Home Forums Hunting & Shooting Custom Rifles & Wildcats 7.62 x 45 Czech in Mini Action

Like to build a 7.62 x 45 Czech (but necked down to .308) with boxer primers in a mini-action with 2.43" COAL. Anyone run one of these? If so, what do you do for a continual brass supply?

Sounds fun. Buffalo Arms is the only place I know of that carries it. It is made from reformed 220 Swift brass.

You might consider the Barnes 308x1.5” or 308x1.75”. Another would be an improved .308x39 or 30BR pending bolt face…

I have wanted to do the improved .308x39 but have not got around to it.

I have been looking at building a mini bolt rifle in a smaller capacity 30 caliber. I have settled on having a 30 BR built on a Kimber. Wanted the reduced powder charge for running a short barrel with a suppressor. Interested to hear more about what your goal is for your rifle here.

The goal is to run 150's at around 2400 fps with temp. stable powder (Varget or H4895) in an extra-short action 6lb rifle including scope with a 20 " barrel. Need the case to hold around 36 grains of powder with the 150 projectile. Neither the 7.62 x 39 case or the 6.8 SPC case necked up holds quite enough powder. 4 rounds in the internal hinged floorplate mag.

The 30 REM AR would do all the above but you might have 3 down in the mag. There is still enough ammo and/or brass out there to keep it running. It’s a dandy little cartridge.

4 in mag is absolute minimum. 5 would be better. Design of 7.62 x 45 Czech is about perfect for what I want, after necking down to .308.

in a zastava the action opening is 2.29 the mag box is 2.35 . with 6.5G or 7.62x39 you can get 4 down and chamber over the 4th for 5.

I have a 7mm BR which was a 22-250 before. only 3 down and chamber one more.

Vol of water in cc

7.62x45 ==2.79
30 BR === 2.66
7mm BR = 2.56
7.62x39 == 2.30

Out of a 22" bbl 2400fps I can see.

7.62x45 = Sierra 150sp OAL is 2.36.

I'd probably go Howa over Zastava or CZ. more bottom metal options too.

It’s an interesting round. Biggest issue I had with the Russian case head rounds was settling on an action that did all I wanted with the right size bolt face.

I would NOT open a Zastava to a 284 (30rem AR) bolt face.

rim diam. and OAL

6.8 ==========.422=l==2.26
7.62r/grendel==== . 439===2.26
7.62x45======= .445===2.36


308 case =======.473

30 rem AR======.492===2.26

At 2400 fps and using 150 Speer BTSP, scope set at 2.8" high at 100 yds, zero at 200 yds, 4.5" down at 250 yds... for those interested. Rated at maximum 62,366 psi.

It does fill a niche above x39 cartridge but smaller than 308 size.

Did you find a mini rifle that fits?

Brass is formed from 220 swift?

You use a Howa mini action and swap out the plastic for an internal mag and hinged floorplate so you get COAL of 2.43". That will also give you the 6lb weight including scope. Put on a stainless 12 twist .308 barrel at 20" at .600" at muzzle so it balances right and to make weight limit. The case capacity is needed so you can switch from H322 powder to the slower burning H4895 or Varget which needs around 34-36 grains to get reasonable velocity with 150's with temp. stable powder. I have over 300 Swift cases, but would prefer to buy 1000 cases if possible, hence the post. 150's or 140's (but virtually none made) are needed to get complete penetration through the shoulder with their better sectional density, and the .308 hole gives a bigger hole on lung shots for any tracking and faster kills even with negligible expansion if using a hard projectile for mainly the shoulder. The bigger .308 bore gives a bit more velocity for the same weight bullet. A lot less recoil than a .308 and less blast.

Which bullet are you looking at using? I’m planning my build around the 110 and 120 gr TAC-TSX Barnes bullets. I have seen those bullets work well enough that I have faith in them.

I'll start off with the 150 Speer flat base Spitzer HotCors or 150 BTSP (inexpensive). All copper at lower weight should also work...I don't have experience with the 110 and 120 TAC-TSX. I know that the 110 TSX is magnificent in the 6.8 SPC on hogs.

