Another Kimber Montana 8400 WSM conversion ... this time to 6.5 PRC

[MCMXI]

I bought a Kimber Montana 8400 WSM chambered in 300 WSM almost six years ago and it was the rifle that got me hooked on Kimber hunting rifles. In June of 2016 I converted it to .308 Win since I like the size and feel of the 8400 WSM action more than the 84M and wanted a .308 Win hunting rifle. Now I'm in the process of converting it back to a magnum bolt face and the 6.5 PRC to see what it will do. I have a custom Kimber Talkeetna in .375 H&H which turned out really good and I want to do a similar upgrade to the 8400 WSM. I should be able to cover most hunting scenarios up here in MT with a 6.5 PRC and .375 H&H.

This is how the rifle looked when I first bought it back in 2012.



This is how it looked with the .308 Win barrel and bolt.



I received the stock back from dipping today. I chose Cabela's True Timber O2 Octane with a soft touch top coat so that it's "grippy". The stock looks and feels good so now I have to decide on whether I want to dip the barreled action, rings and scope with something that would compliment the stock or simply go with a solid Cerakote color. The barrel should be here any day now so I need to make a decision sooner rather than later. I have reamers and a GO gage so will install and finish ream the chamber myself.

I'll update this thread as the pieces come together. I have a lot of Hornady ammunition on hand, new brass, bullets, a good selection of appropriate powders and primers so am looking forward to shooting some groups.

 

[adcoch1]

that stock look really good, I'd be tempted to leave the action solid color in that stock...

 

[MCMXI]

That's probably the way I'm leaning ... black, brown or green but definitely something darker. I'm not sure if the girl who dipped my Talkeetna can even get the Octane film, but if she can I might be interested.

 

[Corn-Picker]

Looks great. I may be facing a similar decision, so out of curiosity I’ll ask what pushed you towards the PRC rather than the other similar cartridges (6.5x284, 6.5 SAUM, 6.5 WSM, etc...)?

 

[Gtscotty]

The stock looks great, where did you send it off to get the coating done? Any worries about the soft touch eventually rubbing off like is sometimes reported with Browning's and Sako Carbons?

I think if I was going to have an SS barrel or action coated in anything, I'd lean strongly towards single color Cerakote, as opposed to a dip, which I'd be afraid would start looking shabby quickly under tough hunting conditions.

The 6.5 PRC chambering is really interesting, sort of like a modern design .264 WM replacement, better set up for LR shooting. I can get 127gr LRX bullets above 2,900 fps in my 22" Creedmoor with great accuracy, I wonder what velocities you'd get out of the PRC. Maybe 3,200? That would be a laser with great penetration and relatively little recoil.

Very neat project, I wish I had the skills to do barrel swaps like that myself. BTW, was the .308 barrel you used on that action previously, a factory Montana profile? It looks thicker than the WSM barrel.

 

[Robert]

Man I'd just like to be able to put a McMillan stock on my 375...

That's a nice looking rifle and I hope it works out well for you.

 

[Nature Boy]

God I have to quit looking at these threads. They're going to make me go broke

 

[MCMXI]

Thanks to everyone for the feedback and interest. I have high hopes for this project and look forward to showing off a finished rifle and some decent targets.

Looks great. I may be facing a similar decision, so out of curiosity I’ll ask what pushed you towards the PRC rather than the other similar cartridges (6.5x284, 6.5 SAUM, 6.5 WSM, etc...)?

The 6.5-284 Norma would be better suited to the 84L action/rifle and of the others I think only the 6.5 PRC has factory ammunition and brass available. My gf has a 6.5 SAM which uses necked down .300 SAUM brass with no hope of any commercial offering. I plan to reload for the rifle but if the cartridge gains enough traction there might be some Lapua brass in the future. Commercial success is possible for the 6.5 PRC given Hornady's track record.

