The 7mm Geramo.....Shooting It Tomorrow

[jackieschmidt]

This cartridge is a Lapua 6.5x55 necked to 7mm and Ackley Improved. The reamer was ordered by Geramo Villarreal, hence the name. It features a .313 neck and a throat to accept 168 to 190 grn bullets.

I spent some time getting all three of our rifles with identical chambers. Ed Bernabeo, Geramo, and are headed to Walker County tomorrow to shoot at 400 yards.

Here is the Parent case, the case after “blowed out”, and the finished cased after neck turning to .013 thick.

The way I fireform the case is I took a old junk 6.5 x 55 barrel and drilled the throat out to .284. I then reamed it with the 7mm Geramo. When you fire a factory 6.5x 55 round in it, what comes out is a fully formed 7mm Geramo, ready for neck turning.

My rifle is Bat M action, Shehane Stock, 32 inch 1-9 Krieger straight 1.250, Bix & Andy trigger, Valdada 36x scope, ....

just a fun gun.

http://forum.accurateshooter.com/at...5/?temp_hash=0bf8ace1f6273a2f22c0f1ee247e1c92

http://forum.accurateshooter.com/at...7/?temp_hash=0bf8ace1f6273a2f22c0f1ee247e1c92

 

[rardoin]

Jackie, I was up in Oklahoma at the prone state championship matches. A couple of shooters were using a cartridge that is essentially a 40deg shouldered/taper blown out necked up 6.5 x55 case. The designer said it is like a 6.5 x55 Bob Jourdan AI necked up to 7mm. They were running 180 or 184gr Bergers, forgot which one, at 2850 fps and the cases were not getting any signs of overpressure. He said it was capable of getting up to 3000fps. I think your case could shoot a heavy 7 with very repectable and competitive velocity for the LR game. The targets of the gentleman I speak of were very impressive at 1000yds and were competitive with the .284's and 300 WSM's on the line.

pm sent

 

[jackieschmidt]

We were not able to make it to Walker County yesterday to shoot at longer ranges, so we went to our home clobber at Tomball at did load testing at 200 yards.

All three of our rifles are chambered identically. I decided to concentrate on the Hornady 162 grn ELD Match. I had 4831Sc, H1000, and Reloader 25 to work with.

Ed and I shot the 162, Geramo concentrated on the 180 Berger Hybrid.

We worked up loads over Ed’s chronograph. The H1000 proved to be the best powder overall. I settled in on 57.3 grn of H1000 with a light jam, .308 bushing.

shooting over a 4 flag set at 200, I got the Rifle shooting at a pretty close to a 1/4 minute of angle agging capability. Geramo got his rifle with the 180’s shooting equally well. In fact, all three of our Rifles shot quite well.

Velocity out of my 32 inch Krieger averaged in at 2940 FPS, with a pretty decent velocity spread of 10 to 15 FPS in five shot group, with a SD of just under 5.

Geramo loaded me five of the 180’s, average velocity was around 2840.

We had zero pressure problems. Primers stayed tight all day. Bolt lift was effortless.

Here are a few of the better groups I shot with the 162’s, and the one I shot with the 180’s.

I had some other loads with great velocity spreads, but locked into a horizontal tune at about 1.2 inch at 200. My next step will be to add a tuner to my barrel. I figure a 10 ounce tuner will do the trick.

One note. This Lapua 6.5x55 brass is some of the best I have ever seen. Maybe it’s because this round is so popular in Europe. Even though we are using a .313 neck, which requires about a .003 neck turn, I think you could use it in a chamber with about a .316 neck and not turn.

 

[gunsandgunsmithing]

We were not able to make it to Walker County yesterday to shoot at longer ranges, so we went to our home clobber at Tomball at did load testing at 200 yards.

All three of our rifles are chambered identically. I decided to concentrate on the Hornady 162 grn ELD Match. I had 4831Sc, H1000, and Reloader 25 to work with.

Ed and I shot the 162, Geramo concentrated on the 180 Berger Hybrid.

