Mountain Rifle - Kimber 84M Proof Research .308 Win

[horsemen61]

@MCMXI

Awesome build!

quick question though wouldn’t you want a lighter monolithic copper bullet so you can push it faster which will cause it to more reliably expand?

 

[Gtscotty]

The build looks good, from the pictures it looks like you're using the standard 140 degree opening 84M action on this build, are you using the 70 degree opening prototype on another build?

Sans the 2.5lb of suppressor, scope, rail and mounts, it sounds like you've gotten the base rifle down to 6.5lbs; pretty light for a full featured AICS fed rifle with a long barrel. That's really the draw for me of the light and ultralight rifles, once you add a can and decent scope, they still wind up at a good weight for packing and shooting (my sub-5lb naked Montana winds up at 7.1 lb with a can, scope, mounts, sling, etc).

On the subject of TBAC, they are great folks who make great cans. They actually do a lot of testing at my local range, so I've heard or shot everything they make, some of it before it was introduced. I think it'd be very hard to go wrong with an appropriate length ultra series for a hunting or precision rifle can, and the new Dominus looks like more of a good thing.

Powder wise, I'm with you on sticking to relatively temp insensitive powders. Having just played with load workups for the 6.5 Grendel a bit (which uses the same burn rate powders) the first powders I'm going to try in my new .308 are Varget, AR-Comp, H4895 and 8208 XBR. I've burned mostly mostly Varget in my past .308s with some AR-Comp, and those are really the two I expect to use, but I've had success with 8208 in .223 and 6.5G, and H4895 in 6.5G, so I figure why not.

@LoonWulf Mentioned Staball 6.5, but I think that's going to be too slow for good velocities in the .308 (I've read it's in the 4831 burn speed range). I've been playing with a few lbs of Staball and have been able to get 190gr ABLRs up to 2,640 fps out of an 18.5" .30-06, so it will probably be a pretty good powder for velocity in cartridges like .30-06, 7mm-08, 6.5 CM, etc.

 

[Nature Boy]

My best target loads with 185g Berger Hybrids uses H4895. That powder produces higher FPS with less powder. I also get pressure signs with Varget when attempting to achieve the same node.

I have some excellent hunting loads with both Varget and VV N140 using hunting bullets in the 150-165g range. I’m not pushing those as hard as my target loads

 

[Gtscotty]

My best target loads with 185g Berger Hybrids uses H4895. That powder produces higher FPS with less powder. I also get pressure signs with Varget when attempting to achieve the same node.

I have some excellent hunting loads with both Varget and VV N140 using hunting bullets in the 150-165g range. I’m not pushing those as hard as my target loads

H4895 was definitely good performer in the Grendel, right up there with AR-Comp. As silly as it sounds the reason I went mostly with ARC was because of the smell. I don't know what it is, but to me the smell of burning H4895 is particularly acrid compared to other powders I use. Since I was shooting a suppressed AR, I was getting a puff directly into my face with every shot, obviously not a consideration for a bolt gun, but the difference caught me by surprise.

 

[MCMXI]

The build looks good, from the pictures it looks like you're using the standard 140 degree opening 84M action on this build, are you using the 70 degree opening prototype on another build?

I'm using the 70° ejection port receiver now. The receiver that Proof originally installed the barrel on and shown at the start of this thread is the 140° receiver. Here's a closeup of the receiver. You can see the machining that I had to do to allow empty cases to eject properly. Funnily enough, I was using loaded rounds to figure out what I had to do, but they react very differently to empty cases .... duh! I apologize for the rough appearance of the action and stock but as I mentioned, I'll get it all cleaned up and nicely finished once I'm happy with everything. As it sits now it looks like a project rifle with mismatched parts and finishes.