The stock looks great, where did you send it off to get the coating done? Any worries about the soft touch eventually rubbing off like is sometimes reported with Browning's and Sako Carbons?

I think if I was going to have an SS barrel or action coated in anything, I'd lean strongly towards single color Cerakote, as opposed to a dip, which I'd be afraid would start looking shabby quickly under tough hunting conditions.

The 6.5 PRC chambering is really interesting, sort of like a modern design .264 WM replacement, better set up for LR shooting. I can get 127gr LRX bullets above 2,900 fps in my 22" Creedmoor with great accuracy, I wonder what velocities you'd get out of the PRC. Maybe 3,200? That would be a laser with great penetration and relatively little recoil.

Very neat project, I wish I had the skills to do barrel swaps like that myself. BTW, was the .308 barrel you used on that action previously, a factory Montana profile? It looks thicker than the WSM barrel.

I had the stock dipped by a company specializing in OEM products rather than retail but their process is one of the best out there with a clear coat over the dip and then soft touch over the clear coat. The girl who dipped my Talkeetna also put a clear coat over the dip so it's a tough and durable finish but she doesn't do soft touch. All of the metal on my Talkeetna was dipped and it's been great over the last two hunting seasons with no sign of wear or damage so I have no problem with a dip rather than Cerakote on the barrel and action.

A 143gr ELD-X at 3,100 fps isn't much trouble at all with the 6.5 PRC out of a 26" barrel. I'm going to use a 24" barrel and expect to be up around 3,100 fps with 140gr bullets. The trick will be to find a good load with a tough bullet suitable for 600 yard shots on elk and deer. I'd rather go as heavy as possible so maybe the 147gr ELD-X.

The .308 Win barrel shown above has the same profile but is 22" long vs. the standard 24" barrel.


The photos of the stock that I posted earlier aren't quite representative of the color and tone of the dipped pattern so I took some better photos this morning that I feel are more accurate. It's more subdued than it looks in the photos above. As is common with dipped stocks using timber patterns, one side looks different to the other. With this stock, the left side has a darker appearance compared to the right side.

 

[MCMXI]

Update: Two stainless steel barrels will be here early next week and will go out for sand blast and engraving. I ordered 500 Nosler AccuBond Long Range 142gr bullets yesterday (hope they shoot good) and have some of the Octane film arriving next week so that the girl who dipped my Talkeetna can dip the barreled action, scope and rings to match the stock. I'll be using a Zeiss Conquest MC 3.5-10x44mm RZ800 scope. I plan on shooting the rifle using factory Hornady 143gr ELD-X and 147gr ELD Match before I get the metal dipped to establish a baseline. Photos coming soon.

 

[MCMXI]

Update 2: Two 24" stainless steel barrels arrived today along with 500 Nosler 6.5mm 142gr AccuBond Long Range bullets. I'm helping out with 60+ kids tomorrow with a hunters ed course, but on Sunday I plan on screwing on one of the barrels, using a finish reamer to set the correct headspace and then shooting some factory ammunition to see what the rifle might be capable of. I'll then pull the barrel off and send both barrels out to get sand blasted and engraved. If I decide that I don't have any interest in the 6.5 PRC I can always sell the barrel that isn't finish reamed. If I discover that the 6.5 PRC is a great fit in that rifle and leaves me feeling all warm and fuzzy, I'll send out the barreled action and scope along with the extra barrel to get dipped in the O2 Octane pattern. That way I'll have a spare barrel that will sort of match the rest of the rifle and will only need finish reaming. I should have some data and a photo or two to share on Monday.

