.300RUM & .260 Results....

[Powerstroke]

So my Son & I made it out in the wind-blown flat lands today to do a little shooting before hunting season.
#1 To play with the .300RUM a little more to see if I can find a load I like.
(A) Unfortunately found two
#2 Shoot the remaining .260 bullets so I'm starting from ground zero on the cases again.

Question on the .260 however.... can & or how much does temperature play into the velocity role ? I had shot a group earlier this summer when it was fairly hot out that averaged 3500fps.
Today it was fairly cool and windy..potentially a 40 degree difference in temps. Todays average was 3460fps. Not that I'm complaining as I'm still really happy with this gun, just curious on the difference....?

 

[FOTIS]

Powerstroke:
Sir I am worried.....

Your 260 is shooting like a 264 win mag/ 100 grains at 3500 fps

300 rum like a 30-378 200 at 3365 fps and 180 gr at 3475 fps.

Everything is 200 fps or a little more than normal for caliber speeds. Unless you're using a magic powder .....you're pushing the envelope.

TINSTAAFL!

(There is no such thing as a free lunch.)


What are your loads exactly?

 

[JD338]

Powerstroke,

Nice shooting!
The 260 Rem with the 100 gr BT is smokin'! Great accuracy. ANy pressure signs?

The 300 RUM is almost there. Have you tried changing the COL? Might shrink those groups. What is your current load?

JD338

 

[Powerstroke]

POP,
I hear ya, and starting to doubt the chrony, but don't know how that's possible as long as it's opened up completely......Chrony aprox 12ft off the barrel.
.260 using H414 w/49.0 Grains ( Nosler #6 Max charge ) & 100 Grain B-tip. " my " COAL is .015 off the lands @ 2.8045.

The RUM
I backed off the max charge from last week because I was having hard extractions issues with the Retumbo so
97.5 Grains of Retumbo & 180 Grain B-tip again "MY" COAL is beyond magazine max @ 3.7840 and again 15 off the lands.

200 Grn A-bond with 91.5 grains of RL-25 " my " COAL is 3.7760

 

[JD338]

The RUM
I backed off the max charge from last week because I was having hard extractions issues with the Retumbo so
97.5 Grains of Retumbo & 180 Grain B-tip again "MY" COAL is beyond magazine max @ 3.7840 and again 15 off the lands.

200 Grn A-bond with 91.5 grains of RL-25 " my " COAL is 3.7760

Powerstroke,

Try seating your bullets deeper. Adjust your COL to fit the magazine, don't worry about how far you are off the lands and see what happens. This is how I load my 338 RUM. Lots of free bore but I get sub .5 MOA. :wink:

JD338

 

[FOTIS]

Your loads do jive as far as "safe" loads go but your speeds attest to other conclusions.

But the chrony is fully opened huh????????? :?

I had a 22" barrel 308 Norma mag clock a 200 grain Nosler Partition at 3100 fps!!!!!!!!
I rechecked the Chrony. Opened her all the way up and she did 2880 fps.

 

[Powerstroke]

These are the only two I've had concerns about... my .280 & .223 both shoot slightly below what the book claims.

JD,
I started out with the bullets @ magazine max length and havent' had much luck there.... that's when I decided to strecth them out close to the lands....I think putting the brake on the RUM will help me out more than anything with the groups.

I don't have any pressure signs on either ....

Other results are as follows....
130gr A-bond @ 2917 fps with 43.0 H414 ( shot at a previous time )
107SMK w/ 48.4 RL-19 @ 3169 ( also a a different time )

 

[JD338]

Powerstroke

What do you have for a recoil pad? My 338 RUM LSS factory recoil pad (the old style hard as a brick recoil pad that Remington used to offer) was replaced with a Pachmyer Decelerator pad. It made all the difference in felt recoil.
If you decide to go with Williams Gun Sight for their brake, let me know when you are ready. I will give Rob a call for you and grease the skids for ya.