We worked up loads over Ed’s chronograph. The H1000 proved to be the best powder overall. I settled in on 57.3 grn of H1000 with a light jam, .308 bushing.

shooting over a 4 flag set at 200, I got the Rifle shooting at a pretty close to a 1/4 minute of angle agging capability. Geramo got his rifle with the 180’s shooting equally well. In fact, all three of our Rifles shot quite well.

Velocity out of my 32 inch Krieger averaged in at 2940 FPS, with a pretty decent velocity spread of 10 to 15 FPS in five shot group, with a SD of just under 5.

Geramo loaded me five of the 180’s, average velocity was around 2840.

We had zero pressure problems. Primers stayed tight all day. Bolt lift was effortless.

Here are a few of the better groups I shot with the 162’s, and the one I shot with the 180’s.

I had some other loads with great velocity spreads, but locked into a horizontal tune at about 1.2 inch at 200. My next step will be to add a tuner to my barrel. I figure a 10 ounce tuner will do the trick.

One note. This Lapua 6.5x55 brass is some of the best I have ever seen. Maybe it’s because this round is so popular in Europe. Even though we are using a .313 neck, which requires about a .003 neck turn, I think you could use it in a chamber with about a .316 neck and not turn.

It may seem counter intuitive Jackie, but your 32" 1.250 straight actually has more muzzle deflection(less stiff) than say a 23-24" hv bbl. I mention this because you stated you thought a 10 oz tuner should do the trick.

As you know, I've done tons of tuner testing and much of what I've learned is quite intuitive. Some, not so much.

Lilja has a barrel stiffness calculator as part of his weight calculator program. It's interesting to put different numbers in and see the results.
https://riflebarrels.com/computer-software/

 

[jackieschmidt]

I agree. But it’s difficult to get 2900+ FPS with a 24 inch barrel. I had this barrel, I figured I would use it.

I have had tuners of my own design on my short range Benchrest Rifles for years. I was one of the NBRSA members who openly campaigned to legalize tuners in registered competition.

I tune a HV 22 inch 30BR barrel with a 5 ounce tuner that also includes a dampener. The 10 once figure is kinda pulled out of the air. Since this is an ongoing project, I can try different weights.

 

[gunsandgunsmithing]

I agree. But it’s difficult to get 2900+ FPS with a 24 inch barrel. I had this barrel, I figured I would use it.

I have had tuners of my own design on my short range Benchrest Rifles for years. I was one of the NBRSA members who openly campaigned to legalize tuners in registered competition.

I tune a HV 22 inch 30BR barrel with a 5 ounce tuner that also includes a dampener. The 10 once figure is kinda pulled out of the air. Since this is an ongoing project, I can try different weights.

I do remember you campaigning for them. That wasn't my point. It was in regard to barrel stiffness being not what we assume and the reasoning for changing weight of what you know works on a barrel of similar stiffness, relatively. Just play with the calculator I linked. Good info there if you care to check it out.

 

[jackieschmidt]

I do remember you campaigning for them. That wasn't my point. It was in regard to barrel stiffness being not what we assume and the reasoning for changing weight of what you know works on a barrel of similar stiffness, relatively. Just play with the calculator I linked. Good info there if you care to check it out.

When I get home, I’ll get on my wife’s laptop and download that. My IPad won’t do it.
I’m in a learning curve with barrels this long.

 

[gunsandgunsmithing]

When I get home, I’ll get on my wife’s laptop and download that. My IPad won’t do it.
I’m in a learning curve with barrels this long.

It's interesting to put in different contours and see the results. It's very common for folks to believe a barrel of whatever length, is stiffer, just because it's bigger around. You can modify the contour just about any way you want in the program.

I find it a good tool.

 

[gunsandgunsmithing]

Before, I used an indicator and a fixture to hold the barrel in a mill vice to measure how much the barrel would deflect with a weight at the muzzle. The program is way easier and very precise.

 

[MattPeetz]

Jackie

Do you know the water capacity of the case? Just wondering it’s relation to the shehane.

 

[jackieschmidt]

Jackie

Do you know the water capacity of the case? Just wondering it’s relation to the shehane.

it obviously has less capacity than a 284 based chambering. That 57.3 grns of H1000 comes just a tad below the neck shoulder junction.