 

[MCMXI]

Update 3: I got the barrel on and timed yesterday and used a finish reamer to get the proper headspace. The bolt handle won't fall on a GO gauge and requires a bit of pressure to close the bolt which indicates that the chamber is very close to minimum SAAMI. I ran some oil soaked, alcohol soaked and finally dry patches through the barrel to remove any crap from the reaming step. I also spent some time removing "soft touch and primer" from the barrel channel of the stock but didn't address the same issue where the receiver mates to the stock (need to address that). I was able to mount and bore sight the scope, shoot three rounds to figure out scope adjustment and then shoot a five-round group which was ok but nothing special (see below). I was using Hornady's 143gr ELD-X blemished ammunition and the outside temperature was about 45F and DA was around 3,000 feet. Hornady advertises a MV of 2,960 fps from a 24" barrel which is the same length as the barrel I screwed on. I was getting about 35 fps slower than advertised for eight shots and the ES of 54 fps was surprising. As the second photo shows, the rifle/scope combination comes in at just under 7-3/4lb which makes it very nice to shoot. The scope is an older Zeiss Conquest MC 3.5-10x44mm with an RZ800 reticle.

AVG MV: 2,925 fps
ES: 54 fps
SD: 15 fps

I loaded five rounds last night using Nosler 142gr AccuBond bullets, 60.5gr of H1000, CCI magnum primers and new Hornady brass. I plan on shooting those today or tomorrow to see what the velocity looks like. QuickLOAD predicts around 3,100 fps but we'll see.


Here's the rifle with a shiny new barrel.




Here's the weight of the rifle, scope, rings and bases.



Here's the 5-shot group using factory Hornady 143gr ELD-X blemished ammunition. A decent start with a brand new barrel but I hope it gets a lot better than this.

 

[MCMXI]

Update 4: So I shot the five loads described above during lunch and got the results shown below. I wanted to get some idea of velocity, and obviously hoped for a good group but it was around 2" forming a "circle" around my point of aim. All shots felt good and certainly more felt recoil than Hornady's load but this clearly isn't an accuracy node. I'll start some proper load development this weekend and will most likely work backwards from here. I might change to Federal GM210M primers rather than the CCI 250 primers that I used for the five rounds shot today. Bolt lift was fine, the primers look good and I think that there's still a bit more room in the case (used a drop tube to dump powder) but I'd rather find a good load south of 60.5gr, initially at least.

3,115 fps
3,079 fps
3,101 fps
3,073 fps
3,102 fps

 

[MCMXI]

Update 5: I've been swamped with other projects for the past few months but managed to shoot a few groups yesterday using a new lot of Hornady 147gr ELD Match ammunition. I shot the groups in the order shown and made a 0.2 mil scope adjustment (up) after the second group. I was starting to settle into the rifle when a big thunderstorm rolled in and dumped a lot of rain which basically ended my testing. Overall I'm quite pleased with how this rifle is doing so far. It's too early to tell if I'll put the original 300 WSM barrel back on, or the .308 Win barrel or keep the 6.5 PRC barrel where it is. Once I've put more shots downrange and put some real effort into working up a load or two I should have a better idea of the direction I want to go in.

On a side note, I don't let the barrel cool between shots but will let the barrel cool between groups. I try to shoot five rounds in under 3 minutes which often means dealing with mirage but that's part of the real-world use of a rifle. Here are the three 5-shot groups shot yesterday along with the velocity data. The bore is really smooth but I'm getting a fair amount of copper fouling which might account for the increase in ES/SD from group to group. I didn't start out with a clean barrel but ran some Sharp Shoot-R Wipe-Out through the barrel last night and this morning and there's plenty of blue on the paper towel.

I've decided that I despise the Caldwell rest that I have and want to build my own stable platform for load development and rifle testing.

 

[mshootnit]

I convert my 8400M 270WSM....from full to empty. And then repeat.

 

[MCMXI]

I convert my 8400M 270WSM....from full to empty. And then repeat.

Your mother must be very proud ...

Update 6: I shot a group at 400 yards and one at 700 yards this past Saturday using the factory 147gr ELD Match ammunition from Hornady. I was populating the Applied Ballistics app for this rifle/ammo combination and wanted to confirm some variables such as the G7 BC. I had to lower the BC from 0.351 to 0.320 to get the theoretical vs. real-world numbers to match up in terms of bullet drop, but I think I'm close now.

