Mountain Rifle - Kimber 84M Proof Research .308 Win

[MCMXI]

It was overcast and fairly calm this morning so I shot the 10 rounds that I put together yesterday. The first shot of the morning was the impact near 12 o'clock on the left target. The next four rounds appeared to make one ragged hole and I was excited since I thought I'd shot one of the best .308 Win groups of my life only to discover that it was larger than the 5-shot group shown previously. However, it's clearly a great combination for this rifle pushing the bullet about .005" into the lands in front of 44.1gr of Varget. Maybe .0025" into the lands would be the best load given the "touch" and .005" jam results. That would give some margin for less than perfect handloads. As far as groups go, anything better than about 0.5 moa will be luck on my part since I feel that I'm at the limit of my abilities here, particularly given the weight of the rifle and my shooting set up. I'm going to shoot a couple more groups just like the one below left (maybe .0025" jam) to confirm that everything is good, followed by the same COAL but +/- 0.3gr to see what it looks like. If the bracketing loads look decent I'll move onto the 175gr LRX load. So far I'm very pleased with how few rounds I've shot to get to this point and "jamming" the bullet into the lands is something I'll be investigating with other rifles/loads.

The bloody LabRadar has been acting up despite formatting the SD card so I only got one velocity reading which was 2,701 fps. I need to tighten up some of my reloading skills such as bumping the shoulder back. I mentioned earlier that the chamber is tight i.e. the bolt has some resistance closing on a GO gage, but the fired cases are coming out at about .0015" over minimum SAAMI. I was trying to bump the shoulder back .002" but ended up with more like .004" to .005" of bump. It's amazing how much case lube and press velocity affect shoulder bump.

 

[MCMXI]

I can't explain the groups shifting to the right towards the end.

Could the suppressor be the problem

I took the scope off this afternoon in preparation to bed the recoil lug and the EGW Picatinny rail was loose! I had taken the scope, rail and barrel off when I was machining the action and must have forgotten to tighten the screws up to 20 in-lb when I reinstalled the rail and scope. I thought I'd tightened them and have a hard time believing that they shot loose so I guess I didn't. On the bright side, it prompted me to order an EGW 30 moa rail that's a special order item and at least 3 weeks out. Live and learn.

I'm kind of amazed that the rifle shot so well the other day with a loose Picatinny rail ... oh well.

 

[LoonWulf]

Either the guns way more accurate that it has any right to be, or it rattled and settled just right lol.

 

[MCMXI]

Either the guns way more accurate that it has any right to be, or it rattled and settled just right lol.

Seriously! I've never knowingly done this before, and for it to shoot so well as loose as it was is kind of amazing. The Vortex Viper PST and Nightforce rings weigh 1lb-12.7oz which isn't that heavy but maybe enough mass to prevent random movement between shots. Regardless, it's restored my faith in the scope, barrel and load since it explains (most likely) the shift to the right. I adjusted the scope left for the last groups shown since they were wandering right. I don't want to use blue loctite on the rail screws until I have the action salt nitrided but will certainly do that eventually.

 

[MCMXI]

I rebedded the recoil lug yesterday which came out good (nice tight fit), and did some more work on the stock today. I spoke with AG Composites last week to ask which brand of QD cups they use and they pointed me to GroveTech in Oregon. I ordered a pair of limited rotation QD bases (cups) to mount on the left side of the stock, one in the butt stock and one near the end of the forend (left side) to allow me to carry the rifle flat against my back while hunting. I also ordered a set of bases (comes with two) that have a QD sling swivel stud so that I can install a Harris bipod up front if desired. I also installed a gunsmith adapter from Spartan Precision Equipment that interfaces with their various tripods and bipods of which I have a few.

https://grovtec.com/collections/qd-mounts-bases/products/heavy-duty-push-button-bases

https://grovtec.com/collections/attachments-adaptors/products/multi-adaptor-stud

https://javelinbipod.com/collections/adapters/products/gunsmith-adapters

I mentioned a while ago that the stock will either need to be painted or dipped again to fix lots of blemishes, feathering, alterations etc., so I knew going in that any chipping of the dipped Open Country film is ok. I'm very pleased with how the three adapters up front turned out in that they are very secure. The GroveTech bases have external threads so I was able to tap the holes with a 9/16-18 bottom tap after using a 1/2" end mill. I used Devcon on the threads and in the holes to create a permanent connection. The cup in the butt stock I'm not so sure about but I spoke with AG Composites and GroveTech and followed their recommendations. If it seems to be weak I'll figure out a better way of doing it but a thin carbon fiber shell with a low density foam core seems like building a house on the sand ... but we'll see. Oh yeah, I filled the sling swivel stud hole in the butt stock . I like not having sling swivel studs on the stock since they tend to hang up on the bags when shooting/working up loads.

