Home Forums Hunting & Shooting Hunting Rifles Kimber 257 Rob OAL constraints

Kimber 257 Rob OAL constraints

I knew going in this may be a struggle with mag OAL restrictions ....
Longer than 2.820 and a loaded round won't clear ejection port..

Thinking about shortening the ejector and opening up the port...

Mag mod is the easy part...

Any tips besides rebarrel it to 7-08AI or 6XC?

Dave

Dave, while I know the Rob, like the 308, is long-throated because its SAAMI specs were achieved with a RN bullet, is the rifle not shooting with bullets seated at 2.820+/-?

If it's accurate enough for you, I'd live with constraint and go kill stuff. You aren't losing enough velocity to matter, and it's a sweet little rifle/cartridge combo.

I have not wore it out but so far it shows it wants the bullets closer to the lands.
100 Hornady was 2" with 46grs of H4350
100BT was 1.5" triangles with same load above
80TTSX wax 1.5" with double group (4 shots) using 49grs R17

Is everything else copacetic? Cartridge runout, magazine box binding or not, ...

I personally wouldn't compromise the front receiver. There's very little there to begin with. Cutting out an M70 or 700 is one thing, the 84M an entirely different thing.

What I've found with Kimber Robs is not to get wedded to a particular bullet. Try a variety. It will shoot something sub moa within mag constraints, but not everything.

It's a crying shame the 25-08 was never legitimized.

I'd go 6.5 Creed were I thinking of a rebarrel.

I feel your pain. I have a sweet little Browning A-Bolt Micro hunter in 257Rob that has the same issue. I was lucky to find a 100gr Nosler BT load that shoots under 3/4" but everything else is like yours (1-1/2 to 2").
This load has killed a big buck and a few hogs, but I'mm bummed at the lack of bullet options.
Oh well...not going to mess with mine.
Good luck with yours.

Maybe no help for the OP, but someone contemplating a .25 and wanting the most velocity and some flexibility might want to look at a .25/06 instead. The Kimber comes in at 6lbs 2oz.

Going 6.5CR makes sense if he wants to keep the rifle he's got, but I'd be trying a bunch of other bullets before I gave up, with 100gr NPs at the top of the list. Besides, 2" rifles may not impress your friends, but the deer won't notice.

DaveH
I had the same issue with an older M70 Featherweight in 257 Bob.
It did shoot most anything I feed it well, but I was constrained with the short box. Only thing I did to the gun was to put a shim under the front of the action to insure free floating.
I would have liked to load the bullet out more and to squeeze more powder in, but......

Worked up several loads, but did not kill with it before letting it go. Were I younger and/or had fewer hunting rifles, I would have matte finished it and bedded it, but I passed it on.

I could share loads if interested.
Tim

I had to fix the mag box, float on barrel is ok. Loads have .002-.003 runout but no more.
I will try more powder and bullet combos.
Will heed the advice on mods until later. I don't do 6.5's as I have every other caliber and figure that is enough....

Dave

7mm-08AI is a lovely solution, highly recommended...

David

Another bullet you might try is the Nosler 110gr Accubond.

I've got fair accuracy, 1 to 1.5" 3 shot groups and great results on deer in my Kimbers.

Seated to 2.805" I have two loads shooting to almost the same point and velocity.

46gr RL19 @ 2858fps

43gr IMR 4350 @ 2845fps

YMMV

Kimbers are such sweet little rifles and the 257R such a sweet little cartridge. If you exhaust all possibilities just rebarrel.
But like Pappy said, 2MOA will kill stuff just fine.

Mine liked 110 accubonds really well.

Whether the deer notice or not I just couldn't abide 2 MOA.

Never had much success with the 110AB in anything

I will get the 100BT to shoot but all I have left are pulled ones now....

In desperation I will try the 110's if all else fails...

My model 70 will only allow 2.850 OAL, but 2.825 works
pretty well. Most accurate bullet in mine is 115gr
Nosler Partition with 110 Accubond close behind.
Slower powders were a big help, like RL22,and Norma MRP.
I,m working on loads for RL23, RL26, and Rl17.

You could have the barrel set back and rechambered with a shorter throat.

To the OP:

I have a .257 Roberts in the 84M Montana. Yeah, the throat is long but it shoots several bullets well despite that.

It does real well with 100 grain ballistic tips and respectable with the 110 grain Accubond. It seemed to do ok with the 120 grain partition but I ran out.

