Anyone own a 7mm 300 Win Mag?

[joeycoates]

Thanks for the responses guys. Both barrels are 5R rifled so I am not going to run into any issues with bullets coming apart, or I certainly would not expect any issues. We are waiting on both the chamber reamer and the die reamer from PTG right now, so I have a little while to decide. As far as cut rifled to button rifled barrels are concerned, well, I guess that I am not concerned.. I think that either of the barrels will be more than capable of shooting. The barrel, action and bolt are going to be salt bath nitrided after an initial break in which I would imagine should help throat life as well.

My only concern would be the added weight, it is not going to be a pack rifle, but all of those ounces do start to add up. However, heavier with a brake would help with recoil though, and the extra length may give me a wee bit more velocity. I don't think that I can make a bad choice with either. I do know that with either I will have to find a pretty good size case to hold the rifle, a Pelican 1750 is not going to be long enough from my initial measurements. Do you guys know of any good cases that are pretty long? If I go with the Broughton I will be looking at a 29" barrel with a 2-2.5" brake on it. That will make for a pretty long rifle overall.

 

[mrb1982]

I am shooting a Remington Sendero 7RM right now. I am wondering are you guys able to get a 7/300win mag round in the magazine of a remington with a 180 berger hybrid seated out close to the lands without having to put a new mag box on it? I can get a 7RM round in there with it seated out long. Seems like in the 300 case it would get to be too long without using a new mag box.

 

[IdahoCTD]

You'd have to seat 180's a bit deeper than normal to make it run through a factory mag box. My reamer is a .188 throat and with 162 Amax's it is perfect at 3.605 AOL.

 

[mrb1982]

You'd have to seat 180's a bit deeper than normal to make it run through a factory mag box. My reamer is a .188 throat and with 162 Amax's it is perfect at 3.605 AOL.

Kinda what I figured. Thanks

 

[safariexpress]

Need some advice with my 7-300.

New build ,Remi action,broughton 5c 1-8 twist.7-300 312 nk.

Been having some pressure problems during initial fireforming.
Sarting load was 168smk 68-70 gr of H1000 with RWS brass.
The builder told me it ts 312 neck chamber.
Tried turning necks for more clerance and din't change much.flat primers and cratering. bullets seated at 3.400. accuracy seem to be pretty good considering.
Second time around went with Norma brass same load and same results.
Turned the necks on the norma brass as well.
Loaded round neck dia. was .308
With reduce load at 66gr of H1000,still was getting primer cratering, but no flattening of the primer.
Bit discouraged at this point.
Also not my first rodeo with wildcats.done a number of them,but this one is kicking by ***.

 

[.284]

I'm not sure how far your jump to the lands is but are you able to seat the bullets a little deeper in the case. That may help reduce the initial pressure spike.

Another thing to check for is to measure your belts on the case. If they are a little short or if the reamer had cut the recess for the belt a little long the firing pin may be pushing the whole case forward before it fires and expands into the chamber.

 

[IdahoCTD]

It may just be a sloppy firing pin hole. Remington's are notorious for that. It allows the primer to flow back around the firing pin. If there aren't any ejector marks on the cases or the cases aren't growing ahead of the belt I would bet that is the issue.

I shoot 73grs of H-1000 with 162 Amax's in RWS cases so your loads seem really light. What is your velocity like? My 27" barrel is going 3190fps and my 28" barrel is doing 3230fps and both shoot under 3/8".

 

[chuckhammer]

66 gr of H1000 behind a 168 in a 7-300 using roomy Norma brass sounds like a soft load. Can't imagine getting pressure signs at that level. I can double check it in QuickLOAD when I get home tonight.

As a similar reference point, using my 7mm Valkyrie (improved 7-300 WM with 4 gr more H2O capacity) with WW Super brass, a 180 Hybrid, 82 gr Retumbo, and a .060" jump, I am just starting to see pressure signs on my Russian LRM primers. Your load is using a lighter bullet, essentially equal case capacity (roomy Norma in 7-300 vs. thicker WW Super in 7mm Valkyrie), and a MUCH lighter charge of a slightly slower powder. No reason for pressure signs.

Does your approx. 3.400" COL create a particularly tight jam with your throat length? What primers are you using? Was the bolt difficult to open with the 70 gr loads?

 

[Broz]

Our typical load with H-1000 and 180's is between 72 and 77 grains depending on brass used, case volume and powder lot. If you see pressure at 66 gr I would be looking for another issue.

I ignore cratered primers. I have learned that it is all about over sized firing pin bores and seldom about pressure. I have customs that show no cratering even when hard bolt lift is there from over pressure.

Knock the primers out to see if they are only a little flattened or if they are muffin topped. If they are only flat faced and no ejector marks or increased bolt lift on that soft Norma brass, I feel you are fine.

