IMR 4831 and new bullets

[JohnyRingo]

I am currently shooting a Browning XBolt 300 H&H Mag with 180 grain Accubonds with 67 grains of IMR 4831. I am getting decent accuracy, around 1 MOA, but I have 3 other rifles that shoot 1/2 MOA. I am considering changing bullets to see if my rifle likes those bullets better. The issue I have is that my rifle has a detachable box magazine that only gives me about 3.644" of COAL.

The 3 bullets I would like to try are all longer than the Accubonds (1.380" and .507 B.C.) I am currently using. I am looking at the Barnes 175 grain LRX (1.472" and .508 B.C.), Barnes 180 grain TTSX (1.488"and .484 B.C.) and the 174 grain Hammer Hunter (1.4" and .484 B.C.). With the Accubonds, I already feel like bullet is slightly compressing the powder. If I go with a longer bullet, it will only get worse. Plus, I am having a little bit of a feeding problem at 3.644" and was going to try 3.62".

I'm kinda leaning towards the LRX because of it's equivalent B.C. to the Accubonds over the Hammers because of it's lower B.C. Hammer bullets advertise their B.C. at .247 G7. If you convert it to G1, it comes out at .484, which is lower than the Accubonds.

Anyway, I am just wondering if compressing the IMR 4831 a little more to accommodate the longer bullets is going to be a big problem. The only other powder I have is the IMR 4895 and that is too fast for larger bullets.

 

[Jud96]

I would adjust your seating depth with the load you're shooting now to see if the groups tighten up.

 

[JohnyRingo]

I would adjust your seating depth with the load you're shooting now to see if the groups tighten up.

Yep. This was something I was going to try as well. I just felt that I can't go any longer, so shorter is my only option. I would be in the same boat with compressing the powder do this as well.

I've also kicked around the idea of trying 165 grain Accubonds, but I elk hunt with this rifle and would rather stay around 180 grains. I shoot Accubonds in all my rifles with IMR 4831, so I know it's a good combination, but maybe not in this rifle.

 

[Jud96]

You may not have to seat them much deeper to find accuracy. I would just step back in .005 increments and see how they shoot. I would also buy a drop tube and use that when charging your cases. I recently started using one and I gained about a 0.5gr of case capacity in my .284 and no longer have a lot of powder compression.

 

[GLTaylor]

A drop tube will be your friend. 6" makes a huge difference.

 

[Another Casual]

If you're slightly compressed now without doing anything to settle the powder, a drop tube may make enough of a difference to try the newer bullets. Won't know until you try!

 

[JohnyRingo]

Thanks fellas for the advice. I didn't know this thing even existed. I own RCBS reloading equipment and I see that they sell a drop tube kit. I will check into it.

 

[GLTaylor]

Or you can make your own with an old powder funnel, piece of tubing and tape (my current version).

 

[JohnyRingo]

I did some reading yesterday and maybe I am diving down the wrong rabbit hole. My last 5-shot group with the Accubonds was right at 1 MOA with an ES or 26 fps. What I read is if the ES spread is that good, then I should be looking at barrel harmonics.

 

[GLTaylor]

Have you tried diff seating depths?

 

[JohnyRingo]

No. See below.

 

[JohnyRingo]

Have you tried diff seating depths?

Not exactly. I shot factory ammo through the rifle when I first bought it to break the rifle in and to accumulate some brass. I noticed that the teflon tips where being damaged in the detachable box magazine from the recoil, so I loaded my first batch of reloads just long enough to fit into the box. This took care of the damaged tips issue. They are still a little long because I have had some feeding issues. I'm at 3.64" and I was going to try 3.63" or 3.62" and reduce the powder charge a little.

I started at 65 grains of powder and increased by 0.3 grains until I got to 67.5 grains, which showed the best accuracy and an ES of 26 fps. With my limited knowledge of hand loading, I just assumed that once I found the load that did not increase velocity with a larger powder charge and had a real small ES, then my accuracy would be great. I am wanting better than 1 MOA and I am all ears to messing with the seating depth.

 

[GLTaylor]

Do you have any idea how far you are off of the lands? I see OAL listed as anywhere from 3.515 to 3.700, depending upon the bullet used. That's a bunch!

Max charge for 4831 is listed as 73.0 grs, so I am surprised you are already somewhat compressed. I believe you definitely need a drop tube - but not sure you can gain 5 more grs of powder with it. That's also a bunch!

I usually find where "0" is (touching the lands) and start seating depth testing at .020 off the lands. If I jump more, it is usually in at least 10 thousandths increments. For Bergers and other VLD designs it can be MUCH more. Same with Hammers, which are my favorite. They are very insensitive to seating depth.

Edited to add: feeding is most important. Shorten cartridges until they feed flawlessly. Then re-work your loads from scratch.

 

[JohnyRingo]

Do you have any idea how far you are off of the lands? I see OAL listed as anywhere from 3.515 to 3.700, depending upon the bullet used. That's a bunch!

Max charge for 4831 is listed as 73.0 grs, so I am surprised you are already somewhat compressed. I believe you definitely need a drop tube - but not sure you can gain 5 more grs of powder with it. That's also a bunch!

I usually find where "0" is (touching the lands) and start seating depth testing at .020 off the lands. If I jump more, it is usually in at least 10 thousandths increments. For Bergers and other VLD designs it can be MUCH more. Same with Hammers, which are my favorite. They are very insensitive to seating depth.

Edited to add: feeding is most important. Shorten cartridges until they feed flawlessly. Then re-work your loads from scratch.

It would be a good idea to see where 0 is to see how far I am away when I am able to feed cleanly. In my old Rem 700, I used the bullet in a spent case trick to measure 0.