and turning. the neck in the chamber is going to be 290 so loaded rounds will need the neck to be in the .282-.285 range which gives you a neck thickness of 12-14.5 thousandths.

Brass trim length is 1.645 wall in chamber is at 1.655

Lapua brass prep procedure:

.257 Bobcat Forming tools:I just did a few cases and made another video, will get it posted up a little later here is what you will need to make the bobcat cases if you are going to use the dies i am going to offer with the kits. the 6.5x47 lapua hornady bushing dies.
forster power adapter # PA1000
forster .257 neck reamer # NR1257
forster original trimmer # CT1010
forster neck turn for original trimmer # OT1010
6.5 rcbs neck reaming pilot # 98881
279 redding bushing
.257 hornady expander # 396279
Modified 6.5x47 lapua hornady bushing dies available through me or
6.5x47 lapua bushing dies with sizer modified by shortening the sizer .125 inch

rcbs case neck turner/reamer pilot 6.5 mm

orster neck turn kit for forster classic lathe.
21st century neck turn lathe part number 908-30-BR

Forming procedure:

start with the modified bushing die with no guts in it.

lube the 6.5x47 lapua cases and run through the press pushing the shoulder back .120

neck ream and trim with forster lathe using the 257 forster reamer in the lathe so you ream and trim at the same time trim to 1.656 at this time, final trim length is 1.646 which will the the last step after final sizing.

now with the trimmed and reamed case you are ready to neck turn. install the forster neck turner on the lathe and install the 6.5 rcbs neck reaming pilot. now set the lathe to just touch at the case mouth and turn to the neck shoulder union. neck should come out at .013 give or take.

now install a 279 bushing in the die with a 257 expander and run the cases through the die. now chamfer and anneal the brass clean and they are load ready.

you can use the redding 6.5x47 bushing die by shortening the die .125 and using the appropriate bushing it will fall in the 278-281 range. 
Whidden gun works is also making the 270AR dies as custom die sets. if you get the bushing die sizer set the micrometer seater die works for seating the 25 cal bullets.
AR15Performance will have the 270AR whidden dies in stock late october early november. there again get the bushing die and use appropriate bushings

I will be working with Whidden dies to make a forming die or bushing die that will work a little bit better than using all the different bushings when sizing down.



100gn nosler ballistic tip, sierra 100gn sp bt, 85gn nosler ballistic tip


.257 Bobcat quickload predicted velocities with 24” barrel

100 sierra pro hunter sp 3050-3200 fps
100 sierra game king bt 3100-3250 fps
100 nosler partition 3050-3200 fps
100 nosler ballistic tip 3100-3250 fps
100 barnes ttsx 3050-3150 fps
110 nosler accubond 2850-3000 fps
115 berger hunting vld 2825-2950 fps
115 nosler partition 2850-2975 fps
117 sierra pro hunter sp 2800-2950 fps
117 hornady sst 2800-2925 fps
117 hornady sp 2850-2975 fps
120 nosler partition 2750-2875 fps
120 hornady interlock sp 2800-2900 fps
120 speer grand slam 2800-2900 fps



Posts: 49
Reply with quote  #2 
WOW! You’re talking.243’ish ballistics with a 100 grain .257 bullet!!
Previous Topic | Next Topic

Quick Navigation:

Easily create a Forum Website with Website Toolbox.