Sans the 2.5lb of suppressor, scope, rail and mounts, it sounds like you've gotten the base rifle down to 6.5lbs; pretty light for a full featured AICS fed rifle with a long barrel. That's really the draw for me of the light and ultralight rifles, once you add a can and decent scope, they still wind up at a good weight for packing and shooting (my sub-5lb naked Montana winds up at 7.1 lb with a can, scope, mounts, sling, etc).

The rifle is about 6lb 4oz without scope, suppressor, rings, rail, etc. The Proof barrel takes about 12oz off the weight of the standard Open Country.

 

[MCMXI]

quick question though wouldn’t you want a lighter monolithic copper bullet so you can push it faster which will cause it to more reliably expand?

The LRX is supposed to offer reliable expansion down to around 1,600 fps but I'd like to stay above 1,800 fps. I like the high BC and relatively high mass of the 175gr bullet which out performs the best 6.5mm monolithic bullets such as the 129gr LRX. Barnes doesn't offer a .30 cal LRX lighter than 175gr.

 

[MCMXI]

Vargets never a bad choice, its kinda the h1000 for the 45gr cases.

I have a bunch of H1000 for my .338 Lapua Mag and find it to be an excellent powder although not the best choice if you're looking for maximum velocity. I'll take temperature stability over maximum velocity, and have so much Varget that I will most likely stick with it for now at least.

 

[MCMXI]

My best target loads with 185g Berger Hybrids uses H4895. That powder produces higher FPS with less powder. I also get pressure signs with Varget when attempting to achieve the same node.

I have some excellent hunting loads with both Varget and VV N140 using hunting bullets in the 150-165g range. I’m not pushing those as hard as my target loads

@Nature Boy, I'd never argue with you about load data, or anything else for that matter, but Hodgdon shows higher velocity and lower pressure with Varget compared to H4895. Here's their load data for a 175gr bullet. Can you remind me of the velocity you get with those 185gr Berger bullets? You're using a 26" barrel if I remember correctly. I'm starting to get excited about working up loads for this rifle. It's been a tough few months for me for a number of reasons and I need something to look forward to.

 

[horsemen61]

The LRX is supposed to offer reliable expansion down to around 1,600 fps but I'd like to stay above 1,800 fps. I like the high BC and relatively high mass of the 175gr bullet which out performs the best 6.5mm monolithic bullets such as the 129gr LRX. Barnes doesn't offer a .30 cal LRX lighter than 175gr.

Ahh I see well carry on then good Chap! I am looking forward to see what you end up with!

 

[Gtscotty]

The LRX is supposed to offer reliable expansion down to around 1,600 fps but I'd like to stay above 1,800 fps. I like the high BC and relatively high mass of the 175gr bullet which out performs the best 6.5mm monolithic bullets such as the 129gr LRX. Barnes doesn't offer a .30 cal LRX lighter than 175gr.

Just an FYI, when I called Barnes about their recommended bullet for my short barrel .30-06, the tech recommended the 168gr TTSX over the 175gr LRX for my uses. According to the tech, the 168gr TTSX was really the first of the LRX series in terms of design, opening velocities and BCs. After the 168gr proved successful, they followed with the LRX line, but elected not to change the name on the 168gr. I'm sure either would work for what you want, but the 168gr TTSX might be another slightly faster and cheaper option.

 

[Nature Boy]

@Nature Boy, I'd never argue with you about load data, or anything else for that matter, but Hodgdon shows higher velocity and lower pressure with Varget compared to H4895. Here's their load data for a 175gr bullet. Can you remind me of the velocity you get with those 185gr Berger bullets? You're using a 26" barrel if I remember correctly. I'm starting to get excited about working up loads for this rifle. It's been a tough few months for me for a number of reasons and I need something to look forward to.

View attachment 916458

I know. I found the results counter to my expectations too, but here they are.

