243 to 6mm AI Savage donor barrel

[wildcatter]

I thought I would show the results with the first range trip testing the factory take off barrel I had rechambered for a fireform barrel. When I built my 6mm BR last year this was the barrel from the donor action, I had planned to keep it for whitetail and speedgoats.

But when I decided I needed more reach for varmints than the 6mm BR and started the 6mm Remington AI build I decided to make it the same chambering for a fire forming barrel to prep brass instead of unneeded wear on the premium barrel, and maybe hunt with having a little more oomph.


I didn't expect a lot, but was hoping to get around 3100 fps from the Sierra 100 grain Pro Hunters w/ somewhere around 3/4 moa accuracy. So after blowing the 50 8x57 Lapua cases I had formed to 6mm Remington, I turned the necks to a loaded 272 dia for the 274 chamber throat. It was time to see how this thing would shoot on it's original action, and get some idea if it was capable to my standards for a hunting barrel. Keep in mind it is only a 22" sporter barrel, I was happy with both accuracy and the performance of the load for a first guestimate range trip!

This barrel is not only capable of 400 yard or a little better hunting accuracy for both whitetail and speedgoats, it proved to be quite stable. It is only 3 shot's at 46 grains of H-4831, but those three shots gave me an extreme spread of 8.31 fps for an SD of 5.19! Not shabby velocity for a short barrel either at 3053 fps av. with an approx. .478" group. That was starting with a fresh clean barrel.


I also took along 47, 47.5, 48, 48.5 and 49 grain loads with the 100 Pro Hunter flat base Spitzer seated to .005" cram, to see where pressure started showing to much. 48.5 started show a change in bolt lift, and 48.5 it was obviously stiffer, not hard but I stopped their and didn't shoot the 49.0 grain load. But I think after shooting 47, 47.5 and 48 grain loads into just over 1/2" long hole, and recording my velocities for each somewhere around 47 and 47.5 grains I will get as good of groups and hopefully as consistent of an ES. with a little improvement in speed. But the 48.5 load was just low and left of the 3 shots in this photo, and feeling a slight difference in bolt lift, as well as less velocity gain, I will call 47.5 grains of H-4831 with .005" cram and ww-Mag Primers my max load with this bullet and powder.


The speed for each shot recorded with the 100 grain Sierra Pro Hunter in Lapua brass with a loaded neck dia of .272" for 274" chamber neck, is as follows
3 shots @ 46 grains H-4831 Fed 215 primer 1st clean barrel shot 3044 fps,
2nd-3053 fps,
3rd-3053 = 3050 fps w/8.41 ES and 5.91 SD when I can cover 3 with dime from a cold clean barrel, I consider that a useable hunting load!


Then one shot each using ww-mag LR primer notice the change of primer here!
47.0 grain H-4831 3104 fps ***
47.5 grain H-4831 3148 fps ***
48.0 grain H-4831 3176 fps
48.5 grain H-4831 3197 fps

The last shot I took was with one case I had loaded at 49.0 grains with IMR-7828 using the Berger 108 gr. Elite Hunter, also with a .005" jam. This is the powder I plan on starting with and bullet in the new 6mm AI build when I start load development. In this short 22" 1-9.5 twist barrel it gave me 3167 fps with no signs of pressure in this barrel. I will start 1 grain lighter in the 27" 1-8 twist .336" bore Krieger when Fred say's we have a go! I think this would be around 3350 fps in that barrel if pressures allow, and I think I'm still going to be able to go a little more before I see pressure being an issue, but we will start 1 grain lower and see?


All in all, I went home with a grin on my face, and happy I didn't get rid of this little 243 barrel when I built the 6BR, in fact I am now wondering just how good the factory stainless 30-06 barrel would shoot I took off the stainless Axis action I'm using for the donor on the 5mm Remington AI. I'm also setting the standards much higher after this on the new build with the heavy Krieger barrel!