The load with the 180 Berger was also with H1000 That 2840 fps average velocity is within about 150 fps of what most shooters shoot the 180 in a 284.

I think this is a very efficient case.

 

[MattPeetz]

it obviously has less capacity than a 284 based chambering. That 57.3 grns of H1000 comes just a tad below the neck shoulder junction.

The load with the 180 Berger was also with H1000 That 2840 fps average velocity is within about 150 fps of what most shooters shoot the 180 in a 284.

I think this is a very efficient case.

The 2840 is right there where most shoot the 180’s in 284. No one is shooting the 180’s 2990 in a 284


It’s an interesting case

 

[SweaterDood]

Jackie,

What OAL and freebore are you running?
Also, was the .316” dimension for no-turn neck the brass dimension or chamber neck ID?

Really interested in this cartridge for a second barrel on my XM action. Just odd enough and minimal effort to get there.


Thanks,

Chris

 

[jackieschmidt]

Jackie,

What OAL and freebore are you running?
Also, was the .316” dimension for no-turn neck the brass dimension or chamber neck ID?

Really interested in this cartridge for a second barrel on my XM action. Just odd enough and minimal effort to get there.


Thanks,

Chris

I will measure the overall length tomorrow. It will be with the 162 Hornady ELD Match.
The chamber neck is .313.

 

[sandwarrior]

Wow! I'm glad this cartridge got a name and some furtherance in it's development. Back in the mid-eighties, just after I had gotten out of the Army, I hung around Ron Ryders gunshop. It was actually Skip Talbot and Wes Ugalde's. Or, at least they were the senior partners.

Anyhow, this very thing was one of the cartridges Skip was experimenting with. He then gravitated first to 6.5mm, then to the 6mm's and this 7mm got dropped. Without a name, just a number. Keep in mind that back in the '80's we really didn't have the BC's in 7mm that we do today. The Sierra 175 SMK was rated at .711, but in reality, was nowhere near that. It wasn't until Berger came along with the 7mm VLD's that we really had some BC in that caliber. Now, we're finally getting more high BC 7mm bullets.

This cartridge is about perfect for the heavies in 7mm. I've been shooting a 1-8" twisted 7mm-08, but many times I've wished for just a bit more cartridge. I don't need a magnum, just a bit more oomph. FWIW, one of the reasons Skip played with this cartridge is because he could get Lapua brass. And, as you know, can run it hotter than any other brass. At my age, I'm happier to make the brass last. Lapua does that.

I have a Dumoulin Mauser or an M85 Parker Hale that I am considering putting this cartridge into. Feeding will be a trick. Maybe consider blowing the shoulder forward to 40 deg., but not blowing it out? Possibly even blow the shoulder forward .026" for a smidge more capacity. That's for feeding from a magazine. I fully understand what you're doing with a cartridge like this for F-Class and single feeding, though.

 

[SweaterDood]

Wow! I'm glad this cartridge got a name and some furtherance in it's development. Back in the mid-eighties, just after I had gotten out of the Army, I hung around Ron Ryders gunshop. It was actually Skip Talbot and Wes Ugalde's. Or, at least they were the senior partners.

Anyhow, this very thing was one of the cartridges Skip was experimenting with. He then gravitated first to 6.5mm, then to the 6mm's and this 7mm got dropped. Without a name, just a number. Keep in mind that back in the '80's we really didn't have the BC's in 7mm that we do today. The Sierra 175 SMK was rated at .711, but in reality, was nowhere near that. It wasn't until Berger came along with the 7mm VLD's that we really had some BC in that caliber. Now, we're finally getting more high BC 7mm bullets.

This cartridge is about perfect for the heavies in 7mm. I've been shooting a 1-8" twisted 7mm-08, but many times I've wished for just a bit more cartridge. I don't need a magnum, just a bit more oomph. FWIW, one of the reasons Skip played with this cartridge is because he could get Lapua brass. And, as you know, can run it hotter than any other brass. At my age, I'm happier to make the brass last. Lapua does that.

