DrMike
Ballistician
- Nov 8, 2006
- 37,409
- 6,234
Wow! A new rifle and cartridge that will get 95% of what your Mashburn does! That is truly amazing. It is almost as good as what government does with our tax dollars.
Shorter, lighter bullets in the 7mm PRC?
- Thread starter NYDAN
- Start date
Oh my God... They are definitely an investment.... In someone else's future.Wow! A new rifle and cartridge that will get 95% of what your Mashburn does! That is truly amazing. It is almost as good as what government does with our tax dollars.
Guy Miner
Master Loader
- Apr 6, 2006
- 17,802
- 6,101
Well, have only shot with 160's and 175's so far from the PRC.
It's -5 and I can't even get to the rifle range because of the snow right now. Maybe next week.
Guy
It's -5 and I can't even get to the rifle range because of the snow right now. Maybe next week.
Guy
Charlie-NY
Handloader
- Mar 11, 2005
- 1,432
- 887
Guy,Well, have only shot with 160's and 175's so far from the PRC.
It's -5 and I can't even get to the rifle range because of the snow right now. Maybe next week.
Guy
Throw another log in the fireplace, will ya? You're making me cold!
Charlie-NY
Handloader
- Mar 11, 2005
- 1,432
- 887
Well - it was 7 degrees here this morning. I don't ever remember it being quite that cold. My golden retriever was standing at the sliding door waiting to be let out. When I opened the door, a rush of frigid air hit him right in the face. You never saw a dog turn tail and rush back into the house so fast. LMAO
DrMike
Ballistician
- Nov 8, 2006
- 37,409
- 6,234
Dogs can be amazingly smart when it comes to weather conditions.
wvbuckbuster
Handloader
- Nov 5, 2015
- 2,687
- 2,414
-2 last night in my part of WV. Coldest it's been for some time. Dan.Well, have only shot with 160's and 175's so far from the PRC.
It's -5 and I can't even get to the rifle range because of the snow right now. Maybe next week.
Guy
Sounds just like mine.
- Thread starter
- #29
I have attempted to answer my own question by printing out the Saami chamber drawing for the 7mm PRC, buying a 7mm PRC modified case (from Precision Reloading), using my Hornaday bullet comparator, and measuring the Base-to-ogive for a variety of Nosler bullets.
Here is the Saami drawing.
It indicates a base-to-bore distance of 2.6851".
My Hornaday 7mm bullet comparator measures about .274" - .275" on the internal diameter. If I compare the base-to-ogive measurement for a bullet to the base-to-bore measurement of 2.6851, I can calculate the approximate amount of bullet jump. That will probably be the worst-case scenario in that the bullet will probably make first contact along the slope of the leade before making contact at the bore diameter. See the exaggerated drawing below.
My analysis is based on diagram 1. However, the Hornady bullet comparator is measuring at a diameter of .274"-.275" instead of the bore diameter of .277". Also, the initial contact point is more likely to be along the leade. So whatever bullet jump I calculate will probably be more that we would see in real life.
This photo shows how I set-up to Hornady bullet comparator. I eyeballed the amount of bullet that should be in the neck of the case and place a tape band around the bullet.
Then I inserted the bullet into the modified case until the tape band contacted the mouth of the case. I brought the stem of the comparative up to the base of the bullet and fixed it in place with the set screw.
Next I measured the base-to-ogive for several Nosler bullets. I assumed that the boattails were uniform across Ballistic Tip and AccuBond bullets.
These are my results:
Bullet BTO COAL Approx. bullet Jump
150 BT 2.637" 3.203" .048"
140 AB 2.582" 3.153" .103"
150 AB 2.639" 3.210" .046"
160 AB 2.714" 3.275" .029" Jam
Assuming that it would be desirable to have bullet jumps starting at about .010" for the BT bullets, and about .100" for the AB bullets, it appears that the free bore might be a bit long for these bullets to have enough bullet in the neck of the case.
However, it appears that the 150 AB and 160 AB bullets would load up just fine with enough bullet in the neck of the case.
The long boat tail on the 168 gr. ABLR presents a problem.
This sets the bullet back pretty far in the case and with the long-tapered point, the base-to-ogive becomes relatively short at only 2.565".
That would result in a bullet jump of .120". I was a little disappointed in this finding.