But even if I got lucky with that first 3 shot test, and that is the best this little barrel will do using the 100 grain Pro Hunters, I'll hunt quite confident, and I sure won't put a whole lot more into my testing for this load. But I am going to shoot 47.0, and 47.5 grains and see how consistent they shoot. But I'm thinking between them I will have my best load with my most efficient velocity around 3125 for this barrel and bullet?

 

[AckleymanII]

Maybe a safe option to start 2.0g lighter load in your 8t, and 3 would not be unreasonable....no need in blowing the primer pocket on a great piece of brass. Used barrel bore dimensions should be larger than the new barrel.

Web on my Win brass measures .466-.467 in the web, what does the lapua brass measure in the web?

 

[wildcatter]

Overall the cases I have untouched measure .4694" to 4697" The brass I have fire formed trimmed to min length 2.222" and neck turned to .271" for the .274" chamber neck, using this 8X57 IS case are weighting within .4 grain of each other with 50% hitting right on with each other, surprisingly consistent for such a large case. I expect this brass to be the best choice one will find for this task. We will see after some firing, as I will be standing on these loads as long as I can find a top end window to load in.

 

[AckleymanII]

Have you determined the web dia in your chamber?

untouched brass measures .4694-.4697 unfired, so what is the dimension after a stiff fire form load or twice fired brass? Many of us struggle with these dimensions, and you are the pioneer on this lapua brass.

Thanks in advance

 

[wildcatter]

This is getting better and better! Getting bored so I broke out 67 rounds of the old Berger MEF 80 grain Varmint loads I had left when I retired the 6mm AI Pence barrel over 20 years ago, (the one I just cut down to 21.5" from 27.25" and chambered for this Axis in 6mm BR Norma). This was loaded with Remington 6mm Remington Brass Turned for the then tight neck .265" chamber, ww Large Rifle Primers, using 50.0 grains of H-4831 Powder in the old cardboard containers. Back then it would agg 1/4" at 100 yards in the original rifle they were developed in

Freds Reamer uses less free boar, for better seating of the 108 Elite as we set up this factory fireform barrel to be the same as the new Krieger build that is in progress. So I ran them through the Wilson seater to the same .010 cram the 100 grainers were seated to. Over 20 year old ammo, that was worked up in a 27" hand cut rifled Pence barrel, on a 722 Remington action some 22 to 25 years ago. Who woulda thunk it?


I was not expecting to get less than 1/4 moa groups, but that's what the target on the left proved, and since they were only three shots, and this was starting fresh, including the first shot out of the freshly cleaned barrel, @ 100 yards this was average for the load from that old barrel in the Remington that I developed it for years ago that weighed 17#.

I decided to not risk ruining the three shot group with a wimpy factory Axis Barrel heating up, and knowing I would never use this barrel for anything but field use where one shot or 2 at the max would ever be used for varmint at one time.


So knowing I was hitting a little right, but no flags out in a good wind out o the s-sw as we were shooting to the north, I decided to just take 1/2 the windage out and leave the elevation alone. As I wanted to move to 200 yards and make that my zero range for this Rapid-Z Varmint reticle in the 6.5-20 Conquest MC to work for the 6 100 yard aiming points.

As you can see in the target on the right, I was holding center bull and hit high and left, but still with no flags I'll let the windage alone till I can make certain it's correct on a calmer day with flags, but wanted the elevation dead nut. So after moving the elevation down I held center of the first two shots that were 1/2" apart and fired the 3rd proving shot, and prove it did. Had I held center of targets for windage like I should have, and in line with the first two shots for elevation,,, well I would have hit right between the first two. I still don't know why I didn't but I'm sure when I set final windage, this old ammo will get finished off in the field and I can count on 1/4 moa accuracy from it.

I am getting very anxious for this new build, but the more I play with this factory barrel, the more impressed I am, plus the more I am expecting from the new gun when it is finished.