The importance of sizing correctly

[AndyC]

Before anything else I have to say that my AK47's barrel is likely going to be replaced, even though the rifling is still strong.

I cast some 7.62x39 boolits (Lee C312-155-2R) and PC'd / gas-checked them, sized to .312":

https://i.imgur.com/5LhAI9k.jpg

Why? Because I had a .312 sizer but mostly (to my chagrin) because I "assumed" my bore size. Target at 25 yards with 2" stickers (and yeah, I know how to shoot):

https://i.imgur.com/SxAPUF6.png

To fix the shotgun-pattern, I went back home and added more and more PC to the .312" boolits (I had to coat/cool a further 3 times before they were at .314", even using Eastwood's Ford Blue) and got the tighter results in the pic to the right on the next day.

I know, still not great but 1) it's a really narrow bench (front to back is like 8" long) to rest on with zero support at the rear and at the worst possible height for me and 2) it was an experiment to see whether a) fatter boolits made a difference or b) whether the boolit-design just didn't suit my barrel.

I'm convinced enough that the design seems to be just fine (given the stable holes in paper, primarily) and I just need to get the size right. I'll undoubtedly get a new barrel soon, but in the meantime I'm having an interesting time experimenting and my results might be a good heads-up to anyone who may have some doubts that fit is king ;)

[Winger Ed.]

All things considered---- For a issue grade gun, and load that hasn't been tweaked out, that's really pretty good.

Not sure if it'd matter, but it looks like some of the gas checks aren't seat square on with the bases.

[gwpercle]

All things considered---- For a issue grade gun, and load that hasn't been tweaked out, that's really pretty good.

Not sure if it'd matter, but it looks like some of the gas checks aren't seat square on with the bases.

I agree with Winger Ed ... if the checks are on square you will get some unexplained flyers ...
Make sure they are on flat , square and level .

I looked at photo closely ... you have some definite lopsided checks on the bases of some ...
accuracy will be much better if these are eliminated .
May not be your barrel , just a little boolit tweaking and load tweaking is all you need to make her shoot .
Gary

[AndyC]

Yes, I culled those out to redo them - I'm using a Star sizer, and that was just a quick photo I took to show a friend.

I also forgot to mention - that target was at only 25 yards (indoor range near me) and the stickers are 2", so I'm not satisfied.

[GregLaROCHE]

Did you ever slug the bore to know what it was? Why are you going to change the barrel? Maybe casting a larger boolit and then running it through an appropriate sizer for your bore, is what you need.

[AndyC]

I did, Greg - it mics at .314":

https://i.imgur.com/OwCjqD5.jpg

I don't think I can get this boolit much bigger without extensive and repeated PC'ing - sure, I could *make* it work but I'm not content with work-arounds; although the rifling appears to be still strong, I really want a good barrel of proper bore-diameter.

In the meantime I have a .315 NOE sizer on the way so I can putter around with it some more - the sizer is less for sizing than to give the Star sizer some resistance to seat the checks.

[Pirate69]

Can you "Beagle" the mold?

[358429]

Have you tried Eastwood Ultra gloss clear? It makes my bullets fat. Would be way less work than replacing a barrel, if it works.

Sent from my SM-G930T using Tapatalk

[Winger Ed.]

Oh. AKs aren't renowned for their tack driving accuracy, but I thought those were 100 yd. targets.:bigsmyl2:

[AndyC]

Touche - I've edited the post to clarify, sorry ;)


Can you "Beagle" the mold?

Have you tried Eastwood Ultra gloss clear? It makes my bullets fat. Would be way less work than replacing a barrel, if it works.
I appreciate the fixes, lads, but no, I'm not going to band-aid the issue - if it was the end of the world and we had to run what we brung, then sure - but I've ordered a new barrel.

The whole point of this post was to illustrate the effect of poor sizing - but until the new barrel gets installed I'm going to carry on experimenting anyway and get some knowledge out of it.

[sutherpride59]

For fun beagle the mold, works pretty well and might get you to .314 without the pc

[Bazoo]

What if one of your workarounds ends up giving you real good accuracy? You still going to replace the barrel then? Buy a mould that drops larger is the easiest and probably cheapest route.

[DougGuy]

If that isn't a dead soft slug, which it looks like it is a boolit alloy, you will get springback once it leaves the barrel so your measurement won't be that accurate. Calipers are also low on the list of choices of measuring devices. You may get a different reading using soft lead and a micrometer.

[AndyC]

Cast boolits for the AK is a fallback (thanks, Biden) - I need the rifle to primarily shoot my j-word stash accurately and those are .311-.312, so ... may as well bite the bullet, pardon the pun.

[AndyC]

I finally got the opportunity to install the new AK barrel as well as the KOP rear-sight block, thanks to my buddy's time and tools. It was more work than expected and provoked a lot of anxiety at times, but actually went quite smoothly:

https://i.imgur.com/vuWO2xv.jpg

I know, looks crappy and incomplete but that's because it's going to be parkerized/painted soon.

[popper]

GC not only not square but look like home made, punch not centered on the disk. Try some factory GCs and compare.

[TyGuy]

I finally got the opportunity to install the new AK barrel as well as the KOP rear-sight block, thanks to my buddy's time and tools. It was more work than expected and provoked a lot of anxiety at times, but actually went quite smoothly:

https://i.imgur.com/vuWO2xv.jpg

I know, looks crappy and incomplete but that's because it's going to be parkerized/painted soon.

Was the barrel you started with the original Yugo non chrome lined or a US repop for 922r? The original barrels were pretty bad about being poorly maintained.

Who did you go through for the new barrel?

AK barrel work can be intimidating at first but with the right tooling and some practice it’s not so bad. Good choice on the Sabrewerks KOP. I have been wanting to get me hands on one of them for quite a while but haven’t pulled the trigger. I talked with one of their guys down at KCR a few years back and was really impressed with their products.

[AndyC]

Was the barrel you started with the original Yugo non chrome lined or a US repop for 922r? The original barrels were pretty bad about being poorly maintained.

Who did you go through for the new barrel?

AK barrel work can be intimidating at first but with the right tooling and some practice it’s not so bad. Good choice on the Sabrewerks KOP. I have been wanting to get me hands on one of them for quite a while but haven’t pulled the trigger. I talked with one of their guys down at KCR a few years back and was really impressed with their products.
The original was a Yugo parts-kit - the new barrel is a US-made repro I acquired via Apex Arms.

I'd always liked the Sabrewerks KOP but didn't buy one until I realized I'd have to rebarrel anyway, in which case it made sense - and it was the easiest part of the install, no fuss.

[AndyC]

A successful upgrade and shoots very nicely:

https://i.imgur.com/dDsRa4D.jpg

Sighting-in using the rear-sight on the KOP rail:

https://i.imgur.com/ICjn9r5.jpg

First 2 shots at 25 yards:

https://i.imgur.com/BM7nwp8.jpg

Once I had the rear dialed-in, I mounted a Vortex Sparc II and, after cranking the dials, shot this 1/2" 3-shot group at 50 yards. The red dot is 2 MOA, so it covers 1 inch at 50 - getting a 1/2" group using a 1" dot is very gratifying:

https://i.imgur.com/6a45qE9.jpg

Very pleased/impressed with this new barrel and the KOP system was worth the money and effort. I have a 1-6x scope I also want to sight-in; just waiting on the KOP long rail to arrive:

https://i.imgur.com/gXJ3QzQ.jpg