26” Bartlein 5R, MTU contour barrel

43.5g Varget = 2,671 fps, and pressure signs
43.5g H4895 = 2,740 fps, no pressure signs

 

[MCMXI]

Just an FYI, when I called Barnes about their recommended bullet for my short barrel .30-06, the tech recommended the 168gr TTSX over the 175gr LRX for my uses. According to the tech, the 168gr TTSX was really the first of the LRX series in terms of design, opening velocities and BCs. After the 168gr proved successful, they followed with the LRX line, but elected not to change the name on the 168gr. I'm sure either would work for what you want, but the 168gr TTSX might be another slightly faster and cheaper option.

Thanks. I have lots of the TTSX bullets in 150gr, 165gr and 168gr so I might try those if I'm not happy with the 175gr LRX. I do like the BC of the LRX though and the fact that it's supposed to have a larger cavity in the nose that helps it open up at lower velocities.

 

[MCMXI]

I know. I found the results counter to my expectations too, but here they are.

26” Bartlein 5R, MTU contour barrel

43.5g Varget = 2,671 fps, and pressure signs
43.5g H4895 = 2,740 fps, no pressure signs

It's hard to argue with empirical data! Are you using Lapua brass? What's your COAL for those loads? I hope I can get to 2,650 fps without pressure signs using Varget.

 

[Nature Boy]

It's hard to argue with empirical data! Are you using Lapua brass? What's your COAL for those loads? I hope I can get to 2,650 fps without pressure signs using Varget.

My target loads use Lapua Palma SRP brass. Laupua 308 win LRP brass will only last ~4 cycles before primer pockets are too loose (I guess that required a disclaimer: Kids, work up to this load, never start here).

I’ll measure the COAL when I get home and let you know. It’s going to be LONG. Won’t fit in a magazine

 

[Gtscotty]

One of my best performing loads in my Tikka CTR was:

44.3gr Varget, 178gr Amax, Hornady case @ 2.885".

That load was a real hammer, unfortunately it turned out to be a bit too hot and I was losing primer pockets in a few firings.

When Amax's got scarce around here I worked up a new load with ELDx and arrived at:

43.8gr Varget, 178gr ELDx, Hornady case @ 2.885".

With Winchester cases I needed a few tenths more powder to hit the same velocity. Given how different the profiles of the Amax and ELDx are I thought it was odd that they liked the same OAL, but that's how it shook out.

I guess I got rid of my notes when I sold that rifle, but I think the velocity was ~2,580 fps, so I wouldn't think you'd have a problem hitting 2,650 fps with 6 extra inches of barrel, with the Amax anyway. Don't know about the LRX, most of the Barnes load data for the .30-06 I've looked at runs a bit lower than equivalent jacketed bullet velocity. Doing a load range test on my .30-06 with the 168gr, I only got up to velocities on the top end that were barely over my 180gr Accubond hunting load.

 

[LoonWulf]

As it sits now it looks like a project rifle with mismatched parts and finishes.

BOOOOOOO! i thought the random patterns were intentional....like abstract art.....dissapointed now....

 

[redneck2]

had the LabRadar set up but forgot to add the microphone so didn't get a velocity for any of the shots. That Harvester suppressor is quite effective so the sound wasn't enough to trip the unit.

That is awesome

 

[MCMXI]

Added in edit: OK ... so I messed up which might explain the wacko velocity variations and some of the accuracy/precision issues. I neck sized the new Lapua brass and in a moment of stupidity ran the brass through a .329" neck sizing bushing which is NUTS! The neck wall thickness is .016", the brass comes new with a neck O.D. of .335" and fired brass is coming out at .342" O.D. for the neck. The factory neck O.D. gives about .005" of neck tension. No wonder the case necks of the brass were coming out of the die with a very odd look. I thought the bushing was dirty or something. I'm going to repeat this test with brass that has only been deburred and run through a .335" neck sizing bushing just to make sure that the case mouth isn't out of round. Once I've shot the brass I'll probably use a .337" or .338" neck sizing bushing to give a couple of thousandths of neck tension. I apologize for the crap that follows!