The .30 cal 110 and 120 tac-tsx are designed for 300 blackout velocities. I used the 110 loads through a 9” sbr for a while on hogs. Bullet opens up quickly at those velocities while sticking together enough to penetrate. My experience was that a hit anywhere on a pig was enough to pin him in place long enough for a follow up shot. A hit in the mid section would put a basketball sized collection of guts out the exit wound.

My original plan was to try to build a 300 blackout or a 30 Ham’r. However, getting the characteristics I desired in an action built for a 223 case head was proving to be difficult. The 30 BR let’s me use the 308 casehead while still putting me in the right velocity window with 29 or 30 grains of H4198.

What action?

I wanted stainless, CRF, and 3 position safety in as trim a package as possible. So I had picked up a Kimber hunter on a trade and while messing with it I realized it gave me most of what I was looking for for this project.

I've also thought about the 30 BR on a Hunter! The factory 308 barrel should be able to be set back, to minimize expense. I've tried feeding of BR cases in the Hunter magazine, and they worked slick. So the Kimber Hunter seems like a good candidate for just what you're looking to do.

I’m probably going to go a bit further with it just because I’m that way. Going to have a carbon fiber stock put on it, custom profiled barrel of some sort to keep weight down but still have threaded. Stock will have some sort of internal box magazine. However, the 30 BR seems to match case capacity to velocity very well. Quick load shows with a 14” barrel I can push the 110 grains to 2500 fps and have about 86% of powder burned

If I were to make the 7.62 x 45 cases from .220 Swift brass, I would cut the Swift cases at the case body/shoulder junction (1.723") before running them through a full-length 7.62 x 45 sizing die. The case diameter of the Swift case at that point is .402 inches and it would need to be squeezed down to .341 inches to form the neck. Does anyone know whether squeezing down the cut-off case .061 inches would be easily done with a full-length sizing die without buying a forming die?

This is what Donnelly says.

Thanks for that. It seems that only a full-length sizing die is necessary as I suspected.

I ran a Grendel reamer into a 7.62x39 Howa mini to clean up to the shoulder, creating a .311 bore Grendel cartridge. Don’t think it was enough to get a 150 to 24-2500 fps, but it gave the 125’s a bit of a boost. Easy fire form with loaded Starline 7.62x39.

Would you happen to know what velocity you get with the 150's?

What dies are you using after the clean up?

Only shot 125’s, no 150’s. I have a Grendel bushing die w/ 30 bushing. Haven’t played w/ it much since I built it. Had several takeoff mini barrels and was just messing around one day.

Riflehunter,

Thanks for starting this thread.

I'm considering something semi-similar...

I've got a Rem. M7 in 300 Blackout, really love shooting subsonics, but I've also shot a lot of super's through it and have been looking at building something with a bit more zip.

So been looking at the 300 Ham'r, 150's allegedly at 2,300 fps (in a 16" barrel). No brass issues, should be easily formed from .223, plus Starline brass is avail., 223 bolt face... opens up a lot of rifle options.

Some of the above options sound intriguing too... particularly the Kimber Hunter.

Jerry

More like 2100 fps with 150's in an 18 inch barrel- see Hodgdon load data. To get reasonable performance in a .30 caliber, the case needs to hold about 36 grains or more IMO to duplicate .30-30 performance with 150's.

You're estimation is off a bit...

My Remington Model 7 in 300BO has a 16" barrel, shooting Speer's 150 grain bullet (#308150BLKGDB) I get approx. 2,150 fps using Speers load data for Lil'Gun. Granted this is the only powder they list as doing 2,100+ fps.

Regarding Speers load data, my results are pretty close to their velocity, except with Accurate 1680, which is a little faster in my rifle.

So, getting 2,150 fps in a 300BO, I'm confident that 2,300 fps in the 300 Ham'r should be doable... But I would like to see some real world data.

Jerry

It's often the case that the most accurate load is less than maximum. If they list 2154 fps as maximum, the accurate loading is quite probably somewhere around 2100 fps. Also, I don't usually want to be on maximum, unless the pressure isn't close to maximum (such as when the case is full). Do you know what barrel length Speer is using for its figures?

This is the Speer 150 grain 300 Blackout bullet load I settled on. As you note... I settled for less velocity for the accuracy, even though the faster loads were far from inaccurate. Probably couldn't do this again if I had to (note that it's only 50 yards);



16" Barrel.

Here's the first page with the details;