.30cal big bore PCP build
My mission is to build a light weight short .30cal big bore PCP from scratch suitable for taking deer and pigs with cast projectiles.
I have 3 different barrels to test with a range of twist rates and bore diameters for the range of .308 cast projectiles which are in themselves tunable in weight and balance with an adjustable depth hollow point.
Ive got my money on the 1-14″ twist .307.5 match barrel for the 105gr cast projectiles but also have a 1-18″ twist for 80gr -120gr projectiles and a 1-10.5″ twist shallow cut microgroove for up to 160gr projectiles.
This is the bullet I have chosen, it is a 115gr Lyman bullet
The mould has been modified into a hollow point that now casts a 95-110gr HP pure lead bullet depending on hollow point depths.
My goal is to get about 170-180ftlbs from this rifle so although making a bullet for a barrel before the rifle is even built may seem a little backwards but it was a big part of the R&D process for this project and I needed to be very sure there was a bullet that would suit my needs and will be stable at a lower than intended velocity range in one or more of my barrels. I pushed a sized one through the microgroove bore to get a feel of the bore friction and check out the rifling groove cuts in the bullet.. the weight and balance can be fine tuned by altering the hollow point depth and diameter at a later date if needed.
For the action I cut a piece of 1-1/4″ 6061 T6-51 alloy to length and skimmed one side down on the mill to 1″ to form the start of the receiver.
Then I marked the barrel/bolt centre, fitted up my 4 jaw chuck and drilled the pilot hole with a long series 8mm drill bit..
Followed by the 1/2″ barrel clearance size drill and a 10mm bore for the bolt.
I then cut the loading port for the feed tray and the 45 degree chamfers to pretty it up..
A little more milling and the basic shaping is done.. It will get a raius to mate up with the cylinder, transfer port and then the bolt and cocking pin cut outs on the underside..
A few more components to the list.. the rear plug is yet to be bored out and threaded for an external power adjuster/spring guide and the bolt still needs the probe, O ring groove and handle to be made.
The 1-14″ twist match barrel has been pre fitted and is ready for the transfer port to be drilled.
I have decided to use a modified German made Gecardo trigger because Im too lazy to make one from scratch.. 🙄
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Wow! Sub MOA with 100grains OUCH! Amazing work
Yup Im liking this 7.62mm too… it will be a bit of work horse so I didnt spend a lot of time on finishing etc but have plans of some really ornate and unique work on a future build..
I’ve just got done giving it a registered identity (legal requirement in arms manufacturing).. but still haven’t filled out the “model” box yet.. I’m stuck for a fitting name…
Those hundert grainers are good shooten sum bitches. I’m really liken that rifle wing!
With a huge THANK YOU to my big bore buddies Neil and Danny, I now have a good selection of .30 bullets to test in the pup today.. the sun is shining and there is not a breath of wind.. I will tether it and unleash the thunder on paper..
Heres the line up, Danny made me a double mould cavity with a 85gr HP and a 105gr HP to try too.
The first two bullets beside the .30cal JSB pellet are both his designs one has a bigger hollow point than the other. The 5th from the left is his new 105gr HP with a larger hollow point than my one which is an attempt to get a better performing deer bullet. All the rest apart from my duller looking 100gr HP in the middle are Neils bullets.
L/H to R/H: 47gr JSB, 85gr HP, 85gr bucket mouth HP, 118gr Flat Point, 105gr HP, 100gr HP, 128gr HP 132gr Spitzer, 158gr Spitzer, 163gr HP, and for a scale reference 8.44gr .177 JSB 18.1gr .22 JSB
To say it was nice to get out of the house and put 100+ shots through the .30 would be an understatement..
Here’s the results from several groups from each bullet at 100 yards prone of the rest.. some could be refined with velocity adjustments and different hollow point and sizing options but Im happy with the results I got.
Top group of the three
Middle group of the three
Bottom group of the three
Two groups from JSBs which are actually far too small for this barrel, they are designed for a .300″ bore not my .3074″ bore.. they did quite well considering..
The clear winners were the 100gr HPs with a 3/4″ group!
Top group
Bottom group, these new 85gr HPs from Danny consistently printed 1″ to 1.5″ groups and will be my “go to bullet for lighter game like rabbits and goats as they have better expansion and velocity advantages over the 100gr that I will use on larger game.
It seems to like the spitzers too, particularly the heavier 158gr which brings the theoretical down range energy up a touch but in real world tests on game the tend to pass through with little terminal damage unless tipped over and sent tumbling by contact with bone.. Still they have a draw card for me and the lower muzzle report, the increase in recoil and loud thump from down range from this heavier pill just seems to feel right in this pup.. the lighter bullets seem softer to shoot but really crack in comparison.
I think its time to strip it down for anodizing black then get it out bush ;D
One of the most beutifull and scenic places I’ve been to!
Only the Swedish Viper Vildo Ballbaggens, you must never look at his hairy feet..
I thought Hobbit’s were dangerous? 😆
Classic mix up with New Zealand and Australia mate… there’s nothing deadly here other than maybe a pissed off porker with a lump of lead that missed its mark…
No snakes or deadly spiders, no crocks or piranha.. just a few marine fish that have toxic spikes and a rare coastal spider that at best could only make you sick.
Weather has packed it in here over the last week so have not been able to test the pup again.. hope it clears soon.
Most of my deer hunting is inside 50 yards due to our steep thick woodlands I hunt in but at a push I might get a 100y shot up a river bed.
I certainly does have some recoil but the muzzle break has reduced that considerably. It doe require ear protection to shoot it comfortable for sure, I would liken the report to a 9mm handgun sound.. Im not worried about scaring everything in the forest as I normally hunt with a much louder centerfire, besides if I do my part I will only need one shot and the game on the receiving end wont hear a thing 😉
your lucky wingman to live in NZ. lots of places look serene like this
not so lucky cause just about everything is deadly there.
luck of the draw i guess.
keep up this pcp man, i have been reading and wanna see what it can accomplish at 100Y without wind
I have made them in the past but this one is a 20MOA one off my Steyr LG110.. its a little higher than the flat picatinny bar stock I normally machine them from also.
Nice work Phil. Question, where did you get the rail for the rifle? Did you make it from scratch?
Beautiful build and just marvelous countryside to enjoy as well. Can’t wait to see her first real work.
Most of my deer hunting is inside 50 yards due to our steep thick woodlands I hunt in but at a push I might get a 100y shot up a river bed.
I certainly does have some recoil but the muzzle break has reduced that considerably. It doe require ear protection to shoot it comfortable for sure, I would liken the report to a 9mm handgun sound.. Im not worried about scaring everything in the forest as I normally hunt with a much louder centerfire, besides if I do my part I will only need one shot and the game on the receiving end wont hear a thing 😉
LarryW 
Thanks Larry, Ive got a few more big bore builds on the go, a .44cal handgun and a .357 (9mm) carbine..
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You just have to love that serial number :8:
Loving your work Wingman, that is an absolute cannon !
The Cad