The group at 400 yards was sub moa, and if it weren't for the one shot to the left at 700 yards I would have had a group close to 1 moa, still a dead elk though. Now I need to get serious about load development which will be fun since shooing this rifle/cartridge combo is quite addictive. Shooting and hitting targets at long range using heavy "tactical" rifles is fun for sure, but doing the same with a rifle/scope combo that only weighs 7-3/4 lb is very satisfying.

Here's the first 5-shot group at 400 yards. The steel target is a little over 11.75" wide and the group was 2.9" (0.69 moa). Clearly my scope adjustments based on the AB app and a 100 zero were fairly close but this is a hunting rifle so I want to be much closer to the point of aim.



I changed some inputs to the AB app, and based on new data dialed in 4.0 mils for elevation to shoot a group at 700 yards shooting at an upward angle of 10 degrees or so. The top target is 8" x 8" and the gong below it has a diameter of 18". The shot to the left was the third shot and the wind most likely dropped off enough to cause a problem. I'm getting fairly large ES numbers with the Hornady ammunition so can't expect great results until that's under control, which basically means handloads. I'm really starting to like this combination, and given the potential of this cartridge I might need to consider a better long range optic. I have an 18" gong at 1,050 yards and a steel plate at 1,300 yards. Getting a first round hit on the 18" gong at 1,050 yards followed by four more hits will be my holy grail for this rifle/optic combination. This in no way, shape or form means that I would shoot an elk at that range, but I would seriously consider shooting an elk at 700 yards under the right circumstances, and once I have a load worked up with a good bonded or solid copper bullet.

Added in edit: For those of you paying attention, clearly I'm not using the Zeiss Conquest MC shown earlier. I put on a Vortex Viper PST 4-16x50mm FFP for testing and it may very well stay on the rifle, or once I get a load worked up I might put the Zeiss back on which has an RZ800 reticle but no illumination. Decisions, decisions.

700 yards, factory Hornady 147gr ELD Match, 18" gong.

 

[MCMXI]

Update 7: I decided to get serious about load development over the weekend given the ES and velocity issues I've had with Hornady's factory loads and the ok accuracy/precision This is what I get shooting Hornady's loads.

143gr ELD-X: 2,966 fps (20 rounds, ES 38 fps) - Hornady lists 2,960 fps from a 24" barrel
147gr ELD Match: 2,856 fps (24 rounds, ES 78 fps) - Hornady lists 2,910 fps from a 24" barrel

I don't know why the 147gr load is shooting 50 fps slower than Hornady claims and the 143gr load is within 6 fps. I would have expected both to be slower or both to be close to the advertised spec, or both to be faster, rather than one a lot slower.

The 8400 WSM mag has an internal length of 3.030". Hornady isn't offering a modified 6.5 PRC case yet for the COL gauge so I ordered a 5/16-36 tap and made my own from a fired case. I used it to determine COL and bullet jump and this is what I found.

Nosler 142gr ABLR - COL of 3.020" - bullet ogive into lands
Hornady 143gr ELD-X - COL of 3.000" - bullet ogive into lands
Hornady 147gr ELD Match - COL of 3.020" - bullet ogive into lands
Hornady factory 143gr ELD-X load with COL of 2.950" - bullet ogive 0.052" off the lands
Hornady factory 147gr ELD Match load with COL of 2.950" - bullet ogive 0.071" off the lands

The bottom line is that the handloader has the option to put all three bullets listed up against the lands and have the loaded round fit in and feed from the internal magazine.

Hornady load data for the 147gr ELD Match bullet and H1000 powder lists a COL of 2.950", a max velocity of 3,000 fps and charge of 57.4gr from a 24" barrel. I decided to start with the bullet .020" off the lands so went with a COL of 3.000". Here's the data with the understanding that my COL is .050" longer than Hornady's so the pressure would be lower across the board. All primers used are Federal GM210M.

