Thread: Kimber Load Development

Did some load develop of my sibling Kimbers in 280AI and 7mm08.



7mm08 loaded up some 162s at mag length did a quick ladder to attempt to find pressure limits and test Rl16 which the Internet seemed to have determined was too bulky for the 7mm08 case.

I didn't need up finding pressure but did model it in Quickload and stopped at the theoretical max load (above my Book data for the 162 by a fair bit but I'm seating longer. It's also only marginally more powder oddly than the book data for the 180 ELD so was pretty sure it would be OK especially coming up from lower down. Top load Velocity shows me a bit under 63kpsi so warm but nothing unreasonable and producing less bolt thrust than a 270 at full Saami pressure of 65kpsi.

Wasnt intending to use the upper end but without pressure signs and I ended up finding a node at the top load with a velocity of 2739 and an ES of 15 for 5 shots including a clean bore shot. First clean bore shot (CLP and then brake cleaner to make sure chamber wasn't lubed) went high but the following 4 shots went into .784 so will load a few extra up to check to see how close to pressure signs I am but if I'm not right on a pressure spike I will LOAD UP. Few more groups around this node to try dial it in and play with seating depth. It's turned the 7mm08 into quite a potent little rifle. My shoulders feeling it even with only 25 shots fire (it's 2.6kgs all up)



Somehow I forgot to take a picture of groups will take one when I get home.

Then a ran a ladder with the 280AI and 180 ELD m at mag length with RL26. Used some Peterson brass which is lower case capacity as such I ran into early pressure (a slight swipe just visible under the right light but there all the same) slightly earlier than expected at 59.5grains. I may try the norma I have to see if I can get to the node that kimbers seem to have around 2860fps. There was a bit of node at 2750 where 4 shots where touching with loads from 57 to 58.5 grains but considering its got an extra 2 inchs of barrel vs the 7mm08 I'd really like to get to the next node if possible to warrant the extra heft and length as realistically the 7mm08 isn't that far behind. Was quite nice to shoot however with the bit of extra weight from the scope and with the brake fitted. Definitely kicks less than the 7mm08 with bare barrel.

I've been considering suppressing the 7mm08 but these groups and velocities have me wondering if its too risky to loose the 3inchs of barrel and potentially these groups. I will see what this load can do and if I can get it to 1/2 inch I'll likely leave it and suck up the recoil.

Anyone had much experience with a rifle that shoots in the sub moa range then cutting and suppressing it and the effects on handloads accuracy. Being on the edge of pressure I'm a bit scared if I cut it down I might lose this upper pressure node and potentially loose way more velocity than I'd like.

Will update as things progress.

I wouldn't expect the same load to shoot well after a chop. I subscribe to the OBT method and the goalposts are moved when you shorten the barrel. That's not to say you won't get lucky or find that the old load shoots acceptably.

Recently had my 6.5x47L chopped from 28" to 20". It was sub-MOA before and is definitely still sub-MOA now but the loads are different.

Nice going with the load development all sounds very promising. I also have two kimbers a 280ai and a 6.5 CM. I recently had the 6.5 shortened from 22 inches down to 16 inches. I had been running re26 with 135 berger classic hunters at 2915fps at 22 inches and shooting well under 0.5moa. I had expected that I would need to redo the load/change powders etc but it still shoots well under 0.5moa. Velocity now 2700fps.

Ben

I did that with my 7 saum, went from suppressed 22” cut down to 17.5” suppressed using the same loads, lost around 200fps but load stayed under moa without having to change anything.
Just swapped back again to a factory 22”barrel I got off another forum member, same suppressor, early days but the ladder to finish nd pressure looks very promising(no chrony readings though)

I havnt done much with the heavier pills (am about to try them) but my 708 montana can do close to 1/2 moa since chopping to 18" if im doing my bit.
Am using 140 accubonds and gamekings over Re17
Is a bit over 2700 fps. about max in this rifle.

