Hello James. I don't think it is the action that is the variable. I see this in A LOT of cartridge loads. I believe the variable lies in 2 areas. 1.) Variations in the diameter of individual barrels; and 2.) slight variations in the diameter of the bullets. Some bullets containing "pressure rings" etc... I think these 2 areas are where people see differences when all else is equal, such as the freebore..
6 BRA loads
- Thread starter waybones
- Start date
Now that is a stumper! Now you really got me...
Yea it has me as well. Only difference I can find is firing pin fall. The old M has .197 FP fall where the new one has .243 FP fall.
Those kinds of issues are beyond my capacity to ascertain.. You may be right about the firing pin fall.. That may very well be correct...
Jet
Gold $$ Contributor
Head space difference between the two actions using the same barrel? Your bolt should be interchangeable. Can you use the bolt from the old M in the new M and see if the problem goes away?
Good shooting
Rich
johnnyi
Gold $$ Contributor
Yes I have gone up to 31.0 grains with this 28” Krieger .237 bore 1:8 twist. At about 30.8 I believe the bolt started getting some resistance. If you go back to page 1 I showed the groups up to 31.0. I got a weird flier at the 30.8 and one of the lowest velocities was that low shot reading at that set. However I had another duplicate the velocity and the shot flew into the group... so you got me why I had this single low flier..? Then the 31.0 shot pretty nice group. One of the best in that series. I tried another series with the CCI 400 and ditched that test as I was already getting heavy bolt lift at 30.4. I believe 30.6 I nearly pierced a primer. Perhaps I have a odd batch of CCI 400 or ..? I’m not sure but I stopped as I didn’t feel comfortable with these results. So I flipped back to the CCI 450. And tested up to 30.6 in every .1 to see if the results repeated. All of them impacted nearly the same vertical quadrant, so that made me feel pretty good. I hope to retest again with some seating depths. My first go around I was testing at 600 with Varget and seemed the .003 to .010 off produced the best groups. So these H4895 I tested at .010 off. I will revisit the seating depth with the H4895 now.
johnnyi
Gold $$ Contributor
I fire formed 15 more after my test at 300. Mirage was pretty angry by the time I got to this stage. Looking at how this little bra fire forms it makes me keep chasing better results. Most of the shots went into that bughole. I may just slow the whole thing down and shoot some groups that will produce those 2750-2770 velocities!
. Here are a couple of 10 shot groups at 600 again fire forming...
This little booger shoots so well fireforming. The Red Bull is 2” for reference.
X-Caveman
Gold $$ Contributor
View attachment 1028543
I fire formed 15 more after my test at 300. Mirage was pretty angry by the time I got to this stage. Looking at how this little bra fire forms it makes me keep chasing better results. Most of the shots went into that bughole. I may just slow the whole thing down and shoot some groups that will produce those 2750-2770 velocities!
Here are a couple of 10 shot groups at 600 again fire forming...
View attachment 1028545
View attachment 1028546
This little booger shoots so well fireforming. The Red Bull is 2” for reference.
There are a few of us in the Dallas area that have been astonished by FF accuracy at short range with 8 twists and 105 class bullets. Same was true with my 12 TW and 80gr Berger flat base varmint. Problem is, we haven't been able to duplicate the consistency with full house loads.
I think a big part of our struggles is because we don't have access to longer ranges outside of matches. We're trying to tune & practice at 100 & 200 and shoot matches at 400-600. Recipe for mediocrity.
johnnyi
Gold $$ Contributor
All of my fire forming has been with 105 VLD and a mild load of Varget. 29.2 jammed about 15k. My next outing I will load up some remaining VLD’s to see what it does. Perhaps my barrel likes the 105’s a little better. Hard overlook when the slow FF loads shoot 2.5-3” @ 600. Search continues..!
urbanrifleman
Site $$ Sponsor
Maybe it's the hard jam making them shoot?
did you choose 30.4 because it has the tightest vertical or the smallest group?
These loads are using Lapua or Peterson brass?
Alex Wheeler
Site $$ Sponsor
Lapua. Those are ball park high nodes
ditto on that load
urbanrifleman
Site $$ Sponsor
I think that is exactly what I have been saying.
Just shoot it as 6br, win win.
It shoots better at the 6br node in my experience. Certainly more consistent. Lower pressure. Some actions flex too much for that kind of pressure is my guess.
The brass last forever, and never grows.
Happy accident I say. That 60 FPS does not make any difference. I will take small groups over that little bit of wind every single day.
.5 lower to start with Peterson I assume should be safe
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