Jeff

 

[safariexpress]

66 gr of H1000 behind a 168 in a 7-300 using roomy Norma brass sounds like a soft load. Can't imagine getting pressure signs at that level. I can double check it in QuickLOAD when I get home tonight.

As a similar reference point, using my 7mm Valkyrie (improved 7-300 WM with 4 gr more H2O capacity) with WW Super brass, a 180 Hybrid, 82 gr Retumbo, and a .060" jump, I am just starting to see pressure signs on my Russian LRM primers. Your load is using a lighter bullet, essentially equal case capacity (roomy Norma in 7-300 vs. thicker WW Super in 7mm Valkyrie), and a MUCH lighter charge of a slightly slower powder. No reason for pressure signs.

Does your approx. 3.400" COL create a particularly tight jam with your throat length? What primers are you using? Was the bolt difficult to open with the 70 gr loads?

Chuck,
I agree on the 66 gr load.
To me it seemed like a soft load as well with Norma brass.
I compared the load density between the RWS & Norma,using the same load side by side, the Norma density was much lower with both the 66 - 70 gr loads.
I thought i haded in the bag.
But after firing 2 loads with the Norma, 68 and 70 grains,the primers were still cratering on both loads.bolt lift wasn't to bad.
I even tried sitting the bullets a little deaper in the case thinking that maybe i was jamming them.but there was no rifling marks on eather loads when initialy chambering and taking the round out for inspection.

I even tried 71gr load with the Norma brass,thinking that maybe the low density might be the cause of op,but the primers were flat and cratering again..

 

[safariexpress]

Our typical load with H-1000 and 180's is between 72 and 77 grains depending on brass used, case volume and powder lot. If you see pressure at 66 gr I would be looking for another issue.

I ignore cratered primers. I have learned that it is all about over sized firing pin bores and seldom about pressure. I have customs that show no cratering even when hard bolt lift is there from over pressure.

Knock the primers out to see if they are only a little flattened or if they are muffin topped. If they are only flat faced and no ejector marks or increased bolt lift on that soft Norma brass, I feel you are fine.

Jeff

Broz,

66 gr to me seems like a low charge as well ,like i metioned to Chuckhammer ,even with RWS brass.
The rifle has a brand new PTG bolt and firing pin assembly,so i kinda ruled thar out,but i will check it myself.
On the original loads of 67-71 with RWS brass,the primers were quite flat and cratered,din't check after i knock them out.
I thing i noticed was there were no ejector marks on the cases ,accept the 71 gr load had very slight mark and bolt lift was a little tight.
I'm going to go back and check loaded round OAL .the problem may there.
But i felt that 3.400 was adequate.
The smith told me that its chambered for the Berger 180s.
I hear that the 7mm don't to run with tightneck chambers.

 

[IdahoCTD]

If it is chambered for 180 Berger's then your OAL would be more like 3.7"+. Jumping .300" wont do anything for your accuracy and it will reduce your working capacity by quite a bit. I would figure out the max OAL to the rifling and start from there.

 

[Petersen]

Need some advice with my 7-300.

New build ,Remi action,broughton 5c 1-8 twist.7-300 312 nk.

Been having some pressure problems during initial fireforming.
Sarting load was 168smk 68-70 gr of H1000 with RWS brass.
The builder told me it ts 312 neck chamber.
Tried turning necks for more clerance and din't change much.flat primers and cratering. bullets seated at 3.400. accuracy seem to be pretty good considering.
Second time around went with Norma brass same load and same results.
Turned the necks on the norma brass as well.
Loaded round neck dia. was .308
With reduce load at 66gr of H1000,still was getting primer cratering, but no flattening of the primer.
Bit discouraged at this point.
Also not my first rodeo with wildcats.done a number of them,but this one is kicking by ***.

I ran into similar troubles with mine. Two things related to brass you should do -

#1 properly anneal them after you size the 300 brass down to 7mm. When you size the brass down it gets stiffer/harder. I knew I had issues when I checked my overall neck diameter after firing and it was the same as the loaded round.

#2 - through the sizing process my brass developed the 'donut' on the inside of the case at the neck shoulder junction. this needed to be removed. I know they make fancy precision tools for this but I used a round file to remove them. This is most important when using bushing dies as most of us do with this wildcat. We don't pull the case over a sizing button on the inside.

on a side note, I think if I would have annealed the brass before turning the necks the formation of the 'donut' would have been minimal or not developed.

 

[Broz]

Broz,
The rifle has a brand new PTG bolt and firing pin assembly,so i kinda ruled thar out,but i will check it myself.

Do this, there are two sized firing pins for the 700. Make sure you do not have a large bore and a small pin.

Jeff