I have a Dumoulin Mauser or an M85 Parker Hale that I am considering putting this cartridge into. Feeding will be a trick. Maybe consider blowing the shoulder forward to 40 deg., but not blowing it out? Possibly even blow the shoulder forward .026" for a smidge more capacity. That's for feeding from a magazine. I fully understand what you're doing with a cartridge like this for F-Class and single feeding, though.

I would be running it in a repeater in the full Geramo/BJAI shape. I currently run a blown out and forward 40* .257 cal wildcat. It’s basically a 257 Rob AI, but with slightly less taper even, and retaining the 40* shoulder. I don’t have any issues feeding in my XM action, but there is a small reliance on magazine spring force. It doesn’t like to feed the last round as well, but my mags are 12rds, so just run a dummy at the bottom.

I have also noticed that the shoulder location has the potential to affect feeding as well in my mags. Since my case is based on the 7x57mm the shoulder is forward of the Swede shoulder. That translates to the cartridge needing to travel further forward before the shoulder/case body contacts the follower ramp for that extra pitch upward. With a .257 caliber this seems to have a greater effect since the case neck doesn’t contact the forward portion of the follower. I believe a .284 caliber would have less issue, if any, because of the larger neck diameter. I know for a fact that .308 caliber is not affected in this way, since I can long load a 308win to the same 3.200” and feed flawlessly despite the shoulder location being significantly rearward of the follower ramp.

 

[SweaterDood]

Jackie,

Were you ever able to get an OAL measurement? Also, do you know the distance to the neck/shoulder junction, from the base?

Thanks again.

 

[Dimner]

We were not able to make it to Walker County yesterday to shoot at longer ranges, so we went to our home clobber at Tomball at did load testing at 200 yards.

All three of our rifles are chambered identically. I decided to concentrate on the Hornady 162 grn ELD Match. I had 4831Sc, H1000, and Reloader 25 to work with.

Ed and I shot the 162, Geramo concentrated on the 180 Berger Hybrid.

We worked up loads over Ed’s chronograph. The H1000 proved to be the best powder overall. I settled in on 57.3 grn of H1000 with a light jam, .308 bushing.

shooting over a 4 flag set at 200, I got the Rifle shooting at a pretty close to a 1/4 minute of angle agging capability. Geramo got his rifle with the 180’s shooting equally well. In fact, all three of our Rifles shot quite well.

Velocity out of my 32 inch Krieger averaged in at 2940 FPS, with a pretty decent velocity spread of 10 to 15 FPS in five shot group, with a SD of just under 5.

Geramo loaded me five of the 180’s, average velocity was around 2840.

We had zero pressure problems. Primers stayed tight all day. Bolt lift was effortless.

Here are a few of the better groups I shot with the 162’s, and the one I shot with the 180’s.

I had some other loads with great velocity spreads, but locked into a horizontal tune at about 1.2 inch at 200. My next step will be to add a tuner to my barrel. I figure a 10 ounce tuner will do the trick.

One note. This Lapua 6.5x55 brass is some of the best I have ever seen. Maybe it’s because this round is so popular in Europe. Even though we are using a .313 neck, which requires about a .003 neck turn, I think you could use it in a chamber with about a .316 neck and not turn.

@jackieschmidt

Did you every get back to playing around with this cartridge? I'd be interested to see what you think a few years later.

 

[jackieschmidt]

Just too busy to mess with it lately. We do not have anyplace to shoot past 200 yards At this time.

 

[Rope2horns]

Jackie, I was up in Oklahoma at the prone state championship matches. A couple of shooters were using a cartridge that is essentially a 40deg shouldered/taper blown out necked up 6.5 x55 case. The designer said it is like a 6.5 x55 Bob Jourdan AI necked up to 7mm. They were running 180 or 184gr Bergers, forgot which one, at 2850 fps and the cases were not getting any signs of overpressure. He said it was capable of getting up to 3000fps. I think your case could shoot a heavy 7 with very repectable and competitive velocity for the LR game. The targets of the gentleman I speak of were very impressive at 1000yds and were competitive with the .284's and 300 WSM's on the line.

pm sent

I believe that was Rod Brakhage and Kevin Shepherd...they developed what they called the 284 BS IIRC.