7mm-08 question - truly Baffled

[scootrd]

Wasn't sure where to post this , But I thought Handloaders have so much knowledge you all might be able to help.

My Mod Seven has never ever liked factory 150 grain SP's . I tried them early on and never could get a decent grouping.
So I  settled in on factory 140's (still haven't had opportunity to try Hornady 139 grain SST's yet)

My last outing shooting Fed Fusion 140 grain BT's at 100 Yards .
Groups were pretty decent about 1  to 1 and 1/2 inches apart. I shot about 50 rounds in groups of 3 all with about the same precision. Temp was in high 50's no wind. (I know this cause I wrote it on the Targets)

Today , I went out and shot about 50 rounds of Fed Fusion 140 grain BT's at 100 yards again, no wind , groupings of 3 had a larger spread than previous outing.  Consistently 2 inches apart or more.  At the end of the day I was about to pack it in when I remembered I had a Box of Fed Power Shok  150 grain SP's in my backpack left over from my previous attempts. I cracked the box open and fired 6  - 3 shot groups. Each group could be covered with a quarter or less. I checked the thermometer when I got back to the house it was 5 degrees above zero.

Only difference I can gather is a drop in temp between the two outings of about 53 degrees Fahrenheit.  

• Can temperature play this significant a role between the 2 outings with what my Mod seven likes and account for the difference in the  performance between the 140 grain BT's?
  
  Can temperature be the difference in why the 150 G SP's which my Mod seven has never liked be the reason they performed so well today?

I am truly Baffled, any advice offered would be greatly appreciated.  
 

[burntmuch]

Dont have an answer for ya. Just posted so I can follow this thread. Ive got a model 7 7mm-08 thats kinda picky too

[Graybeard]

You seem to be overlooking another MAJOR factor in accuracy and that is barrel condition.

I'm not sure if you cleaned that barrel between the two 50 round sessions or not but since you do not mention cleaning I will assume you at least did not clean during the last 50 round session.

Each barrel is a rule unto itself and you just never know until you shoot them and experiment what condition each barrel wants to be when it shoots its best. It sounds like yours might want to be fouled to shoot those 150s and who knows it might want to be for others as well. On the other hand it seems to not shoot better heavily fouled with the 140s you used just prior to the 150s.

This is why you should do lots of shooting with your guns to learn their characteristics and what level of fouling the barrel needs to do its best.

I've had barrels that didn't even begin to deliver decent much less its best accuracy until 20-50 rounds had been fired since last cleaning. I've had barrels that the first group fired was the best and it just got worse from there. If it gets worse really slowly that's OK but if it gets worse real fast that's one that I use as trading material as I'm not willing to put up with it.

Each and every barrel has a level of fouling it will work best with. They each have a certain number of shots it takes to move them beyond that level they prefer to begin to shoot poorly. If you are lucky you get one that begins shooting good groups with minimal fouling and continues to do so for hundreds of rounds before it needs to be cleaned again. When you find one like that don't ever let it go.

[Varmintnut260]

A friend of mine has a model 7 stainless in a 7mm-08, he hasn't tried hand loading for it due the rem factory 140gr cor-lock bullets. I haven't seen his groups but, I HAVE SEEN these bullets perform in deer and they work great. That said, this guy won't go into the woods with a gun that groups over 1 in at 100 yrds. I would give them a try, and Remington does sell the bullets so you can load them if you'd like. Remember powder can be temperature sensitive, groups can change per barrel temp too, you need to give it time to cool down between shots.


My experience with my model 7 in a 260, is it shoots good cold, the colder the barrel the better. I haven't been able to shoot it above 30 degrees yet b/c I bought it just b4 Christmas.

[LaOtto222]

Barrel cleanness can effect accuracy. Some barrels shoot better after they get many rounds down the tube. I have had barrels that just do not shoot well until there are 50 or more shots down the tube. I have had some that shoot 1 bullet better than another when clean, but the opposite when dirty. I had a Remington 700 VS in 222 that would not shoot worth a poop until it had over 100 shots down the tube. Clean it up and again the accuracy would go South. I try other bullets in it and again no matter if it was clean or dirty, it would not shoot. It liked 50 grain Hornady SXSP bullets and those only when it was good and dirty. I do not think the temperature had that much to do with it, unless there is a huge difference in velocity. I have had guns that did not shoot well when new, but after a lot of shots, it got better. Every single gun is different, even the same model and the same case. You just have to find out what it likes. Good Luck and Good Shooting

[brownie]

I load for my fathers m7 7-08 and the only thing we could get to group real good was the Speer 145 Grand Slam with IMR 4350. Grand slams are Pricey but grouped the best worked real nice on all the whitetail he has used it on.

We had bad luck with Hornady, velocity spread was quite large. Remington were the best for factory. I also found the thin barrel would heat up real fast effecting group. Shoot one take a minute shoot the next and so on. Cant do the 1 after the other thing with his. The stock is also light weight and if you rested right on the end of the stock it would change the POI. Keep the rest back twords the trigger as far as is comfortable. Absolutely bad groups using a Harris bi-pod. Hope this helps.

[scootrd]

Thank you all for responding.

As GB suspected I did not clean between shoots.

I will do so tonight and reply back what happens after my next shoot regarding 140's and 150's groupings.
If fouling is indeed the issue , I am assuming 140's groupings will be nice and tight again , and the 150's spread
will go back to being awful as before through a clean pipe once again.

Thanks again, I greatly appreciated the responses.  

I have heard good reviews regarding Hornady 139g SST's as well and will eventually get around to trying them as well.
Albeit with a clean barrel.

[Steve P]

Temperature can play a BIG role in how ammo shoots.  As temperature raises, so can pressures inside your rounds.  This could explain why the 150s shot better in the cold.  Lower temperature = lower pressure = slower velocity.  Slower velocity with the 150s may be the sweet spot for your gun.  Did you chrono so you have velocity?

Could be same with your 140.  They slowed down too much and came out of the sweet spot.  Warmer temperature or a little more powder could speed them up to attain the velocity for that sweet spot.

Read some of the threads on which powders are "temperature sensative".   You may be suprised how much these rounds really can change.

Steve

[BBF]

I'll add my 1 1/2 cents to it. 53 deg spread is a big difference and will affect your rifle and ammo