Loose Brech Plug or to much powder????

[volsgo1]

Shooting a slufoot HR4570 conversion the first time with FullStream and 280longshot this weekend.

I had Bore sighted the scope prior to coming out to shoot and it was pretty dang close on the first shot at 50 yards made several follow up shots to get it dialed in at 50. Moved out to a hundred yards expecting similiar results.

At 100 I was not even on paper. After a few shots to verify what was going on I assumed Id blown up my ZA-3 Minox scope. We removed the breech plug to check the bores alignment with the cross hairs (poor mans Bore siter).
What we found was the breech plug was extremely loose. Probably my fault for not snugging it down enough. But the bore and the crosshairs of the scope were dead on.

Thinking that the loose breech plug might be the problem but not knowing how that could have affected accuracy We cleaned the plug, snugged it in the barrel with a socket and then shot at 25 yards. 1/2 low of bullseye??? Im back in business so I think. I shoot one last shot at 100 yards and vertically I am good but about 6 inches low. That was my last shot for the day.

Questions:
1. Could the loose breech plug have caused the accuracy issues?
2. Was 62 grains of n120 to much and did that cause the issue at longer distances as it was fairly accurate out to 50. I might add that FullStream was shooting 58 grains of the n120 out of his 45/70 conversion and getting great groups at 200 yards. Can 4 grains make such a huge difference?

I waited for a cool barrell between all shots
62 grains, barnes 195, light blue harvester sabots
Chroned speed 2830
None of the recovered sabots appreared to be blown

Thoughts from the experts???

 

[Rubberduck270]

You'll probly get a different answer from the boys on Doug's but here's my suggestion (based off my stainless H&R conversion).

Scrub the barrel good and make sure you don't have any plastic fouling. A single blown sabot can cause plastic build up instantly AND warm sabots in a warm barrel causes the gradual build up to escalate quickly. Polishing the barrel with JB Bore paste will help from getting plastic build up.

On your next outing take an infrared thermometer with you and verify barrel temp shot to shot. A cooling rod will help your efforts too. A hot barrel acts a lot like a loose scope mount or base. Always in the ballpark but never consistent and very random.

I personally don't think the plug could have caused this much trouble. I don't tighten mine down with a wrench, I just run it in and out with a socket and extension so it's pretty much just finger tight. If the plug was several turns out then the action wouldn't have closed and locked with a primer in it.

 

[fullstream]

You'll probly get a different answer from the boys on Doug's but here's my suggestion (based off my stainless H&R conversion).

Scrub the barrel good and make sure you don't have any plastic fouling. A single blown sabot can cause plastic build up instantly AND warm sabots in a warm barrel causes the gradual build up to escalate quickly. Polishing the barrel with JB Bore paste will help from getting plastic build up.

On your next outing take an infrared thermometer with you and verify barrel temp shot to shot. A cooling rod will help your efforts too. A hot barrel acts a lot like a loose scope mount or base. Always in the ballpark but never consistent and very random.

I personally don't think the plug could have caused this much trouble. I don't tighten mine down with a wrench, I just run it in and out with a socket and extension so it's pretty much just finger tight. If the plug was several turns out then the action wouldn't have closed and locked with a primer in it.

I believe based on what he was shooting (2830) it was a combination of too hot of a load plus loose breech plug. He is gonna back it down to 58gns for next weekend & cooler temps & I believe we will have alot better rests from hei H&R.

 

[Rubberduck270]

If his sabots looked good the load shouldn't have been too hot.

 

[KPH]

Now I am not only going to have to take my infrared now I have to take my torque wrench. Witch those maybe some good ideas.

 

[Rubberduck270]

Ya'll can do as you wish but I'm not going more than hand tight. Teflon tape will help if it keeps wanting to work loose but I wouldn't start trying to torque it down.

 

[volsgo1]

Thx guys for the input. A shooting i will go. Cleaned it good tonight. No visible signs of plastic.

 

[Rubberduck270]

Lol you'll have to take my word for it but a lot of the time the plastic is invisible. It takes very little to start causing problems, especially in the heat.

Whats your loading pressure with the barnes? I never could get them to group in mine without knurling.

 

[volsgo1]

Was a bad scope. Put on a new one today problem solved

 

[Rubberduck270]

What kind of scope did you kill?

 

[volsgo1]

Minox but Ill say they were good about it brand new one on the way,

 

[tasaman]

I know you solved your problem but yes a loose breach plug will cause wild flyers. I missed a doe at about 120 yards and had killed a coyote at 150 the day before so I was miffed as to the cause was. When I got back I turned the plug in about 3/4 of a turn by hand before it was snug. I am guessing heating up and cooling down and the miles of walking had something to do with it.