Now, I am not saying that the 140 AB, 150 BT, or 168 ABLR bullets won't shoot well in the 7mm PRC with longer jumps. There are lots and lots of loads that shoot great in longer throated barrels. Just look at the Weatherby cartridges. I am just saying that for building a rifle for shooting 150 gr. BT's and 140 gr. AB's I may be better served with staying with the 7mm RM. After all, I have a 300 WM and a 300 WSM for my "heavy" work.
I am anxiously awaiting Guy's results. Dan
Here is the Saami drawing.
It indicates a base-to-bore distance of 2.6851".
My Hornaday 7mm bullet comparator measures about .274" - .275" on the internal diameter. If I compare the base-to-ogive measurement for a bullet to the base-to-bore measurement of 2.6851, I can calculate the approximate amount of bullet jump. That will probably be the worst-case scenario in that the bullet will probably make first contact along the slope of the leade before making contact at the bore diameter. See the exaggerated drawing below.
My analysis is based on diagram 1. However, the Hornady bullet comparator is measuring at a diameter of .274"-.275" instead of the bore diameter of .277". Also, the initial contact point is more likely to be along the leade. So whatever bullet jump I calculate will probably be more that we would see in real life.
This photo shows how I set-up to Hornady bullet comparator. I eyeballed the amount of bullet that should be in the neck of the case and place a tape band around the bullet.
Then I inserted the bullet into the modified case until the tape band contacted the mouth of the case. I brought the stem of the comparative up to the base of the bullet and fixed it in place with the set screw.
Next I measured the base-to-ogive for several Nosler bullets. I assumed that the boattails were uniform across Ballistic Tip and AccuBond bullets.
These are my results:
Bullet BTO COAL Approx. bullet Jump
150 BT 2.637" 3.203" .048"
140 AB 2.582" 3.153" .103"
150 AB 2.639" 3.210" .046"
160 AB 2.714" 3.275" .029" Jam
Assuming that it would be desirable to have bullet jumps starting at about .010" for the BT bullets, and about .100" for the AB bullets, it appears that the free bore might be a bit long for these bullets to have enough bullet in the neck of the case.
However, it appears that the 150 AB and 160 AB bullets would load up just fine with enough bullet in the neck of the case.
The long boat tail on the 168 gr. ABLR presents a problem.
This sets the bullet back pretty far in the case and with the long-tapered point, the base-to-ogive becomes relatively short at only 2.565".
That would result in a bullet jump of .120". I was a little disappointed in this finding.
Now, I am not saying that the 140 AB, 150 BT, or 168 ABLR bullets won't shoot well in the 7mm PRC with longer jumps. There are lots and lots of loads that shoot great in longer throated barrels. Just look at the Weatherby cartridges. I am just saying that for building a rifle for shooting 150 gr. BT's and 140 gr. AB's I may be better served with staying with the 7mm RM. After all, I have a 300 WM and a 300 WSM for my "heavy" work.
I am anxiously awaiting Guy's results. Dan
nhenry
Handloader
- Feb 7, 2022
- 610
- 1,060
Excellent writeup
DrMike
Ballistician
- Nov 8, 2006
- 37,409
- 6,234
Thorough, Dan. You done well.
RL338
Handloader
- Mar 23, 2017
- 3,373
- 5,496
Roy was all about speed. Granted there where no high bc heavy for caliber bullets back in his day.
Seat the top of boattail to the neck/shoulder junction and let her rip.
Joec7651
Handloader
- Apr 7, 2019
- 943
- 1,201
^^THIS
Ive got a 1:8 twist 26” barrel on my 7mm RM. I put PT&G bottom metal on it to accept AICS mags. I can load all the way out to 3.615” OAL. Now, I’m not loading anywhere near that length even with 175gr ELD-Xs. Which is my preferred load in this rifle. RL25 and the heavy ELD-X hauls the mail at 3000 fps and that’s without lengthening the throat. So it will shoot anything from 139gr on up better than I’m able to. As said above, maybe opening up the magazine would be a viable option while having more readily available brass. The 7mm PRC didn’t make the 7RM obsolete by any stretch of imagination. Do I want one? Of course I do but it’s not putting my 7RMs out to pasture either. The determining factor is this. If you want a 7mm PRC then make it happen. have what you want and be happy. I don’t think you could go wrong either way.