It doesn't shoot for [bleep] with the 115 grain partition or ballistic tip nor with the 100 grain partition.

It would be worth trying your gun with 100 grain TTSX and 100 grain E-tips since both of those like some jump to the lands anyway. I have a number of other bullets to try still, just a matter of finding time.

I probably wouldn't use the 110 grain accubond on game again, the deer both died but there was a LOT of meat loss. Both bullets stopped between the ribs and shoulder blade on the off side and shook things real bad. Couple quarts each of purple goo ... 'bout the consistency of snot.

I wouldn't mess with the gun itself. Rebarrel, yes, try to open it up for longer cartridges, no.

Tom

I have a Kimber Select 257 Roberts that is more accurate with heavy bullets compared to light.


Shoots 117 SGK's very well.

Thanks Tom, Sam, etc.

Good info and thread, reminds me of the old days. Ask a legit question and get legit answers from guys that have experience....

Dave, I just went and looked at notes...



257 Roberts


44 grains H4350

117 SGK

Remington brass

CCI 200

2.800" COL


And according to that batch of brass it was on 9x firings but of course work up accordingly.

I guess I fall into the camp of trying more bullet / powder combos before modifying things. Both of my Kimbers (257 Roberts and 325 WSM) seem to be particular about what they like. Lots of loads in both shoot well enough to kill stuff, but they both have one load combo that stands out. I was a bit frustrated with the 257 until I tried the 100 TTSX with RL19...

I have 100TTSX and R19. I may have time to throw 3 together before Friday...I have some sort Sierra in my 25 cal box...thinking they are 100gr GK or Prohunters.

I have a Kimber MT in 25 Bob and have the same issue with mag box length v L&G location. Mine likes to shoot 1.5" groups - until I tried Ramshot Hunter. I run 47.5 gr under a 115 Partition and a Fed 210 seated to 2.82. A couple of things - first 47.5 is a +P load. It runs the 115 at 2900 in my rifle. Second 2.82 only has a couple thousands clearance.

My gun also likes H4350 and likes to shoot 4/5 into 3/4" and 1/5 to make a nice 1.25-1.5" group. The Hunter keeps them at 1". I haven't tried other bullets because ID rather have a 1.5" Partition group than a 1/2" cup/core bullet. I've shot enough deer with cup/core at 2900+ to know what is going to happen when bullet hits real bone. I had planned to try 100 TTSX if the Part didn't shoot. I'm cool with 1-1.25" groups in that rifle. It works well for its intended purpose.

In previous 25 Cal rifles I've had struggles getting 115/120 gr Part to group much better than 1.5". Conversely the 100 TSX has been stellar. I hated the on-game performance of the TSX which is why I don't use them now. I'm hoping the early issues have been resolved and the TTSX is the answer. I may try TTSX in my gun. I expect they'll shoot well - they have in the other 25 Cal guns I've owned.

Good luck and let us know what you find.

That... Modern speeds for the Roberts is right at the 2800-2850 area.. No one need to go further.. Personally, it's one of my favorite rounds and I was lucky enough to obtain a M70 FWT about 20+ years ago in pristine condition and it's just a total pleasure to shoot..

Snuck out to the range...getting better.
100BT and R17 shot 1" for 3 at a TOO hot 3180
80TTSX and H4350 shot 1.25 for 4 at a warm 3280

I will back those off a half grain or so and see....

When you say "too hot" and "warm" was the rifle telling you that, or was that your impression of the chrono output?

Both. Stiff extraction and fast speed

You should be able to sling the 80's at 3400fps without breaking a sweat

The reason I asked was comparison with Hodgdon 6mm Rem data for the same case with a smaller neck. The 257 should be capable of at least the same speeds.

Good analogy!

Will try the 80's R17

I am also concerned on the explosion factor with a 100BT doing 3100+

Try 100 grain Sierra Pro Hunters and H-4350 before you give up.

I am not giving up as I now have some definite promising loads....

According to my latest book, you're right at max speed for a 100 gr. boolit.. But if you're getting a bit of bolt-lift issues at that speed it's best to back it off about 50 fps and see what happens.


Oh, and I should have noted in my post above that I was referring to 117 gr. bullets.. My bad.

45grs R15 with 80TTSX - 3500fps (hot) 1.25" 4 shots (44 next time should be perfect at 3400)

45.5grs R17 with 100 Hornady SP - 3180 (warmish) 1" 3 shots (first 2 in one hole)

45grs R17 with 100 Partition - 3150 1.25" 3 shots (good load and not hot)

It's good enough now with any of these and will probably abandon the BT as these are all known to be tougher.