Next up is to install the 30 moa Picatinny rail when it comes in, work up a Barnes 175gr LRX hunting load, play with bullet seating depth for the 178gr A-MAX load shown above and then wrap up the project by finishing the stock (dip or paint) and having the receiver and bolt salt nitrided. I guess the final step will be figuring out which scope to mount "permanently" on the rifle for hunting and general use.

 

[LoonWulf]

Bedding looks great!
Ive never used QD sockets, you did a good job at getting them mounted clean. I never get inserts that nicely set, much less big ones like the qd cups.

 

[troy fairweather]

Some nice improvements

 

[Walkalong]

Either the guns way more accurate that it has any right to be, or it rattled and settled just right lol.

I shot some a couple of fair groups in a match with my scope hanging on with one ring, it had slid forward until the front ring was off the rail, just hanging in front. I thought something was wrong, and finally noticed the problem. Aha! No wonder it seemed like some shots were not going where they should have! It was amazing the groups I shot that way.

 

[horsemen61]

@MCMXI

great work keep it up quick question though who is doing your salt nitriding?

 

[Nature Boy]

I shot some a couple of fair groups in a match with my scope hanging on with one ring, it had slid forward until the front ring was off the rail, just hanging in front.

same thing happened to me in a match

I’m shooting 10s and Xs at 600 then all of a sudden I hear the scorer say, “7, 5 on”. What the hell?!?. Shot another round and it comes up 7 again, right next to the previous shot. Looked at my rifle and the front scope ring is hanging off the dovetail in mid air. The whole scope/ring assembly had slid forward under recoil. So I quickly get everything back in place and tightened down but now I have to re-zero while the match is in progress and all my shots are for record. First shot was a 9, next was a 10 and I’m back in business.

The Kelbly Panda action has an integral dove tail, not a pic rail, so to solve the problem I took a spare scope ring, cut the ring off and made a dove tail locking device

 

[MCMXI]

to solve the problem I took a spare scope ring, cut the ring off and made a dove tail locking device

That's a clever solution ... nice job!

Bedding looks great!
Ive never used QD sockets, you did a good job at getting them mounted clean. I never get inserts that nicely set, much less big ones like the qd cups.

Thanks @LoonWulf . The gunsmith at GroveTech told me to make sure that the cup is slightly proud of the stock to prevent the QD fitting from rubbing on the stock so I did my best. Devcon takes 24 hours to fully cure so it won't be until later today that I can get a sense of how much faith I have in the rear cup. Personally, I like the QD cup concept for the reasons already mentioned, and the QD sling swivel stud is a bonus since it allows the use of a Harris bipod.

great work keep it up quick question though who is doing your salt nitriding?

Probably H&M Blacknitride. I can get four to five receivers/bolts nitrided for $250 total so I plan on sending them five receivers at the moment and possibly one barrel.

http://blacknitride.com/

 

[LoonWulf]

Nice scope stop!
Im mildly surprised they dont have some form of scope stop built in. I doubt its an oversight, so it must have a reason. Not a realm of rifles Ive ever played in tho, so no real idea.

 

[Walkalong]

Kelbly Panda

Same here, tightened it all back up and it never moved again, but I like your insurance, great idea.

 

[MCMXI]

No Picatinny rail problems today!

I started load development this weekend for the Barnes 175gr LRX. I decided to start with a bullet jump test along the lines of what Berger describes for the VLD. I put four rounds together using 44.0gr of Varget but decided that I would drop down to 42.0gr to be on the safe side. I assembled 20 rounds with 42.0gr of Varget and with bullet jumps of .000", .040", .080" and .120" (5 of each). I used two rounds with 44.0gr of Varget and .000" bullet jump to see if the optic was close and I figured it was close enough (see bottom row, middle target on the 1st target). I then shot the four loads in a "round robin" test in the hope that one load would really stand out.

So after this test I was going to focus on a bullet jump of .120" and play with the charge weight but I didn't like the 3/2 grouping of that load. In addition, the shot to the far right of the .080" jump load was the first shot of that group but the next four shoots were inside 1/2". I decided to shoot .080" and .120" again but add 0.5gr of powder to the case to get more data. I made a scope adjustment before shooting these groups and once again shot "round robin". Thank goodness I did this since the 3/2 trend of the .120" jump load got worse, and the .080" jump load did quite well. To get an idea of possible velocity and pressure limitations I shot the other two 44.0gr loads with .040" of bullet jump (see right target, top row on the 2nd target).