Yeh I didn't expect the same load to shoot as I'll have to find another load. My limited experience with previously suppressed rifles before and after has been an improvement in accuracy/a wider node (maybe the extra can weight and contact points help dampen the barrel). Being on the edge of what I'm comfortable running pressure wise and being in the node does scare me a bit as the next node I wound was much lower and wasn't as stable (around 2550fps so a far cry from the 2740 I'm getting now and if I lose say 50-60fps chopping 3 inchs but get knocked down I node I'd be pretty gutted to end up at 2500fps as I primarily hunt the tops. Plus I have tonnes of 162s so would like to stick with them as I like there performance at these velocity ranges. Positive of the can would be managed recoil and obviously suppression (both are nice but not essentials. I think if I could maintain 2650 give or take 50fps with a can if be happy.

One thing I noticed with the suppressor on my 6.5x47 was that I would generally get higher ES usually with a trend to climb shot to shot (it was a 5fps es load with 10 shot groups rifle with a bare barrel but with a can almost religiously it would gain 6-7fps on the second shot and then keep gaining 2-3fps continuing for the next couple leading to an ES usually around 20. Anyone had similar or was it potentially just barrel harmonics changing?

What's the bbl length on your 7-08? Have you considered leaving the bbl where it is but threading for suppressor ?
I've got a similar dilema with my 7-08, its a 22in bbl and have a "long" (500yd) load worked up with 150 ELDx doing 2750fps w RL16.
If I chop to end up with shorter over all length with suppressor, then I'm going to have to chop at least 4in off it.... and loose 100 - 150 fps. When bush hunting I use a milder pill/load & run the rifle non suppressed. For long range shots you usually have got time to whack on the suppressor & set up for shot. So I'm debating going to 20in bbl & hopefully only loose 50-60 fps, bare rifle for bush hunting (same overall length as 16in bbl plus suppressor) & add suppressor for tops/longer range stuff.

Good info thanks. I’ve been going the other way and loading 120 Ballistic Tips in my Kimber 7mm08 because the mag length is pretty short (and I have a long action 284 with 162s for longer range) but your loads are very impressive. I’m interested how many gns of RE16 you got in - PM if you don’t want to post.

Originally Posted by chainsaw

What's the bbl length on your 7-08? Have you considered leaving the bbl where it is but threading for suppressor ?
I've got a similar dilema with my 7-08, its a 22in bbl and have a "long" (500yd) load worked up with 150 ELDx doing 2750fps w RL16.
If I chop to end up with shorter over all length with suppressor, then I'm going to have to chop at least 4in off it.... and loose 100 - 150 fps. When bush hunting I use a milder pill/load & run the rifle non suppressed. For long range shots you usually have got time to whack on the suppressor & set up for shot. So I'm debating going to 20in bbl & hopefully only loose 50-60 fps, bare rifle for bush hunting (same overall length as 16in bbl plus suppressor) & add suppressor for tops/longer range stuff.

22 inchs I'm in exactly the same boat. I will use a Maniatis can as they are light and only 3 inchs muzzle forward. I don't really care about nit picking suppression volume in a super sonic rifle as I shot it bare barrel anyway and just chuck in plugs if I have time or if not a beanie is usually enough to buffer the sound so you ears don't ring.

Benefits I see from a can are potentially damped barrel harmonics, better for myself and the dog (who usually just gets told to sit 10 or so metres back), and reduced recoil.

Potential negatives I can see is loss of muzzle velocity (probably 60fps ish at max charge cutting down 3 inchs to maintain overall length) but potentially much more if I have to drop much to find another node (no real control its a game of luck here), I have to thread it and the only thread that will work is a 1/2x28 which I'm not that keen on. (It's what's on my 280AI but just doesn't seem like much meat. In saying that to get that thread not much meat is actually being removed as the barrels a pencil. Also potentially a wider ES due to the can, adds weight to what is my arounder beater ultralight carry alps rifle, 0-600 type rifle. That and of course suppressors cost money.

