breech seating bore diameter pp

[bruce moulds]

a contentious issue, but here goes.
previous thinking was that creedmoor was shot with fixed ammo, but recent reading of maj hinman suggested that at least at the end of the era breech seating was the norm. a recently posted photo of a famous shooter's reloading gear included a breech seater, which reinforces hinman.
local scheutzen shooters have been on at me to try breech seating for some time, so I had to go cap in hand to them seeking advice.
they recommended trying the bullet 1/16" to 1/8" in front of the case, and that best accuracy would come once the bullet base was in front of the leade angle.
my rifle has a 7 degree per side combined transition/leade angle, meaning that pure barrel diameter starts about 1/10" in front of the case.
experiments started at 1/16", which returned accuracy similar to the fixed ammo control.
at 1/10", the rifle came alive with a pronounced improvement in group size, and at 1/8" I could not believe how well shooting was happening. no point in going further.
I am not worried about ringing the barrel with this airspace using bore diameter pp bullets, as compressed air cannot be retained until the bullet bumps up, as well as the fact that none of the local scheutzen guys have ringed a barrel with small airgaps. time might prove me wrong, and if it does, it will be part of learning.
case was droptubed full of powder with a 0.060 wad level with the top of the neck. the odg used a "pasteboard" wad for this.
confetti was absolutely perfect, unlike fixed ammo where the bases were blown off, probably as the bullet cleared the transition.
this seems to be part of the reason for improved accuracy. total avoidance of the transition offers one less chance for inconsistency.
now it is necessary to shoot this ammo at all ranges from 300 to 1000 to see how it holds up, and if it does, go on out to 1200. this will probably take a year, a job requiring patience.
this ammo requires wiping, which can be dealt with in sil, but the added loading time would make things tough in this discipline.
long range paper shooting on the other hand could benefit from breech seating if vert is diminished significantly.
with bore diameter pp bullets, seating requires little force, eliminating the need to use a leverage device.
keep safe,
bruce

[Kurt]

Bruce.

I will give you some of what I have found breach seating bullets.

I have done quite a bit breach seating shooting on paper and snow to see what is happening to the breach seated bullets.
Breach seating does enhance the accuracy and I might start using it for the Creedmoor matches where I feel that there is enough time to load this way.
To cut down all of the typing I have trouble doing I will cut it short.
My best results breach seating is using a tool that will allow you to seat a PP bullet that is at least .003 over bore diameter. A palm seater is not the best for this because it takes a lot of pressure to get that diameter in the bore. What I found was that if I seat this diameter it fills the grooves and helps seal the bore to hold the gases back and prevents gas cuts because I just use a .012" card over the powder and I use a cup based bullet with a twisted tail tucked into the cup flush. This protects the bullet base from powder gradual damage. The tight bullet also holds a consistent lack of vertical by keeping all the gas behind the bullet.
I think that is what started the cup (not hollow base) bullet when they twisted the paper under the base and tucked it into the cup to keep flush mating with the over the powder wad.
I do not use lube when I breach seat but I have to wipe between shots.
I have not found any seeable difference seating the bullet deep past the lead or just in front of the case mouth.
I would take caution seating the bullet to deep with a compressed load of powder and even a thin paper wad in front of the powder to hold it in. If you look at the compressed powder in the photo you will see that the front of the compressed powder gets packed very tight starting at about .200" and .300" that hard compressed powder will act like a wad pushing a blast of air against the bullet base and this compressed air is what does the damage. How much of a gap does it take? I don't know because I do not want to find this out with my rifles.

Let us know your progress breach seating.

[Gunlaker]

Kurt, I remember you telling me about the slightly over bore diameter bullets. I haven't tried that yet but have had similar results to Bruce, although my rifles are .38's and set up for 200m shooting.

The only thing I've found is that a 0.060" LDPE wad seated under the bullet seems to seal well, but admittedly I've recovered none of the bullets. 200m accuracy is excellent with both rifles ( Winchesters in .38-55 and .38-50RH) getting very close to submoa ten shot groups. I'm not quite there yet, but getting very close.