JD338

 

[FOTIS]

Cartridge : .300 Rem Ultra Mag
Bullet : .308, 200, Nosler AccuBond 54618
Cartridge O.A.L. L6: 3.776 inch or 95.91 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : Alliant Reloder-25

Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-20.0 78 73.20 2517 2813 35757 10875 99.9 1.710
-18.0 80 75.03 2573 2940 38304 11024 100.0 1.659
-16.0 82 76.86 2628 3068 41051 11162 100.0 1.608
-14.0 84 78.69 2682 3196 43956 11297 100.0 1.559
-12.0 86 80.52 2736 3324 47023 11429 100.0 1.511
-10.0 88 82.35 2788 3453 50278 11558 100.0 1.467
-08.0 90 84.18 2840 3583 53735 11683 100.0 1.423
-06.0 92 86.01 2892 3713 57406 11806 100.0 1.382 ! Near Maximum !
-04.0 94 87.84 2942 3844 61306 11925 100.0 1.342 ! Near Maximum !
-02.0 96 89.67 2992 3977 65449 12041 100.0 1.304 !DANGEROUS LOAD-DO NOT USE!
+00.0 98 91.50 3042 4110 69854 12154 100.0 1.268 !DANGEROUS LOAD-DO NOT USE!
+02.0 100 93.33 3091 4244 74537 12262 100.0 1.233 !DANGEROUS LOAD-DO NOT USE!
+04.0 102 95.16 3140 4379 79521 12367 100.0 1.199 !DANGEROUS LOAD-DO NOT USE!
+06.0 104 96.99 3189 4515 84827 12469 100.0 1.167 !DANGEROUS LOAD-DO NOT USE!
+08.0 106 98.82 3237 4653 90481 12566 100.0 1.135 !DANGEROUS LOAD-DO NOT USE!
+10.0 107 100.65 3285 4792 96511 12659 100.0 1.105 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 98 91.50 3126 4338 83497 11827 100.0 1.181 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 98 91.50 2917 3778 55936 12627 100.0 1.388 ! Near Maximum !

 

[Powerstroke]

Why such the drastic velocity difference between quick-load and Nosler #6? RL-25 w/95.0 as Max = 3359fps ??

 

[Powerstroke]

Scratch the above.... I was using the 180 grain data....
Still.....91.5 grains of RL-25 ( max charge ) = 3185 fps ?? per No 6 with the 200 grain A-bond

 

[FOTIS]

Power. I have owned and played with over 20 300 RUMS. All of them did what I considered max with 91-92 gr of RL 25 with 200 grain AB at 3100-3150 fps.

BTW:

My 30-378 does 3268 fps max with 106 gr of Retumbo with 200 grain AB.

 

[Powerstroke]

Looks like I had better send the chrony back for calibration.... today was on a tri-pod... last week was just setting on a sheet of ply-wood.
Last weeks results were
93.0grains of Retumbo @ 3187 fps with 200 grn A-bonds
95.0 grains of Retumbo @ 3255 fps with 200 grn A-bonds

I did launch some 165grn B-tips today with the RL-25 that showed 3552fps with 96.0 grians. 168gr VLD's @ 3484 with the same charge...

Last week same sitting with the .280 showed...
55.0 grians of RL-19 & 150 grain b-tip @ 2860fps ( No 6 shows 2995fps )

57.0 grains of N-165 ( my go to load ) w/150 grain b-tips @ 2829fps ( No 6 shows 2923fps )

57.5 grains of RL-19 w/120gr B-tip @ 3035fps ( No 6 shows 3250 fps )

those would be more of what I would expect.... last weeks sitting was back and forth between the .280 & .300

 

[FOTIS]

Now.....These #'s I can swallow!!!
Ensure the apparatus is fully open prior to mounting on the tripod.

 

[Powerstroke]

Last weeks results were still high with the .300 though... only about 68fps over what books states, which is certinaly better than the 180 fps from today.
I'm still thinking
#1 Find another chrony and set them up side by side ie use another.

#2 Still send this one back for calibration....Hard pic to see, but can see the chrony from today in the background on the tri-pod. This tri-pod actually has an attachment that comes off the pod to make it easier to attach any components... with doing so it has a fairly large base to it that will make it almost impossible to not allow the chrony to be open all the way....

 

[Antelope_Sniper]

Powerstroike, I always figure I will shoot 100 FPS faster on a 100 degree day then I will on a 60 degree day. Yes, it makes that much difference.
So does Brass, primers, and barrel length. A change in brass and primers can give you an extra 100 fps as well.