I've got a short barrel 308 so don't really want or need another stubby gun.

Originally Posted by Forestry

Good info thanks. I’ve been going the other way and loading 120 Ballistic Tips in my Kimber 7mm08 because the mag length is pretty short (and I have a long action 284 with 162s for longer range) but your loads are very impressive. I’m interested how many gns of RE16 you got in - PM if you don’t want to post.

It's a lot and is compressed even using a drop tube and electric tooth brush and requires seating each case invidually to ensure consistent seating depths but I don't really mind doing it for good accuracy. I've also found to eject a live 2.835 case I need to trim the ejection port a bit or it will break of the tips.

So here's the 7mm08 5 shot group



1 was the clean bore shot. For reference all load development in my kimbers is down allowing 1 minute between shots as this is most relevant to me as I care what a cold bore does. I don't clean between hunts I leave the bore fouled and just rush a dry bore snake through before and after a hunt. Once I sort a load I do usually do a 3 shot group with about 10 second between each shot (just however long it takes to set back up without rushing like you would with a follow up shot on an animal) to give me an idea of what to expect if I ever needed to use the whole magazine. (I try to avoid this though as by 3 shots the barrels warm and I don't like to burn barrels).

Here's the 280s 10 round ladder mainly just looking for velocity nodes on the labradar but interestingly they often line up with groups on paper.



Rifle wasnt sighted in at all do #1 was a slighter then after #2 I adjusted 6 clicks (1.5 Swaro MOA or 1.5648inchs at 107 yards this is shown by the circle I drew to represent its adjusted point in the ladder. As you can see a pretty good 4 shot group between shot 2 and 5 (1.5 grains difference). I did hit pressure signs at 6 with a marginal swipe that didn't occur at load 6 but returned for in shots 7-10 not sticky bolt lift or any other signs showed except a significant jump in velocity at load 10 I feel comfortable that in this setup a node between load 2-5 will be fine.

I figured I will post pictures of the brass for people's opinions.


The brass above is from the 7mm08 the scratches on the face occur pre firing the Lapua brass for some reason when loaded seems to cause the rough edge of the ejector slot to scrape brass. I confirmed this by loading and ejecting loaded brass and without fail unfired loaded ammo comes out like this. Primers are flatish but these federal primers are flat right from the get go in every rifle I own.

Having a closer look at the 280 AI brass
I couldn't get the swipe on photo until I managed to get the light just right and aligning the primer impact location so I knew where to look. By using HDR I managed to actually see way more than I could with my naked eye. It appears what I'm calling a wipe occurs much lower down in the powder charges and maybe isn't what I thought it was. I'd like some thoughts.









Thoughts any one it clearly a pressure sign but I think the sharp edge on the bolt face ejector slot is potentially exaggerating this sign. When the rifle arrived it did have a kind of thin coating of brass dust on the bolt face that just kind of wiped off. Will pull out brass that came with it and inspect. Photos show shinyness that is not visible to the human eye except on the last couple.

The two 280 cases on the left in last pic look to have ejector stamp marks to my eyes.

Upon inspection of fired brass that came with the rifle shows about 75% of the hornady has this sign typically with more of the swipe rather than just a stamp. With the norma about 50% of the brass has this mark. May have to try debur the edges of the bolt face.

Originally Posted by chainsaw

The two 280 cases on the left in last pic look to have ejector stamp marks to my eyes.

They almost all have that mark it's the ejector slot (kimber is controlled round feed similar to a mauser). There's not edge etc can't feel it with a needle tip. The photos exaggerate it as I played with contrast to make it visible the last those two are however the most visible of the bunch and not a load I will be repeating due to velocitys being to high. The fact probably the 3rd worst mark is on the far right case which is the lowest load as is 2.5grains under book max and according to quickload would only be around 50kpsi and almost perfectly predicts my velocity when tuned to the peterson brass case capacity.