### The Honorab le Russell G. Clark, United States District Judge 1 

### for the Western District of Missouri. ___________ No. 95-1229

___________ United States of America, * * Appellee, * * Appeal from the United States v. * District Court for the * Western District of Missouri. Johnny Boyce, * * [UNPUBLISHED] Appellant. *

___________ Submitted: July 5, 1996 Filed: July 19, 1996

___________ Before BOWMAN, LOKEN, and HANSEN, Circuit Judges.

___________ PER CURIAM. Johnny Boyce challenges the fifty-seven-month sentence imposed by the Dis trict Court following his guilty plea to conspiring to provide 1 a pr ohibited object (heroin) to an inmate, in violation of 18 U.S.C
. §§ 371, 1791(a)(1) (1994). Counsel has filed a brief pursuant to Anders v. Cal ifornia , 386 U.S. 738 (1967), and Boyce has filed a pro s e supplemental brief raising additional issues. We affirm.

In his Anders brief, counsel suggests he rendered ineffectiv e assist ance in advising Boyce to waive a reduction for acceptin g responsibility, and Boyce joins in this argument. Because the record is undev eloped as to such a claim, it is more properly the subject of a 2 8 U.S.C. § 2255 (1994) motion where Boyce can first

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present it to the District Court. See United States v. Taylor , 82 F.3 d 200, 201 (8th Cir. 1996).
In his su pplemental pro se brief, Boyce contends the District Court wrongly assessed a fo ur-level aggravating-role enhancement under U.S.S.G. § 3B1.1(a) (1995). This contention is baseless because Boyce stipulated in his plea agreement that he should receive the enhancement and admitted at the change-of-plea hearing that he had read the plea agreement and had consulted with counsel before signing it. See U nited States v. Nguyen , 46 F.3d 781, 783 (8th Ci r. 1995) (holding that defendant who voluntarily and explicitly acknowledges that specific guidelines provision applies may not challenge punishment on appeal). For the same r eason, any challenge Boyce makes to the District Court's decision not to grant him an acceptance-ofrespo nsibilityreduction also fails. We also reject as vague an d conclu sory Boyce's contentions that the District Court failed to compl y with Federal Rules of Criminal Procedure 11(f) and 32(c)(3)(D). See Fed. R. App. P. 28(a)(6) ( 1996); see also Sidebottom v. Delo , 46 F.3d 744, 750 (8th Cir.) (holding that habeas petitioner waived argument by failing to specify why grounds a sserted entitled him to evidentiary hearing) (citing predecessor to Rule 28(a)(6)), cert. denied , 116 S. Ct. 144 (1995).

For the first time, Boyce also argues that he was entitled to a three-level decrease under U.S.S.G. § 2X1.1(b)(2). After conducting plain

error review, see United States v. Montanye , 996 F.2d 190, 192 (8th Cir. 1993) (en banc), we r eject the claim, as the undisputed facts reveal that one of Boyce's co-conspirators was about to receive heroin from another co

conspirator--for subsequent delivery to Boyce--when the individua l delivering the heroin suspected she had been dis covered by authorities and quick lydisposed of the drugs. See U.S.S.G. § 2X1.1(b)(2) (1995 ) (providing that three-level decrease in conspiracy cases unavailable if co

conspirators were about to complete all acts

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believed necessary for successful completion of substantive offense "but for ap prehension or interruption by some similar event beyond thei r control"). Finally, Boyce lodges a general ineffective-assistance claim, a rguing that he was prejudiced by counsel's advice to st ipulate to "untrue" facts, and by counsel's failure "to properly mitigate f actors that [were] clearly in [Boyce's] best interest[s]." Boyce's Supplemental Brief at 6. These shortcomings, Boyce m aintains, resulted in his receiving the aggravatingrole enhancement and not receiving a § 2X1.1(b)(2) decrease. Again, such claims are more properly the subject of a § 2255 motion. See Taylor , 82 F.3d at 201. Having carefully reviewed the record, we have found no othe r nonfrivolous issue for appeal. See Penson v. Ohio , 488 U.S. 75, 80 (1988) . Accordingly, the judgment of the District Court is affirmed.
A true copy.

Attest:
CLERK, U. S. COURT OF APPEALS, EIGHTH CIRCUIT.