57.0gr Avg: 2,968 fps, ES: 19 fps (5 rounds)
57.5gr Avg: 2,996 fps, ES: 12 fps (5 rounds)
57.8gr Avg: 3,006 fps, ES: 11 fps (5 rounds)
58.0gr Avg: 3,013 fps, ES: 13 fps (5 rounds)
58.5gr Avg: 3,029 fps, ES: 10 fps (5 rounds)

Based on the data above, only one decent group at 0.882 moa, Hornady's load data and some QuickLOAD simulations I decided to try 56.5gr of H1000, and a COL of 2.990" to put the bullet .030" off the lands.

56.5gr COL 2.990" Avg 2,948 fps, ES 7 fps (5 rounds) QL predicted 2,950 fps which is close to 100 fps faster than the factory 147gr load from this barrel!!

Here's the 56.5gr target and I know that I screwed up the 2nd shot which is the lower left shot. The four shots are inside a 0.65 moa group so I'm hoping that this is a good sub 0.75 moa load once I learn to shoot properly! I'll shoot some more next weekend after I completely screw up the rifle with my first bedding job! I've had a LabRadar for quite a while now and I highly recommend one if you're looking for a super reliable and easy to use tool for collecting useful data. As for QuickLOAD, it's a very powerful tool but one that requires plenty of thought. For example, the pressure for the 56.5gr load is 58,761 psi according the QL but is this accurate? One way to increase the confidence in QL simulations is to start with factory load data such as Hornady's data for the 6.5 PRC. If you assume that they aren't going to list a load that exceeds 65,000 psi you can infer some of the input variables such as Weighting Factor and Powder Burn Rate (Ba) and use those values along with velocity data from the actual rifle in question to pick the most likely model scenario that is a good predictor of actual performance. I can say for certain that none of the loads shot resulted in excessively flattened primers, excessive primer flow around the firing pin, heavy bolt lift or hard extraction.

I use a foaming bore cleaner and typically I'll see lots of blue during the initial squirt down the barrel and subsequent squirts a few hours later. I foamed the barrel this morning and barely any blue at all, actually, no blue. This was after 30 rounds of my handloads so not sure if the barrel is "breaking in" or Hornady's factory loads cause more fouling.



LabRadar data.

 

[mshootnit]

Nice, I bet that would whack a big muley!

 

[MCMXI]

Thanks @mshootnit . Once I have this load dialed in I want to work up a good hunting load using Nosler 142gr ABLR bullets and shouldn't have a problem getting to 3,000 fps with those using H1000 and GM210M primers. I've heard very mixed reviews of the ELD-X bullets for hunting so bonded or solid copper is the way I want to go. The problem with 6.5mm solid copper bullets is that they get too long for typical barrel twist rates when the weight exceeds 130gr. For that reason I'm sticking with bonded bullets which are much tougher and short enough for those really cold hunting days in MT.

 

[MCMXI]

Update 8:
It's been very windy here today but I figured I'd shoot the 20 rounds I put together over the weekend. The good news is that the ES numbers aren't bad for a hunting weight rifle, but the best I'm getting with this charge weight is around 1" 5-shot groups at 100 yards so I don't think that this is "the load" despite my hopes based on the last session. .010" and .020" off the lands were ok and .030" seemed to open up a fair bit. I bedded the action over the weekend and the rifle feels great, and maybe that changed a few things for load development, but I'm not there yet. I did change scopes and mounted a Vortex Viper PST 4-16x50mm FFP. I bought Redding's Imperial Dry Neck Lube kit last week and I like it. It's easy to use and I'm sure that I'm getting consistent neck tension results with new brass. Here's the LabRadar data which shows that my loading technique is ok. 19 fps ES for 20 rounds with three different COL values isn't bad. Close to or single digit ES values for each of the 5 shot groups isn't bad either. I'm pleased to see that the cold/clean bore shot is right in the group too with no significant shift, and a hot barrel doesn't seem to be a problem at all. Now I just need to find "the load" for this bullet so that I can get onto the 142gr Nosler ABLR load that I want to use this fall .... maybe.

