NRL22 / Cold Bore POI Shift

[littlepod]

I haven't tested how long it takes for a rimfire to cooldown to the point where cold bore poi shift happens again and was curious what people do. I have a Tikka T1X w/ a SilencerCo Sparrow Suppressor. With the suppressor on, it usually groups 20% better, but it also exaggerates my cold bore. Generally unsuppressed, my cold bore shot is about .5" high on my first shot @ 100 yards. Suppressed, my cold bore shot / first shot of the day through the suppressor, it'll be 1" high, and 1.5" to the right. That's a pretty big change.

Now when I compete, I get a sight in period, that's probably about 30-40 min before the match starts. Then I probably shoot every 30min where I get my turn at the stage. I don't get any more sighters, so I'm curious how that would impact me. How long until the rifle resumes cold bore behavior? And with the suppressor, is it impacting based on cold bore, or more of that "first round pop" mechanic?

I will need to be more scientific with my tests over the next few weeks.

Cold Bore w/o Suppressor
Cold Bore, then second shot with Suppressor (to see if there's a Cold Suppressor POI)
Cold Bore w/ Suppressor

I have measured in the past that I get no POI shift suppressed vs unsuppressed with the Sparrow, so that's good.

 

[cab0154]

what ammo? I am waiting on my sparrow, so i cant give you any suppressed advice, but i have found that cold bore, eley lube is a little better for keeping the cold bore shot close to the group. i would probably guess that the lube goes cold in about 10 minutes in mid 70* air, and seems like i got one the other day after letting the rifle sit for about 15 minutes in mid 90* heat. i did the sparrow because everything i had seen i noticed that stuff got more accurate with it. so good to know that was the case with your gun as well.

 

[littlepod]

I'm shooting Eley Target right now. And switching to Tenex > 100 yards (for 200+ yard steel matches). I just ordered another brick of Target, Club, and Match to see how Club/Match perform. Haven't shot Club/Match before, so we'll see how it compares with Target.

With my Tenex, I'm getting a .3mil shift on zero @ 25 yards, so basically I take my Eley Target Dope, and subtract .3-.4mil for all the ranges, works out pretty well. I'm hoping that since Match/Club have the round nose instead of the flat nose, they'll have the same zero POI and it's just higher quality (lower standard deviation) and I won't have to adjust anything. We'll see!

What Eley ammo do you shoot?

 

[cab0154]

it will be lot dependent. its good to have lots to test every day you are going to shoot. at least here in N TX where the humidity and fronts can change every few hours. right now i have a batch of tenex, and a really old batch of team. bang for the buck, with eley, club has worked really well for me. but the EPS square bullet in (Team, Match, Tenex, and maybe in some of the other newer stuff that i havent shot) seems to buck the wind a little better further out than the round nose stuff. just my observation. some days some lots shoot and others dont. i would try to shoot a group or two out of each lot the morning you are gonna shoot to pick what you are gonna use.

some guys in different climates dont seem to have that problem though, i guess conditions dont change as much. you may just be able to lot test and let it eat. the other day, my 7 year old batch of team that usually doesnt shoot in high humidity was shooting better than my fresh batch of tenex. so you never know. overall, i would say that club has probably been the most consistent for me over the years. some barrels i have dont like the EPS bullet, my 64 MPR usually shoots sub 1/4" down to zeros at 50y with lots of lapua that are shooting on the day. that barrel just doesnt like eley as much. doesnt shoot bad, just shoots tighter with sk/lapua.

you are ahead of the game having so many different lots on hand. zero seems to be pretty close with all of them, but you may have some shift from changing lots. i would probably just do like you are doing and just hold over some if i thought it would be a cold bore shot. .3-.4 mils, i wouldnt have expected that much, but it is what it is i guess. hard to say. let us know what you find. cant wait to get my sparrow out of ATF jail to start doing some testing.

 

[littlepod]

Yeh my rifle doesn't like to eject the Tenex rounds for whatever reason. The spent casings tend to not eject all the way and get stuck in the chamber. Only happens with the Tenex EPS rounds so far. Haven't had any issues cycling SK stuff, or Eley Target. I am hopeful for Club being a solid performer...I can live with everyday shooting for $6.50 a box. I am only shooting Tenex right now because i got it on sale for $10 a box. I bought the Match round nose version, since my rifle hasn't had luck with the Tenex EPS stuff.

The Tenex does group well for me, avging .75" @ 100 yards. Eley Target, is around 1.1", SK+ is at 1" but has random flyers sometimes which is why I don't shoot it in matches... I'll group from .5 - 1.7" on my 6x5s whereas Tenex, everything will be sub 1". I bought a brick of SK Long Range Match and it doesn't perform any better for me than SK+. I should get a brick of Rifle Match, but decided to go the Eley route since I didn't like my hands getting all greasy from the SK ammo.

Yeh this rimfire game is a lot of time and testing... only been really shooting since June, and I've gone through 2000 rounds so far.

 

[cab0154]

Thats weird about tenex cases not wanting to eject. i have never run into that.

 

[hlee]

My Kidd 10/22 exhibits no cold bore POI shift, so I just take a shot or 2 to confirm zero, then start smashing steel...

 

[natdscott]

My Kidd 10/22 exhibits no cold bore POI shift, so I just take a shot or 2 to confirm zero, then start smashing steel...

Does your Kidd shoot well enough, and/or do you “smash” small enough steel—COLD—to see a shift?

The point here IS that first shot.. not “...or 2...”. The FIRST.

Great smallbore shooters shoot like they are on a stopwatch. I’m not great, but I try to keep it to no longer than 45 seconds.

Does that basically force you to shoot the condition?

Yeah. Yeah, it does.

Rimfire precision wasn’t intended to be easy, so shoot, a lot. Record mentally, or otherwise, what your rifle does in certain situations, and don’t try to manage 3 rifles and 8 ammo types... at least not if you want to be really good.