riflescope sight-in on a custom rig using factory ammo question

[IA_shooter]

I have a question to ask.

I was considering going out to do a preliminary sight-in for my scope (Sightron 8-32) on my new custom built .243 today but seeing how it's a 28" Criterion bull barrel and I assume using a lot longer barrel than most factory rigs will equate into elevated speed and pressures would I have to worry about using some factory Hornady 75 gr HP's that are running 3400 fps according to the info on the box? My loads I will eventually be using exclusively when I can get them done will be 107 gr Sierra Moly MK's running in the 2900-3000 fps range ideally. It's the first day in weeks where the sun is actually shining, even though it's still a tad chilly (in the upper 30's for highs today) and I've got cabin fever so badly I have to get out and shoot today or I'm gonna go bonkers.

The action was matched to the barrel using go/no go gauges at a gunsmith's shop so I'm not too worried about anything in that area. I'll just do a close inspection of the first few cases I fire to make sure there are no overwhelming pressure issues I suppose?

Maybe I'm being worried over nothing but these will be the first rounds down my new toy and I don't want to upset her in any way. :-*

 

[firearmdoc1]

Should not be a problem using factory loads, just use them to get on paper with your scope and break your barrel in.

 

[Savage99]

Sounds like a superb rifle!

I like the .243!

Do what you want, I have that same cabin fever also. It's windy and 32F here today!

If it were my rifle I would only shoot my handloads in it.

What's the main purpose of the rifle?

What action?

For getting on the paper I would bore sight it first or use the Bushnell bore sighter that I have.

 

[IA_shooter]

Sounds like a superb rifle!

I like the .243!

Do what you want, I have that same cabin fever also. It's windy and 32F here today!

If it were my rifle I would only shoot my handloads in it.

What's the main purpose of the rifle?

What action?

For getting on the paper I would bore sight it first or use the Bushnell bore sighter that I have.

The action is a Savage Varmint Action and this rifle's main purpose is for shooting LR competition in the near future, I've never done it before but I wanted to start. I had already boresighted it at my buddy's gunshop.

So I took my 20 rounds of Hornady 75 gr HP's out to "the farm" (family ground). It took 2 rounds to get her close to zeroed, then I shot a 3 shot group @ 100 yards with her (and I almost one holed the first 2 shots and KNEW I screwed up on the 3rd when I shot it) and this was the result...............

I then went out to 200 yards and shot a 5 shot group and this was the result................

and for the last 10 rounds I had I took the target out to 300 yards and according to my handy ballistic chart app on my phone it said it would be a 6.5" drop from 200 so I clicked 2 1/4 MOA adjustment on the scope and shot the last 10 and here was the result..............

So all in all considering this was just some low BC factory ammo I thought the gun shot pretty good considering the gusty 8-12 mph wind I was dealing with coming from behind me slightly quartering across my left shoulder. I could clearly see the mirage @ 300 was a boiling mess that would occasionally straighten out from left to right. Here's a picture of what I was shooting off of and the down range look. I had a home made wooden benchrest made out of a couple sawhorses and some 3/4" plywood placed in the back of my P/U truck and the rest I have/use is a Caldwell Rock BR.

Can't wait to get my reloading started and start rolling out some quality ammo/test loads to try in her and see how she does.

Trevor

 

[IA_shooter]

The 100 yd and 200 yd spot where I was shooting was fairly well protected from the wind, hence the great groups, but to get out to 300 I had to go to the spot pictured and was dealing with the wind. I'm sure that's why the spread really opened up @ 300 vs 200. Plus like I said the factory ammo I was shooting wasn't ideal for longer range shooting as it's BC is only 0.236. The Sierra 107 gr Matchkings I'll be shooting out of her when I can get them loaded up has a BC of 0.527. That's a BIG difference in how the bullet is going to react to the wind in the 300-500 yd range. The ballistics show a 10 mph quartering crosswind over my left shoulder the way it was causing 8.5" of drift for that factory ammo @ 300 yds vs only 3.85" of drift for the Sierra's I plan on shooting. I use the Nikon Spot On Ballistic Match Technology app I have on my phone to figure all this stuff out. I should be able to tighten up groups quite a bit after I figure out what this rifle really likes for powder charge/speed and position to the lans using the Sierras.