Thanks guys!

Thinking about a 243 Montana now.............

Anyone tried the 90 gr. GMX bullet? My Bob is a 700 Mtn rifle so I have COL issues too but I have had no issues shooting 117 Game Kings, 115 Partitions and 100 BT's & TTSX accurately. I did not get good results with the 110 Accubond but I only tried a couple powders and still have a few 100 on hand to try with other powders.

Don't be concerned.

The .257" 100 grain Ballistic Tip is one of the "thicker jacketed" models, and is designed for at least 25-06 speeds.

I know because I've sent quite a few through good sized mule deer and whitetail bucks from a 25-06, and seen them used on older cow elk. Quite often the bullets exited on broadside shots.

In addition, my Kimber MT 257 Roberts shoots 110 Accubonds really well.

Billy, what's your load and how does it shoot.

Thx

Brad,

The 110 Accubond load uses 45 grains of H4350. Not around my notes for exact speeds but seemed like 2950 or thereabouts. 3 shot groups are in the occasional 1/2" range on up to 1" depending on the day.

Mine isn't terribly finicky, likes several 100 grain and 75 grain bullets. Haven't messed with heavier. Love the little rifle.

100 grain Hornady soft point was good for 3 antelope this year. I think 4350 was the powder, but I'm in Mexico and can't look at the box. Maybe my reloading factory (dad) will chime in with the loads.

After the shot-

Brad,

Prairie Goat's 110 grain works well in my Bob's as well. Tis a good one to say the least!!

100 Hornady over H4350 is the load for Cheesys rifle. Same load I use in my Ruger except for seating depth. Quite a difference between the two rifles, but both shoot very well with this load. Sure wish that Ruger was as light as the Kimber.

This is good info. y Roberts is not a Kimber but shoots the 100 gr BT very well and I am too lazy to change bullets.Load is 46 -H4350, Remington brass.

this what they do at 300 yds, so far:

80TTSX at 3375 still has stiff bolt lift but shot well. 100gr Hornady shot 1-1.25 at 3150 and they are a little stiff also....
Dunno
Will back them off just a smidge and call it good as pressures just shouldn't be high at those velocities

Bob- what speed are you running with 46grs ??

May have found my pressure issue...saw this before but thought it was a die or brass issue...... Fired brass is also a PAIN to size, again I was thinking a largish chamber but there was no swelling at the web....
See pics>>

Possibly chatter marks in the chamber? Never had this happen so didn't even occur to me until today.

Confirmed the chamber looks similar so Back it goes to Kimber!

Dave I don't know velocity in this rifle. It's a Ruger Hawkeye and to be honest the first load I put together. OAL is a bit longer than your Kimber i think but not much.

That load gave 3050 or so in a Kimber Select I had.

Looks like you have a chamber issue.

Heading to UPS in a bit!!

Looks the same as the chamber that was on my Kimber 257. I sent it back they told me tough [bleep] it's within specs. I hope it turns out better for you.

If not I will polish it up and use it....

Got it back tonight.
Polished the chamber. Haven't unboxed it yet but I will see how it goes Friday.....

Try 3031 and see if that makes a difference.

Unboxed it and it does NOT look like they did anything.....

Chamber still has the linear chatter marks......

So much for Kimber repair.....👎👎👎

I took it shooting this AM.
I won't know if the little polishing they did helps brass appearance until I get some sized that hadn't already been marred by the chamber. I polished it just a smidgen more last night with steel wool.

Seemed like they didn't stick in the chamber quite as bad but still size hard unless you shoot soft loads.

It shoots well so I am not going to worry about it and I guess the 6 week cross country travel never hurt it....

Kimber Classic .308 with marked tight spot 2" from muzzle. Shot 1 1/2" on a good day. Kimber with same response, it's within spec. Theirs, maybe. Not mine.

23" Broughton 5C fixed that problem. Sub half inch.

DF

I would be surprised if steel wool would fix that. Maybe a fired case with a little valve grinding compound would work. You might end up with a slightly O/S chamber but could polish out your sizer to match.
Too bad they make such nice rifles but Barney Google is the QA inspector.

Yep I bought a bunch of seconds from MWUSA when they were CRAZY cheap. With a moderately warm load of Hunter in my 257 AI it's shot & killed beautifully.

I really like that bullet.