I started load development today using 178gr A-MAX bullets that I bought at least 10 years ago. I used new Lapua brass which I neck sized and deburred, Varget and GM210M primers. I shot ten 3-shot groups in the order shown (left to right, top to bottom) and ended up with mixed feelings about my first effort. I felt that I messed up the first 44.4gr group (#4) with the last shot at top right so I went back in the house and put three more of the same load together and shot another group using 44.4gr with similar results (#5). I can't explain why the groups started to move to the right, particularly comparing the first 44.1gr group (#3) to the first 44.0gr group (#8). I started to play with bullet jump for the bottom row of 44.0gr groups. I didn't try seating the bullet into the lands but it might be worth a try.

The good: It seems easy to get 2,700 fps without any pressure signs, in fact, I didn't have any obvious pressure signs with any of these loads. 44.0gr seems to be a good load. No group was over an inch.
The bad: ES numbers are not particularly good and I can't explain the groups shifting to the right towards the end. No group is outstanding and I probably need to sort the A-MAX bullets by base to ogive which is what I used to do when shooting them in F-Class matches.

 

[troy fairweather]

Could the suppressor be the problem

 

[MCMXI]

Could the suppressor be the problem

It could be. The Harvester has an integral brake and I noticed that the suppressor cover tends to slide forward under recoil and might be partially and unevenly blocking part of the first port but that's pure conjecture at this stage. The groups seemed to move to the right for the last five groups. If all the loads were different I would put it down to the charge weight, but the last three 44.0gr groups are well right of the first 44.1gr group (#3). It could be my fault too.

Like I said, the results left me with mixed feelings but I think 44.0gr +/- 0.1gr is probably the sweet spot. I plan on putting more effort into the reloading process by sorting the bullets. I remember that these bullets appeared to come off three different machines. I asked Hornady about that at a SHOT show in 2010 or so and they got all ruffled up by my suggestion that I noticed inconsistencies in the ogives in the same box of bullets.

 

[Nature Boy]

What's your COAL for those loads?

185 Hybrid, -0.20 off, 2.907”

 

[MCMXI]

185 Hybrid, -0.20 off, 2.907”

Those would fit in the AICS magazines with plenty of room to spare. -.20 off the lands .... is the decimal place in the wrong spot?

I checked the COAL for both 178gr A-MAX and 175gr LRX bullets to see if I can get the bullet to touch the lands but still fit in the AICS magazines. With the 178gr bullet on the lands the COAL is 2.840", and with the 175gr LRX on the lands the COAL is 2.915". Both of those loads will fit in the AICS magazine which has an internal length of 2.985" after I removed the front binder plate.

 

[Nature Boy]

Those would fit in the AICS magazines with plenty of room to spare. -.20 off the lands .... is the decimal place in the wrong spot?

yes, meant to be -0.020” off

 

[MCMXI]

I don't typically put loads together with the bullet on the lands and definitely not into the lands but I decided to try that this morning. I've used the Stoney Point tool for years but tried the method described in the video below.



I did my best to get the bullet on the lands with these five rounds and the 5-shot group was decent. 44.1gr of Varget still seems to be a good load so that's what I tried here. After this result I put 10 rounds together with 44.1gr of Varget and with five 178gr A-MAX bullets about .005" into the lands and five about .010" into the lands so will shoot those this week. I've always been "fearful" of jamming bullets into the lands but @Nature Boy cured me of that with his results. I wonder if jamming the bullet is more consistent than trying to just touch the lands since if you jam enough it assures that the bullet isn't a few thousandths off or a few thousandths into the lands. The LabRadar unit was acting up this morning so I didn't get any velocity data but it's probably in the 2,675 fps range.

The rifle still appears to be shooting to the right of where it started for the first five targets shown above so something changed. I'll do some bedding this week.

5-shot group using 178gr A-MAX, 44.1gr of Varget, GM210M primer, new Lapua brass, and the bullet "touching" the lands ... in theory.

 

[Nature Boy]

That’s looking great!