 

[LoonWulf]

Looks like your load work ups are progressing well, your consistency is excellent.
If i get any shots this weekend, I'll have some input on how the eldxs work on cows from my 6.5-284 at about 2850.

 

[MCMXI]

Looks like your load work ups are progressing well, your consistency is excellent.
If i get any shots this weekend, I'll have some input on how the eldxs work on cows from my 6.5-284 at about 2850.

Thanks ... I'm almost in @taliv and @Nature Boy territory with the ES numbers. I'm not expecting to get down to the 5 fps range or lower for 5-shot groups but anything under 10 fps is very respectable. I don't understand why the Hornady 147gr load is all over the map. I'm getting 75 to 100 fps ES numbers for 20 shots. My handloads were under 20 fps and that's with three different COLs! Their 143gr ELD-X load was in the 40 fps range for 20 shots. Still not great but half the error of the 147gr load.

Any info on terminal performance of those 143gr ELD-X bullets would be great (or any other ELD-X bullet). A couple of coworkers were less than impressed with the peformance of the 162gr ELD-X on elk last year. I've read very mixed reveiws on the ELD-X bullets in general. They're plenty accurate but that's just half of the equation. I only hunt with well-established solid copper or bonded bullets because I don't want bullet construction to be an issue.

 

[LoonWulf]

I'll let you know how it turns out. We'll have both my 06 and 6.5-284 shooting them so hopefully someone gets a shot.

 

[MCMXI]

Update 9:
I did some more load development today and am kind of pleased with the results despite somewhat average 5-shot groups. I think that I now have something to work with and will try to tweak the 58.0gr load a bit when I'm back from a business trip in a week or two. Maybe I'll try sorting bullets by weight, playing with the COL, annealing the case necks etc. Four shots of the 58.0gr load are inside 0.75 moa but it's too early to know if the group is typical of the load.

I'm impressed with how consistent the 147gr ELD Match bullets are in terms of base to ogive dimension. It's very easy to control the jump to the lands when the bullets are consistent. I'm not seeing any pressure signs with any of these loads, but I do need to figure out the Hornady sizing die a bit. My fired cases are coming out around .0005" under the GO gauge when measured to the shoulder. I discovered that my sized cases are actually being stretched to .003" over the GO gauge which made the last three loads a little hard to chamber. Anyway, I'm pleased that the 58.0gr load is bracketed by loads that shoot to virtually the same average POI (OCW objective) and that I'm getting around 3,000 fps with a low ES number. I didn't make any scope adjustment for these loads so the POI is moving low and right as the charge weight increases, but appears to stabilize for the last three loads. Once I was all done I did dial up and left for the next time I'm testing 58.0gr of H1000.

I've been messing with this 147gr ELD Match bullet just to get some data but I really intend to get on with the 142gr ABLR load ASAP. I'd be ok with similar results with a 142gr load producing 5 shots under 1 moa and bracketed by loads that aren't terrible and have similar POI. Obviously I'd be even happier with a 1/2 moa load but it might not happen. Here are the results from today.

 

[mshootnit]

Go for "one ragged hole" groups in load development if you plan to shoot at range.
My best groups came with a Shilen select match #5, and Lee collet neck sizer.

I sincerely think with the bullets and quality rifle, loads you have that 1/2 moa at 300 yds is possible. (1.5" 5 shot group)

 

[LoonWulf]

Just wanted to follow up on the 143 eld-x's. Im pretty unimpressed, with how they performed.
Not only did they penetrate fairly shallowly, less than a similar 7mm 162 amax with a launch velocity of around 3k, they also didnt cause as much internal damage as i would expect from said Amax, or a Berger VLD.