working out a 20 Grendel reamer specs

[msalm]

You should be able to easily hit 4K with a 40gr bullet, and then some. Especially since you will have significantly more case capacity than the standard 20 PPC.

I might twist the barrel to try the 50gr Bergers and take it long.

I didn't want to get my hopes up, but I was thinking 4000 would be pretty easily achieved. As for twist, I have a REALLY good Mullerworks 1-11 twist tube sitting here, and that's what I'll use. I'm trying to use up actions and barrels I have laying about and complete rifles out of the piles of 'stuff' I have laying about...my last 20 cal went to a friend and I've been missing it.

 

[Ledd Slinger]

Yeah 1 in 11" twist is the way to go for 40gr and lighter.

Some guys use the 20 PPC in Benchrest and are launching the 55gr Berger at 3800 fps. So a 40gr at 4000 fps in your larger case should be a walk in the park.

I'm doing the same on a build with a Savage. Havent owned a Savage in many years but I had some parts lying around for a 110 that I didn't know what to do with. Then I found an action for dirt cheap that that just happened to be missing all the left over parts I had lying around. Like it was meant to be. So I'm gonna build a rifle out of it and sell it off.

 

[Tommie]

3800 FPS with 55’s is wild. Chamber pressures must be in the scary zone. Western Powder manual shows a PPC load with a 50 grain Berger doing 3598 FPS at 62,950 PSI.

 

[Ledd Slinger]

3800 FPS with 55’s is wild. Chamber pressures must be in the scary zone. Western Powder manual shows a PPC load with a 50 grain Berger doing 3598 FPS at 62,950 PSI.

I apologize. I meant 50gr Berger. I mistook an article I read on this site. Below is the excerpt from the article. I'll admit it does seem a little crazy to me as well. I'm sure thos guys are shooting very long barreled rifles to get that speed.

 

[Tommie]

With all due respects, Todd Kindler tends be be very “optimistic” with small caliber velocities. There’s NO WAY I’d try to get 3800 FPS with 50 grainers

 

[Ledd Slinger]

With all due respects, Todd Kindler tends be be very “optomistic” with small caliber velocities. There’s NO WAY I’d try to get 3000 FPS with 50 grainers

Looks like that velocity is a typo, but I know what you are saying.

I'm running 39gr Sierra BK in a 204 Ruger at 4030 fps from a 26" barrel. So 3800 fps with a 50gr in perhaps a 28-30" barrel definitely seems "possible".

Its good to be cautious about what others claim and of course work loads up carefully. With more normal varmint rifle barrel lengths of 24"-26", I think 3600 fps with a 50gr in the 20 PPC would be a more realistic goal.

However, the 50gr velocitiy in a 20 PPC doesn't really matter since the OP is building a 20 Grendel and wants to shoot 40gr bullets. The main point was that the OP's 20 Grendel does have a good bit more case capacity than the 20 PPC and should be able to achieve 4000 fps with a 40gr in a 24"-26" barrel.

 

[Tommie]

Typo corrected. Thanks.

 

[msalm]

With the 40 BIBs, and most likely a 23, MAYBE a 24” barrel, I’ll get what I get. If that’s an easy 3800 so be it. I’m looking at a light, handy walkabout calling rifle for here in the Midwest (SW Wisconsin). Ranges of 2-300 most often Max in these areas. Reamer is ordered from JGS, .236 neck zero fb. I’ll have to do a light cleanup neck turn on the Lapua brass or no turn on the Starline brass. Figured if I do one on an AR platform I can just shoot Starline and use Lapua on the bolt rifle.

 

[457ciSBC]

I was one of the first persons necking the Grendel down to .20. I'm pretty sure I was the first person to show Bill A. the Grendel necked down to .20 which I had loaded with a 57 grain VLD. Later, I had a second reamer made up just for the Berger 55 grain pills, which have been discontinued as have the 50 grain bullets.

IMHO, considering the small cross section of the bore, there's not much if any advantage of the 20G over the 20PPC or 20 Beggs when using 40 grain bullets. The later both can drive a 40 grain bullet 4000+, even the 20 PUP ( .185 short 20PPC ) with only about 21 grains of powder can push the Berger 40 BT pretty fast

 

[msalm]

Well I’m kind of doing the whole theme of Howa Mini handy Rifles. When I have this one complete I’ll have the 20, 224, 6mm, 6.5, and a .311 Grendel (opened up a factory 7.62x39 chamber with a Grendel reamer)...no real reason other than I think they’re neat little rifles and I see a fun use in every iteration from predators to deer. Not to mention great youth rifles for the same.