The velocity data for all shots is shown below and ES numbers aren't good at this stage and I don't know why. So what do I know at this point? First, .080" bullet jump with 42.0gr and 42.5gr produced two 5-shot groups under 1 inch with the better group being a little over 3/4". Second, neither of the 44.0gr loads with bullet jumps of .000" and .040" indicated an over pressure issue. Velocity for 44.0gr of Varget is in excess of 2,650 fps which is the minimum I'm hoping for. My next test will keep bullet jump at .080" and try 42.8gr, 43.1gr 43.4gr 43.7gr and 44.0gr of Varget. I'm hoping that something in that range will be the last step in identifying a good 175gr LRX load that achieves a velocity in the 2,650 fps range, puts 5 shots into < .75" and shows no pressure signs. I'm quite optimistic at this stage given the 42.5gr load with .080" of jump.

The LabRadar worked great today running off an ANKER PowerCore Essential 20000 power supply so something is going on with the LabRadar running of 110V (GFCI) and a long extension cord. I did order an inertial trigger system from JKL Precision that will be here this week but I probably don't need it based on the 34 rounds shot without any errors or issues. It'll be a good option to have though and wasn't expensive.

DA = 4,892 feet
T = 67F
RH = 54%

 

[Nature Boy]

That 3/2 group at -0.120 is odd

 

[MCMXI]

That 3/2 group at -0.120 is odd

You can see the trend starting at 42.0gr and becoming more obvious at 42.5gr. The bullet appears to be exiting the muzzle when the barrel is in one of two positions so not a good accuracy node.

 

[MCMXI]

I ordered MAGPUL GEN M3 AICS PMAGs yesterday from RSRGroup, three 5-round and two 10-round. They allow a COAL of 2.860" which works for both the 178gr A-MAX and 175gr LRX loads. I'm hoping that they feed well. Based on reviews that I've read they seem to be a decent alternative to the more expensive metal magazines out there. I have quite a few AI and AM 5 and 10-round magazines but figured I'd try something different.

https://magpul.com/firearm-accessor...2x51-aicsshortaction.html?mp_global_color=118
https://magpul.com/pmag107-62ac-7-62x51-aicsshortaction.html

 

[MCMXI]

Quick update on 175gr LRX load development. I would be ok using 42.8gr with .080" jump given the results today. The 5-shot group is under 1/2" at 100 yards with an average velocity of 2,618 fps. Velocity isn't quite where I'd like it but 2,650 fps would only get me an additional 25 fps at 600 yards so not a deal breaker. Comparing the 42.5gr/-.080" load in a previous post that resulted in a .779" 5-shot group at 2,605 fps and the 43.1gr group shown below I think that the 42.8gr load is nicely bracketed. I need to improve my handloads to get the ES numbers a little better.

Interestingly, Barnes shows the max velocity from a 24" Krieger barrel using Varget to be 2,615 fps.

 

[troy fairweather]

Looking good, maybe your barrel will speed up a little soon.

 

[MCMXI]

Looking good, maybe your barrel will speed up a little soon.

I wouldn't expect it to given that it's single point cut and lapped but you never know. I did try 43.4gr, 43.7gr and 44.0gr but the results indicate that the load is unstable with those charge weights. The 43.4gr load had four shots inside 3/8" with one possible error but the group center moved significantly. I might revisit these charge weights with once fired brass.

 

[troy fairweather]

Maybe try some different primers to. Sometimes that can make the difference.

 

[Nature Boy]

Maybe try some different primers to. Sometimes that can make the difference.

Different brands and makes of primers have a measurable impact on accuracy and ES/SD. It’s worth the effort to test as many as you can.

@MCMXI , It looks like you have it nailed down. Nice shooting

 

[MCMXI]

Maybe try some different primers to. Sometimes that can make the difference.

Different brands and makes of primers have a measurable impact on accuracy and ES/SD. It’s worth the effort to test as many as you can.

@MCMXI , It looks like you have it nailed down. Nice shooting

Thanks, I think I'm getting close with these 175gr and 178gr loads. I'm not sure why the ES numbers are as bad as they are but that's something I need to work on. I tried different primers when working up a 6.5x47 load for one of my AI rifles after reading one your posts @Nature Boy in which you showed significant differences based on the primer used. These are the large rifle primers that I have on hand. I don't know if it's worth trying magnum primers but I can run a test with CCI 200 and Wolf PP along with GM210M.

Federal GM210M
Federal GM215M (magnum)
CCI 200
CCI 250 (magnum)
Wolf PP

https://www.thehighroad.org/index.p...in-6-5x47mm-lapua.851022/page-3#post-11154270

 

[Nature Boy]

I’d try 5 rounds each of the ones you have in inventory.

I know this gets down to the nitty gritty of load development but the results are often surprising

 

[redneck2]

There was a thing years ago on Steve’s Pages where he had a rifle that wouldn’t shoot under 2”. Tried all kinds of powders, bullets, and O.A.L. Finally tried a different primer and it instantly dropped to the 1/2” range.

If you ask Mr. Google, you may find something on primer bristance. It shows the flame pattern given off by different brands of primers. It varies a LOT.