HodgemanAK
Beginner
- Oct 23, 2020
- 240
- 220
I've been thinking about the 7PRC quite a bit. The only thing I think it really does better than the 7RM is that you can buy the whole enchilada over the counter and have a match chamber, match factory ammo loaded with high BC bullets, and a barrel twisted tight enough to stabilize them.
You can do that with any 7RM, but it won't be something you can buy off the rack at any hook and bullet store. I think it's smart, but for dedicated gun geeks who like building rifles and loading ammo I don't know that it's really a game changer.
Of course, I'll probably buy one to find out.
You can do that with any 7RM, but it won't be something you can buy off the rack at any hook and bullet store. I think it's smart, but for dedicated gun geeks who like building rifles and loading ammo I don't know that it's really a game changer.
Of course, I'll probably buy one to find out.
Powerstroke
Handloader
- Feb 24, 2006
- 1,799
- 60
Ok, delima folks..........
Due to multiple factors in front of the CO elk herd this year, I chose to put the bow in the closet and........... yes, draw a second season bull tag. With that said, i haven't added a new round to the safe in years, so enter stage right....... Seekins PH2 7PRC.
I figured brass/ammo would be difficult to find, so I purchased ammo prior to the rifle. (Side note, I bleed Remington Green)
Ammo has been plentiful here, but I have never shot factory. Issue arises I have no line on bullets, and second guessing on what to load this thing with.
Can I get away with the 160AB? I have a line on 175LRAB's, but $100+ a box I pretty much refuse to do. Looking line current options available are pretty much anything Hornady which I haven't shot for years. 168gr Bergers, or 160gr AB's. Do I just bite it, and shoot factory ammo this year for the first time, or continue my search? At the moment, I'm leaning towards the 160AB, but not sure if it's a bit lite ? Thoughts, suggestions?
Thank you!
Due to multiple factors in front of the CO elk herd this year, I chose to put the bow in the closet and........... yes, draw a second season bull tag. With that said, i haven't added a new round to the safe in years, so enter stage right....... Seekins PH2 7PRC.
I figured brass/ammo would be difficult to find, so I purchased ammo prior to the rifle. (Side note, I bleed Remington Green)
Ammo has been plentiful here, but I have never shot factory. Issue arises I have no line on bullets, and second guessing on what to load this thing with.
Can I get away with the 160AB? I have a line on 175LRAB's, but $100+ a box I pretty much refuse to do. Looking line current options available are pretty much anything Hornady which I haven't shot for years. 168gr Bergers, or 160gr AB's. Do I just bite it, and shoot factory ammo this year for the first time, or continue my search? At the moment, I'm leaning towards the 160AB, but not sure if it's a bit lite ? Thoughts, suggestions?
Thank you!
Charlie-NY
Handloader
- Mar 11, 2005
- 1,432
- 887
I've shot a load of 160 Accubonds between 3,000-3,200 fps from a custom 7WSM. Terminal performance of the bullet was always great. They may not have the highest BC but they are a very reliable bullet for hunting and it's easy to find a good load with them.
Just my 2 cents.
nhenry
Handloader
- Feb 7, 2022
- 610
- 1,060
Guy Miner
Master Loader
- Apr 6, 2006
- 17,802
- 6,101
Never ended up shooting anything lighter than the 160's. Except to gather some chrono data. Sorry. Other projects took priority. Sigh.
The rifle shot the 175 & 180 grain Hornady bullets very well.
Regards, Guy
Ridge_Runner
Handloader
- Sep 29, 2006
- 1,388
- 740
why not an STW, twisted 9 and outperform both by alot.
Joec7651
Handloader
- Apr 7, 2019
- 943
- 1,201
For PS, I think the 160’s will do fine. I have two 7mm RM’s with 1:8 barrels and both put 160 grain Partitions and HotCor’s under 1” at 100 yards. They also put 175 grain ELD-X’s under 1/2”.
You’re not giving anything up at all with a 1:8 twist rate. A fast twist tends to give better expansion with mono bullets as well. So that’s an option.
You’re not giving anything up at all with a 1:8 twist rate. A fast twist tends to give better expansion with mono bullets as well. So that’s an option.
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