Bruce I'd love to hear how it works out for you for long range, as well as any more historical stuff you find on the topic.

Chris.

[Don McDowell]

Good topic Bruce, thanks for sharing and thanks in advance for keeping us updated.

[bruce moulds]

kurt,
thank you for the reply.
that compressed powder certainly looks like a projectile!
that slamming into the back of a bullet could offer much unhappiness.
my scheutzen friend and reading suggest that droptubing is all that is required. most cases will hold sufficient powder for long range by this method.
their 38/55 cases are using 60+gns, and I use 85 to 90 gns in the 40/72, depending on powder lots.
your photo has convinced me not to try compression, at least yet.
with droptubed powder and a gap, you probably have loose powder at primer pop, but we will never really know this.
it is easy to confuse creedmoor ammo with bison hunting ammo as they are from the same era. as well, compressed charges have become the norm because of the domination of sil shooting with fixed ammo.
it is just a mental adjustment to pursue creedmoor ammo if that is your interest. long range accuracy is the priority at all costs, and the odg seemed to breech seat to be competitive.
keep safe,
bruce.

[bruce moulds]

chris and don,
I am determined to explore creedmoor to its fullest extent possible. I will update as time permits shooting to happen.
I hope others experiment with this technique and we all share the knowledge for mutual benefit.
chris if you are like me you would have been amazed at what these guns can do when fed right.
I did not know I could shoot that well!
those ragged one holers are lovely to behold, and when you are repeating that with 10 shot groups at 200 the stats start to suggest something.
in the pursuit of accuracy, you never quite get there as you say. you always have to seek more.
keep safe,
bruce.

[bruce moulds]

the opportunity arose today to shoot 300 metres at the fullbore club.
we shoot the same range twice, and I elected to shoot once with swiss 1f, and once with swiss 1.5f.
the 1f needed about 1 more moa on the staff than 1.5f, 85 gns of each.
both powders held similar vert, which was approx. 1 1/2 moa, shooting off cross sticks in the rain sometimes, and sun the rest of the time.
dropped 3 points the first range using 1.5, all being bad windcalls.
dropped 9 points using 1f, but this was in part not winding the sight up in order to compare elevation of the two powders.
both loads were capable of shooting a perfect score with a reasonable v count. (v is equivalent to the American x)
can we continue this as we go to longer ranges.
it was obvious that shooting on the open range makes accuracy harder to achieve than off a bench with sandbags.
part of the learning curve involved discovering logistical issues.
getting patched bullets to the firing line needs attention, as does protecting them from rain.
also getting charged cases to the line is an issue if the wads are not tight in the case mouths. I lost 2 wads and some powder from those cases, and it was lucky I had a few spares.
and it could be easy to forget to seat a projectile if you are more used to loading fixed ammo.
I have heard of this. it might be like crossfiring - there are those who have done it and those who will do it.
all in all the best vert I have shot, and a pbe score in one range.
adjustments of 1/2 moa are worthwhile for elevation to centre the group.
keep safe,
bruce.

[Gunlaker]

I've shot without seating a bullet a few times. You sure notice it when the rifle goes off and there is almost no recoil :-). That would be an easy way to loose a few points.

Chris.

[MikeT]

I have not tried breech seating my PP bullets yet [no time to play].
But, I was thinking when I get to that point, I will try a 1/8" cork wad that is partially out of the case mouth and then tapper crimp it to keep it in place.

Now, I have not considered how to transport and handle the PP bullets.
I was hoping that they will not loose the 'diaper' in transit.

This is very interesting stuff.

Keep on hav'n fun!
MikeT

[bruce moulds]

should have included this in previous post.
all testing was done with full wet and dry wiping, in order to establish true potential. bore condition was as consistent as possible.
when I shoot with the fullbore guys, I have 15 minutes to fire 10 to count, which can mean 12 shots, so I push a bore pig with a dry arsenal patch.
hinman commented on the need for an absolutely clean bore for every shot, amd he was right.
the pig, although good the way I do it is fairly good, is not perfect.
some variation can be felt when seating the bullet, and this is reflected on the target.
keep safe,
bruce.