308 155 Scenar Load Question

[Skigolfmike]

So, I did some load testing with 155 Scenars a while back for my re-barreled 308. (Krieger 5R 11.25 twist) and I thought I had come up with a decent accuracy load. However, I discovered later that I had loaded the OALs about .011" to long. (I did not know that at the time.) Despite that, I saw no pressure signs running up to 45.8gr of Varget with CCI 400 primers in Lapua brass. The 45.4 gr load seemed to be the most accurate and it shot well at TVP out to 1000. However, it was about 20* colder at TVP and I started seeing mild pressure signs with flattened primers. MV calculated at 2920 fps.

So, I got home and measured the chamber to see what was going on. Turns out 155 Scenars are touching the lands at 2.829" and the ogive measures 2.192.

I backed the load off to .006" off the lands; however, now the accuracy is inconsistent. I was thinking of loading more test loads, but not sure what to try next. .002" off the lands, touching the lands, .002" into the lands? What next?

 

[phreakmode]

Re: 308 155 Scenar Load Question

Those projos are notorious for not settling in to an acceptable accuracy until they reach 2900fps. You more than likely will not get the required velocity for the 155gr Scenars using varget.

 

[ncboiler]

Re: 308 155 Scenar Load Question

The 155's are jump tolerant so you can play with the seating depth somewhat I would think.

If 2900fps is the number you're looking for you may look at the XBR 8208 as it's supposed to be temp insensitive. I have a buddy that has tried it and it always seems to chrono at 2870 fps. However his pet load is with Varget about the same speed, maybe a tad under 2900.

 

[Skigolfmike]

Re: 308 155 Scenar Load Question

According to Shooter using the Litz G7 BC, they were shooting 2920. That was with the bullet .011" in the lands. I have good dope from 300 to 1000.

I am thinking I can seat the bullet on the lands. Maybe I'll do some of each and see show they shoot.

 

[Dave-O]

Re: 308 155 Scenar Load Question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: phreakmode</div><div class="ubbcode-body"> Those projos are notorious for not settling in to an acceptable accuracy until they reach 2900fps. You more than likely will not get the required velocity for the 155gr Scenars using varget. </div></div>

I don't necessarily believe that statement to be true. My current 308 with a 23in barrel loves the 155 at 2880, the one before that was a krieger barreled remington that was happy at 2830.. Varget has enough oooomph for the 155, just need to find the happy spot.

To the OP.
Do you know what reamer was used to chamber your rifle?

 

[Skigolfmike]

Re: 308 155 Scenar Load Question

I'd have to call the 'smith to find out what reamer he used.

Using the Hornaday comparator, the 155 Scenar touches the lands at 2.192" and with 175 SMK it's 2.235". OALs are 2.829" and 2.825" respectively.

 

[Dave-O]

Re: 308 155 Scenar Load Question

I'm running the scenars .005 off the lands, ncboiler is running them at least .090 off the lands.
They are very tolerant to jump. Back them off and sneak back up on it.

 

[Skigolfmike]

Re: 308 155 Scenar Load Question

I tried backing them up to 2.800 for a .029" jump and that didn't seem to work well either. .011" into the lands was problematic as once it's in there, it's not coming out without pulling the trigger.

45.4 gr of Varget is a slightly compressed load at 2.800 OAL. I can't imagine loading much shorter than that. I could try .005" off the lands. I did notice there is enough variance bullet to bullet that the OALs can change up to .004 while the comparitor will only vary about .001".